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Cresol

Cresols are a group of organic compounds with the chemical formula C6H4(CH3)OH.
They are isomeric phenol derivatives, with the methyl group (-CH3) attached to the benzene ring.
Cresols have diverse applications in industry, pharmaceuticals, and research, and are commonly used as solvents, disinfectants, and intermediates in chemical synthesis.
Researchers can leverage PubCompare.ai to optimize their cresol-related studies, easily locating the best protocols from literature, preprints, and patents, while receiving accurate comparisons to enhance reproducibility and accuracy.
This streamlined approach can help accelerate cresol research and discovery.

Most cited protocols related to «Cresol»

Effects of PCBs on Hippocampal Neuron Morphology and Calcium Signaling

Cited 11 times

A complete listing of reagents is provided in Supplemental Material, p. 3 (http://dx.doi.org/10.1289/ehp.1104833). Animals were treated humanely and with regard for alleviation of suffering according to protocols approved by the Institutional Animal Care and Use Committees of Oregon Health & Science University, University of California, Davis, and Washington State University, Pullman.
Cell culture. Hippocampal neurons were dissociated from postnatal day–1 Sprague-Dawley rats (Charles River Laboratories, Wilmington, MA) and cultured at high density (10⁵ cells/cm²) in Neurobasal-A medium (Invitrogen, Carlsbad, CA) supplemented with B27 (Invitrogen) as described previously (Wayman et al. 2006 (link)). To visualize dendritic arbors, cultures were transfected at 6 days in vitro (DIV) with the plasmid-encoding microtubule-associated-protein-2B MAP2B (which labels the somatodendritic domain) fused to enhanced green fluorescent protein (EGFP) using Lipofectamine-2000 (Invitrogen) according to the manufacturer’s protocol. A subset of cultures was simultaneously transfected with plasmids encoding dominant negative (dn) CaMKI (dnCaMKI), dnCREB (also referred to as ACREB), or Wnt inhibitory factor (Wif). PCBs or vehicle (DMSO at 1:1000 dilution) was added to the culture medium for 48 hr beginning at 7 DIV; in a subset of cultures, a CaMK kinase inhibitor (STO-609, 5 μM) or a MEK inhibitor (U0126, 10 μM) was also added to the medium during the same period.
Organotypic hippocampal slices from postnatal day–5 rats were cultured for 3 days as described previously (Lein et al. 2011 (link)). At 3 DIV, slice cultures were biolistically transfected with plasmid-encoding tomato fluorescent protein (TFP) using the Helios gene gun (Bio-Rad, Hercules, CA) per the manufacturer’s directions. A subset of slice cultures was simultaneously transfected with siRNA (small interfering RNA) specific for RyR1 or RyR2. Slice cultures were exposed to vehicle, and PCBs were added to the culture medium during 4–6 DIV. A subset of cultures was also exposed to FLA365 [4-(2-aminopropyl)-3,5-dichloro-N,N-dimethylaniline] (10 μM), which was added to the culture medium during the same period.
Dendritic morphology was quantified from digital images of green fluorescent protein–positive (GFP⁺) or TFP⁺ neurons using Image J version 1.44p with the Neuron J plug-in version 1.42 to trace neurons (Meijering et al. 2004 (link)).
Calcium imaging. Spontaneous and electrically evoked Ca²⁺ transients were measured in dissociated hippocampal neurons cultured on Greiner CELLSTAR® micro-clear wells (Sigma-Aldrich, St. Louis, MO). Cells were loaded with the Ca²⁺-sensitive dye Fluo-4 AM (5 µM; Invitrogen) at 37°C for 30 min in imaging buffer consisting of 140 mM sodium choride (NaCl), 5 mM potassium chloride (KCl), 2 mM magnesium chloride (MgCl₂), 2 mM calcium chloride (CaCl₂), 10 mM HEPES, and 10 mM glucose, at pH 7.4, and supplemented with 0.05% BSA (bovine serum albumin). Cultures were washed three times with imaging buffer and transferred to the stage of an inverted Olympus IX70 microscope (Olympus America, Center Valley, PA) equipped with a 60 × 1.25 numeric aperture objective. Fluo-4 was excited at 494 nm using a DeltaRam illuminator (Photon Technologies Int’l., Birmingham, NJ); fluorescence emission was captured at 510 nm. Full-frame images were captured with an Evolve® cooled charge coupled device camera (Photometrics, Tucson, AZ) at 30 frames/sec (fps) using EasyRatioPro software (Photon Technologies Int’l.). In a subset of experiments, cultures were exposed to PCB-95 (2,2´,3,5´6-pentachlorobiphenyl; 2, 20, or 200 nM) from 7–9 DIV before loading with Fluo-4. After baseline recording, cultures were sequentially stimulated with electrical bipolar field pulses (0.5 millisec) at 1, 2.5, 5, and 10 Hz for 10 sec with 50-sec interstimulus rest periods using platinum electrodes connected to a Master 8 stimulator (A.M.P.I, Jerusalem, Israel). After acquisition, regions of interest were drawn freehand to encompass soma and distal dendrites (separated from the soma by a length of > 2 times the soma diameter). Movies were replayed to quantitatively measure changes in Fluo-4 fluorescence within the regions of interest.
At 7 DIV in separate experiments, spontaneous synchronized Ca²⁺ transients were measured from hippocampal neurons that had not been previously exposed to PCB-95 before loading with Fluo-A. PCB-95 (200 nM) or vehicle (DMSO at 1:1,000 dilution) in imaging buffer was acutely introduced into cultures by continuous flow perfusion (~ 1 mL/min). In a subset of cultures, ryanodine (500 µM; EMD Biosciences, Philadelphia, PA) was added to the culture medium 1 hr before loading the cells with Fluo-A to irreversibly block RyR channel activity (Buck et al. 1992 (link); Zimanyi et al. 1992 (link)), which was verified by a challenge with 4-chloro-m-cresol (4CmC, 100 µM; Sigma-Aldrich). Changes in cytoplasmic Ca²⁺ were continuously recorded at 30 fps. Ca²⁺ transients > 2 times the baseline amplitude were scored as oscillations. The number of oscillations was compared between vehicle and PCB-95–treated neurons. Transient amplitude was measured by normalizing peak change in Fluo-A fluorescence (ΔF) to the fluorescence baseline (F₀) and presented as mean ΔF/F₀ for each neuron included in the analysis. Statistical comparisons were made using neurons (n = 30) obtained from three separate dissections. Statistical analysis was performed using unpaired Student’s t test.
Quantitative polymerase chain reaction (qPCR). Total RNA was isolated from dissociated hippocampal neuron cultures (9 DIV) using Trizol (Invitrogen) according to manufacturer’s instructions. Levels of Wnt2 mRNA were quantified by qPCR and normalized to GAPDH (glyceraldehyde 3-phosphate dehydrogenase gene) mRNA levels in the same sample. Primer sequences and a more detailed description are provided in Supplemental Material, p. 4 (http://dx.doi.org/10.1289/ehp.1104833).

Wayman G.A., Bose D.D., Yang D., Lesiak A., Bruun D., Impey S., Ledoux V., Pessah I.N, & Lein P.J. (2012). PCB-95 Modulates the Calcium-Dependent Signaling Pathway Responsible for Activity-Dependent Dendritic Growth. Environmental Health Perspectives, 120(7), 1003-1009.

