Peak Potential Difference Research Articles

An electrochemical sensor employing β-cyclodextrin chiral cross-linked metal organic framework and graphene oxide for chiral enantiomer recognition

Chirality is a universal feature of nature, and the effective differentiation of chiral molecules is still a challenge. Here we propose a method for recognizing chiral molecules based on an electrochemical detection method. We use β-cyclodextrin as an organic ligand and coordinate it with K ions to form a metal–organic framework (MOF), then we use diphenyl carbonate to connect MOFs to obtain chiral Cross-Linked MOF (CLMOF). This CLMOF is different from the cyclodextrin MOFs reported in previous literature in that it can maintain a stable structure in the aqueous environment. CLMOF and graphene oxide (GO) are jointly modified on the glassy carbon electrode (GCE) surface to build a GO-CLMOF/GCE electrochemical sensor which is used for the chiral recognition of the enantiomers of mandelic acid (MA). The DL enantiomers of MA exhibit different electrochemical behaviors on the GO-CLMOF/GCE sensor. Their peak current ratio (IL/ID) reaches 1.8, and the peak potential difference ΔE (ED-EL) is 96 mV. It shows good linearity in the range of 0.5–30 mM. The detection limits of D-MA and L-MA are 0.15 mM and 0.09 mM, respectively. The method was successfully applied to the detection of DL-MA enantiomer of unknown concentration in urine. The recognition of DL enantiomers on the electrode surface is possible because DL-MA forms diastereomers with CLMOF. The electrochemical sensor made of CLMOF and GO is simple to prepare and has excellent selectivity for DL enantiomers of MA, and provides a possible idea for the identification and quantification of chiral isomers.

MIL-53(Fe)-derived ant nest structured porous carbon nanospheres CuFeS2 /C for the determination of atropine enantiomeric impurity L-hyoscyamine.

In this work, an ant nest structured porous carbon nanosphere had been developed for the recognition detection of the atropine (ATP) enantiomers D-hyoscyamine (D-HSM) and L-hyoscyamine (L-HSM). Firstly, Fe-based organic framework was used as the substrate, and Cu ions and sulfur ions were separately introduced to obtain CuFeS2 with ant nest structure by hydrothermal incubation. Then CuFeS2 /C porous nanospheres (PNSs) were obtained by high-temperature calcination. The composite-modified electrode exhibited superior electrochemical performance for L-HSM due to the synergistic effect of CuFeS2 cubic crystals and porous carbon, which has the high specific surface area of the ant nest structure. In addition, the molecularly imprinted polymer (MIP) about L-HSM formed with sulfonated-β-cyclodextrin (S-β-CD) and L-arginine (L-Arg) by cyclic voltammetry showed strong chiral recognition of D/L-HSM (ATP). Therefore, a novel electrochemical sensor was constructed based on CuFeS2 /C PNSs and MIP to detect L-HSM by differential pulse voltammetry. Under the optimal conditions, the peak current density of L-HSM showed a good linearity in the concentration range of 0.02-4.6μM with LOD and LOQ of 0.45 and 1.5nM, respectively. The oxidation peaks of L-HSM and D-HSM were successfully identified from the racemic ATP, and the oxidation peak potential difference (ΔEp ) between them was 0.138 V. In conclusion, the sensor showed excellent reproducibility, repeatability, and stability and had been applied to the determination of L-HSM in human serum, saliva, and ATP sulfate tablets with satisfactory results.

