One-pot facile simultaneous in situ synthesis of conductive Ag–polyaniline composites using Keggin and Preyssler-type phosphotungstates

Two heteropolytungstate structures, Keggin (H₃PW₁₂O₄₀) and Preyssler (H₁₄[NaP₅W₃₀O₁₁₀]), were used to synthesize conductive silver nanoparticle–polyaniline–heteropolytungstate (AgNPs–PAni–HPW) nanocomposites. During the oxidative polymerization of aniline, heteropolyblue was generated and served as the reducing agent to stabilize and distribute AgNPs within “PAni–Keggin” and “PAni–Preyssler” matrixes as well as on their surfaces. The prepared nanocomposites and AgNPs were characterized using UV-visible (UV-Vis) and Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), pore size distribution BET, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). UV-Vis results showed different stages of the formation of metal NPs embedded in the polymer–HPW composites, and FT-IR spectra presented characteristic bands of PAni, Keggin and Preyssler anions in the composites confirming no changes in their structures. The presence of AgNPs and an intensely crystalline matrix were confirmed by the XRD pattern. The BET surface areas were found to be 38.426 m² g⁻¹ for “AgNPs–PAni–Keggin” and 29.977 m² g⁻¹ for “AgNPs–PAni–Preyssler” nanocomposites with broad distributions of meso-porous structure for both nanocomposites. TEM and SEM images confirmed that the type of heteropolyacids affected the size of AgNPs. This is the first report that uses Keggin and Preyssler-type heteropolytungstate to synthesize “AgNPs–PAni–HPW” nanocomposites in an ambient condition through a low-cost, facile, one-pot, environmentally friendly and simultaneous in situ oxidative polymerization protocol.

Two heteropolytungstate structures, (a) Keggin (H₃PW₁₂O₄₀) and (b) Preyssler (H₁₄(NaP₅W₃₀O₁₁₀]), have been used to synthesize conductive silver nanoparticle–polyaniline–heteropolytungstate, (AgNPs–PAni–HPW) nanocomposites.     

Enhancement effect of reduced graphene oxide and silver nanocomposite supported on poly brilliant blue platform for ultra-trace voltammetric analysis of rosuvastatin in tablets and human plasma

The enhancement effect of reduced graphene oxide (rGO) combined with silver nanocomposite supported on poly brilliant blue (PBB) platform was investigated for ultra-trace analysis of rosuvastatin (RS). Herein, in situ electrochemical deposition of the silver nanoparticles (AgNPs) and rGO hybrid was performed on the surface of the polymerized brilliant blue (PBB) platform. The developed (AgNPs–rGO/PBB) electrode showed an enhanced catalytic activity toward the oxidation of RS. The modified electrodes AgNPs–rGO/PBB and AgNPs/PBB required an overpotential of 0.68 and 1.06 V to achieve a current density of 10 mA cm⁻², and their corresponding Tafel slopes were calculated to be 70 and 105 mV dec⁻¹, respectively. Further, rGO and silver nanocomposites properties were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), square wave voltammetry (SWV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). Additionally, the formation of GO and AgNPs–rGO was confirmed by Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Under the optimized conditions, the electrochemical sensor showed a remarkable response for quantitation of RS over a wide range of concentrations 5 × 10⁻⁹ to 5 × 10⁻⁷ mol L⁻¹ (r = 0.9988), with a limit of detection 2.17 × 10⁻⁹ mol L⁻¹. The electrochemical performance of the studied electrode showed high reproducibility and suitability for tablets and human plasma.

In situ electrodeposition of AgNPs–rGO was carried out on PBB using CV, SWV methods were used for characterization, and the Tafel slope and overpotential were calculated.     

