Oxidation Of Hydroquinone Research Articles

Poly(phenol red) hierarchical micro-structure interface enhanced electrode kinetics for adsorption and determination of hydroquinone

A simple, new strategy for enhancing the electrochemical adsorption and determination of hydroquinone was proposed that involved modifying a glassy carbon electrode with a hierarchical structure of poly(phenol red) microparticles (P(PhR)MPs electrode). The electrochemical oxidation of hydroquinone at the P(PhR)MPs electrode displayed quasi-reversible behavior. The electrocatalysis and adsorption kinetics of the P(PhR)MPs toward hydroquinone were proved using chronoamperometry and EIS. Hydroquinone was determined by the P(PhR)MPs electrode at concentrations from 10 ng mL−1 to 100 μg mL−1 (91 nmol L−1 to 908 μmol L−1) using adsorptive anodic stripping voltammetry (AdASV) with an accumulation time of 30 s. Electrode sensitivity was 3.54 μA μg−1 mL cm−2, and limits of detection (LOD) and quantitation (LOQ) were 2.7 ng mL−1 (25 nmol L−1) and 10 ng mL−1 (91 nmol L−1), respectively. The P(PhR)MPs electrode preparation exhibited good repeatability (RSDs between 1.66 and 3.87% (n = 15)), good reproducibility (RSD < 3.2% n = 6) and excellent anti-interference properties. The proposed method successfully quantified hydroquinone in skin whitening products with recoveries between 93 ± 2 and 102 ± 1% and there was no significant difference at a 95% confidence level between the results from the proposed sensor and those from UV-derivative spectrophotometry. The developed poly(phenol red) hierarchical micro-structure showed that it could be used as an interface for application in electrochemical sensors or biosensors.

Silver nanoparticles decorated phthalocyanine doped polyaniline for the simultaneous electrochemical detection of hydroquinone and catechol

Abstract In this proposed study, the new electrocatalyst was synthesized by incorporating the supramolecular electrocatalyst tetra amino cobalt phthalocyanine (TACoPc) into the conducting polyaniline (PANI) and which was subsequently used to decorate silver nanoparticles (AgNPs) using Ag+ solution on the surface of TACoPc/PANI composite to form a supramolecular hybrid system. The decoration of AgNPs on the surface of TACoPc/PANI was carried out in an aqueous media at room temperature and which was confirmed by various spectroscopic techniques. The synthesized catalyst AgNPs decorated TACoPc doped PANI (TACoPc/PANI/AgNPs) modified the glassy carbon electrode (GCE) used to construct the electrochemical sensor for simultaneous detection of hydroquinone (HQ) and catechol (CC). The modified electrode showed the two distinct peaks for HQ and CC in CV analysis with a considerable potential difference of 0.080 V vs SHE. The presence of central cobalt metal in TACoPc macromolecular electrocatalyst mediates the oxidation of HQ and CC, which was successively enhanced by the incorporation of conducting PANI and AgNPs. The sensor exhibited excellent electrocatalytic activity with good stability, selectivity, reproducibility, and a very low limit of detection in the electrochemical sensing of HQ and CC in a 0.1 M H2SO4 electrolyte solution.

DNA-targeted formation and catalytic reactions of DNAzymes for label-free ratiometric electrochemiluminescence biosensing

A label-free ratiometric electrochemiluminescence (ECL) sensing strategy for the sensitive detection of target DNA (T-DNA) was proposed on the basis of G-quadruplex/hemin-regulated ECL emissions of CdS quantum dots (QDs) and luminol with their common coreactant of H2O2. The ECL biosensor was constructed through stepwise assemblies of CdS QDs and hairpin DNA (H-DNA) on a glassy carbon electrode, and subsequent introduction of T-DNA resulted in the development of G-quadruplex/hemin DNAzymes via the specific recognition of T-DNA and H-DNA in the presence of hemin and K+ ions. The formed DNAzymes not only prompted the catalytic oxidation of hydroquinone followed by deposition of insoluble oxidation oligomers on the electrode surface to attenuate the cathodic ECL emission of CdS QDs but also triggered the catalytic oxidation of luminol to enhance the anodic ECL emission. The label-free ratiometric ECL biosensor for the detection of T-DNA showed a wide response range from 1 to 10,000 fM (10−15 M) with a low detection limit of 0.2 fM and exhibited excellent selectivity against mismatched base sequences. This work provides a reliable and sensitive sensing platform for the detection of targets in analytical community by means of rational design of DNA sequences.