Salicylaldehyde functionalized chitosan for electrochemical sensitive sensor: Simultaneous determination of catechol and hydroquinone

Salicylaldehyde functionalized chitosan (S-CHIT) was prepared and electrochemical sensor based on the above material and acetylene black paste electrode (ABPE) were constructed. A new method for the simultaneous detection of catechol (CC) and hydroquinone (HQ) was established. The results of Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) showed that S-CHIT had been successfully synthesized and attached to the surface of ABPE. Cyclic voltammetry (CV) and second-order derivative linear sweep voltammetry (SDLSV) were used to investigate the electrochemical behaviors of CC and HQ on the S-CHIT/ABPE. In 0.1 M H2SO4 solution, CC and HQ produced a pair of reversible redox peaks with good shape on the modified electrode. The quantitative determination of CC and HQ was performed by SDLSV using the oxidation signal. The difference of the oxidation peak potentials between CC and HQ was 112 mV. In the presence of 50 µM of the respective isomer, the linear concentration range of CC and HQ is 0.6 μM to 80 μM and 1.0 μM to 80 μM respectively, and the corresponding detection limits are 0.1 μM and 0.4 μM. The method was applied to the simultaneous determination of CC and HQ in water samples. The results show that S-CHIT/ABPE is a promising electrochemical sensor for the simultaneous detection of CC and HQ.

Lead-modified graphite felt electrode with improved [formula omitted] electrochemical activity for vanadium redox flow battery

Graphite felt is disadvantageous of lower electrochemical reaction activity, which is improved by introducing catalysts. Especially, cheaper materials and simple fabrication are popular for reducing cost. In this work, electrodeposited-lead electrode is proposed for improving electrochemical reaction activity of VO2+/VO2+ couple as well as charge-discharge performance of the battery. Experiment platform is established for vanadium redox flow battery. Cyclic voltammetry and charge-discharge performance measurements are carried out. Electron scanning microscope (SEM) is employed to investigate the surface morphology of electrode. Results show that peak potential difference (ΔE+) and peak current ratio (Ia+/Ic+) with electrodeposited-lead electrode is 103.7 mV lower and 0.249 lower than that with untreated electrode for VO2+/VO2+ electrochemical reaction. Electron scanning microscope images exhibit that lead particles are adhered extensively on carbon fiber of electrodeposited-lead electrode, which improves electrochemical activity of VO2+/VO2+ couple. Energy efficiency of the battery with electrodeposited-lead electrode in positive side is higher than that with untreated electrode by 8.5% at 60 mAcm−2. Electrodeposited-lead electrode exhibits higher activity to VO2+/VO2+ reaction and brings about higher energy efficiency of battery. This work provides a suitable electrode for vanadium redox flow battery.

Nanoscale engineering to control mass transfer on carbon-based electrodes

Here we use an electrode consisting of carbon nanofibers (CNFs), the lengths and surface population density of which can be effectively controlled. It is shown that (i) a thin liquid layer forms when the thickness of the diffusion layer has a specific ratio to the dimensions of the nanostructured carbon surface. (ii) This leads to a decrease in the peak potential difference and a subsequent increase in the apparent heterogeneous electron transfer (HET) constant, both of which could be interpreted as a result of increased catalytic activity. (iii) However, we show that this explanation is not likely, as our materials are chemically identical, and we use an outer sphere redox (OSR) probe to minimize any specific chemical interactions. On the contrary, (iv) the results clearly show that the observed behavior is caused by a combination of the formation of a thin liquid layer and the increased apparent surface area of the electrodes.

A film electrode composed of micron-diamond embedded in phenolic resin derived amorphous carbon for electroanalysis of dopamine in the presence of uric acid

A self-supporting array-like film electrode composed of micron-diamond particles distributed in amorphous carbon matrix was synthesized by vacuum annealing the mixture of phenolic resin and micro-diamond for electroanalysis of dopamine in the presence of uric acid. • The D/AC electrode was prepared by vacuum annealing the PR and micro-diamond. • The AC matrix was divided by micron-diamond to realize array-like structure. • The D/AC exhibited low LOD for DA (0.238 μM, 0.334 μM in the presence of UA). • Excellent selectivity to DA on D/AC in the presence of UA (300 mV) was confirmed. Levels of dopamine (DA) in the human body is directly related to an individual’s health status. It is crucial to detect DA via economical and effective means, especially when it coexists with other molecules. A self-supporting array-like electrode composed of micron-diamond particles distributed in amorphous carbon (AC) matrix (D/AC) was synthesized by vacuum annealing the mixture of phenolic resin (PR) and micro-diamond. During the annealing process, the PR was converted to AC. The AC was divided into micron-level areas using micron-diamond particles to obtain an array-like electrode, which improved the response of electroanalysis signals. The D/AC exhibited a low limit of detection for DA (0.238 μM), which was attributed to the array-like structure. Moreover, outstanding selectivity towards DA on D/AC in the presence of uric acid was confirmed, and the evident peak potential differences (300 mV) facilitated detection of DA. The detection limit of DA on D/AC in the presence of uric acid was 0.334 μM. Accordingly, D/AC may be suitable as biosensor candidate due to its decent stability, reproducibility and selectivity.