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Publication 2012

Kinetic Analysis of Phosphotriesterase Activity

Cited 10 times

The time course of ethyl-paraoxon hydrolysis by SisLac at 70°C was monitored following the p-nitrophenolate production at 405 nm (ε_405nm = 17 000 M⁻¹cm⁻¹) in 1-cm path length cell with a Cary WinUV spectrophotometer (Varian, Australia) and using the Cary WinUV software. Standard assays (500 µL) were performed in paraoxonase buffer CHES 50 mM pH 9, NaCl 150 mM, CoCl₂ 0.2 mM, EtOH 6% (v/v), with pH adjusted with NaOH at 70°C.
At 25°C, the phosphotriesterase, esterase and lactonase activities were analyzed monitoring absorbance variations in 200 µL reaction volumes using 96-well plates (6.2-mm path length cell) and a microplate reader (Synergy HT) using the Gen5.1 software at 25°C. For each substrate, assays were performed using organic solvent concentrations below 1%. The monitoring wavelength, the solvent used, the molar extinction coefficient and the concentration range for each substrate (Fig. 1, S1 & S2) are summarized in Table S2. Phosphotriesterase and esterase activities were performed in activity buffer. When required, DTNB at 2 mM was added to the buffer to follow hydrolysis of substrate releasing thiolate group (malathion (Fig. S1V)). Catalytic parameters for some phosphotriesters were also recorded using SDS at concentrations 0.01 and 0.1% (w/v). Lactone hydrolysis assays were performed in lactonase buffer (Bicine 2.5 mM pH 8.3, NaCl 150 mM, CoCl₂ 0.2 mM, Cresol purple 0.25 mM and 0.5% DMSO) using cresol purple (pK_a 8.3 at 25°C) as pH indicator to follow the acidification related to the lactone ring hydrolysis. Molar coefficient extinction was measured by recording absorbance of the buffer over a range of acetic acid concentrations (0–0.35 mM). The absorbance values versus acetic acid concentration were fitted to a linear regression (GraphPad Prism 5 software) with a slope corresponding to molar extinction coefficient (see Table S2). For all experiments, each point was made in triplicate and the Gen5.1 software was used to evaluate the initial velocity at each substrate concentration. Mean values were fitted to the Michaelis-Menten equation using Graph-Pad Prism 5 software to obtain the catalytic parameters. In the case of C4 AHL hydrolysis for which the substrate concentration that enable to determine the enzyme V_max could not be reached, the catalytic efficiency has been determined by fitting the linear part of the Michaelis-Menten plot to a linear regression.

Hiblot J., Gotthard G., Chabriere E, & Elias M. (2012). Structural and Enzymatic characterization of the lactonase SisLac from Sulfolobus islandicus. PLoS ONE, 7(10), e47028.

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Publication 2012

2-(N-cyclohexylamino)ethanesulfonic acid Acetic Acid Aryldialkylphosphatase Biological Assay Buffers Catalysis Cells cresol Dithionitrobenzoic Acid Enzymes Esterases Ethanol ethylparaoxon Extinction, Psychological gluconolactonase Hydrolysis Lactones Malathion Molar N,N-bis(2-hydroxyethyl)glycine Phosphoric Triester Hydrolases prisma Sodium Chloride Solvents Sulfoxide, Dimethyl

Plasma Fatty Acid Composition Analysis

Cited 9 times

We analyzed the total plasma FA composition according to a reference method to compare the results with that obtained by the new method. For this purpose, we used the standard procedure established in our laboratory, which is based on Folch extraction. In detail, 100 µl of internal standard was added to 250 µl plasma and lipids were extracted by a modified Folch method [21] (link) using chloroform/methanol (2∶1, v/v). The extract was washed two times with NaCl solution (2% in water) and subsequently dried at 30°C under reduced pressure. For methyl ester synthesis the extract was taken up in 400 µl chloroform/methanol and 1.5 ml methanolic HCl (3 N) were added. The tubes were closed, shaken for 30 s, and heated to 85°C for 45 min. Samples were neutralized with carbonate buffer after cooling to room temperature. 1 ml hexane was added for FAME extraction. After centrifugation at 900×g for 5 min the upper hexane phase was transferred into a further glass tube and the extraction was repeated. The extracts were combined, taken to dryness under nitrogen flow at room temperature, and taken up in 50 µl hexane (containing 2 g/l 2,6-di-tert-butyl-p-cresol) for GC analysis.

Glaser C., Demmelmair H, & Koletzko B. (2010). High-Throughput Analysis of Total Plasma Fatty Acid Composition with Direct In Situ Transesterification. PLoS ONE, 5(8), e12045.

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Publication 2010

Anabolism Buffers Carbonates Centrifugation Chloroform cresol Esters Lipids Methanol n-hexane Nitrogen Plasma Pressure Sodium Chloride TERT protein, human

Metabolite Profiling by GC/MS

Cited 8 times

Raw data obtained from GC/MS measurements were processed by applying version 2.2 N-2013-01-15 of the in-house developed software MetaboliteDetector [49 (link)]. The peak identification was performed non-targeted with a combined compound library for each GC column applied. After processing, non-biological peaks and artefacts were eliminated by the aid of blanks. Peak areas were normalized to the corresponding internal standards (o-cresol or ribitol) and derivatives were summarized. Data were fitted sigmoidally after Boltzmann and uptake rates were determined using Origin9.0G software when applicable.
For leucine and phenylalanine fermentation products, peak areas were estimated after normalization on the relative proportion of the specific quantification ion compared to the total ion chromatogram but we cannot exclude differences of the two compounds during drying or derivatization procedures.

Neumann-Schaal M., Hofmann J.D., Will S.E, & Schomburg D. (2015). Time-resolved amino acid uptake of Clostridium difficile 630Δerm and concomitant fermentation product and toxin formation. BMC Microbiology, 15, 281.

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Publication 2015

2-cresol Biopharmaceuticals cDNA Library derivatives Fermentation Gas Chromatography-Mass Spectrometry Leucine Phenylalanine Ribitol

Fecal Metabolite Profiling Protocol

Cited 8 times

The short-chain fatty acid (SCFA), amines, ammonia, and phenolic and indolic compounds were selected as markers of GIT microbiota metabolism. The concentrations of SCFA were analyzed by gas chromatography as described previously [21 (link)], with slight modifications. Briefly, approximately 0.4 g of fecal samples were weighed into a 2-mL centrifuge tube, 1.6 mL of double distilled water was added. The mixture was vortexed for 10 min until the material was homogenized and then centrifuged at 13,000×g for 10 min at 4 °C. A portion of 1 mL of the clear supernatant was transferred into a new tube, and then added 0.2 mL 25% (w/v) metaphosphoric acid. After homogenization, the mixture was frozen at −20 °C and kept overnight to precipitate the proteins. After thawing, a portion of 100 μL internal standard (0.64% (w/v) crotonic acid solution) was added. The tubes were vortexed for 1 min and then centrifuged at 13,000×g for 10 min at 4 °C. The supernatant was filtered through a 0.22-μm syringe filter and then analyzed on an Aglient 7890B system with a flame ionization detector (Agilent Technologies Inc.). The following column conditions were used: nitrogen was used as the carrier gas with a flow rate of (17.68 mL/min); the oven, detector and injector port temperature were 130 °C, 250 °C, 220 °C, respectively. These acids were identified by their specific retention times and the concentrations determined and expressed as umol/g.
Amine concentrations in feces were determined by high-performance liquid chromatography (HPLC) with a method according to Yang et al. [22 (link)]. Briefly, 1.5 g of feces were treated with 3 mL of 5% trichloroacetic acid, homogenized for 10 min and then centrifuged at 3600×g for 10 min at 4 °C. The supernatant was mixed with an equal volume of n-hexane and vortexed for 5 min, the water phase (0.5 mL) was transferred into a new tube, and then added with 1.5 mL saturated Na₂CO₃, 1 mL dansyl chloride, and 1 mL NaOH (2 mol/L). The mixed solution was heated at 60 °C for 45 min, and then added with 100 μL ammonia (2.8%) to stop the reaction. The mixture was kept in the water bath until the acetone was vaporized under nitrogen at 40 °C. Finally, the sample was extracted with 3 mL diethyl ether. The extracts were dried under nitrogen and then re-dissolved in acetonitrile. The mixture filtered through 0.22-μm syringe filter and then analyzed on an Aglient 1220 Infinity LC system with an UV detector (Agilent Technologies Inc.).
The ammonia concentration in feces was analyzed using UV spectrophotometer according to Chaney and Marbach [23 (link)]. Phenolic and indolic compounds concentration was determined by HPLC as previously described [24 (link)]. Briefly, 0.1 g of fecal sample was treated with 1 mL acetonitrile, homogenized for 10 min and then frozen at −20 °C for 20 min. Finally, the mixture was centrifuged at 3000×g for 10 min at 4 °C. The supernatant was filtered through a 0.22-μm syringe filter and analyzed for phenolic and indolic compounds (i.e., p-cresol, skatole, indole, and phenol) using HPLC with an UV detector (Agilent Technologies Inc.).