Electrodeposition of Thiolated Polymer-based Hydrogels via Disulfide Formation Using Electrogenerated Benzoquinone

Abstract We present an electrodeposition method for fabricating thiolated polymer-based hydrogels through oxidation of hydroquinone (HQ). HQ is oxidized to benzoquinone (BQ) at an electrode, and the generated BQ is utilized for disulfide formation through an electrocatalytic reaction. As a simple demonstration of bioapplications, an electrodeposited hydrogel containing glucose oxidase was applied for glucose sensing. To the best of our knowledge, this is the first report on the electrodeposition of thiolated polymer-based hydrogels via disulfide formation using the indirect approach.

Highly Efficient Photocatalytic Disinfection of Escherichia coli by Rose Bengal-Functionalized Graphene Oxide Nanosheets.

Rose Bengal (RB) was used as a functional pigment and poly dimethyl diallyl ammonium chloride was used as a coupling agent to modify Graphene Oxide (GO) in order to enhance the light absorption and ROS generation of GO. GO, RB and the obtained RB-PDDA-GO were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, thermogravimetric analysis, Raman spectroscopy, UV-visible spectrophotometry, and X-ray photoelectron spectroscopy. The oxidation of hydroquinone to p-benzoquinone was used to evaluate the oxidation ability. Three kinds of reactive oxygen species (O₂·-, 1O₂ and ·OH) produced by the materials under light irradiation were detected by the ESR method using TEMP (2,2,6,6-tetramethyl-4-piperidine) and DMPO (5,5-dimethyl-1-pyrroline-N-oxide) as capture agents. The results showed that RB-PDDA-GO produced more ROS under light than GO. Antibacterial experiments were carried out with E. coli as the target strain to detect the actual utility of ROS produced by the materials. The results showed that RB-PDDA-GO had a significant sterilization effect.

Simultaneous Determination of Benzenediols Isomers Using Copper Nanoparticles/Poly (Glycine)/Graphene Oxide Nanosheets Modified Glassy Carbon Electrode

In this research, a new and suitable electrochemical sensor for simultaneous determination of benzenediols (BD) isomers is fabricated by dripping well-dispersed graphene oxide nanosheets (GONs) and in situ plating of poly glycine (P-Gly)-metal copper nanoparticles at the glassy carbon electrode (GCE), Cu-NPs/P-Gly/GONs/GCE, successively. Besides, the as-prepared modified electrode was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and electrochemical techniques. The proposed electrochemical sensor excellently enhanced the selectivity in the determination of BD isomers by differential pulse voltammetry (DPVs). Compared between the unmodified and modified electrode, unmodified electrode failure to dispel the voltammetric response of BD isomers in a mixture solution, Cu-NPs/P-Gly/GONs/GCE shows larger electrocatalytic activity for the oxidation of hydroquinone (HQ) and catechol (CC) with an enhancement in peak currents and a decrement in peak separation (ΔEp). Consequently, the two isomers can be determined simultaneously. Under the best response experimental, the linear response range was from 3 μM to 200 μM for CC with a detection limit of 1.015 μM and from 2 μM to 300 μM for HQ with a detection limit of 1.067 μM. Further, the suggested sensor was successfully applied for the detection of BD isomers in actual samples.

Can Donor Ligands Make Pd(OAc)2 a Stronger Oxidant? Access to Elusive Palladium(II) Reduction Potentials and Effects of Ancillary Ligands via Palladium(II)/Hydroquinone Redox Equilibria.