Redox Chemistry of tris(β-diketonate)cobalt(III) Complexes: A Molecular View

Reduction of low spin S = 0 tris(β-diketonate)cobalt(III) complexes leads to an intermediate spin S = 3/2 anion. This electron rearrangement upon reduction could be the reason why a large peak potential difference between the reduction and re-oxidation peaks was observed during electrochemical analysis, using cyclic voltammetry. It is shown that experimental redox potentials obtained from the following methods, namely (i) polarography, (ii) cyclic voltammetry on a hanging Hg electrode, as well as (iii) cyclic voltammetry on a carbon fibre surface, related linearly to various empirical (Gordy scale group electronegativities, Hammett meta-substituent constants, pK a and the Lever electronic parameters) and density functional theory (DFT) calculated (LUMO energy, adiabatic electron affinity, chemical potential, global electrophilicity index and molecular electrostatic potential on Co) reactivity parameters. Deviations from these linear trends were due to a resonance effect of aromatic substituent groups. The linear relationships obtained for complexes containing aliphatic substituent groups can be used to predict redox potential and the electrophilic reactivity of related tris(β-diketonate)cobalt(III) complexes.

Molecularly imprinted electrochemical sensing platform for 2-Aminoadipic acid, a diabetes biomarker

A silylatedgraphene oxide (Si-GO) based electrochemical sensor was fabricated for the selective and specific detection of a diabetes biomarker 2-Aminoadipic Acid (2-AAA). The fabrication was preceded by molecularly imprinting technology accompanied by electrochemical sensing. Different molecularly imprinted polymers (MIPs) were prepared using different monomers such as 2-Acrylamido-2-methylpropanesulfonicacid (AMPS), Methacrylic acid (MAA) and Vinyl pyridine (VPy) with different ratios. Ethylene glycol dimethacrylate (EGDMA) and potassium peroxodisulphate (KPS) were used as a cross linker and an initiator, respectively. Cyclic voltametry (CV), differential pulse voltametry (DPV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the modified electrode. Modified electrode can be prepared by the surface modification of a glassy carbon electrode (GCE) with MIP (MIP/GCE) by drop-casting method. The prepared materials were characterized using Fourier Transforms Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). The modified MIP electrode shows an enhanced redox peak with a peak potential difference of 0.70 V with redox current of 0.015 mA, which indicates the presence of complementary active sites of 2-AAA in MIP. The NIP electrode shows a weaker redox peak difference compared to MIP. The optimum time response and pH were found to be 15 min and 5, respectively. DPV analysis gives good linearity with R2 value 0.9932. Limit of detection (LOD) and Limit of quantification (LOQ) were obtained as 0.40 × 10−11 and 1.34 × 10−11 M, respectively.

Sensitive Simultaneous Detection of Methyldopa and Hydrochlorothiazide on Ce3+-NiO Hexagonal Nanoparticles-Modified Electrode

We applied GCE modified with Ce3+-NiO hexagonal nanoparticles (Ce3+-NiO HNPs) for preparing methyldopa electrochemical sensor. Electrochemical study of the modified electrode showed that within the optimal conditions of phosphate buffer solution (PBS) at a pH of 7.0 in CV, oxidation potency of methyldopa decline to ~100 mV at the modified electrode in comparison with an unmodified GCE. The sensor exhibits a sensitive response to methyldopa in range between 0.1 and 80.0 μM with a limit of detection (LOD) equal to 0.03 μM. In addition, as sensing materials for simultaneously determine hydro-chlorothiazide and methyldopa, Ce3+-NiO HNPs/GCE, exhibited high sensitivity. The defined and separated oxidation peaks of a mixture of methyldopa and hydrochlorothiazide were obtained with significant peak potential differences of 390 V. The proposed electrochemical sensor was employed in analysis of both drugs in the real specimens.

