Enhanced Sensitive Electrochemical Sensor for Simultaneous Catechol and Hydroquinone Detection by Using Ultrasmall Ternary Pt-based Nanomaterial

The simple and effective method for the novel synthesis of Pt-based nanoparticle was presented with high efficiency. The sensitive catalyst for the simultaneous detection of catechol and hydroquinone was prepared by depositing ternary metal complex on fluorine-doped tin-oxide (FTO). The composition and morphology of nanomaterials were characterized by TEM, HRTEM, XRD, XPS, and EDS (energy dispersive spectroscopy). The size of the Pt-based nanomaterial was about 5±1 nm. The electrochemical performance of the modified catalyst was studied by CV, DPV, and EIS. The modified PtNiCu@FTO catalyst possessed good electro-oxidation activity for hydroquinone and catechol and used for simultaneous detection of catechol and hydroquinone at scan rate of 20 mV s⁻¹ (vs. Ag/AgCl). Detection responses were found in the ranges of 5–2900 μM for hydroquinone and 5–3000 μM for catechol. The detection limits (LOD) for HQ and CC were observed as 0.35 and 0.29 μM, respectively. The sensitivity of HQ and CC were 1515.55 and 1485 μA mM⁻¹ cm⁻², respectively. The prepared nanomaterial were effectively applied for the determination of CC and HQ in real samples.     

Simultaneous Determination of Hydroquinone and Catechol by Differential Alternative Pulses Voltammetry

The second order voltammetric technique of high resolution, Differential Alternative Pulses Voltammetry (DAPV), was applied for the simultaneous determination of hydroquinone (HQ) and catechol (CC) on bare spectroscopic graphite electrode. Well resolved anodic and cathodic peaks situated on both sides of the zero line were obtained, while the differential pulse voltammograms were overlapped. The linear concentration range for HQ and CC quantification by DAPV was extended up to 20 μmol L⁻¹ for both the isomers. The sensitivity of the determination was found to be 6.00 μA L μmol⁻¹ and 3.61 μA L μmol⁻¹, while the limit of detection reached was 0.2 μmol L⁻¹ and 0.5 μmol L⁻¹ for HQ and CC, respectively. No interference was observed from the commonly coexisting organic species such as resorcinol, phenol and p‐benzoquinone. The great resolution power of DAPV permitted obtaining excellent results without any electrode modification and any mathematical data processing.     

Rational Design of Highly Efficient One-pot Synthesis of Ternary PtNiCo/FTO Nanocatalyst for Hydroquinone and Catechol Sensing

In this work, we present a simple and efficient method for preparation of widely dispersed PtNiCo nanocatalyst on FTO without the use of any heavy complex structure. The proposed nanocatalyst enhances the chemical interaction of PtNiCo/FTO and increases its catalytic activity, which was used for electrochemical sensing of catechol and hydroquinone. The surface morphology was characterized by TEM, HRTEM, and XRD. The size of the PtNiCo/FTO octahedrons nanocatalyst was about 0.35–4 nm. Gradual increase of concentration exhibited linearity in oxidation peak response up to 1100 μM with a low detection limit of 0.79 μM for HQ and 1.05 μM for CC. The sensitivity is 1035 μAmM⁻¹ cm⁻² for catechol and 1197 μAmM⁻¹ cm⁻² for hydroquinone. The prepared nanomaterial/sensor applied to real water samples with good reproducibility (98–99 %).     

Special Pore-Space-Partition CoFePBA Hollow Framework Realizing High-Performance Glucose Sensing

In this work for the first time pore-space-partition (PSP)-CoFePBA hollow framework is elaborately designed and successfully obtained via self-template internal dissolution strategy. As is demonstrated by our previous report, Prussian blue analogue (PBA) with hollow morphology is very beneficial to improve sensing performance. As expected, the PSP-CoFePBA hollow framework in this work exhibits far superior glucose sensing performance compared with classic CoFePBA nanoparticles and nanoboxes as well as most of reported PBA-based glucose sensors. Herein, very high sensitivity of 1184.18 μA mM⁻¹ cm⁻² and 267.63 μA mM⁻¹ cm⁻² in the concentration range of 5–325 μM and 325–1025 μM, respectively, as well as low detection limit of 0.4 μM (S/N=3) and high stability can be observed. In a word, this work proposes and develops a simple and general synthetic strategy for constructing PBA-based hollow material, that will be very helpful in this field.     