Palladium(II)-catalyzed oxidation reactions represent an important class of methods for selective modification and functionalization of organic molecules. This field has benefitted greatly from the discovery of ancillary ligands that expand the scope, reactivity, and selectivity in these reactions; however, ancillary ligands also commonly poison these reactions. The different influences of ligands in these reactions remain poorly understood. For example, over the 60-year history of this field, the PdII/0 redox potentials for catalytically relevant Pd complexes have never been determined. Here, we report the unexpected discovery of (L)PdII(OAc)2-mediated oxidation of hydroquinones, the microscopic reverse of quinone-mediated oxidation of Pd0 commonly employed in PdII-catalyzed oxidation reactions. Analysis of redox equilibria arising from the reaction of (L)Pd(OAc)2 and hydroquinones (L = bathocuproine, 4,5-diazafluoren-9-one), generating reduced (L)Pd species and benzoquinones, provides the basis for determination of (L)PdII(OAc)2 reduction potentials. Experimental results are complemented by density functional theory calculations to show how a series of nitrogen-based ligands modulate the (L)PdII(OAc)2 reduction potential, thereby tuning the ability of PdII to serve as an effective oxidant of organic molecules in catalytic reactions.

Electrocatalytic Activity of Heteroatom-Doped Graphene for Oxidation of Hydroquinones

Electrocatalytic Activity of Heteroatom-Doped Graphene for Oxidation of Hydroquinones

A Dipeptide-Based Hierarchical Nanoarchitecture with Enhanced Catalytic Activity.

Achieving synthetic architectures with simple structures and robust biomimetic catalytic activities remains a great challenge. Herein, we explore a facile supramolecular assembly approach to construct a dipeptide-based hierarchical nanoarchitecture with enhanced enzyme-like catalytic activity. In this nanoarchitecture, nanospheres are put in a chain-like arrangement through coordination-driven directional self-assembly. The reversible transformation of anisotropic nanochains to isotropic nanospheres switches biomimetic activity. Notably, the assembled nanoarchitecture exhibits a high enzyme-like activity and remarkable long-term stability to promote hydroquinone oxidation, superior to the natural counterpart. This work will pave the way to develop reversible and reusable supramolecular biocatalysts with ordered hierarchical structures for accelerating chemical transformations.

Metal organic framework (ZIF-67)-derived Co nanoparticles/N-doped carbon nanotubes composites for electrochemical detecting of tert-butyl hydroquinone

In this work, the framework of Co nanoparticles and nitrogen-doped carbon nanotubes (Co/NCNTs) derived from metal–organic frameworks (MOFs) through solid pyrolysis was successfully synthesized in the atmosphere of H2 and Ar gases. The Co/NCNTs composites exhibited superior electrocatalytic performance for tert-butyl hydroquinone (TBHQ) oxidation due to the synergistic effect between chemical composition and the specific structure of Co nanoparticles and nitrogen-doped carbon nanotubes. It was found that the reaction underwent a quasi-reversible redox reaction with 37-fold higher anodic current for TBHQ at Co/NCNT-modified electrode when compared to bare glassy carbon electrode (GCE). In optimal condition, Co/NCNTs/GCE exhibited a linear range of 0.05–80.00 μmol·L−1 for detecting TBHQ, and the limit of detection (LOD) was estimated to be as low as 10 nmol·L−1 (signal/noise of S/N = 3). Moreover, the as-obtained modified electrode was successfully used to assay the content of TBHQ in edible oil samples.

Brominated plastoquinone analogs: Synthesis, structural characterization, and biological evaluation

A series of brominated PQ analogs (BrPQ1-13) was synthesized by employing two different routes: 1) dibromination followed by oxidation and amination of dimethyl hydroquinone, respectively, 2) oxidation of dimethyl hydroquinone followed by amination and bromination, respectively. In addition to the single-crystal X-ray structural characterization of two analogs (BrPQ2 and BrPQ3), the structures of all analogs were determined based on spectral (FTIR, 1H NMR, 13C NMR, and HRMS) data. We evaluated the analogs for in vitro antibacterial and antifungal activity against ATCC® strains (panel of seven bacterial strains with three Gram-positive and four Gram-negative bacteria and three fungi) using the broth microdilution method. The structure–activity relationship of brominated PQ analogs indicated that the electron-withdrawing group (EWG) on the phenyl ring (-CF3, trifluoromethyl group) has a positive effect on antibacterial activity. These in vitro data show that brominated analogs, especially for BrPQ1, BrPQ2, and BrPQ3, have the potential to be developed as new antibacterial agents against S. aureus and/or S. epidermidis with low MIC values.