Ammonium heptamolybdate preloaded on flexible carbon-matrix film electrode for the electrochemical phosphate sensor in a river water sample

This work designed ammonium heptamolybdate (AHM) preloaded on a polyaniline (PANI)/coconut shell-derived carbon (CC)/poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF) composite flexible film electrode. The as-prepared novel AHM@PANI/CC/PVDF composite film electrode allowed to the selective and sensitive determination of phosphate in river water samples. The optimized AHM@PANI/CC/PVDF film delivered excellent ionic conductivity (6.58 × 10−5 S cm−1). The analysis of the flexible composite matrix film confirmed the presence of three AHM redox couples, and their formal potential, peak potential difference, and surface coverage (τ) were calculated. The AHM@PANI/CC/PVDF film comprised an excellent microenvironment for phosphate (H2PO4−) detection, while the resulting electroactive phosphomolybdic complex species were stabilized by the composite matrix. The product of phosphomolybdic complex was electrochemically reduced at +0.25 V vs. saturated calomel electrode (SCE). The Keggin-type phosphomolybdic complex on the composite film was ex-situ examined by elemental mapping, X-ray diffraction pattern and X-ray photoelectron spectroscopy. From the spectroscopic studies individual composite materials interaction with molybdate mechanism provided. The AHM@PANI/CC/PVDF film electrode revealed a good phosphate detection concentration range of 10–114 µM, and it exhibited a low detection limit (0.6 µM). Besides, AHM@PANI/CC/PVDF was used to analyze a tap and river water sample and validated the obtained data through the spectrophotometric method which yielded an excellent recovery range (101.3%–113.3%).

Growth of monolayer and multilayer graphene on glassy carbon electrode for simultaneous determination of guanine, adenine, thymine, and cytosine

• Graphene (Gr) was grown vertically on a glassy carbon (GC) electrode with Au catalyst. • Monolayer and multilayer Gr films were deposited on GC to form a novel carbon electrode. • The carbon electrode responds directly to all four DNA bases and various other biomarkers. • The carbon electrode has excellent stability and reliability in DNA base analysis. A novel carbon film composed of glassy carbon (GC), monolayer graphene (Gr), and multilayer Gr was prepared by continuously growing Gr sheets on a GC substrate, using Au nanoparticles as catalysts. The formation of the monolayer Gr sheets and the vertical growth mechanism of the multilayer Gr sheets were investigated by analyzing the morphology, microstructure, and composition variations. The carbon multilayer film can recognize biomolecules and inorganic ions, and can respond to up to 10 species. This function is based on the inherent electrocatalytic activity of the carbon film without modification using additional sensitive materials. The use of the multilayer carbon film as an electrochemical biosensor was investigated with the four DNA bases: guanine (G), adenine (A), thymine (T), and cytosine (C). The carbon film clearly identified G, A, T, and C in a neutral electrolyte environment, with detection limits of 0.3, 0.4, 6.5, and 4.5 μM, respectively; the peak potential differences for A–G, T–A, and C–T were 164, 216, and 184 mV, respectively. This carbon film can replace commercial GC, Au, and carbon paste electrodes and function as a basic electrode to explore new electrochemical sensors with high functionality and sensitivity.