Binder Free Modification of Glassy Carbon Electrode by Employing Reduced Graphene Oxide/ZnO Composite for Voltammetric Determination of Certain Nitroaromatics

Reduced Graphene oxide/ZnO nanoflowers ( rGO/ZnO‐NFs ) composite has been synthesized in‐situ using asymmetric Zn complex ( 1 ) as a single‐source molecular precursor (SSMP) with GO at 150 °C. The rGO/ZnO‐NFs composite was characterized by PXRD, UV‐vis, SEM, EDX mapping, TEM and SAED pattern to confirm its purity and morphology. The rGO/ZnO‐NFs composite shows uniform distribution of nanoflowers on graphene sheets. The modified glassy carbon electrode ( GCE ) was fabricated by drop wise layering of the rGO/ZnO‐NFs composite at the surface of the GCE without using binder. The binder free modified electrode ( GCE‐rGO/ZnO ) was explored for detection of nitroaromatics such as p‐nitro‐phenol ( p ‐NP ), 2,4‐dinitrophenol ( 2,4‐DNP ), 2,4‐dinitrotoluene ( 2,4‐DNT ) and 2,4,6‐trinitrophenol ( 2,4,6‐TNP ). The fabricated sensor showed remarkable response for the both toxicants and explosives. The LOD, sensitivity and linear range for the studied toxicants and explosives were found to be in a good range: p ‐NP= 0.93 μM, 240 μA mM⁻¹ cm⁻² and 0.2–0.9 mM; 2,4‐DNP= 6.2 μM, 203 μA mM⁻¹ cm⁻² and 0.1–0.9 mM; 2,4‐DNT= 10 μM, 371 μA mM⁻¹ cm⁻² and 0.2–0.9 mM; 2,4,6‐TNP= 16 μM, 514 μA mM⁻¹ cm⁻² and 0.2–0.9 mM, respectively.     

Amplified Electrochemical Response of Phenol by Oxygenation of Tyrosinase Coupling with Electrochemical‐chemical‐chemical Redox Cycle

In this work, an novel electrochemical‐chemical‐chemical (ECC) redox cycle was designed in an enzyme‐based sensor for acquiring additional signal amplification. The tyrosinase (Tyr) was entrapped in a sulfonated polyaniline?chitosan (SPAN?CS) composite which was used as a redox capacitor on a glass carbon electrode. Firstly, the substrate, phenol was catalyzed to catechol and further catalyzed to o‐benzoquinone by Tyr. Next, in the presence of Ru(NH₃)₆Cl₂, the reduced state of SPAN(SPAN_red) was reacted with o‐benzoquinone to form it's oxidized state (SPAN_ox) and catechol, then SPAN_ox was reduced back to SPAN_red by Ru(II) in the solution. Finally, the amplified anodic current of catechol was obtained on electrode through above ECC redox cycle system. In addition, the ECC redox cycling led to a high signal‐to‐background ratio. The voltammetric response showed excellent analytical performance to phenol over two linear range of 3.5 to 200.0 nmol L^?1 and 200.0 to 2000.0 nmol L^?1 with a high sensitivity of 2204 μA mM^?1. The detection limit was obtained to be 0.8 nmol L^?1 (S/N=3). Furthermore, the proposed approach exhibited good repeatability, stability and specificity, and could offer practicality in the detection of phenol in tap water.     

Improvement of an enzyme electrode by poly(vinyl alcohol) coating for amperometric measurement of phenol

A poly(vinyl alcohol) film cross-linked with glutaraldehyde (PVA-GA) was introduced to the surface of a tyrosinase-based carbon paste electrode. The coated PVA-GA film was beneficial in terms of increasing the stability and reproducibility of the enzyme electrode. The electrode showed a sensitive current response to the reduction of the o-quinone, which was the oxidation product of phenol, by the tyrosinase, in the presence of oxygen. The effects of the PVA and PVA-GA coating, the pH, and the GA:PVA ratio on the current response were investigated. The sensitivity of the PVA-GA-Tyr electrode was 130.56 μA/mM (1.8 μA/μM cm²) and the linear range of phenol was 0.5-100 μM. At a higher concentration of phenol (>100 μM), the current response showed the Michaelis-Menten behavior. Using the PVA-GA-Tyr electrode, a two-electrode system was tested as a prototype sensor for portable applications.     

Sensitive Electrochemical Determination of Trifluralin at a Disposable Pencil Graphite Electrode

A sensitive differential pulse (DP) voltammetric method has been proposed for the determination of trifluralin (TFA) based on both its reduction and oxidation at a disposable pencil graphite electrode (PGE). DP voltammograms recorded under optimized conditions show that oxidation and reduction peak currents increased linearly in the range from 1.0 to 75.0 μM and from 0.50 to 100.0 μM TFA, respectively. LOD and sensitivity values have been determined as 0.39 μM and 11170 μA mM⁻¹ cm⁻² for oxidation and as 0.20 μM and 22167 μA mM⁻¹ cm⁻² for reduction. The acceptable recovery values (95.2–104.8 %) were obtained from real water samples.     