Yu M., Zhang C., Yang Y., Mu C., Su Y., Yu K, & Zhu W. (2017). Long-term effects of early antibiotic intervention on blood parameters, apparent nutrient digestibility, and fecal microbial fermentation profile in pigs with different dietary protein levels. Journal of Animal Science and Biotechnology, 8, 60.

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Publication 2017

Most recents protocols related to «Cresol»

Evaluating P-Cresol's Impact on Rat Cognition

Not available on PMC !

Animals: Animal care during the experimental procedures was carried out by the recommendation of the Ilia State University Research Projects Ethics Commission (Decision no. R/429-23) and by the Council of Europe Directive 2010/63/EU for animal experiments. A total of 14 male young (10 weeks old) rats (weight, 150-180 g) male Wistar rats were obtained from the breeding colony of the vivarium of I. Beritashvili Center of Experimental Biomedicine (Tbilisi, Georgia), were housed in cages (7 rats per cage) and provided with food and water available ad libitum and maintained under conditions at a temperature of 20-22 C and 40-55% humidity on a 12-light/dark cycle (lights on at 7:00 a.m.). The rats were subjected to an enforced swimming test in order to exclude endogenic depression.
Prior to commencing treatment, all rats were marked and separated for 24 h.
Treatment with p-cresol: After testing rats were randomly assigned into the following subgroups: I) The control group (n=7); and II) The p-cresol-treated group (n=7). P-cresol treatment initiated after a 3-day acclimatization period. The amount of p-cresol and timing is defined according to previous experiments (Tevzadze, 2018 1 ) to avoid depressionlike behavior induced through the administration of high doses of p-cresol.
. CC-BY-NC-ND 4.0 International license made available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is
The copyright holder for this preprint this version posted March 28, 2024. ; https://doi.org/10.1101/2024.03.25.586517 doi: bioRxiv preprint P-cresol (20 mg/kg/day) in 1% ethanol saline solution was administered intraperitoneally during 10 days, whereas control group were subjected for the 1% ethanol saline injection (placebo).
Active avoidance test: Active avoidance is a classical conditioning test in which rodents must pair the presence of a conditioned stimulus with moving between two chambers to avoid an electric shock (unconditional stimulus). In the active avoidance test, the test animal learns to avoid an aversive stimulus by changing locations. At the start of the test, a rat is placed in one of two compartments. After habituation, a stimulus (light) is presented for a fixed period of time and followed by electrical stimulation of the paws. The rat learns to avoid the shock by moving into the adjacent compartment upon the appearance of the conditioned stimulus (Jänicke, Coper, 1996; (link)Choi, 2010) (link). the faster the rat learns the avoidance, the better its learning ability and the number of avoidance while pairing. In total, each rat in both groups received 25 pairings.
On the second day after the last treatment, the active avoidance test (AAT) was conducted in operant chambers (12.0'' L x 9.5'' W x 8.25'') inside sound-attenuating cabinets. Chambers were fitted with footshock grids, retractable levers, cue lights above the levers, a house light, and speakers for cue tone and white noise. Statistical Analysis: We used the paired samples t-test to compare the means of two samples (control versus p-cresol-administered) since each observation in the control sample could be paired with an observation in the experimental sample. As a complementary analytical tool, we used the logistic curve model -a popular approach when analyzing learning curves in animal groups (Gallistel et al. 2004 (link)). For our case, in which the learning curve shows the change in the number of avoidance reactions as dependent on the number of trials, the model can be presented as follows:
where y is the learned avoidance rate and x is the number of trials, a is the maximum rate of the learned avoidance reached at the sufficiently large number of trials, b is the steepness of the curve and c represents the inflection point, the value of x at which the curve growth turns accelerated to decelerated. The model fitting was assessed by the Akaike Information Criterion (AIC) and the determination coefficient R². Both characteristics showed an acceptable to good accuracy of model fitting: AIC < 7.56, R² > 0.99. The paired test was performed, the logistic models have been constructed and their parameters calculated using the software PAST 4 (Hammer and Harper, 2001) .

Tevzadze G., Zhuravliova E., Kikvidze Z., Kiknadze N., Shetekauri T., & Tkemaladze N. (2024). Bettering of Learning Activity through Elevated P-Cresol Levels in the Brain: Insights from Active Avoidance Testing in Wistar Rats.

Publication 2024

Cresol-Stabilized Carbon Nanotube Dispersions

Not available on PMC !

Example 2

This Example illustrates the use of cresols as a minority cosolvent to form surfactant-free dispersion of SWCNTs and MWCNTs in combination with organic solvents without the need for surface functionalization.

Experimental

Materials

m-cresol (98% purity), n-hexane, 1,4-dioxane, toluene, anisole, n-methyl-2-pyrrolidone, chloroform, and acetone, CDCl₃, and DMSO-d₆were purchased from Sigma-Aldrich and used as is. Ethanol (200 proof) was purchased from Fisher Scientific and used as received. All the nanotubes used in this example, including powders of MWCNTs (TNGM2) and SWCNTs (TNSR), were obtained from the manufacturer Timesnano under Chengdu Organic Chemicals Co. Ltd.

Spectroscopy

¹H-NMR was conducted using a Bruker Au400 NMR. Each NMR sample was made by diluting a 100 μL of m-cresol/nanotube sample with 1 mL of deuterated solvents. These dispersions were then loaded into a standard liquid NMR tube and inserted into the NMR device. The NMR experiment was done at 32 scans per spectrum at room temperature. The samples used for obtaining the spectra in FIG. 17A were prepared by adding 100 μL of m-cresol/MWCNTs dispersions with concentrations of 1.0 mg/ml, 0.8 mg/ml, 0.6 mg/ml, 0.4 mg/ml, and 0.2 mg/ml into 1 ml of CDCl₃. While the concentration of the MWCNTs was varied, the concentration of m-cresol remained the same for all the NMR samples. Raman spectroscopy studies were conducted using a HORIBA LabRAM HR Evolution confocal Raman spectrometer. The m-cresol/nanotube samples were prepared in a mortar and pestle at 60 mg/ml for SWCNTs and 100 mg/ml for MWCNTs. After grinding for 10 minutes, the nanotube pastes were transferred to a glass slide for Raman study using a fixed excitation wavelength of 532 nm. The laser power was modulated with neutral density filters to avoid overheating the samples and completely evaporating off m-cresol at the sampling spots. Each spectrum was recorded by averaging 30 scans at a rate of 1 s per scan. FTIR spectroscopy was carried out using a Nicolet IS50 spectrometer in transmission mode using potassium bromide windows (Alfa Aesar). For each m-cresol/MWCNTs sample, a small volume was sandwiched between two potassium bromide windows and squeezed to make the MWCNT layer as thin and homogeneous as possible before taking the transmission measurement.

Dilution of m-Cresol/MWCNTs in Common Organic Solvents

The initial MWCNT stock dispersion was made by adding 150 mg of MWCNT powders to 30 ml of m-cresol. The mixture was then sonicated at 90% power for a total of 2 hours at 2 s/2 s on/off cycles using a Qsonica Q125 sonicator rated at 125 W. After sonication, the dispersion was centrifuged for 1 hour at 11,000 rpm using an Eppendorf 5804 desktop centrifuge (equivalent to 15,554×g). The dark supernatant was then used as the stock dispersion and was diluted with selected organic solvents so that the fraction of m-cresol is eventually at 20 vol %. The solvents tested include n-hexane, 1,4-dioxane, toluene, anisole, chloroform, acetone, and ethanol. Each diluted dispersion was sealed in a 20 ml scintillation vial for visual inspection at selected times.

LB Assembly

LB assembly was performed on a homemade mini LB trough (2.5×13 cm), which was carefully cleaned with acetone and deionized (DI) water, and finally filled with DI water. Spreading samples of MWCNTs were pipetted from the bottom of the corresponding vials, instead of from the supernatant, to avoid sampling bias favoring only the well-dispersed part of the samples. After spreading, the floating monolayers were densified by moving barriers and transferred to silicon wafers (1 cm×1 cm) by dip coating.