Electrochemical sensing for naphthol isomers based on the in situ growth of zeolitic imidazole framework-67 on ultrathin CoAl layered double hydroxide nanosheets by a reaction–diffusion technique

It is established that ultrathin layered double hydroxide nanosheets (LDHNS) and zeolitic imidazole frameworks (ZIF) are desirable electrochemical sensing modifiers owing to their large surface area and abundant catalytic sites. Integration of them is thus an effective solution to maximize their electrocatalytic activity. Herein, a novel reaction–diffusion framework (RDF) technique is applied for the in situ growth of ZIF-67 on ultrathin CoAl-LDHNS (CoAl-LDHNS@ZIF-67). In a confined space of the agar gel matrix of RDF, the coordination reaction between organic ligands and CoAl-LDHNS without an additional Co2+ source achieves the controllable growth of ZIF-67 crystals through a long vertical diffusion. The prepared composite comprises both CoAl-LDHNS and ZIF-67 components with a certain ratio and provides a large surface area and amply catalytic sites, thus realizing a rapid transfer of electron and mass. The CoAl-LDHNS@ZIF-67 modified electrode is employed for the simultaneous detection of naphthol isomers by differential pulse voltammetry. Naphthol isomers display anodic reactions with a wide peak potential difference, allowing their simultaneous detection feasible. Voltammetric responses of α-naphthol and β-naphthol follow good linearity against the concentration in a wide range from 0.3 to 150 μM with limits of detection of 54 and 82 nM, respectively. The proposed sensor also demonstrates excellent selectivity, stability, reproducibility, and practicability for the simultaneous detection of naphthol isomers.

Chiral Biobased Ionic Liquids with Cations or Anions including Bile Acid Building Blocks as Chiral Selectors in Voltammetry

AbstractChiral ionic liquids (CILs), or ionic liquids (ILs) with chiral additives, are very attractive chiral media for enantioselective electroanalysis, on account of their high chiral structural order at the electrochemical interphase. A family of molecular salts with CIL properties is now introduced, based on the chiral steroid building block of deoxycholic acid implemented either in the anion or cation. Testing them as chiral additives in a commercial achiral IL, they enable voltammetric discrimination of the enantiomers of a model chiral probe on disposable screen‐printed electrodes in terms of peak potential differences, which is the most desirable transduction mode of the enantiorecognition event. The probe enantiomer sequence is the same for all selectors, consistent with their sharing the same chiral building block configuration. This proof‐of‐concept widens the application fields of bile acid derivatives as chiral selectors, while also enriching the still very few CIL families so far explored for applications in chiral electroanalysis.

Study on the electron transfer capability of porphyrin ring and the mechanisms in the catalytic denitrification

In this study, electron transfer capability and mechanisms the porphyrin ring in metalloporphyrins were explored through the performance of tetraphenylporphyrin tetrasulfonic acid (TPPS) in denitrification system. The calculation of frontier orbitals of hemin, chlorophyll c and TPPS indicated the great importance of the porphyrin ring in metalloporphyrin for their electron transfer properties. Batch experiments showed that the nitrate and nitrite reduction rate with 0.25 mM TPPS were 1.88 and 1.95 fold than that of TPPS ­ free system, respectively. With respect to the catalytic mechanism, the electron transfer rate and the consumption efficiency was enhanced in TPPS ­ supplemented system. The oxidation-reduction potential and redox peak potential difference in TPPS ­ supplemented system were 127 mV and 291 mV lower than that of TPPS ­ free system, respectively, which indicated that TPPS effectively enhanced the electron transfer capability in denitrification system. The activation energy of TPPS ­ supplemented system reduced 55 % compared with TPPS ­ free system. The levels of protein and humic acid like compounds in the extracellular polymeric substances increased, which facilitated electron transfer. TPPS accelerated the electron transfer of the complex I and complex III in denitrification electron transfer chain. As for electron consumption efficiency, nitrate reductase activity in TPPS ­ supplemented system was 1.30 fold that of TPPS ­ free system. This study was conducive to better understanding of the mechanisms of electron transfer of metallporphyrins compounds.

