Ru nh3 6 cl3

AgNO₃ (>99.8%), HCl (32%), NaH₂PO₄ (99.5%), Na₂HPO₄ (99%) and NaOH (99%) were acquired from Merck, and HNO₃ (65%) and H₂SO₄ (95%) from Panreac. AgNO₃ aqueous solution (0.1 M) was obtained from Riedel-de Haën. Ascorbic acid (≥99.0%), D-Sorbitol (>8%), H₂O₂ (35%), H₂PtCl₆ (99.9%), (NH₄)₂Fe(SO₄)₂.6H₂O (≥9%), Ru(NH₃)₆Cl₃ (98%) and xylenol orange disodium salt were purchased from Sigma-Aldrich. KNO₃ (>99.5%) was obtained from Fluka and K₄Fe(CN)₆·3H₂O (98%) from Probus S.A. All the reagents were used as received without further purification. Ultrapure water (Milli-Q purification system, 18.2 MΩ cm, Millipore Corp, Bedford, MA, USA) was used for the preparation of all solutions. Two laundry detergent boosters and an antiseptic product were used as real samples for the determination of H₂O₂. The first ones are a bleaching agent (stated composition: 5–15% oxygenated whitening agents, <5% anionic and non-ionic surfactants, perfume and optical whiteners) and a brightener (stated composition: 5–15% oxygenated whiteners, <5% anionic and non-ionic surfactants, perfume, methylchloroisothiazolinone and methylisothiazolinone), while the antiseptic compound contains 3% hydrogen peroxide. All of them were purchased from a local supermarket.

All electrochemical experiments were carried out using a Bioanalytical Systems Epsilon potentiostat with a three-electrode system featuring a Ag/AgCl reference electrode and a platinum wire auxiliary electrode. Electrochemical signals were measured in a Tris buffer solution (50 mM, pH 9) containing 10 μM [Ru(NH₃)₆]Cl₃ (Sigma-Aldrich, MO), 0.5 mM 3-mercaptopropionoic acid (MPA) (Sigma-Aldrich, MO) and 0.5 mM cysteamine (Cys) (Sigma-Aldrich, MO). DC potential amperometry (DCPA) signals were obtained at +250 mV for 10 s. Signal changes, ΔI, were calculated with ΔI=I_c–I₀ (where I_c is the current at a given concentration and I₀ is the current without analyte).

The stock solution of 0.1 mol L⁻¹ KCl was prepared by dissolution of the appropriate amount of powder (Ing. Petr Švec-PENTA s.r.o., Prague, Czech Republic) in the distilled water and the standard solutions of 6.25 × 10⁻⁴ and 2.5 × 10⁻³ mol L⁻¹ K₃[Fe(CN)₆] and [Ru(NH₃)₆]Cl₃ (both of purity ≤99%, Sigma-Aldrich, Merck, Prague, Czech Republic) were prepared in the solution of 0.1 mol L⁻¹ KCl. Britton–Robinson buffer (BRB) consisting of the mixture of an acidic (H₃PO₄, H₃BO₃, and CH₃COOH (0.4 mol L⁻¹), Penta-Švec, Czech Republic) and alkaline component (NaOH (0.2 mol L⁻¹), Penta-Švec, Czech Republic) was used as a supporting electrolyte. The stock solution of 0.001 mol L⁻¹ lornoxicam (≥98%, Sigma-Aldrich) was prepared by dissolution of its powder in methanol (Penta-Švec, Czech Republic) and stored in a refrigerator (+4 °C) without light access. Solutions of lower concentrations were prepared daily fresh by dilution with a supporting electrolyte.

Bulk MoS₂ single crystals were purchased from Nanjing MKNANO Tech. Co., Ltd. 1-Octadecanethiol and [Ru(NH₃)₆]Cl₃ were purchased from Sigma Aldrich. The MoS₂ monolayers were fabricated by a surface plasmon polariton-driven etching approach recently developed by our group. A laser diode with a wavelength of 660 nm (OBIS LX, Coherent Inc.) was adopted as the light source to induce layer thinning of the MoS₂ nanosheets. The power density of red light was generally set at 3 mW·mm⁻². The MoS₂ multilayers were mechanically exfoliated from bulk MoS₂ single crystals and transferred onto 1-Octadecanethiol-modified gold films. The MoS₂ multilayers were directly converted into corresponding monolayers under surface plasmon-driven etching in deionized water^{26 (link)}.