Air-Brushing

SWCNT ink for air brushing was made by diluting 100 ml of 1.0 mg/mL SWCNTs in m-cresol with 100 mL of toluene. Spraying was done using a Paasche VLST-Pro air brush with a 0.7 mm diameter spray nozzle attachment. The dispersion was then sprayed onto a substrate, including cotton cloth, paper, and copper foil, placed on a hot plate preheated at around 200° C.

Sheet Resistance

Measurements were made using a 4-point probe made by Alessi industries. The probe head has a line of 4 equally spaced needle electrodes with diameter of around 0.7 mm and end-to-end distance around 6 mm. For each 9 cm×9 cm sample, 72 measurements were made at different positions roughly 8 mm apart. Sheet resistance was calculated based on the I-V curve scanned between −0.5 to 0.5 mV.

Results and Discussion

Spectroscopic Studies of Cresol-Nanotube Interaction

Finding compatible solvents requires the understanding of how cresol molecules interact with nanotubes to disperse them so well, which was investigated with several spectroscopic techniques. To start, ¹H-NMR and Raman spectroscopy were used to understand why cresols can disperse nanotubes so well. Since non-functionalized nanotubes should not have any signal in ¹H-NMR, the technique is particularly well suited to investigate the changes in the local chemical environment of the solvent molecules before and after interacting with CNTs. Proton signals detected by ¹H-NMR are determined by the electron density of hydrogen atoms on the cresol molecules, which can help to identify the part of the m-cresol molecule that interacts with the carbon surface. On the other hand, Raman spectroscopy can detect the change in electron density at the sp²-conjugated surface of nanotubes. If corroborating evidences can be obtained from ¹H-NMR and Raman spectroscopy studies, an interaction mechanism can be elucidated.

For simplicity, m-cresol was used throughout the study because it is the only liquid cresol isomer at room temperature. Since m-cresol is an aromatic methylphenol, intuitively one would expect it to be attracted to the graphenic surface of nanotubes through n-n interactions, as noted in earlier reports. However, ¹H-NMR spectroscopy studies of m-cresol/nanotube dispersion diluted in CDCl₃revealed an evident shift of the resonance peak corresponding to the phenolic hydroxyl proton, but not for the protons attached to the aromatic ring. Without the nanotubes, the chemical shift of the phenolic hydroxyl proton is at 5.68 ppm (FIG. 17A, bottom). In the presence of dispersed MWCNTs, the chemical shift moves upfield to 5.38 ppm (FIG. 17A, top). A lower chemical shift suggests that the phenolic hydroxyl proton has become more shielded due to increased local electron density when interacting with nanotubes. Notably, the peaks corresponding to all the other protons in m-cresol, including the four aromatic protons in the range of 6.60 ppm to 7.10 ppm and the three methyl protons at 2.25 ppm, remain unchanged.

In a cresol-nanotube dispersion, there should be both free m-cresol molecules and those interacting with nanotubes. However, only a single phenolic hydroxyl proton peak is observed in the ¹H-NMR spectra, indicating that the exchange speed between the two types of m-cresol molecules is much faster than the timescale of each NMR scan. Therefore, the recorded chemical shift represents a population average of the two types of m-cresol molecules. Increasing the concentration of nanotubes in the dispersion increases the fraction of interacting m-cresol molecules, which should move the chemical shift further upfield. As shown in FIG. 17A, this has indeed been observed. The chemical shift of phenolic hydroxyl proton has a largely linear correlation with the MWCNT concentration, suggesting that this is a fast exchange system (FIG. 17B) involving two types of m-cresol molecules.

Results from the ¹H-NMR study suggest that the electron density around the phenol hydroxyl proton has increased after interacting with the CNTs, so the electron density of the CNTs should be decreased accordingly. This is reflected in the Raman spectra of CNTs taken before and after interacting with m-cresol. As shown in FIG. 17C, a blue shift in the G-band of MWCNTs from 1577 cm⁻¹to 1584 cm⁻¹is observed after interacting with m-cresol, which is also observed for SWCNTs. The charge-transfer between m-cresol and nanotubes should increase the polarity of the phenolic hydroxyl bond, which should affect its vibrational modes. These changes were detected by Fourier transform infrared spectroscopy.

Criteria of Compatible Solvents for Cresol-Nanotube Complex

Since charge-transfer is electrostatic in nature, binding strength of the cresol-CNT complex should be sensitive to the dielectric constant of its surrounding solvent, which describes the solvent's ability to screen charges. Polar solvents with high dielectric constants are more effective at screening charges, and they should be able to break the cresol-nanotube complex. Here, ¹H-NMR becomes a very useful tool for examining the stability of the cresol-nanotube charge-transfer complex in a particular solvent, which can be used to identify compatible solvents for the cresol-nanotube dispersions. To prepare samples for the NMR experiments, the nanotube dispersions in m-cresol need to be diluted in a miscible deuterated solvent. If the complex is stable in a selected solvent, one would expect to see an upfield shift of the resonance peak of phenolic hydroxyl proton as seen in FIG. 17A. Otherwise, the peak position would not be affected by the presence of nanotubes. The ¹H-NMR measurements in FIG. 17A were carried out in deuterated chloroform, which has a low dielectric constant of 4.81. It was found that both the SWCNT and MWCNT dispersions in m-cresol can be diluted with CDCl₃without any sign of aggregation even after months. In the corresponding ¹H-NMR spectra, the upfield shift of the phenolic hydroxyl proton resonance can be clearly seen (FIG. 18A) for both the SWCNT and MWCNT dispersions. In contrast, when the dispersions were diluted in deuterated dimethyl sulfoxide (DMSO-d₆), which is a polar solvent with a high dielectric constant of 46.7, significant aggregation occurred after about 2 hours. In the corresponding ¹H-NMR spectra taken while the dispersion in DMSO-d appeared homogeneous, the phenolic hydroxyl proton peak remained unchanged with or without nanotubes (FIG. 18B). These results indicate that ¹H-NMR can be used as an analytical tool to mechanistically search and evaluate compatible solvents for the cresol-nanotube systems.

The results of the NMR experiments lead to the hypothesis that cresol-compatible solvents for dispersing nanotubes should be miscible with cresols and have relatively low dielectric constants. As illustrated by the schematic drawing in FIG. 18C, these less polar solvents won't break the cresol-nanotube charge-transfer complex and essentially disperse the cresol-nanotube complex as a whole. This helps to greatly reduce the amount of cresols needed to disperse CNTs. In contrast, high dielectric constant solvents are better at screening the electrostatic interaction, leading to dissociation of cresol molecules from the nanotubes and the aggregation of nanotubes. Therefore, solvents with high dielectric constants can very effectively wash cresols away from nanotubes after solution processing, avoiding contamination of the functional nanotube surface.

Additive-Free Nanotube Dispersions in Mixed Solvents

With the above insight, a number of common organic solvents have been evaluated, which are sorted in Table I based on their dielectric constants. These solvents are selected because they are all miscible but do not react with m-cresol, and they cannot disperse nanotubes themselves. Each of these poor solvents was added to a concentrated m-cresol/MWCNTs dispersion (1.0 mg/ml) to a final volumetric ratio of 80% poor solvent. In a cresol-compatible solvent, the nanotube dispersion should stay stable, but in an incompatible solvent, the nanotubes should agglomerate. Photographs of the MWCNTs samples in the diluted solvent mixtures were taken at multiple time intervals to observe the colloidal stability of the nanotubes. The m-cresol/MWCNTs samples in non-polar, low dielectric constant solvents, including hexanes, 1,4-dioxane, toluene, anisole and chloroform, maintain visibly stable dispersions for at least 1 week. However, when diluted with polar, high dielectric constant solvents such as acetone and ethanol, the m-cresol/MWCNTs are unable to maintain stable dispersions and sediment after just 1 day.

TABLE 1

Selected common organic solvents for diluting m-cresol/MWCNTs

dispersion based on the values of their dielectric constants.