The phenol efficient degradation using co-culture coupled with enhanced electricity generation capability

The co-culture of strain Citrobacter sp. RDC and Geobacter sulfurreducens PCA was used in this study and it was found that the co-culture using 200 mg/L phenol as carbon source exhibited higher maximum current density than using the single strain RDC and G. sulfurreducens PCA, respectively. Meanwhile, the co-culture was used to generate electricity by degrading phenol with the current density of 699.07 μA/cm² by using 200 mg/L phenol as the sole carbon source, which was higher than that only using G. sulfurreducens PCA (236.20 μA/cm²). Especially, the degradation efficiency of 200 mg/L phenol by co-culture can reach 55.16 % within 36 h being 4.16-fold higher than the single strain G. sulfurreducens PCA. Furthermore, the component ratio of two strains was optimized for increasing electricity generation using 500 mg/L phenol as carbon source. The maximum current density was 501.54 μA/cm² under the ratio of 3 : 1 for strain RDC to G. sulfurreducens PCA. These results highlight that phenol is good carbon source for co-culture to produce electricity. The co-culture system provides a promising application pathway for phenol degradation treatment coupled with electricity generation in the future.     

Poly(dicarbazole-N-hydroxysuccinimide) film: a new polymer for the reagentless grafting of enzymes and redox mediators

Upon oxidative electropolymerisation of a new dicarbazole derivative functionalised by a N-hydroxysuccinimide group in acetonitrile, electroactive poly(dicarbazole) films were formed on electrodes. The subsequent chemical functionalisation of the poly(dicarbazole) film was easily performed by successive immersions in aqueous enzyme and mediator solutions. Investigations by cyclic voltammetry showed that thionine and toluidine blue o have been irreversible bound to the poly(dicarbazole) backbone. The amperometric responses of the poly(dicarbazole) films grafted with polyphenol oxidase (PPO) and thionine to catechol were then investigated at −0.2 V vs. SCE. The catechol sensitivity and the maximum current at saturating catechol concentrations were 14.57 mA M⁻¹cm⁻² and 15.43 μA cm⁻², respectively. The comparison of this catechol sensitivity with that of a poly(dicarbazole) film only modified with PPO (3.40 mA M⁻¹cm⁻²) highlighted the improvement of the biosensor performance brought by thionine as immobilised redox mediator.     

Voltammetric Detection of Ethinylestradiol in Water and Synthetic Urine Samples using a Ni(II) Phthalocyanine/Iron Oxide Nanocomposite Electrode

A novel nickel phthalocyanine/iron oxide nanoparticle (NiTsPc/ION) nanocomposite electrode is proposed for the voltammetric detection of ethinyl estradiol. The method shows a wide linear range (0.07–30 μmol L⁻¹, R² >0.99), sensitivity of 0.308 μA cm⁻²/μmol L⁻¹ and limit of detection of 7.8 nmol L⁻¹ (3.3 Sb/b). Recoveries are above 95 % for quantification in tap and treatment plant water samples and synthetic urine. A single electrode can be used in seven consecutive runs (RSD=2.85 %) and responses of different electrodes vary only 7–9 %. The excellent sensing performance of the proposed sensor is ascribed to its porous morphology and efficient charge-transfer between ION and NiTsPc.     

Electro Catalytic Properties of α, β, γ, ϵ ‐ MnO2 and γ ‐ MnOOH Nanoparticles: Role of Polymorphs on Enzyme Free H2O2 Sensing

Polymorphs of Manganese di oxide (MnO₂) such as alpha (α), beta (β), gamma (γ), epsilon (ϵ), and MnOOH type materials were prepared via hydrothermal approach under different conditions. The samples were characterized by XRD, FESEM, FT‐IR, Raman and BET analysis. Cyclic voltammetry (CV) analysis confirm that α ‐ MnO₂ shows better electro‐catalytic ability. Amperometry sensing of hydrogen peroxide (H₂O₂) was carried out by varying applied potential value with the polymorphs of MnO₂. Compared with the other phases of MnO₂, α ‐ MnO₂ shows high linear range up to 20μM. The calculated sensitivity value for H₂O₂ sensing of different phases is in the order of α ‐ MnO₂, β ‐ MnO₂, ϵ ‐ MnO₂, γ ‐ MnO_2, MnOOH and found to be 0.094 mA μM⁻¹ cm⁻² > 0.072 mA μM⁻¹ cm⁻² > 0.07 mA μM⁻¹ cm⁻² > 0.03 mA μM⁻¹ cm⁻² > 0.01 mA μM⁻¹ cm⁻² respectively. All the characterization results reveal that crystalline phase plays a vital role in electrochemical behavior rather than crystalline size, morphology, surface charge, surface area.     