Facile synthesis of a zeolitic imidazolate framework-8 with reduced graphene oxide hybrid material as an efficient electrocatalyst for nonenzymatic H2O2 sensing

A zeolitic imidazolate framework-8 (ZIF-8)/reduced graphene oxide (rGO) nanocomposite was formed by using an efficient synthetic method. The morphology and structure of the ZIF-8/rGO nanocomposite were characterized by scanning electron spectroscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) mapping. The ZIF-8/rGO nanocomposites were immobilized on a carbon paste electrode (CPE) to construct a high-performance nonenzymatic electrochemical H₂O₂ sensor. A cyclic voltammetry (CV) study showed that the ZIF-8/rGO nanocomposites displayed better electrocatalytic activity toward H₂O₂ reduction compared to that of ZIF-8. An amperometric study indicated that the H₂O₂ sensor displayed high performance, which offered a low detection limit (0.05 μM) (S/N = 3), a high sensitivity (4.01 μA mM⁻¹ cm⁻²), and a wide linear range (from 1.0 to 625 μM). An electrochemical reaction mechanism was proposed for H₂O₂ reduction on the ZIF-8/rGO/CPE. Importantly, the as-fabricated H₂O₂ sensor exhibited good reproducibility and excellent selectivity. Furthermore, the constructed high-performance sensor was utilized to monitor the H₂O₂ levels in real samples, and satisfactory results were obtained. These results demonstrated that the ZIF-8/rGO nanocomposite can be used as a good electrochemical sensor material in practical applications.

A zeolitic imidazolate framework-8 (ZIF-8)/reduced graphene oxide (rGO) nanocomposite was formed by using an efficient synthetic method.     

Sulfur encapsulated in thermally reduced graphite oxide as a cathode for Li–S batteries

Rechargeable Li–S batteries are receiving ever-increasing attention due to their high theoretical energy density and inexpensive raw sulfur materials. However, their practical applications have been hindered by short cycle life and limited power density owing to the poor electronic conductivity of sulfur species, diffusion of soluble polysulfide intermediates (Li₂S_n, n = 4–8) and the large volume change of the S cathode during charge/discharge. Optimizing the carbon framework is considered as an effective approach for constructing high performance S/carbon cathodes because the microstructure of the carbon host plays an important role in stabilizing S and restricting the “shuttle reaction” of polysulfides in Li–S batteries. In this work, reduced graphite oxide (rGO) materials with different oxidation degree were investigated as the matrix to load the active material by an in situ thermally reducing graphite oxide (GO) and intercalation strategy under vacuum at 600 °C. It has been found that the loaded amount of S embedded in the rGO layer for the S/carbon cathode and its electrochemical performance strongly depended on the oxidation degree of GO. In particular, on undergoing CS₂ treatment, the rGO–S cathode exhibits extraordinary performances in Li–S batteries. For instance, at a current density of 0.2 A g⁻¹, the optimized rGO–S cathode shows a columbic efficiency close to 100% and retains a capacity of around 750 mA h g⁻¹ with progressive cycling up to over 250 cycles.

Reduced graphite oxide materials with different oxidation degree were investigated as the matrix to load sulfur by an in situ thermal-reduction and intercalation strategy. The C/S composite cathode exhibits a superior electrochemical properties.     

Low-cost electrochemical detection of l-tyrosine using an rGO–Cu modified pencil graphite electrode and its surface orientation on a Ag electrode using an ex situ spectroelectrochemical method

A low cost reduced graphene oxide–copper hybrid nano thin-film modified Pencil Graphite Electrode has been employed to detect the l-tyrosine enantiomer. The free-standing rGO–Cu hybrid nano-thin film was prepared by a simple one-step liquid–liquid interface method. Electrochemical Cyclic Voltammetry, Differential Pulse Voltammetry, pH-dependent and scan rate dependent studies on bare PGE, Cu, rGO, and rGO–Cu for l-tyrosine have been explained in detail. The rGO–Cu modified PGE based biosensor exhibits good detection of l-tyrosine. The linear range detection limit was estimated to be 1 × 10⁻⁷ M. The calculated sensitivity is 0.4 μA ppm⁻¹ mm². This electroactive biosensor is easily fabricated and controlled and is cost-effective. The surface orientation of l-tyrosine on the Ag electrode at a particular potential and its comparison with vibrational DFT calculations have been studied for the first time.