SolventDielectric constant

1n-Hexane1.99

21,4-Dioxane2.21

3Toluene2.38

4Anisole4.33

5Chloroform4.81

61,2-Dichloroethane10.4

7Pyridine12.4

8Isopropyl alcohol17.9

9Acetone21.0

10Ethanol24.6

11Dimethyl sulfoxide46.7

Visual inspection alone cannot differentiate whether particles in a suspension are truly well dispersed, especially when the suspension becomes opaque with high loadings of particles. Since dispersions of colloidal materials are often used to create thin films by solution processing, the degree of homogeneity of the final thin film directly reflects the quality of the dispersion. In this regard, LB assembly was employed to create closely packed thin films of CNTs for evaluation by SEM. In LB assembly, the colloidal dispersions are first spread on water surface and then transferred onto a solid substrate to yield a colloidal monolayer. If the nanotubes are indeed well dispersed, they would form a monolayer-like LB film made of a nanotube network. If the nanotubes are not well dispersed, they would form a monolayer of distinctly visible aggregated nanotube islands in addition to some dispersed ones.

FIGS. 19A-19C are SEM images of LB films made from the m-cresol/MWCNTs dispersions immediately after being diluted by toluene and after 1 and 7 days, respectively. All of the images show a continuous monolayer-like network of MWCNTs (FIGS. 19A-19C). In contrast, for the m-cresol/MWCNT sample in acetone, the SEM images of its LB films show mostly clumps of aggregated nanotubes, starting from right after dilution (FIGS. 19D-19F). With a high dielectric constant of 21.0, acetone can destabilize the charge-transfer complex of m-cresol and nanotubes, leading to rapid aggregation of the MWCNTs.

Long Term Stability of Cresol-Nanotubes Complex in Compatible Solvents

It has now been established that compatible solvents that can stabilize a cresol-nanotube charge-transfer complex should be non-polar, miscible, and non-reactive with cresols. Polar, high dielectric constant solvents are incompatible with the cresol-nanotube dispersion. After 2 months, a m-cresol/MWCNTs dispersion was found to sediment in both compatible solvents (e.g., toluene) and incompatible solvents (e.g., acetone). However, the MWCNT sediment in 80 vol % of toluene can be readily re-dispersed by gentle agitation to produce a continuous and uniform LB monolayer of nanotubes. In contrast, the sediment in 80 vol % of acetone cannot be re-dispersed and is still made of aggregates. (FIGS. 20A and 20B) Being able to re-disperse sedimented nanotubes easily and on-demand is highly beneficial for practical applications, which is equally important to having a dispersion with long shelf life.

Diluting a nanotube dispersion in m-cresol with a compatible solvent reduces the viscosity and the time needed for drying the products, which are beneficial for fabricating thin films or coatings based on common solution-processing techniques such as air brushing. Here, SWCNTs were chosen as a model system for demonstration, since they exhibit more drastic morphological differences between the starting powders and the final coating. FIG. 21A is a SEM image of the starting SWCNT powders, showing heavily bundled nanotubes with widths of several microns to tens of microns. These powders can be readily dispersed in m-cresol by sonication or grinding to yield a thick dispersion. With m-cresol itself as the solvent, the SWCNT dispersions were usually too viscous for air brushing (FIG. 21B). If used at low loading levels, the deposited film was usually still wet after spraying, even on heated substrates, due to the slow evaporation speed of m-cresol. Adding toluene to m-cresol/SWCNT did not alter the colloidal stability of the nanotubes but greatly lowered the viscosity of the solvent and increased the drying speed, resulting in an ink readily usable for air brushing. The toluene-based ink was then sprayed onto different substrates such as cloth, paper, and copper foil placed on a hotplate pre-heated to 200° C. Uniform coating was achieved on all these substrates without a trace of the micron-scale ribbons observed in the starting SWCNT powders (FIGS. 21C-21H). SEM studies revealed that the SWCNT coatings are continuous, smooth, and uniform over both the porous and highly uneven substrates (e.g., FIG. 21C, cloth and FIG. 21E, paper) and the flat and impermeable surface (e.g. FIGS. 21G and 21H, copper foil). Notably, on cloth and paper, the SWCNT coating not only uniformly covered the fibers and replicated the textile morphologies, but also formed bridging films connecting the neighboring fibers (FIGS. 21D, 21F). These can only be achieved when the SWCNTs are well-dispersed in the ink.

The morphological uniformity of air-brushed SWCNT coatings leads to their uniform electrical conductivities for potential applications that need light weight, homogeneous, and highly conductive coatings. Sheet resistances of the SWCNT coatings on cloth and paper were measured using the 4-point probe method. The electrical homogeneity of SWCNT coatings on paper and cloth over an area of 9 cm×9 cm were mapped with a periodic displacement of 8 mm using a probe head equipped with a set of 4 equally spaced probes with end-to-end distance of around 6 mm. The average sheet resistivity for SWCNT coating on cotton cloth was measured to be 5.62 Ω/sq with a standard deviation of 0.86 Ω/sq from 72 measurements. The average sheet resistivity for SWCNT coated printer paper was measured to be 4.59 Ω/sq with a standard deviation of 0.64 Ω/sq from 72 measurements. These values led to coefficients of variation of 0.15 for the coated cloth and 0.14 for the coated paper, which was comparable to a commercial sample of graphite film with a coefficient of variation of 0.12. The low coefficient of variation indicated that the coatings had good homogeneities and could exhibit sufficiently predictable properties for applications.

Conclusion

Using cresols as a minority cosolvent, unfunctionalized CNTs can be dispersed in common organic solvents with low dielectric constants without the need for any dispersing agent. ¹H-NMR, Raman. and Fourier transform infrared spectroscopy studies confirmed that cresol molecules form a charge-transfer complex with CNTs through their phenolic hydroxyl protons. ¹H-NMR can also be used to identify solvents that are compatible with cresols to disperse CNTs, offering mechanistic insights when it is hard to evaluate colloidal dispersity based on visual inspection or microscopy. Non-polar solvents stabilize the cresol-nanotube complex and can be added to create nanotube formulations with desirable solvent properties for solution processing. Polar solvents screen the charge-transfer interaction and destabilize the complex, and they can be used to remove cresols after solution processing. As a proof of concept demonstration, SWCNTs dispersed in a blend of m-cresol and toluene or hexane were used directly for air brushing to create continuous and uniform coatings of nanotubes on various surfaces.

US11873223B2. Additive-free carbon particle dispersions, pastes, gels and doughs (2024-01-16). Northwestern University [US]. Inventors: Jiaxing Huang [US], Kevin Chiou [US].

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Patent 2024

Quantifying Smoke-Affected Grapes and Wine

Not available on PMC !

A method for measuring VPGs using Orbitrap mass spectrometry was developed and used to identify the VPGs most indicative of smoke exposure in grapes and wine in CA. Guaiacol, 4-methylguaiacol, cresol and phenol rutinosides, syringol and 4-methylsyringol gentiobiosides, cresol pentose glucoside, and phenol glucoside were consistently found at elevated concentrations (>20 µg/L) in smoke-affected wine. These concentrations were several-fold higher than those of wines from vintages minimally affected by smoke. Satellite imaging data were used to compare the location and density of smoke plumes during the 2018 and 2020 wildfire seasons. Measurement of the above subset of VPGs in grapes sampled during 2018 and 2020 showed they were positively correlated with total glycoconjugates (i.e., the sum of cresol rutinoside, guaiacol rutinoside, 4-methylguaiacol rutinoside, phenol rutinoside, syringol gentiobioside, and 4-methylsyringol gentiobioside concentrations), despite varied levels of total glycoconjugates.

Szeto C., Feng H., Sui Q., Blair B., Mayfield S., Pan B.S., & Wilkinson K.L. (2024). Exploring Variation in Grape and Wine Volatile Phenol Glycoconjugates to Improve Evaluation of Smoke Taint Risk. American Journal of Enology and Viticulture, 75(1), 0750013-0750013.

Publication 2024

Versatile Cresol-Based Carbon Nanotube Processing

Not available on PMC !

Example 1

This example demonstrates the use of cresols as generic solvents for processing various kinds of carbon nanotubes, and further demonstrates that they can also be easily removed afterwards by washing or evaporation. Most strikingly, cresols can process carbon nanotubes over a very broad range of concentrations, reaching the level of tens of weight percent. As the concentration of carbon nanotubes increases, a continuous transition of four distinctive states—namely dilute dispersions, thick pastes, freestanding gels, and viscoelastic doughs—is observed, all of which are readily usable by a wide array of material processing techniques.

