Ch3cooh

All reagents were purchased from Sigma-Aldrich (Sigma-Aldrich, Germany) at their highest available purity and were used without any further purification steps. The DHBs studied are detailed in Figure 2. The H₃BO₃, H₃PO₄, and CH₃COOH used for the Britton-Robinson buffer preparation were supplied by Merck (Merck, Germany).

N, N-Dimethylformamide (DMF), 3-mercaptopropyltrimethoxysilane (MTPMS), allyl glycidyl ether (AGE) and 2, 2-azoisobutyronitrile (AIBN), were products of Aldrich (Steinheim, Germany). 1, 4-Dioxane, 2-naphtol, NaCl, C₂H₅OH, CH₃COOH, FeCl₂.4H₂O, FeCl₃.6H₂O, NH₄OH, C₁₄H₁₀, C₁₆H₁₀ were supplied by Merck (Darmstadt, Germany). Anthracen (ANT) and pyren (PYR) Figure 1, were purchased from Fluka Chemical (Buchs Switzerland). The molecular structure of ANT and PYR is shown in Figure 1.
All the reagents were of analytical grade and used without any further purification. Because of the low solubility of ANT and PYR the first stock solution (2000 mg/L) was prepared by dissolving appropriate amounts of ANT and PYR, in first acetonitrile and diluting with distilled water. The secondary stock solution (10 mg/L) was prepared by dilution. 10 mL of 0.1 M acetic acid–acetate buffer (pH 3–6.5) was used wherever required to adjust pH of the solution.

The LPS was hydrolyzed with 1% aqueous CH₃COOH (100 °C, 3 h; Merck Life Science, Rome, Italy) [27 (link)]. The obtained suspension was centrifuged (8000 rpm, 4 °C, 30 min). The precipitate (lipid A) was washed twice with water and lyophilized. The supernatant, containing the saccharide portion, was fractioned on a Biogel P-10 column (Bio-Rad, Segrate (MI), Italy 0.75 cm × 95 cm, flow rate 11.4 mL/h, fraction volume 2.5 mL) and eluted with water. The obtained fractions were then lyophilized [28 (link)].

Graphene oxide (GO) was fabricated from graphite (99.995%, Alfa Aesar, Ward Hill, MA, USA) using a modified Hummers method [34 (link)]. Hydroxyapatite (HA, an average size of ca. 50 nm) and chitosan (CTS, M_w of 150 kDa, deacetylated degree of about 93%) were prepared from catfish bone and shrimp shells, respectively, in the laboratory using the optimum conditions of previous reports [35 (link),36 (link)]. Sodium tripolyphosphate (TPP, >99%, Aldrich, St. Louis, MO, USA), CH₃COOH (99.6%, Merck, Darmstadt, Germany), and other chemicals were of reagent grade and used as received.

Chemicals employed throughout the study were CH₃COONa (99%, Merck, India), CH₃COOH (99%, Merck, India), ninhydrin (99%, Merck, India), glycylleucine (99%, Loba Chemie, India) and zinc sulfate heptahydrate (99%, Merck, India). All of the above chemicals were used without any further surplus purification. For synthesizing gemini surfactants employed chemicals were 1,6-dibromohexane (>97%), 1,5-dibromopentane (>98%), 1,4-dibromobutane (>98%) and N,N-dimethylhexadecylamine (95.0%). These chemicals were purchased from Fluka, Germany. Other chemicals used in the current experiments were of AR grade. The specific conductivity of water employed during the whole study was (1–2) × 10⁻⁶ ohm⁻¹ cm⁻¹. Stock solutions of reactants and surfactants were prepared by dissolving requisite amounts in CH₃COONa-CH₃COOH buffer solution (pH 5.0). The buffer of pH 5.0 prepared by mixing of 30 cm³ of 200 mmol.kg⁻¹ CH₃COOH and 70 cm³ of 200 mmol.kg⁻¹ CH₃COONa⁴³ . The solutions were made freshly as per the necessities. To note the pH of the solutions, measurements were carried out on pH meter (ELICO LI-122, Hyderabad, India). In respect to achieving the composition of reaction products produced on the title reaction, Job’s method was applied in gemini surfactant media. It was identified that both the reactants (each mole of ninhydrin and [Zn(II)-Gly-Leu]⁺) associated to form the product.