A low cost reduced graphene oxide–copper hybrid nano thin-film modified pencil graphite electrode has been employed to detect the l-tyrosine enantiomer.     

A novel,highly sensitive electrochemical 1,4-dioxane sensor based on reduced graphene oxide–curcumin nanocomposite

1,4-Dioxane is a carcinogenic, non-biodegradable, organic water pollutant which is used as a solvent in various industries. It is also formed as an undesired by-product in the cosmetic and pharmaceutical industry. Given its carcinogenicity and ability to pollute, it is desirable to develop a sensitive and selective sensor to detect it in drinking water and other water bodies. Current works on this sensor are very few and involve complex metal oxide composite systems. A sensitive electrochemical sensor for 1,4-dioxane was developed by modifying a glassy carbon electrode (GCE) with a reduced graphene oxide–curcumin (rGO–CM) nanocomposite synthesized by a simple solution approach. The prepared rGO–CM was characterized by X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, Raman spectroscopy, UV-Vis spectroscopy, and Scanning Electron Microscopy (SEM). The rGO–CM/GCE sensor was employed for the detection of 1,4-dioxane in the range of 0.1–100 μM. Although, the detection range is narrower compared to reported literature, the sensitivity obtained for the proposed sensor is far superior. Moreover, the limit of detection (0.13 μM) is lower than the dioxane detection target defined by the World Health Organization (0.56 μM). The proposed rGO–CM/GCE also showed excellent stability and good recovery values in real sample (tap water and drinking water) analysis.

Reduced graphene oxide–curcumin (rGO–CM) nanocomposite was prepared from graphite oxide using curcumin. The rGO–CM/GCE was used for highly sensitive 1,4-dioxane detection. The LOD obtained (0.13 μM) was lower than the WHO guideline value.     

A novel MnO–CrN nanocomposite based non-enzymatic hydrogen peroxide sensor

A MnO–CrN composite was obtained via the ammonolysis of the low-cost nitride precursors Cr(NO₃)₃·9H₂O and Mn(NO₃)₂·4H₂O at 800 °C for 8 h using a sol–gel method. The specific surface area of the synthesized powder was measured via BET analysis and it was found to be 262 m² g⁻¹. Regarding its application, the electrochemical sensing performance toward hydrogen peroxide (H₂O₂) was studied via applying cyclic voltammetry (CV) and amperometry (i–t) analysis. The linear response range was 0.33–15 000 μM with a correlation coefficient (R²) value of 0.995. Excellent performance toward H₂O₂ was observed with a limit of detection of 0.059 μM, a limit of quantification of 0.199 μM, and sensitivity of 2156.25 μA mM⁻¹ cm⁻². A short response time of within 2 s was achieved. Hence, we develop and offer an efficient approach for synthesizing a new cost-efficient material for H₂O₂ sensing.

A MnO–CrN composite was obtained via the ammonolysis of the low-cost nitride precursors Cr(NO₃)₃·9H₂O and Mn(NO₃)₂·4H₂O at 800 °C for 8 h using a sol–gel method.     

Atmospheric-pressure-plasma-jet processed carbon nanotube (CNT)–reduced graphene oxide (rGO) nanocomposites for gel-electrolyte supercapacitors