The results of the studies described in this Example demonstrate that powders of both SWCNTs and MWCNTs can be well dispersed in m-cresol after sonication or grinding without the need for any surface functionalization. As verified by SEM images, initially the nanotubes were heavily agglomerated and entangled in the powders, but they became well separated after casting from the corresponding m-cresol dispersions. These results indicate that the interaction between m-cresol and the surface of the carbon nanotubes must be sufficiently strong to allow the agglomerated nanotubes to disperse. ¹H-NMR spectroscopy was employed to probe the nature of such interaction. As shown in FIG. 1, in the presence of SWCNTs and MWCNTs, the phenolic hydroxyl proton peak shifted upfield by 0.10 ppm, while other proton peaks remained unchanged. This shift was a result of increased electron density on the phenolic hydroxyl proton, indicating charge-transfer interaction with the nanotubes.

Sonicating or grinding carbon nanotubes in m-cresol does not induce chemical changes to either the solvent or the nanotubes. This is illustrated with SWCNTs due to their higher spectroscopic sensitivity to structural changes. The FTIR spectra in FIG. 2 show that m-cresol itself does not degrade after ultrasonication with or without SWCNTs. As a relatively weak acid, m-cresol does not induce permanent chemical changes to the nanotube surface and can be removed by evaporation or washing. The Raman spectra of the pristine SWCNTs and a dried SWCNT film cast from m-cresol dispersion do not show obvious differences (FIG. 3), suggesting that the pristine SWCNTs are not damaged during processing. The absence of new bands between 400 to 1000 cm⁻¹, where m-cresol shows strong Raman signals, indicates that m-cresol have been successfully removed.

Among the three isomers of cresols, m-cresol is a liquid at room temperature; therefore, it is used for most of the experiments in this Example. While o-cresol and p-cresol are solid at room temperature, they can also process carbon nanotubes at a molten state or when blended with m-cresol at room temperature. This indicates that even the unrefined, crude grade of cresols, which is a liquid mixture of the three isomers, can be directly used for industrial scale processing of carbon nanotubes. Indeed, UV-Vis-NIR spectra of SWCNTs dispersed in a ternary isomer mixture of cresol show characteristic bands of well dispersed nanotubes, which is confirmed by transmission electron microscopy (TEM) studies. Industrial grade cresols often contain phenolic impurities, and it is found that adding an additional 10 wt. % of phenol into the ternary mixture would not negatively affect the stability of the nanotube dispersions. The impurity tolerance and ease of removal make cresols the ideal type of non-reactive solvents for the solution processing of carbon nanotubes. In the sections below, cresol solvents are demonstrated to render carbon nanotubes with polymer-like rheological and viscoelastic properties and processability, making them immediately usable by already available material processing techniques to create desirable structures, form factors, and composites.

Four States of MWCNTs in m-Cresol.

m-cresol alone can disperse and process carbon nanotubes up to tens of weight percent. Since MWCNTs are the more common type of mass-produced carbon nanotubes and are much more affordable and available, they were chosen as the model material for most of the work in the following sections unless otherwise mentioned. Dilute dispersions were typically made by sonication and could remain stable for at least many months. The other higher concentration states were typically made by grinding. Transitions between the four states were accompanied by threshold-like changes in their electrical, rheological, and viscoelastic properties. For example, the transition from a dilute dispersion to a thick paste was accompanied by the onset of electrical conductivity around 3 mg/ml (FIG. 4), which can be attributed to the formation of a percolated nanotube network, establishing a continuous electrically conductive pathway throughout the volume. At higher concentrations, increased density of the MWCNTs network resulted in significant changes in rheological and viscoelastic properties. For example, the transition from a thick paste to a self-standing gel was marked by an inability to free flow around 40-50 mg/ml, after which the viscosity increased significantly (FIG. 5). At concentrations above 100 mg/ml, a viscoelastic, kneadable playdough-like material was obtained, which was highly cohesive and exhibited resistance to compression, as characterized by a rapidly increased compression modulus (FIG. 6).

The continuous transition between these four highly processable, polymer solution-like states indicates that the nanotubes were dispersed and outstretched in m-cresol, forming a cohesive network that densifies at increasing concentrations. If the nanotubes were still agglomerated as in their powders, the corresponding high concentration products would not be cohesive due to segregated domains of agglomerated nanotubes, resulting in poor processability (see schematic illustrations in FIG. 7). These four states were observed for all the carbon nanotubes tested (e.g., unfunctionalized single walled or multiwalled tubes of various sizes). As demonstrated by the examples below, m-cresol indeed offers unprecedented versatility for processing carbon nanotubes for existing and new applications.

Dilute Dispersion and LB Assembly.

The m-cresol dispersion can be directly applied to LB assembly for making monolayer thin films. Successful LB monolayer assembly requires high quality nanotube dispersions without other surface-active materials to disrupt their packing on the water surface, which is challenging for additive-based carbon nanotube dispersions. Since m-cresol can gradually dissolve in water, it dissipated into the sub-phase after spreading the nanotubes on the water surface, leaving clean nanotubes on the water surface. The water-supported monolayers could be further densified by closing two barriers, yielding a positive surface pressure (FIG. 8), which could then be transferred to a substrate by dip-coating. FIG. 9 is a low magnification SEM overview of a MWCNT film on a glass slide collected at a surface pressure of 30 mN/m, which is continuous, uniform, and cohesive. Since many of the starting MWCNTs were curled, twisted, or even kinked, and could not lay flat, the near-monolayer thickness of the film (FIG. 10) also confirmed that the heavily agglomerated MWCNTs in the starting powders indeed had been well separated in m-cresol. Strong van der Waals attraction at the tube-tube junctions contributed to the continuity and cohesiveness of the MWCNT monolayer.

Transferring the nanotube monolayer onto soft plastic substrates such as poly(ethylene terephthalate) formed a flexible transparent conductor. Sheet resistance and optical transparency of the nanotube coating could be fine-tuned further by precisely controlling the number of deposited layers as well as the packing density within each monolayer (FIG. 11). For example, a sheet resistance of 90 kΩ/sq was obtained at 72% of optical transparency. Using m-cresol as a processing medium did not damage the surface of the nanotubes nor leave hard-to-remove residues and resulted in satisfying conductivity of the LB films without the need for extensive further annealing steps. Similarly, LB assembly of SWCNT monolayers was achieved.

Thick Paste, Blade Coating, and Screen-Printing.

Increasing the loading of MWCNTs up to 40 mg/ml resulted in a more viscous paste, which exhibited relatively high viscosity and shear thinning behavior (FIG. 12), with yield stress in the range of 1 to 10 Pa (FIG. 13), making it suitable for use by brushing or painting. In order to make a continuous film using these techniques, the paste should be sufficiently cohesive so that the coating does not break up under the shear during spreading or crack by the capillary action during drying. Therefore, the nanotubes should be interconnected throughout the paste without extensively segregated domains (FIG. 7). The paste was applied by blade coating. The oven-dried coating on glass was continuous and free of cracks over the entire area. SEM images show that it was made of an interwoven, continuous, and high-density network of nanotubes (FIG. 14). Similar to blade coating, industrial screen-printing can directly use the MWCNT paste to generate functional patterns. Blade coating is commonly used to make electrodes for energy storage devices from slurries, which often use carbon nanotubes as a conductive binder for active materials. Highly cohesive, additive-free pastes with well-dispersed nanotubes are readily compatible with these slurry processing techniques and could directly benefit this large scale application of carbon nanotubes.

MWCNT Pastes for Polymer Composites.

