Electrodeposition Of Gold Nanoparticles Research Articles

Supramolecular Electrochemical Sensor for Dopamine Detection Based on Self-Assembled Mixed Surfactants on Gold Nanoparticles Deposited Graphene Oxide.

A new supramolecular electrochemical sensor for highly sensitive detection of dopamine (DA) was fabricated based on supramolecular assemblies of mixed two surfactants, tetra-butylammonium bromide (TBABr) and sodium dodecyl sulphate (SDS), on the electrodeposition of gold nanoparticles on graphene oxide modified on glassy carbon electrode (AuNPs/GO/GCE). Self-assembled mixed surfactants (TBABr/SDS) were added into the solution to increase the sensitivity for the detection of DA. All electrodes were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The supramolecular electrochemical sensor (TBABr/SDS⋅⋅⋅AuNPs/GO/GCE) showed excellent electrocatalytic activity toward the oxidation of DA. Under the optimum conditions, the concentration of DA was obtained in the range from 0.02 µM to 1.00 µM, with a detection limit of 0.01 µM (3s/b). The results displayed that TBABr/SDS⋅⋅⋅AuNPs/GO/GCE exhibited excellent performance, good sensitivity, and reproducibility. In addition, the proposed supramolecular electrochemical sensor was successfully applied to determine DA in human serum samples with satisfactory recoveries (97.26% to 104.21%).

Label-Free Electrochemical Detection of DNA Hybridization: A Method for COVID-19 Diagnosis.

This paper presents label-free electrochemical transduction as a suitable scheme for COVID-19-specific viral RNA/c-DNA detection, with an aim to facilitate point of care diagnosis. In lieu of this, we discuss the proposed electrochemical biosensing scheme, based on electrodeposited gold nanoparticles as the transducing elements. Specific to this approach, here, the protocols associated with the immobilization of the single-stranded probe nucleotide on to the biosensor, have also been laid out. This paper also discusses the methods of electrochemical analysis, to be used for data acquisition and subsequent calibration, in relation to target analyte detection. Towards facilitating portable diagnosis, development of miniaturized sensors and their integration with readout units have also been discussed.

SnO2 nanofibers decorated with Au nanoparticles for Ru(bpy)32+ sensitized photoelectrochemical determination of NO2− in urine

A three-dimensional (3D) network nanocomposite is constructed by electrospinning tin dioxide nanofibers (SnO2 NFs) on the surface of indium tin oxide (ITO) and then in-situ electrodepositing gold nanoparticles (AuNPs). With the aid of large surface area of SnO2 NFs and the surface plasmon resonance (SPR) effect of AuNPs, the novel 3D architecture is beneficial to the mass transfer and the separation efficiency of photogenerated electrons and holes. In the presence of photosensitizer of Ru(bpy)32+ (tris (2,2′-bipyridyl) dichlororuthenium (II) hexahydrate (Ru(bpy)3(PF6)2), the ITO/SnO2-AuNPs electrode shows good photoelectrochemical (PEC) response to nitrite (NO2−) under visible light irradiation. The linear range for NO2− determination is from 10−9 to 10−5 M with a low detection limit of 4.8 × 10−10 M. The ITO/SnO2-AuNPs photoanode based PEC sensor is also successfully applied to analyze trace NO2− in human urine, showing excellent anti-interference and stability. This work may pave the way for designing noble metal-semiconductor heterogeneous materials with tailored properties for the field of biosensor design.

Nanocomposites of poly(l-methionine), carbon nanotube-graphene complexes and Au nanoparticles on screen printed carbon electrodes for electrochemical analyses of dopamine and uric acid in human urine solutions.

A sensitive electrochemical sensor featuring novel composites of gold and carbon nanocomplexes alongside a polymerized amino acid was developed for the determination of uric acid (UA) and dopamine (DA) concentrations in both buffer and human urine sample solutions. The sensor was fabricated by electropolymerization of l-methionine (l-Met) followed by coating of carbon nanotube-graphene complexes and electrodeposition of gold nanoparticles on a screen printed carbon electrode surface. The electrode surfaces were characterized by field emission scanning electron microscopy and energy dispersive spectroscopy, and the electrochemical properties were investigated by cyclic voltammetry and differential pulse voltammetry. Linear ranges of 0.05-3 μM and 1-35 μM with limits of detection of 0.0029 and 0.034 μM were achieved for DA and UA, respectively. In addition, the developed sensor was applied for the analysis of native UA and DA concentrations in undiluted and diluted human urine samples. The UA analysis results were compared to those obtained using high performance liquid chromatography and a fluorometric assay kit while the DA analysis results were compared to those obtained using liquid chromatography-tandem mass spectrometry.

Optimized DNA-based biosensor for monitoring Leishmania infantum in human plasma samples using biomacromolecular interaction: a novel platform for infectious disease diagnosis.

Leishmania parasite identification is very important in clinical studies of leishmaniasis and its diagnosis. Though there are various clinical and epidemiological approaches to identifying Leishmania infantum, due to some limitations of the traditional methods, sensitive and specific techniques are needed and are in great demand. To achieve selective and rapid detection, a sensitive signal transducer with high surface area is necessary. In this work, a new paper sensor was fabricated using silver nanoprisms electrodeposited on the GQD conductive nano-ink (Ag NPr/GQDs nano-ink). A high surface area and suitable interface for anchoring biomolecules was achieved by electrodepositing gold nanoparticles (AuNPs) functionalized with cysteamine (AuNPs-CysA) on the surface of the paper sensor altered by Ag NPr/GQDs nano-ink. To prepare a sensitive and selective bio-device for the recognition of Leishmania in human plasma specimens, a DNA-thiol probe was stabilized on the surface of the platform. Hybridization of DNA was evaluated by chronoamperometry (ChA). The engineered DNA-based paper biosensor showed high sensitivity and selectivity for the identification of Leishmania genomic DNA. Under optimum circumstances, a linear range was obtained using photographic paper from 1 μM to 1 zM and an ivory sheet from 1 nM to 1 zM. The lower limits of quantitation (LLOQ) on the photographic paper and ivory sheet were 1 zM. In addition, the designed DNA-based biosensor revealed well-defined performance in the recognition of mismatched sequences (single base, two base and three base mismatches) and selectivity.