This study evaluates DC-pulse nitrogen atmospheric-pressure-plasma-jet processed carbon nanotube (CNT)–reduced graphene oxide (rGO) nanocomposites for gel-electrolyte supercapacitor applications. X-ray photoelectron spectroscopy (XPS) indicates decreased oxygen content (mainly, C–O bonding content) after nitrogen APPJ processing owing to the oxidation and vaporization of ethyl cellulose. Nitrogen APPJ processing introduces nitrogen doping and improves the hydrophilicity of the CNT–rGO nanocomposites. Raman analysis indicates that nitrogen APPJ processing introduces defects and/or surface functional groups on the nanocomposites. The processed CNT–rGO nanocomposites on carbon cloth are applied to the electrodes of H₂SO₄–polyvinyl alcohol (PVA) gel-electrolyte supercapacitors. The best achieved specific (areal) capacitance is 93.1 F g⁻¹ (9.1 mF cm⁻²) with 15 s APPJ-processed CNT–rGO nanocomposite electrodes, as evaluated by cyclic voltammetry under a potential scan rate of 2 mV s⁻¹. The addition of rGOs in CNTs in the nanoporous electrodes improves the supercapacitor performance.

This study demonstrates ultrafast (15 s) atmospheric-pressure-plasma-jet (APPJ) processed CNT–rGO nanocomposite gel-electrolyte supercapacitors.     

A facile synthesis of a cobalt nanoparticle–graphene nanocomposite with high-performance and triple-band electromagnetic wave absorption properties

Ferromagnetic metal nanoparticle/graphene nanocomposites are promising as excellent electromagnetic (EM) wave absorption materials. In this work, we used a facile method to synthesize a cobalt nanoparticle–graphene (CoNP–G) nanocomposite. The obtained CoNPs–G exhibited a saturation magnetization (M_s) of 31.3 emu g⁻¹ and a coercivity (H_C) of 408.9 Oe at 298.15 K. In particular, the CoNPs–G nanocomposite provided high-performance EM wave absorption with multiband, wide effective absorption bandwidth, which was mainly attributed to the synergy effects generated by the magnetic loss of cobalt and the dielectric loss of graphene. In the range of 2–18 GHz, the sample (55 wt% CoNPs–G) held three effective reflection loss (RL) peaks (frequency ranges of 2.4–3.84, 7.84–11.87 and 13.25–18 GHz, respectively, RL ≤ −10 dB) with the coating thickness of 4.5 mm, and the effective bandwidth reached the maximum of 10.22 GHz, and the minimal RL reached −40.53 dB at 9.50 GHz. Therefore, the CoNPs–G nanocomposite presents a great promising application in the electromagnetic wave absorption field.

Ferromagnetic metal nanoparticle/graphene nanocomposites are promising as excellent electromagnetic (EM) wave absorption materials.     

Simultaneous determination of hydroquinone and catechol by a reduced graphene oxide–polydopamine–carboxylated multi-walled carbon nanotube nanocomposite

A reduced graphene oxide–polydopamine–carboxylated multi-walled carbon nanotube (RGO–PDA–cMWCNT) nanocomposite was fabricated via a facile, one-pot procedure and was characterized by a variety of techniques. A novel electrochemical sensor based on RGO–PDA–cMWCNT was constructed to determine hydroquinone (HQ) and catechol (CT) simultaneously. This newly prepared nanocomposite shows excellent electrocatalytic efficacy in the electrode reaction of the two isomers. Specifically, the peak-to-peak potential difference between the two dihydroxybenzenes is 115 mV for oxidation, which is obviously larger than similar electrochemical sensors. The established method displays a wide linear range from 0.5 to 5000 μM with a detection limit (S/N = 3) of 0.066 μM for HQ and 0.073 μM for CT. In addition, this electrochemical approach has been tested to measure the two dihydroxybenzenes in real samples and satisfactory results were recorded.

A novel reduced graphene oxide–polydopamine–carboxylated multi-walled carbon nanotube nanocomposite (RGO–PDA–cMWCNT) was fabricated for the sensitive and simultaneous determination of hydroquinone (HQ) and catechol (CT).     