Conjoint use of Naphthalene Diimide and Fullerene Derivatives to Generate Organic Semiconductors for n–type Organic Thin Film Transistors

In this paper, we described the design, synthesis, and characterization of two novel naphthalene diimide (NDI) core-based targets modified with terminal fullerene (C₆₀) yield – so called S4 and S5 , in which NDI bearing 1 and 2 molecules of C₆₀, respectively. The absorption, electrochemical and thin-film transistor characteristics of the newly developed targets were investigated in detail. Both S4 and S5 displayed broad absorption in the 450–500 nm region, owing to the effect of conjugation due to fullerene functionalities. The electrochemical measurement suggested that the HOMO and the LUMO energy levels can be altered with the number of C₆₀ units. Both S4 and S5 were employed as organic semiconductor materials in n-channel transistors. The thin film transistor based on S4 exhibited superior electron mobility (μe) values ranging from 1.20×10⁻⁴ to 3.58×10⁻⁴ cm² V⁻¹ s⁻¹ with a current on-off ratio varying from 10² to 10³ in comparison with the performance of S5 based transistor, which exhibited μe ranging from 8.33×10⁻⁵ to 2.03×10⁻⁴ cm² V⁻¹ s⁻¹ depending on channel lengths.     

Constant Electricity Generation in Nanostructured Silicon by Evaporation-Driven Water Flow

Recently, hydrovoltaic technology emerged as a novel renewable energy harvesting method, which dramatically extends the capability to harvest water energy. However, the urgent issue restricting its device performance is poor carrier transport properties of the solid surface if large charged interface is considered simultaneously. Herein, a hydrovoltaic device based on silicon nanowire arrays (SiNWs), which provide large charged surface/volume ratio and excellent carrier transport properties, yields sustained electricity by a carrier concentration gradient induced by evaporation-induced water flow inside nanochannels. The device can yield direct current with a short-circuit current density of over 55 μA cm⁻², which is three orders larger than a previously reported analogous device (approximately 40 nA cm⁻²). Moreover, it exhibits a constant output power density of over 6 μW cm⁻² and an open-circuit voltage of up to 400 mV. Our finding may pave a way for developing energy-harvesting devices from ubiquitous evaporation-driven internal water flow in nature with semiconductor material of silicon.     

A novel tyrosinase biosensor based on hydroxyapatite-chitosan nanocomposite for the detection of phenolic compounds

A novel tyrosinase biosensor based on hydroxyapatite nanoparticles (nano-HA)-chitosan nanocomposite has been developed for the detection of phenolic compounds. The uniform and size controlled nano-HA was synthesized by hydrothermal method, and its morphological characterization was examined by transmission electron microscope (TEM). Tyrosinase was then immobilized on a nano-HA-chitosan nanocomposite-modified gold electrode. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize the sensing film. The prepared biosensor was applied to determine phenolic compounds by monitoring the reduction signal of the biocatalytically produced quinone species at −0.2 V (vs. saturated calomel electrode). The effects of the pH, temperature and applied potential on the biosensor performance were investigated, and experimental conditions were optimized. The biosensor exhibited a linear response to catechol over a wide concentration range from 10 nM to 7 μM, with a high sensitivity of 2.11 × 10³ μA mM⁻¹ cm⁻², and a limit of detection down to 5 nM (based on S/N = 3). The apparent Michaelis-Menten constants of the enzyme electrode were estimated to be 3.16, 1.31 and 3.52 μM for catechol, phenol and m-cresol, respectively. Moreover, the stability and reproducibility of this biosensor were evaluated with satisfactory results.     

Enhanced photoresponse of poly(3-methylthiophene) supported on TiO2

We have investigated the photoelectrochemical behavior of poly(3-methylthiophene) supported on nanostructured n-TiO₂ in a solid-state photoelectrochemical device. As electrolyte we employed the elastomer poly(epichlorohydrin-co-ethylene oxide) filled with NaI/I₂. Under polychromatic light irradiation (60 mW cm⁻²) the device exhibits an open circuit voltage, a short-circuit current and fill factor of 10 μA cm⁻², 0.048 V and 0.29, respectively. The overall efficiency of the cell is 2.3×10⁻²%.     