A double carbon dot system composed of N, Cl-doped carbon dots and N, Cu-doped carbon dots as peroxidase mimics and as fluorescent probes for the determination of hydroquinone by fluorescence.

A fluorescence method isdescribed for the determination of hydroquinone based on the double carbon dot system as peroxide mimic enzymes and fluorescent probes. Deep eutectic solvent (DES)-based fluorescent carbon dots (N/Cl-CDs) and copper-doped carbon dots (N/Cu-CDs) were prepared by the hydrothermal method. Both carbon dots were characterized with transmission electron microscopy (TEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy, X-ray photoelectron spectrometry (XPS), Fourier transform infrared (FT-IR) spectroscopy, and fluorescence spectroscopy. N/Cl-CDs displayed intrinsic peroxidase-like activity and were able to catalyze the oxidation of hydroquinone (H2Q) to p-benzoquinone (BQ) along with an intermediate. The intermediate (BQ) did quench the N/Cu-CD photoluminescence (PL) at 450nm usingan excitation wavelength of 347nm. Based on the results, a fluorescent platform isproposed for the determination of hydroquinone with a promising determination limit of 0.04μM (linear range, 1.0-75μM). The recoveries of spikedwater samples were in the range 89.5-105.1%, with relative standard deviations (RSDs) of 1.5-2.9%. This method was applied to determination ofH2Q in environmental water samples. Graphical abstract A fluorescence method was established for the determination of hydroquinone based on the double carbon dot system as peroxide-mimic enzymes and fluorescent probes. Chlorine-doped carbon dots (N/Cl-CDs) derived from deep eutectic solvent (DES) displayed intrinsic peroxidase-like activity, and were able to catalyze the oxidation of hydroquinone (H2Q) to p-benzoquinone (BQ) along with an intermediate. The intermediate (BQ) did quench the N/Cu-CD photoluminescence (PL). This method was applied to H2Q in environmental water samples.

CuO Nanostructures Based Electrochemical Sensor for Simultaneous Determination of Hydroquinone and Ascorbic Acid

AbstractA simple, sensitive and reliable electrochemical sensor has been developed based on CuO nanostructures modified glassy carbon electrode for simultaneous determination of hydroquinone (HQ) and ascorbic acid (AA). The CuO nano material was synthesized by aqueous chemical growth method using different sources of OH. The characterization of nano material was performed by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy and energy dispersive X‐ray spectroscopy. The glassy carbon electrode was modified by CuO nano material using drop cast method and studied by cyclic voltammetry. The CuO/GCE exhibited excellent electrocatalytic activity towards the oxidations of HQ and AA in borate buffer solution (pH 8.0) and the corresponding electrochemical signals have appeared as two well resolved oxidation peaks with significant peak potential differences of (0.21V vs. Ag/AgCl). Differential pulse voltammetry was used for simultaneous determination of HQ and AA using the CuO/GCE. At the optimum conditions, for simultaneous determination by synchronous change of the analyte concentrations, the linear response ranges were between 0.0003–0.355 mM for HQ and 0.0001–0.30 mM for AA respectively. Furthermore, CuO/GCE was successfully applied for the independent determination of AA in fruit juices as well as for the simultaneous determination of HQ and AA in cosmetic samples.