An electrochemical platform based on a hemin–rGO–cMWCNTs modified aptasensor for sensitive detection of kanamycin

Kanamycin (KANA) residue in meat is particularly harmful to public health and there is an urgent need to establish a fast, accurate and low-cost method to determinate KANA in food quality control. In this paper, hemin–reduced graphene oxide-carboxylated multiwalled carbon nanotubes (hemin–rGO–cMWCNTs) were designed and prepared, and the characteristics of hemin–rGO–cMWCNTs are presented. After that, an aptamer/hemin–rGO–cMWCNTs sensor for determination of KANA was developed. The electrochemical characteristics were studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimal conditions, the sensitive response of the aptasensor towards KANA presented a wide concentration range of 10⁻⁹ to 10⁻⁶ M and a low detection limit of 0.36 nM (S/N = 3). Meanwhile, the aptasensor showed prominent selectivity, high stability and acceptable reproducibility in the application of KANA detection. In addition, the aptasensor detection in real samples correlated well with that obtained by liquid chromatograph mass spectrometer (LCMS).

An electrochemical aptasensor based on hemin–rGO–cMWCNTs was established. The aptasensor exhibited a low detection limit and a wide linear range. Excellent stability, reproducibility and applicability were presented for KANA.     

Poly(pyrrole-co-o-toluidine) wrapped CoFe2O4/R(GO–OXSWCNTs) ternary composite material for Ga3+ sensing ability

In this study, we report a novel ternary conductive hybrid material with high stability, conductivity, and excellent electrochemical Ga³⁺ sensing ability. Ternary poly(pyrrole-co-o-toluidine)/CoFe₂O₄/reduced graphene oxide–oxidized single-wall carbon nanotube nanocomposites in the form of P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs have been synthesized through an in situ chemical polymerization method via a facile three-step approach. Single phase CoFe₂O₄ (CF) nanoparticles (NPs) were synthesized using an egg white method, while reduced graphene oxide–oxidized single-wall carbon nanotubes R(GO–OXSWCNTs) were prepared via co-reduction of graphene oxide along with oxidized SWCNTs flowed by coating CF and R(GO–OXSWCNTs) with a poly(pyrrole-co-o-toluidine) matrix P(Py-co-OT) copolymer. The results of X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR) and Raman indicated that the P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs were effectively synthesized with strong interactions among the constituents. The thermal stability of P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs is considerably enhanced in the composite format. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) demonstrated that CF and R(GO–OXSWCNTs) were well coated by P(Py-co-OT). The electrical conductivity study showed that P(Py-co-OT) and R(GO–OXSWCNTs) might significantly improve the conductivity and the electrochemical performance of the CF. A Ga³⁺ ion selective electrochemical sensor was fabricated by coating a glassy carbon electrode (GCE) with synthesized P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs by using 5% Nafion binder. The slope of the calibration curve was used to calculate the sensor''s analytical parameters, such as sensitivity (13.0569 μA μM⁻¹ cm⁻²), detection limit (96.27 ± 4.81 pM), quantification limit (43.523 pM), response time, reproducibility, large linear dynamic range, and linearity. The validation of the P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs/GCE sensor probe was investigated by a standard addition method (recovery) in the presence of various environmental samples and satisfying results were obtained.

A ternary P(Py-co-OT)/CF/R(GO–OXSWCNTs) nanocomposite has been fabricated as a novel conductive hybrid material with high stability and excellent electrochemical Ga³⁺ sensing ability.     

High performance flexible supercapacitors based on secondary doped PEDOT–PSS–graphene nanocomposite films for large area solid state devices