Supramolecular assemblies of carbon nanocoils and tetraphenylporphyrin derivatives for sensing of catechol and hydroquinone in aqueous solution

Non-enzymatic electrochemical detection of catechol (CC) and hydroquinone (HQ), the xenobiotic pollutants, was carried out at the surface of novel carbon nanocoils/zinc-tetraphenylporphyrin (CNCs/Zn-TPP) nanocomposite supported on glassy carbon electrode. The synergistic effect of chemoresponsive activity of Zn-TPP and a large surface area and electron transfer ability of CNCs lead to efficient detection of CC and HQ. The nanocomposite was characterized by using FT-IR, UV/vis. spectrophotometer, SEM and energy dispersive X-ray spectroscopy (EDS). Cyclic voltammetry, differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy were used for the electrochemical studies. CNCs/Zn-TPP/GCE nanosensor displayed a limit of detection (LOD), limit of quantification (LOQ) and sensitivity for catechol as 0.9 µM, 3.1 µM and 0.48 µA µM−1 cm−2, respectively in a concentration range of 25–1500 µM. Similarly, a linear trend in the concentration of hydroquinone detection was observed between 25 and 1500 µM with an LOD, LOQ and sensitivity of 1.5 µM, 5.1 µM and 0.35 µA µM−1 cm−2, respectively. DPV of binary mixture pictured well resolved peaks with anodic peak potential difference, ∆Epa(CC-HQ), of 110 mV showing efficient sensing of CC and HQ. The developed nanosensor exhibits stability for up to 30 days, better selectivity and good repeatability for eight measurements (4.5% for CC and 5.4% for HQ).

Electroseparation of uranium from lanthanides (La, Ce, Pr, Nd and Sm) on liquid gallium electrode

The aim of this work is to explore the electroseparation of uranium from lanthanides (La, Ce, Pr, Nd and Sm) on a liquid gallium electrode. Cyclic voltammetric results showed that in multi-component melt systems (U/Nd, U/La-Ce-Nd, and U/La-Ce-Pr-Nd-Sm), the reduction potentials of each lanthanides on the Ga cathode are identical and cannot be distinguished and resolved. The peak potential differences between the lanthanides and uranium are all at about 250 mV. The practical electroseparations in U/Nd, U/La-Ce-Nd and U/La-Ce-Pr-Nd-Sm systems were carried out by applying different electrochemical techniques as galvanostatic, potentiostatic and current pulse electrolysis. After electrolysis, the ICP-AES technique was used to determine the composition of molten salt and alloy deposits, and the actual separations factor of U over lanthanides in these multi-component systems were calculated and compared. The results showed that the separation factors of U/La and U/Sm can be both up to 1000, whilst that of U/Nd is relatively low with an average value of about 350. In addition, the separation factor obtained by the current pulse electrolysis is larger than that of galvanostatic and potentiostatic method, and the potentiostatic electrolysis provides the lowest one.

Cyclic Voltammetric studies of the interaction of cupric chloride with (Z)-4-oxo-4-((4-selenocyannatophenyl)amino) but-2-2nonic acid , (Chal) in KCl solutions using glassy carbon electrode.

To predict and analyze the complexation behavior between the challcogen ligand (Chal) (Z)-4-oxo-4-((4-selenocyannatophenyl)amino) but-2-2nonic acid, and metal ion in aqueous solution cyclic voltammetric studies of copper chloride salt [CuCl2] in absence and presence of chalcogen ligand (Chal), (Z)-4-oxo-4-((4-selenocyannatophenyl)amino) but-2-2nonic acid were performed. From these studies, some values were evaluated (the values of solvation and kinetic parameters [Ep (peak potential), Ip (peak current), D (Diffusion coefficient), ΔEP (peak potential difference), E½ (half wave potential), ks (electron transfer rate constant), Г (surface coverage) and Qa (quantity of electricity)]. the effect of different scan rate and concentration of above the calculated quantities were evaluated and discussed.