Investigation of the Electrochemical Behavior of Hydroquinone at Some Conducting Polymer Electrodes and Amperometric Detection

In this paper, a rapid and sensitive modified electrode for the determination of hydroquinone (HQ) is proposed. In this study, active compound HQ was determined from commercial drug form based on electrochemical oxidation properties at various electrodes by voltammetric methods. Electrodes modified by the electrodeposition of conducting organic polymers such as poly(3-methylthiophene, PMT), polypyrrole (PPY) and polyaniline (PAN) were used as chemical sensors for voltammetric analysis and flow injection detection of HQ. The electrochemical behavior of HQ at conducting polymer electrodes was compared and the effects on behavior of electrolyte type and its pH and the film thickness were systematically examined. The results showed that the proposed modified surface catalyzes the oxidation of HQ. Electrocatalytic efficiency decreases in order of PMT &gt; PPY &gt; PAN. Voltammetric peak positions were affected by the nature of the electrolyte and its pH. Also, the effect of increasing film thickness was to observe increased peak heights for oxidation potential of HQ. The best results for the determination of HQ were obtained by DPV in Na2SO4 (pH 2.0) and PMT electrodes. Polymer coated electrodes were also used in an amperometric detector for flow injection analysis of HQ. The responses of the polymer electrode were 5–15 times larger as compared to those of bare platinum. PMT showed improved performance as an amperometric detector for flow injection analysis systems over other types of polymer electrodes. Detection limits as low as 1 × 10–9 M were achieved using the PMT, compared to 1 × 10–6 M using platinum electrodes.

Development of the signal amplification based on Au@Pt/MIL-101(Cr) as mimetic enzyme and RecJf exonuclease-assistant target recycling

A novel electrochemical aptasensor was developed for multiple signal amplification based on Au@Pt/MIL-101(Cr) as mimetic enzyme and RecJf Exo-assisted target recycling. For the detection of ochratoxin A (OTA), the catalytic ability of Au@Pt/MIL-101(Cr) was better than that of Au@Pt toward hydroquinone oxidation in the presence of H2O2, and the peak current increased by 48.3 %. The peak current obtained with RecJf Exo incubation increased by 140 % than that without RecJf Exo incubation. These results demonstrated that the synergistic effect of Au@Pt/MIL-101(Cr) and RecJf Exo realized the signal amplification and enhanced the sensitivity. The prepared aptasensor exhibited a wider linear range of OTA concentration from 0.001 ng/mL to 5 ng/mL with a lower LOD of 0.17 pg/mL. The aptasensor also showed good specificity, reproductibility, and repeatability toward OTA detection. For the application in the spiked white spirit, the obtained recovery was from 97 % to 106 %, indicating that the proposed aptasensor can be applied for OTA analysis in real samples.

Photocatalytic activity of LiMgPO4 in the hydroquinone decomposition and related surface phenomena

We report a study which exhibits for the first time the catalytic activity of LiMgPO4 in the reaction of hydroquinone oxidation. The samples were synthesized by solid state reaction, glycerol-nitrate method and ultrasonic spray pyrolysis. It was proved that LiMgPO4 makes the hydroquinone decomposition possible in the absence of irradiation and accelerates it under the action of light. It was determined that the lager is the specific surface area of the catalyst, the higher is the reaction rate constant. The high catalytic activity of LiMgPO4 in the oxidation reaction was explained by the existence of defects on the LiMgPO4 surface able to adsorb ions, radicals, etc. The UV–vis spectra clearly indicated the existence of defects. The results of voltammetric and NMR studies confirmed that the defective surface of LiMgPO4 easily adsorbs molecular and ionic groups of different nature formed during sorption and electrolysis of water.

Electrochemical Immunosensors for Sensitive Detection of Neuron-Specific Enolase Based on Small-Size Trimetallic Au@Pd^Pt Nanocubes Functionalized on Ultrathin MnO2 Nanosheets as Signal Labels.