In this work, we propose the development of high performance and flexible supercapacitors using reduced graphene oxide (rGO) incorporated poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT–PSS) nanocomposites by secondary doping. The structural and morphological features of the composite film were analyzed in detail using SEM, AFM, FTIR, XPS and TGA. Secondary doping of ethylene glycol (EG) assisted by rGO incorporation significantly enhances the room temperature conductivity of PEDOT–PSS films from 3 S cm⁻¹ to nearly 1225 S cm⁻¹ for a 10 wt% composite. The secondary doped PEDOT–PSS:EG/rGO composite film demonstrated improved electrochemical performances with specific capacitance of 174 (F g⁻¹) and energy density of 810 (W h kg⁻¹) which is nearly 4 times greater than pristine PEDOT–PSS due to synergetic interactions between rGO and PEDOT–PSS. The prepared composite films show long term stability with capacitance retention of over 90% after 5000 cycles of charging–discharging. The nanocomposite films used in the present investigation demonstrates percolative behavior with a percolation threshold at 10 wt% of rGO in PEDOT–PSS. The assembled supercapacitor device could be bent and rolled-up without a decrease in electrochemical performance indicating the potential to be used in practical applications. To demonstrate the practical applicability, a rolled-up supercapacitor device was constructed that demonstrates operation of a red LED for 40 seconds when fully charged. This study will provide new dimensions towards designing cost effective, flexible and all solid-state supercapacitors with improved electrochemical performance using electrodes based on secondary doped PEDOT–PSS/rGO organic thin films.

In this work, we propose the development of high performance and flexible supercapacitors using reduced graphene oxide (rGO) incorporated poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT–PSS) nanocomposites by secondary doping.     

Facile preparation of porous sheet–sheet hierarchical nanostructure NiO/Ni–Co–Mn–Ox with enhanced specific capacity and cycling stability for high performance supercapacitors

NiO, Ni–Co–Mn–O_x and NiO/Ni–Co–Mn–O_x on nickel foam substrates were prepared via a chemical bath deposition–calcination. The thermodynamic behavior was observed by TG/DTA. The chemical structure and composition, phase structure and microstructures were tested by XPS, XRD, FE-SEM and TEM. The electrochemical performance was measured by CV, GCD and EIS. The mechanism for formation and enhancing electrochemical performance is also discussed. Firstly, the precursors such as NiOOH, CoOOH and MnOOH grow on nickel foam substrates from a homogeneous mixed solution via chemical bath deposition. Thereafter, these precursors are calcined and decomposed into NiO, Co₃O₄ and MnO₂ respectively under different temperatures in a muffle furnace. Notably, NiO/Ni–Co–Mn–O_x on nickel foam substrates reveals a high specific capacity with 1023.50 C g⁻¹ at 1 A g⁻¹ and an excellent capacitance retention with 103.94% at 5 A g⁻¹ after 3000 cycles in 2 M KOH, its outstanding electrochemical performance and cycling stability are mainly attributed to a porous sheet–sheet hierarchical nanostructure and synergistic effects of pseudo-capacitive materials and excellent redox reversibility. Therefore, this research offers a facile synthesis route to transition metal oxides for high performance supercapacitors.

NiO, Ni–Co–Mn–O_x and NiO/Ni–Co–Mn–O_x on nickel foam substrates were prepared via a chemical bath deposition–calcination.     

Metal–organic framework derived hollow porous CuO–CuCo2O4 dodecahedrons as a cathode catalyst for Li–O2 batteries

Herein, hollow porous CuO–CuCo₂O₄ dodecahedrons are synthesized by using a simple self-sacrificial metal–organic framework (MOF) template, which resulted in dodecahedron morphology with hierarchically porous architecture. When evaluated as a cathodic electrocatalyst in lithium–oxygen batteries, the CuO–CuCo₂O₄ composite exhibits a significantly enhanced electrochemical performance, delivering an initial capacity of 6844 mA h g⁻¹ with a remarkably decreased discharge/charge overpotential to 1.15 V (vs. Li/Li⁺) at a current density of 100 mA g⁻¹ and showing excellent cyclic stability up to 111 charge/discharge cycles under a cut-off capacity of 1000 mA h g⁻¹ at 400 mA g⁻¹. The outstanding electrochemical performance of CuO–CuCo₂O₄ composite can be owing to the intrinsic catalytic activity, unique porous structure and the presence of substantial electrocatalytic sites. The ex situ XRD and SEM are also carried out to reveal the charge/discharge behavior and demonstrate the excellent reversibility of the CuO–CuCo₂O₄ based electrode.