Polymer nanocomposite is another area that uses a very large scale of carbon nanotubes. The paste state offers a number of potential advantages for manufacturing. To start, the paste can be easily mixed with powders of polymers, which is one of the most common forms of industrial polymers. Moreover, m-cresol itself is a solvent for many commodity polymers such as PMMA, nylons, polyethyelene terephthalate, polystyrene, and phenolic resins, which helps the blending process. Using the paste also drastically reduces the amount of solvent needed for manufacturing and greatly shortens the baking time needed for solvent removal. A proof-of-concept experiment was conducted in which PMMA powders were directly mixed with the paste by mortar and pestle. The product was rolled into a flexible and highly plastic sheet, which sustained over 800% of tensile strain. Upon thermal curing at 150° C., the sheet hardened due to partial removal of m-cresol. At 1 wt. % loading of MWCNTs in PMMA, the Young's modulus of the composite (1.46 GPa) increased by 24% in comparison to a similarly processed PMMA sheet (1.17 GPa). SEM observation confirmed that the MWCNTs had been finely dispersed in the PMMA matrix. Such a soft-hard transition is critical for industrial forming techniques, which turn materials into desirable geometries and form factors. The additive-free carbon nanotube pastes in cresols can be useful for accelerating the development and manufacturing of polymer nanocomposites.

Gel and 3D Printing.

Above 40 mg/ml, the MWCNT network in m-cresol was sufficiently dense to hinder free flow, leading to a freestanding gel. As the nanotube concentration increased, the gel became more solid-like with an increased storage modulus (FIG. 15). The loss modulus increased more slowly than the storage modulus, rendering the gel a sufficient level of liquid character for an extrusion type of processing (FIG. 16). Therefore, the MWCNT gel could deform and reconnect easily. A MWCNT gel was extruded to form self-supporting fibers through a 0.5 mm diameter needle. Since the gel was cohesive, extrusion could be continuously operated even with finer needles (e.g., 0.1 mm diameter). This again reflects that the nanotubes were uniformly dispersed by m-cresol and outstretched like polymers in the gel, rendering it suitable rheological properties for continuous, unhindered extrusion. This gel was immediately usable for programmed and automated printing. As a proof-of-concept, a cup-shaped structure was 3D printed from the gel. The base of the cup was made of two criss-cross layers of close-packed fibers, and the side was made of vertically stacked rings. After drying, the cup structure shrank slightly isotopically but maintained its shape, resulting in a stiff solid object that could be further handled.

MWCNT Dough.

The last state of MWCNTs/m-cresol composition was a viscoelastic dough (>100 mg/ml), which could be kneaded or rolled without fracture. In contrast to a gel, when kneaded on paper, the dough did not leave any stain mark. This was due to the strong attraction between the nanotubes in the densely woven 3D network, which prevented them from leaving residues on the paper. Since the nanotube/m-cresol dough was highly kneadable and stain-free, it must be highly cohesive and free of mechanically weak boundaries between segregated grains of carbon nanotubes. As with a bread dough, the MWCNT dough could be cut into pieces and rejoined when pressed together or molded into arbitrary shapes without altering its viscoelastic properties. A thick film was cold-rolled from the dough, which was still soft and plastic, and could be reshaped using a mold. The MWCNTs doughs could be hardened to fix their shapes after heating at above 200° C. to remove the m-cresol. The hardened structures could then be returned to the soft dough state by absorbing m-cresol. This playdough-like processability is useful for the fabrication of arbitrarily shaped 3D solids of neat carbon nanotubes for a range of electronic, thermal, and energy applications.

Materials and Methods

Materials.

Carbon nanotube powders of various types, sources, and levels of purities from three vendors were tested, and all dispersed well in m-cresol and its liquid mixtures with other isomers. These include: (1) CoMoCAT® MWCNTs (98% carbon content), CoMoCat® SWCNTs (90% carbon content, 90% semi-conducting), and double-walled carbon nanotubes (90% carbon content, made by chemical vapor deposition (CVD)) were obtained from Sigma-Aldrich; (2) SWCNTs (P2, 90% purity) and carboxylic functionalized SWCNTs (P3, 90% purity) were made by arc-discharge and obtained from Carbon Solution Inc.; (3) Graphitized MWCNTs (TNGM2, 99.9% purity, approximate lengths of 50 μm), low density SWCNTs (TNSR, 95% purity, approximate lengths of 5-30 μm, 0.027 g/cm³), high density SWCNTs (TNST, 95% purity, 0.14 g/cm³), short SWCNTs (TNSSR, 95% purity, approximate lengths of 1-3 μm), and short MWCNTs (TNSM2, 95% purity, approximate lengths of 0.5-2 μm) were all made by CVD and obtained from TimesNano.

P2 SWCNTs and MWCNTs (CoMoCat®) were used for demonstrating LB assembly. The results of the pastes, gels, and doughs were demonstrated with CoMoCat® MWCNTs as the model material, although other types of MWCNTs work as well.

Other chemicals were purchased from Sigma-Aldrich and used as received, including m-cresol (99%), o-cresol (99%), p-cresol (98%), toluene (99.9%), phenol (>99%), DMF (99.8%), NMP (anhydrous, 99.5%), PMMA (200,000 Mw), and methyltrichlorosilane (99%). A ternary isomer mixture of cresol (>99 wt. %, 1:1:1 ratio) was purchased from Fisher Scientific and used as received.

LB Assembly and Transparent Conductive Thin Films.

Powders of MWCNTs or SWCNTs were first mixed with m-cresol using a mortar and pestle, then sonicated in pulse mode (2 s on/2 s off cycles for a total of 1 hour) using a Qsonica Q125 sonicator rated at 125 W, equipped with a ¼ inch standard tapered tip at 90% power. After sonication, the dispersion was subject to exhaustive high-speed centrifugation at 11000 rpm for 1 hour using an Eppendorf 5804 desktop centrifuge. The supernatant was recovered and used. Samples for making transparent conductors were first purified by a non-oxidative route, including washing in 3M HCl at 65° C. for 4 hours, followed by baking in a muffled furnace at 250° C. for 1 hour.

All parts of the LB system (Nima Technology) were thoroughly cleaned with acetone before use. Using a glass syringe, 1 ml of m-cresol dispersion (SWCNT or MWCNT) was carefully spread onto the air-water interface. A tensiometer with a Wilhelmy plate was used to monitor the surface pressure while closing the barriers. At surface pressures of around 40 mN/m for SWCNTs and 30 mN/m for MWCNTs, monolayer films were dip-coated onto a substrate (typically glass slides) with a pull speed of 2 mm/min. The obtained LB films were annealed at 150° C. for 30 min before subsequent LB deposition to produce multi-layered films.

Blade-Coating and Screen Printing.

The MWCNTs paste in m-cresol (100 mg/ml) was made by direct mixing using a mortar and pestle, then diluted to 40 mg/ml, and hand ground further to yield a spreadable thick paste. Glass slides were first silanized with 5 wt. % methyltrichlorosilane in toluene for 10 minutes, and then washed thoroughly using toluene followed by acetone. Two strips of Kapton tapes were attached to the sides of the silanized glass slide as spacers to control the thickness of the coating. About 0.3 ml of MWCNT paste was deposited onto the shallow trough created by the Kapton tapes. A razor blade was used to drag the paste to coat the slide. The coating was left to dry at 150° C. for 2 hours. Control experiments were done using NMP instead of m-cresol as the solvent at the same nanotube concentration. Screen-printing was done on paper through a mask using a paste of 10 mg/ml.

Polymer Composite.

To make the MWCNT/PMMA nanocomposite, a MWCNTs/m-cresol paste (40 mg/ml) was ground directly with powders of PMMA (200,000 Mw) using a mortar and pestle for 10 minutes. The composite was then flattened by cold rolling, and it turned flexible and rubbery after being air-dried. Curing at 150° C. for 2 hours significantly hardened the piece and fixed its shape.

3D Printing.

The MWCNTs/m-cresol gel was made by direct mixing using a mortar and pestle at a concentration of 120 mg/ml. The resulting mixture was diluted to 80 mg/ml and ground further. The gel was loaded into a syringe and manually extruded from needles with diameters of 0.1 and 0.5 mm, which could be fitted onto a 3D printer (Hyrel 30M). The printed 3D structure could be removed from the glass substrate after being air-dried for 12 hours and could be further hardened by baking to remove m-cresol.

MWCNTs Dough.