Medically, neuron-specific enolase (NSE) as a specific tumor marker has become an important indicator to diagnose small-cell lung carcinoma. In this study, a sandwich-type electrochemical immunosensor was designed to determine NSE sensitively. Au nanoparticle (Au NP)-embedded zinc-based metal-organic frameworks (Au@MOFs) were prepared as the substrate materials to modify the electrode and immobilize the primary antibody (Ab1). The Au@MOFs with the free amino groups on the MOF surface could effectively increase the immobilization amount of Ab1 through covalent linkage. Simultaneously, the embedding of Au NPs improved the conductivity of MOFs and accelerated interface electron transfer. Sub-30 nm trimetallic Au@Pd^Pt nanocubes (Au@Pd^Pt NCs) loaded onto ultrathin MnO2 nanosheets (MnO2 UNs/Au@Pd^Pt NCs) acted as the labels of secondary antibodies. The small-size Au@Pd^Pt NCs enhanced atomic utilization efficiency and offered more catalytic active sites. The MnO2 UNs with high external surface areas could improve the dispersion of Au@Pd^Pt NCs. The MnO2 UNs/Au@Pd^Pt NCs could catalyze the H2O2 reduction and promote the oxidation of hydroquinone to quinone effectively because of their synergistic effect; thus, the generated quinone achieved amplification of the highly reductive peak current. Furthermore, under the optimal conditions, the immunosensor exhibited a low detection limit (4.17 fg/mL) and broad linear range (10 fg/mL to 100 ng/mL). The results were satisfactory for NSE detection in human serum samples, implying that the presented method had great application potential in clinical bioanalysis.

Poly (benzydamine) sensor for electrochemical resolution of catechol and hydroquinone

The carbon paste electrode was modified with poly (benzydamine) by cyclic voltammetric technique (CV) and its electrocatalytic activity towards the oxidation of catechol (CC) and hydroquinone (HQ) was studied. The detailed investigation on the various parameters influencing the activity was also carried out. From the obtained result, it was concluded that the process was adsorption - controlled and the involvement of same number of electron and proton. The simulations resolution of CC and HQ along with excellent selectivity and sensitivity were also exhibited by the studied MCPE. The detection limits 5.79 and 3.78 μM were found for CC and HQ respectively.

Catalyst-Free, Facile and Green Synthesis of New Symmetric and Asymmetric Benzofurans through Hydroquinones Oxidation in the Presence of Meldrum’s Acid

Electrochemical oxidation of hydroquinones (1a–1b) were studied in the presence of meldrum’s acid (3) as a nucleophile in an ethanol-phosphate buffer (pH 7, 0.20 M) mixture (as a green media), by means of voltammetric techniques. The obtained results indicated that the p-quinones (2a–2b) are derived from 1a–1b participation in a 1,4-Michael addition reaction, with the meldrum’s acid (3) to form the corresponding new symmetric and asymmetric benzofurans (8a and 6b). The electrochemical synthesis of these new compounds (8a and 6b) has been successfully performed in an undivided cell with high yield and good purity.

Electrochemical activation of graphene sheets embedded carbon films for high sensitivity simultaneous determination of hydroquinone, catechol and resorcinol

In this study, the graphene sheets embedded carbon (GSEC) film was electrochemically activated in KOH solution for high sensitivity simultaneous determination of hydroquinone (HQ), catechol (CC) and resorcinol (RC). The electrochemical activation mechanism of GSEC films in alkaline solution was clarified. We found that the embedded graphene sheets were corroded during activation, resulting in the formation of more defective graphene edges and carbonyl functional groups at the surface of carbon film. These corroded graphene edges provided more electrochemical active sites and accelerated the electron transfer. Thus, the activated GSEC film exhibited highly electrocatalytic activity towards the oxidation of HQ, CC and RC. The redox peak separation for HQ and CC decreased from 366 mV to 62 mV and 262 mV to 54 mV, respectively. The oxidation potential of RC also decreased from 714 mV to 590 mV. The electrochemical sensor showed a wide liner response for HQ, CC and RC in the concentration range of 0.5∼200 μM, 0.5∼200 μM and 0.2∼400 μM with detection limit of 0.1 μM, 0.1 μM and 0.05 μM, respectively. These results demonstrate that the KOH-activated GSEC film is a promising electrode material for constructing highly sensitive and selective biosensors.