Metal–organic framework derived porous CuO–CuCo₂O₄ dodecahedrons as a cathode catalyst for Li–O₂ batteries with significantly enhanced rate and cyclic performance.     

TiO2–Au composite nanofibers for photocatalytic hydrogen evolution

TiO₂-based materials for photocatalytic hydrogen (H₂) evolution have attracted much interest as a renewable approach for clean energy applications. TiO₂–Au composite nanofibers (NFs) with an average fiber diameter of ∼160 nm have been fabricated by electrospinning combined with calcination treatment. In situ reduced gold nanoparticles (NPs) with uniform size (∼10 nm) are found to disperse homogenously in the TiO₂ NF matrix. The TiO₂–Au composite NFs catalyst can significantly enhance the photocatalytic H₂ generation with an extremely high rate of 12 440 μmol g⁻¹ h⁻¹, corresponding to an adequate apparent quantum yield of 5.11% at 400 nm, which is 25 times and 10 times those of P25 (584 μmol g⁻¹ h⁻¹) and pure TiO₂ NFs (1254 μmol g⁻¹ h⁻¹), respectively. Furthermore, detailed studies indicate that the H₂ evolution efficiency of the TiO₂–Au composite NF catalyst is highly dependent on the gold content. This work provides a strategy to develop highly efficient catalysts for H₂ evolution.

The H₂ production rate of TiO₂–Au nanofibers is dramatically improved to 12 440 μmol g⁻¹ h⁻¹, 10 times that of pure TiO₂.     

A reduced graphene oxide-β-cyclodextrin nanocomposite-based electrode for electrochemical detection of curcumin

Curcumin is a polyphenolic compound with anti-oxidative and anti-cancer properties that is obtained from turmeric plants. Several studies have demonstrated that cancer cells are not killed unless they are exposed to 5–50 mM of curcumin. Consequently, it is vital to control the concentration of curcumin in cancer therapy. In this study, a sensitive electrochemical sensor was fabricated based on a beta-cyclodextrin–reduced graphene oxide (β-CD–rGO) nanocomposite for measuring curcumin concentration. The effects of experimental factors were investigated and the optimum parametric conditions were determined using the Taguchi optimization method. The β-CD–rGO modified electrode exhibited good electrochemical properties for curcumin detection. The results of differential pulse voltammetry experiments unveiled that the sensor shows a linear response to curcumin concentration over the range of 0.05–10 mM with a detection limit of 33 nM and sensitivity of 4.813 μA μM⁻¹. The fabricated sensor exhibited selectivity in the presence of other electroactive species, e.g., propranolol, clomipramine and clonazepam.

In this study, a sensitive electrochemical sensor was fabricated based on a beta-cyclodextrin–reduced graphene oxide (β-CD–rGO) nanocomposite for measuring curcumin concentration.     

Vitamin C assisted synthesis of rGO–Ag/PANI nanocomposites for improved photocatalytic degradation of pharmaceutical wastes

A highly efficient visible light active polyaniline (PANI)/Ag composites grafted reduced graphene oxide (rGO–Ag/PANI) was prepared for the efficient photocatalytic degradation of paracetamol. The structural, morphological, and light absorption properties of the as-synthesized rGO–Ag/PANI were characterized by UV-Visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Paracetamol was taken as a model water pollutant to investigate the photocatalytic degradation efficiency of the rGO–PANI/Ag nanocomposites under visible light radiation. The result shows the degradation of paracetamol to be 99.6% in the acidic medium (pH 5) and 75.76% in the basic medium (pH 9), respectively. The enhanced degradation efficiency is attributed to the synergetic effect of rGO, PANI, and Ag NPs in the nanocomposites. This synergy of the rGO–Ag/PANI is explained by the strong adsorption efficiency, charge separation, and light absorption in the visible region.

A highly efficient visible light active polyaniline (PANI)/Ag composites grafted reduced graphene oxide (rGO–Ag/PANI) was prepared for the efficient photocatalytic degradation of paracetamol.     