A Sensitive Electrochemical Sensor Based on Dual Co-Doped N, P-rGO for Simultaneous Determination of Hydroquinone and Catechol

In this paper, the N and P co-doped reduce graphene oxide (N, P-rGO) was prepared with one-pot solution method and characterized by using SEM and electrochemical technology. It was found that the N, P-rGO has an outstanding conductivity, large surface area and excellent electrocatalytic activity to hydroquinone (HQ) and catechol (CC), which usually coexist in aqueous environment. Under the optimal conditions, compared with bare glassy carbon electrode (GCE) and N doped reduce graphene oxide (N-rGO) modified GCE (N-rGO/GCE), the N, P-rGO/GCE displayed an excellent simultaneous determination towards HQ and CC. And the oxidation peak potential difference of HQ and CC obtained from N, P-rGO/GCE was 106 mV, indicating N, P-rGO/GCE has excellent resolution. The obtained detection limit was 62.1 nM and 99.7 nM for HQ and CC in a concentration range of 1 μM to 100 μM, respectively. At the same time, N, P-rGO/GCE also displayed satisfied selectivity, decent stability and desirable reproducibility. Furthermore, the fabricated sensor was successfully applied to detect two isomers in tap water and the recoveries of 99.52% to 106.36% and 95.5% to 103.97% for HQ and CC were obtained, which verified the practical application potential of N, P-rGO/GCE.

NiO bio-composite materials: Photocatalytic, electrochemical and supercapacitor applications

Synthesis based on biomaterial technology has high potential in structural applications. Blending metal oxides with plant extract is an attractive alternative for preparing materials with superior material properties. Here, we report for the first time, the synthesis of NiO bio-composite materials by employing Aloe vera leaf extract. The work mainly highlights the synergistic influence of biomolecules of Aloe vera plant on the electrochemical and photocatalytic properties of NiO. The structure, morphology, band gap and bonding features of NiO bio-composites were characterized by XRD, Electron Microscopy, UV-DRS and FT-IR techniques, respectively. The average crystallite size of the composites was within 60 nm. FT-IR spectra confirmed the strong bonding interactions between biomolecules and NiO. A maximum band gap of 3.88 eV with a good thermal stability for the synthesized composites was observed. The addition of biomolecules to NiO resulted in the improvement of the reversibility of the electrode by reducing the anodic (Epa) and cathodic (Epc) peak potential difference in KOH electrolyte. Also, the composite exhibited greater stability due to recyclability and less resistance even after 1000 charge-discharge cycles, revealing a stable electrode material for supercapacitors applications. The photocatalytic experiments confirmed a maximum of 95% dye degradation efficiency by the composite for AR88 dye. It was also found that 50 % of dye degradation occurred within 74.61 min. The encouraging results project out the potential of the synthesized NiO-biocomposites to be a better supercapacitor and photocatalyst.

Improved chromium (VI) reduction performance by bacteria in a biogenic palladium nanoparticle enhanced microbial fuel cell

Hexavalent chromium (Cr(VI)) is discharged from several anthropogenic activities that make use or produce Cr(VI) leading to environmental pollution. In this study, we explore an environmentally friendly process for the treatment of Cr(VI) with a codeposition of zero-valent palladium on the anode electrode of a microbial fuel cell (MFC). The MFC featured a granular activated carbon (GAC) anode modified with biogenic palladium nanoparticles (Bio-PdNPs). Temperature, pH, and initial Cr(VI) concentration were first optimized to 38 °C, pH 4, and 100 mg L−1 Cr(VI), respectively. Thereafter, the GAC average particle size was successfully optimized to 0.6–1.1 mm which was shown to promote the highest cell attachment. GAC below this size range had minimal cell attachment. The results from the study also showed that the GAC can be successfully modified using Bio-PdNPs to improve the performance of Cr(VI)-reducing MFC with Bio-PdNPs loading of 6 mg Bio-PdNPs g−1 GAC resulting in peak output potential difference of 393.1 mV, maximum power density of 1965.4 mW m−3, and complete removal of 100 mg L−1 Cr(VI) in 25 h.