The MWCNT/m-cresol dough was made by direct mixing using a mortar and pestle at a concentration of 300 mg/ml or higher. The mixture was then diluted to 150 mg/ml and ground further to yield a dough-like material, which was kneaded to the shape of a ball. Kneading or rolling a nanotube dough does not stain the substrate, while doing so with a gel or paste would result in significant staining. A kneaded dough was sandwiched between two stainless steel foils and cold rolled to a film with a final thickness of 200 μm, which could be cut into various shapes with a razor blade or cookie cutters.

Characterization.

Dispersions of carbon materials in m-cresol were drop-casted onto silicon wafers and dried at 200-250° C., before SEM (FEI Nova 600 system) and atomic force microscopy (AFM) (Park Systems XE-100, tapping mode). UV/vis spectra were taken with an Agilent 8453 UV/Vis spectrometer. NIR spectra were taken using a Perkin Elmer LAMBDA 1050 spectrometer. TEM images were taken with a JEOL ARM300F GrandARM transmission electron microscope. Drop cast SWCNTs were air dried and rinsed with water and ethanol before Raman spectroscopy measurement (WITec Alpha 300, 532 nm excitation). FTIR spectra were recorded on a PerkinElmer Instrument spectrometer (Spectrum Spotlight 300). ¹H-NMR spectra were acquired on a 400 MHz Agilent DD MR-400 NMR system. The samples were prepared by adding 100 μl of SWCNT or MWCNT dispersions in m-cresol in 1 ml of CDCl₃. The nanotubes were found to be stably dispersed during the entire duration of the NMR experiments. The transparency of the LB films was measured using an Agilent 8453 UV/Vis spectrometer. The sheet resistance of the films was obtained using an in-line four-point probe equipped with a Keithley 2400 source meter. Viscoelastic and rheological properties were measured using an Anton Paar MCR 502 rheometer using a cone-on-plate configuration. The cone had a 25 mm diameter with a 5° gap angle. Viscosity versus concentration measurements were measured with a rotation speed of 1°/s. Yield-stresses were obtained using a Herschel-Bulkley regression included in the Anton Paar software package. Shear-thinning viscosities were measured with a linear ramping shear rate between 0.01 to 100 rad/s. Storage and loss moduli were measured simultaneously using the same rheometer setup at an amplitude of 1%. Tensile and compression tests were done on a Bose electroforce 5500 tester. The composite films were cut into dog bone shapes and pulled at a rate of 0.05 mm/s until failure. Only the results from samples that failed in the middle were considered. Gel and dough samples for compression tests were first molded into cylindrical shapes and carefully transferred to the tester. Compression was done at 0.005 mm/s until the sample ruptured. The slope of the first linear region of the stress-strain curve was taken as the compression modulus.

US11873223B2. Additive-free carbon particle dispersions, pastes, gels and doughs (2024-01-16). Northwestern University [US]. Inventors: Jiaxing Huang [US], Kevin Chiou [US].

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Patent 2024

Synthesis of Aromatic Polymers Precursors

4,4′-BPDA was obtained from China Tech Chemical Co., Ltd. (Tianjin, China), and dried at 250 °C under vacuum prior to use. N-Methylpyrrolidone (NMP), m-cresol, and ethanol were purchased from Energy Chemical Co., Ltd. (Shanghai, China). m-cresol and NMP were distilled over calcium hydride and stored in argon-purged bottles. All other chemicals were obtained from J&K Scientific Ltd. (Beijing, China) and were used as received. The synthesis methods of Br-BPDA [30 (link)], MMBMA, MMBDA [31 (link)], TBDA1, TBDA2 [12 (link)], and DAT [32 (link)] came from publications.

Li Y., Lu Y., Tian C., Wang Z, & Yan J. (2024). Intrinsically Microporous Polyimides Derived from 2,2′-Dibromo-4,4′,5,5′-bipohenyltetracarboxylic Dianhydride for Gas Separation Membranes. Polymers, 16(9), 1198.

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Publication 2024

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M cresol purple by Merck Group

Sourced in Germany, China

M-cresol purple is a pH indicator used in analytical chemistry and biochemistry. It is a purple-to-yellow dye that changes color over the pH range of approximately 7.4 to 9.0, making it useful for monitoring pH levels in various applications.

Bovine serum albumin (bsa) by Merck Group

Sourced in United States, Germany, United Kingdom, China, Italy, Japan, France, Sao Tome and Principe, Canada, Macao, Spain, Switzerland, Australia, India, Israel, Belgium, Poland, Sweden, Denmark, Ireland, Hungary, Netherlands, Czechia, Brazil, Austria, Singapore, Portugal, Panama, Chile, Senegal, Morocco, Slovenia, New Zealand, Finland, Thailand, Uruguay, Argentina, Saudi Arabia, Romania, Greece, Mexico

Bovine serum albumin (BSA) is a common laboratory reagent derived from bovine blood plasma. It is a protein that serves as a stabilizer and blocking agent in various biochemical and immunological applications. BSA is widely used to maintain the activity and solubility of enzymes, proteins, and other biomolecules in experimental settings.

Phenol red by Merck Group

Sourced in United States, Germany, United Kingdom, Macao, France, China, Spain, India, Japan, Switzerland

Phenol red is a pH indicator commonly used in biological and biochemical applications. It is a synthetic organic compound that changes color depending on the pH of the solution it is added to. Phenol red exhibits a range of colors from yellow at acidic pH values to purple at basic pH values, making it a useful tool for monitoring pH changes in various laboratory experiments and processes.

What are the different types or variations of Cresol?

Cresols are a group of three isomeric organic compounds - ortho-cresol (o-cresol), meta-cresol (m-cresol), and para-cresol (p-cresol). These compounds have the same chemical formula (C6H4(CH3)OH) but with the methyl group (-CH3) positioned differently on the benzene ring. The different isomers have slightly varying physical and chemical properties, which can impact their applications and uses.

What are some common applications and uses of Cresol?

Cresols have diverse industrial, pharmaceutical, and research applications. They are commonly used as solvents, disinfectants, and chemical intermediates. Cresols are found in products like disinfectants, antiseptics, personal care items, and in the production of resins, dyes, and pesticides. Researchers also utilize cresols in various experimental protocols and analyses.

What are some common challenges in working with Cresol?

One of the main challenges in working with cresols is their highly corrosive and toxic nature. Cresols can be hazardous to handle, as they can cause skin irritation, eye damage, and respiratory issues upon exposure. Proper safety precautions, such as using personal protective equipment and conducting experiments in well-ventilated areas, are crucial when using cresols. Additionally, the different cresol isomers may have varying reactivity and solubility, requiring careful consideration when selecting the appropriate type for a given application.

How can PubCompare.ai help optimize Cresol research?

PubCompare.ai can greatly assist researchers in optimizing their cresol-related studies. The platform allows you to efficiently screen protocol literature and leverage AI to pinpoint critical insights. PubComapre.ai can help you identify the most effective protocols related to cresol for your specific research goals, highlighting key differences in protocol effectiveness. This enables you to choose the best option for enhancing reproducibility and accuracy in your cresol experiments and analyses. The streamlined approach provided by PubCompare.ai can help accelerate cresol research and discovery.

More about "Cresol"

Cresols are a family of organic compounds that share the chemical formula C6H4(CH3)OH.
These isomeric phenol derivatives have a methyl group (-CH3) attached to the benzene ring, giving rise to the three main cresol variants: o-cresol (o-methylphenol), m-cresol (m-methylphenol), and p-cresol (p-methylphenol).
Cresols possess diverse industrial, pharmaceutical, and research applications, often utilized as solvents, disinfectants, and chemical intermediates.
Researchers can leverage the power of PubCompare.ai to streamline their cresol-related studies.
This AI-powered platform enables easy identification of the best protocols from literature, preprints, and patents, while providing accurate comparisons to enhance reproducibility and accuracy.
By leveraging PubCompare.ai, researchers can accelerate their cresol research and discovery, exploring related compounds like phenol, cresol red, and m-cresol purple, as well as leveraging common laboratory reagents like methanol, hydrochloric acid, FBS, and bovine serum albumin.
This holistic approach to cresol research can lead to groundbreaking discoveries and unlock new avenues for innovation.
With the help of PubCompare.ai, researchers can navigate the complexities of cresol chemistry and applications with greater efficiency and confidence, driving the field forward in a meaningful way.