Potassium permanganate

All chemicals used without further purification in this work comprising graphite powder, potassium permanganate (KMnO₄), hydrogen peroxide (H₂O₂), sodium nitrate (NaNO₃), sulfuric acid (H₂SO₄), sodium borohydride (NaBH₄), sodium hydroxide (NaOH), and methylene blue (MB) were purchased from Merck, USA.

Al(NO₃)₃·9H₂O, (1R)-(−)-camphorsulfonic acid (CSA, 98%), (3-Aminopropyl)trimethoxysilane (APTMS, ≥98%), morpholine, N,N-diisopropylethylamine, acetonitrile, methanol, toluene, absolute ethanol, ethyl acetate, dichloromethane, chloroform, tetrahydrofurane (THF), hexane, HNO₃ (67%), and HCl (37%), Na₂SO₄ anhydrous, potassium permanganate, sodium bisulfite, aqueous ammonia solution (NH₄OH 37%) and HAuCl₄·3H₂O were provided by Merck (Darmstadt, Germany). Benzyltrimethylammoniun chloride and 4-phenylmorpholine were provided by Sigma-Aldrich (Darmstadt, Germany). Toluene was dried over metallic sodium before use. All other reagents were used without further purification. H₂ (99.99%), He (99.99%), synthetic air, and N₂ were provided by Linde Chile (Concepción, Chile).

The chemicals used in this study, including extra pure graphite powder (>99.5%), potassium permanganate (>99%), silver nitrate, and hydrogen peroxide (30%), were supplied from Merck, while the hydrazine hydrate (HH) (80%) was provided by Loa Chemi. The monomers (i.e., styrene (S) and methyl methacrylate (MMA)) and the initiator (i.e., benzoyl peroxide (BP)) used in this study were obtained from Acros Chemical Co. and BDH Chemicals Ltd., Saudi Arbia respectively. All of the chemicals were analytical grade and used without any further purification.

All chemicals used in the experiments were of laboratory-grade purity and were employed without prior preparation. The utilized chemicals included ethanol, tetracycline, hydrochloric acid, iron(II) chloride tetrahydrate, sodium hydroxide, sodium nitrate, acetonitrile, crystal violet dye, potassium permanganate, graphite, iron(III) chloride hexahydrate, silver nitrate, hydrogen peroxide, sodium borohydride, and methanol, all procured from Merck, Germany. Deionized water was used in all experiments. The pH was determined using a pH meter, and sample agitation was performed with a shaker. Analysis of samples containing antibiotic and dye was carried out using UV–Vis spectrophotometer. The morphology, structure, and composition properties of Fe₃O₄/rGO/Ag magnetic nanocomposite were explored using field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), vibrating-sample magnetometer (VSM), and X-ray diffraction (XRD).

Analytical grade ferric chloride, ferrous chloride, ammonia solution (25 wt %), thiophene, 4-hydroxybenzaldehyde, acetonitrile, potassium permanganate, 4-aminophenol, 3-bromothiophene, 1,6-dibromohexane, N-bromosuccinimide, acetic acid, sodium hydrogen bicarbonate, potassium iodide, potassium carbonate, tetrahydrofuran, methanol, hydrochloric acid, acetone and ethyl acetate were purchased from Merck (Darmstadt, Germany). acetone was procured from Fisher Scientific (Loughborough, UK). thiophene carboxaldehyde, polyvinyl alcohol and n-butyllithium (2.0 M in cyclohexane) were obtained from Sigma Aldrich (Milwaukee, WI, USA). Magnesium sulfate anhydrous, ethanol denatured and hexane were received from J. Kollins (Parkwood, Australia), while dimethyl sulfoxide-d₆ (DMSO-d₆) and phthalate esters were purchased from Acros Organics (Geel, Belgium). Ultrapure water was prepared by a model Aqua Max-Ultra ultra-pure water purification system (Zef Scientific Inc., San Diego, CA, USA). Stock solutions of 1000 mg·L⁻¹ of standards were prepared by dissolving appropriate amounts of compounds in methanol, which remain stable for three months if stored in a refrigerator at 4 °C. Working standard solutions were prepared daily by diluting the stock standard solution to the required concentrations.

All reagents were of an analytical grade and all solutions were prepared using deionized water from Milli-Q system (Millipore, Billerica, MA, USA). Samples for electrochemical measurements were prepared on phosphate buffer in the presence of KCl as a background electrolyte, reagents purchased from Merck KGaA (Darmstadt, Germany).
For the graphene synthesis, it was used as a graphite powder (50 µm, sulfuric acid (98%), sodium nitrate (99%), and potassium permanganate (99%), purchased from Merck KGaA (Darmstadt, Germany); hydrogen peroxide (30%) was purchased from Riedel-de Haën (Germany). Used ionic resins were strong cationic resin C100E and weak anionic resin A520E (Purolite) purchased from Merck KGaA. Ba(NO₃)₂ was purchased at Acros Organics (Geel, Belgium).
The material needed for the building of the electrode were: Resineco Epoxy Kit 125 resin supplied from Resineco green composites (Barcelona, Spain) and graphite powder (particle size < 50 μm) was received from BDH (BDH Laboratory Supplies, Poole, UK). For the biosensor, Laccase from Agaricus Bisporus, 7.2 U·mg⁻¹ (EC number: 420-150-4), 1-ethyl-3-(3-dimethylaminopropyl carbodiimide (EDAC), and N-hydroxysulfosuccinimide (sulfo-NHS) (purchased from Merck KGaA) were used.
Finally, catechol, acid benzoic, and EDTA were purchased from Merck KGaA.