Novel mesoporous Co3O4–Sb2O3–SnO2 active material in high-performance capacitive deionization

Capacitive deionization (CDI), as an emerging eco-friendly electrochemical brackish water deionization technology, has widely benefited from carbon/metal oxide composite electrodes. However, this technique still requires further development of the electrode materials to tackle the ion removal capacity/rate issues. In the present work, we introduce a novel active carbon (AC)/Co₃O₄–Sb₂O₃–SnO₂ active material for hybrid electrode capacitive deionization (HECDI) systems. The structure and morphology of the developed electrodes were determined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer–Emmett–Teller (BET)/Barrett–Joyner–Halenda (BJH) techniques, as well as Fourier-transform infrared (FT-IR) spectroscopy. The electrochemical properties were also investigated by cyclic voltammetry (CV) and impedance spectroscopy (EIS). The CDI active materials AC/Co₃O₄ and AC/Co₃O₄–Sb₂O₃–SnO₂ showed a high specific capacity of 96 and 124 F g⁻¹ at the scan rate of 10 mV s⁻¹, respectively. In addition, the newly-developed electrode AC/Co₃O₄–Sb₂O₃–SnO₂ showed high capacity retention of 97.2% after 2000 cycles at 100 mV s⁻¹. Moreover, the electrode displayed excellent CDI performance with an ion removal capacity of 52 mg g⁻¹ at the applied voltage of 1.6 V and in a solution of potable water with initial electrical conductivity of 950 μs cm⁻¹. The electrode displayed a high ion removal rate of 7.1 mg g⁻¹ min⁻¹ with an excellent desalination–regeneration capability while retaining about 99.5% of its ion removal capacity even after 100 CDI cycles.

Capacitive deionization (CDI), as an emerging eco-friendly electrochemical brackish water deionization technology, has widely benefited from carbon/metal oxide composite electrodes.     

Synergistic effect of Ni–Ag–rutile TiO2 ternary nanocomposite for efficient visible-light-driven photocatalytic activity

P25 comprising of mixed anatase and rutile phases is known to be highly photocatalytically active compared to the individual phases. Using a facile wet chemical method, we demonstrate a ternary nanocomposite consisting of Ni and Ag nanoparticles, decorated on the surface of XTiO₂ (X: P25, rutile (R)) as an efficient visible-light-driven photocatalyst. Contrary to the current perspective, RTiO₂-based Ni–Ag–RTiO₂ shows the highest activity with the H₂ evolution rate of ∼86 μmol g⁻¹ W⁻¹ h⁻¹@535 nm. Together with quantitative assessment of active Ni, Ag and XTiO₂ in these ternary systems using high energy synchrotron X-ray diffraction, transmission electron microscopy coupled energy dispersive spectroscopy mapping evidences the metal to semiconductor contact via Ag. The robust photocatalytic activity is attributed to the improved visible light absorption, as noted by the observed band edge of ∼2.67 eV corroborating well with the occurrence of Ti³⁺ in Ti 2p XPS. The effective charge separation due to intimate contact between Ni and RTiO₂via Ag is further evidenced by the plasmon loss peak in Ag 3d XPS. Moreover, density functional theory calculations revealed enhanced adsorption of H₂ on Ti₈O₁₆ clusters when both Ag and Ni are simultaneously present, owing to the hybridization of the metal atoms with d orbitals of Ti and p orbitals of O leading to enhanced bonding characteristics, as substantiated by the density of states. Additionally, the variation in the electronegativity in Bader charge analysis indicates the possibility of hydrogen evolution at the Ni sites, in agreement with the experimental observations.

Robust photocatalytic activity of Ni–Ag–RTiO₂ is attributed to the improved visible light absorption and effective charge separation due to intimate contact between Ni and RTiO₂via Ag, as evidenced by Ti³⁺ in Ti 2p XPS and energy dispersive mapping.