A Flexible Energy Harvester from an Organic Ferroelectric Ammonium Salt

Organic ferroelectrics due to their low cost, easy preparation, light weight, high flexibility and phase stability are gaining tremendous attention in the field of portable electronics. In this work, we report the synthesis, structure and ferroelectric behavior of a two-component ammonium salt 2 , containing a bulky [Bn(4-BrBn)NMe₂]⁺ (Bn=benzyl and 4-BrBn=4-bromobenzyl) cation and tetrahedral (BF₄)⁻ anion. The structural analysis revealed the presence of rich non-classical C−H⋅⋅⋅F and C−H⋅⋅⋅Br interactions in this molecule that were quantified by Hirshfeld surface analysis. The polarization (P) vs. electric field (E) hysteresis loop measurements on 2 gave a remnant polarization (P_r) of 14.4 μC cm⁻² at room temperature. Flexible polymer composites with various (5, 10, 15 and 20) weight percentages (wt%) of 2 in thermoplastic polyurethane (TPU) were prepared and tested for mechanical energy harvesting applications. A notable peak-to-peak output voltage of 20 V, maximum current density of 1.1 μA cm⁻² and power density of 21.1 μW cm⁻² were recorded for the 15 wt% 2 -TPU composite device. Furthermore, the voltage output generated from this device was utilized to rapidly charge a 100 μF capacitor, with stored energies and measured charges of 156 μJ and 121.6 μC, respectively.     

Determination of Phenolic Compounds Based on Co‐Immobilization of Methylene Blue and HRP on Multi‐Wall Carbon Nanotubes

This work evaluated an amperometric biosensor based on multi‐wall carbon nanotubes (MWCNT), chemically modified with methylene blue (Met) and horseradish peroxidase (HRP), for detection of phenolic compounds. The dependences of the biosensor response due to the enzyme immobilization procedure, HRP amounts, pH and working potential were investigated. The amperometric response for catechol using the proposed biosensor showed a very wide linear response range (1 to 150 μmol L^?1), good sensitivity (50 nA cm^?2 μmol^?1 L), excellent operational stability (after 300 determinations the response remained at 97%) and very good storage stability (lifetime>3 months). Based on all these characteristics, it is possible to affirm that the material is promising for phenol detection due to its good electrochemical response and enzyme stabilization. The biosensor response for various phenolic compounds was investigated.     

Construction of amperometric biosensor modified with conducting polymer/carbon dots for the analysis of catechol

Phenolic compounds used in food industries and pesticide industry, are environmentally toxic and pollute the rivers and ground water. For that reason, detection of phenolic compounds such as catechol by using simple, efficient and cost-effective devices have been becoming increasingly popular. In this study, a suitable and a novel matrix was composed using a novel conjugated polymer, namely poly[1-(5-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2-yl)furan-2-yl)-5-(2-ethylhexyl)-3-(furan-2-yl)-4H thieno[3,4-c]pyrrole-4,6(5H)-dione] (PFTBDT) and carbon dots (CDs) to detect catechol. PFTBDT and CDs were synthesized and the optoelectronic properties of PFTBDT were investigated via electrochemical and spectroelectrochemical studies. Laccase enzyme was immobilized onto the constructed film matrix on the graphite electrode. The proposed biosensor was found to have a low detection limit (1.23 μM) and a high sensitivity (737.44 μA/mM.cm⁻²) with a linear range of 1.25–175 μM. Finally, the applicability of the proposed enzymatic biosensor was evaluated in a tap water sample and a satisfactory recovery (96–104%) was obtained for catechol determination.     

Development of an enzymeless biosensor for the determination of phenolic compounds

The construction of amperometric enzymeless biosensors for phenolic compounds determination, using carbon paste electrode modified with copper phtalocyanine (CuPc) and histidine (His), based on the chemistry of the dopamine β-monooxygenase (DβM) enzyme that catalyzes the hydroxylation of the dopamine and its analogs is shown. The modified carbon paste was evaluated on electrodes constructed in two ways: putting the paste into a cavity of a rotating disk electrode and a platinum slide electrode fixed into a glass tube. The sensor in hydrodynamic conditions presented a linear response range between 30 and 250 μmol l⁻¹, with a sensitivity of 4.6±0.1 nA l μmol⁻¹ cm⁻² for catechol, response time of 3 s and lifetime of about 50 days when stored at room temperature. The sensor in static conditions showed a linear response range from 40 to 250 μmol l⁻¹, with a sensitivity of 0.30±0.01 nA l μmol⁻¹ cm⁻² for catechol. The sensors presented the following relative response order for dopamine and some analog species: catechol>dopamine>guaiacol>serotonin>phenol.