Carbon nanotube hollow polyhedrons derived from ZIF-8@ZIF-67 coupled to electro-deposited gold nanoparticles for voltammetric determination of acetaminophen

A comparative study was carried out on the electrochemical behavior of three carbonized zeolitic imidazolate frameworks (ZIFs) synthesized through solvothermal pyrolysis. An electrochemical sensor for acetaminophen (ACT) was subsequently developed. The sensor was made by coating the glassy carbon electrode (GCE) with cobalt-nitrogen co-doped carbon nanotube hollow polyhedron (Co-NCNHP), which was prepared from core shell ZIF-8@ZIF-67, before electrodeposition of gold nanoparticles. Due to the high specific surface area, good electrical conductivity and stability of both Co-NCNHP and the gold nanoparticles, the resultant sensor displayed excellent electrocatalytic activity towards ACT with the catalytic rate constant Kcat of 4.9 × 105M-1s-1, diffusion coefficient D of 1.8 × 10-6cm2s-1, high sensitivity of 1.75μAμM-1cm-2, and best at a working voltage of 0.35V (vs. Ag/AgCl). Benefitting from the synergistic effect of both Co-NCNHP and gold nanoparticles, the modified GCE had a linear response in the 0.1μM-250μM ACT and detection limit of 0.05μM (at S/N = 3). The sensor was successfully applied to quantify ACT in tablets and spiked urine samples with recoveries ranged between 96.0% and 105.2%. Graphical abstractSchematic representation of cobalt-nitrogen co-doped carbon nanotube hollow polyhedrons (Co-NCNHP) exhibiting superior electrocatalytic activity to carbonized ZIF-8 and carbonized ZIF-67. Co-NCNHP were coupled to electrodeposition gold nanoparticles to modify glassy carbon electrode for improving acetaminophen (ACT) redox.

Electrochemical lead(II) biosensor by using an ion-dependent split DNAzyme and a template-free DNA extension reaction for signal amplification.

A voltammetric biosensor for lead(II) (Pb2+) is described that is based on signal amplification by using an ion-dependent split DNAzyme and template-free DNA extension reaction. The Pb2+-dependent split DNAzyme was assembled on gold nanoparticles (Au@Fe3O4),and this nanoprobe then was exposed to Pb2+ which causes the split-off of DNAzymes to release primers containing 3'-OH groups (S1 and S2). The template-free DNA extension reaction triggers the generation of long ssDNA nanotails, which thencan bind the free redox probe N,N'-bis(2-(trimethylammonium iodide)propylene)perylene-3,4,9,10-tetracarboxyldiimide (PDA+) via electrostatic adsorption. Hence, the concentration of PDA+ in solution is reduced. Therefore, less free PDA+ can be immobilized on a glassy carbon electrodemodified with electrodeposited gold nanoparticles (depAu) to produce an electrochemical signal, typically measured at ∼0.38V (vs. SCE) for quantitation of Pb2+. The use of a Pb2+-dependent split DNAzyme avoids the usage of a proteinic enzyme. It also increases the sensitivity of the sensor which has a lower detection limit of 30 pM of Pb2+. Graphical abstract Novel electrochemical biosensor based on the amplification of ion-dependent split DNAzyme and template-free DNA extension reaction for trace detection of Pb2+.

Amperometric immunoassay for the carcinoembryonic antigen by using a peroxidase mimic consisting of palladium nanospheres functionalized with glutathione-capped gold nanoparticles on graphene oxide.

A composite nanoenzyme was used in a sandwich-type electrochemical immunoassay for the carcinoembryonic antigen (CEA). Hierarchically porous palladium nanospheres (Pd NPs) were functionalized with glutathione-capped gold nanoparticles (G-Au NPs) and then loaded onto graphene oxide (GO) to obtain a peroxidase mimicking nanoenzyme of type GO-supported G-Au/Pd. The composite can catalyze the oxidation of the substrate tetramethylbenzidine (TMB) by H2O2 to give blue-colored oxidized TMB within only 20s. This strong peroxidase activity, good conductivity and high specific surface area of the material make it a useful label for secondary antibodies (Ab2) for the detection of CEA. The cotton-like electrodeposited gold nanoparticles with good electrical conductivity were used to immobilize primary antibody (Ab1). The amperometric immunoassay has a detection range that extends from 10fg·mL-1 to 100ng·mL-1 at a working potential of -0.4V with addition of 5mmol·L-1 H2O2 as electrochemically active substrate, and the detection limit is as low as 3.2fg·mL-1 (S/N= 3). Graphical abstract Schematic of sandwich electrochemical immunosensor for the carcinoembryonic antigen. Electrodeposited gold used as substrate material, and Graphene oxide supported G-Au NPs functionalized porous Pd nanospheres (GO supported G-Au/Pd) as signal amplification platform, which catalyze the oxidation of tetramethylbenzidine (TMB).

A hybrid composed of MoS2, reduced graphene oxide and gold nanoparticles for voltammetric determination of hydroquinone, catechol, and resorcinol.

A ternary hybrid composed of molybdenum disulfide (MoS2), reduced graphene oxide (rGO) and gold nanoparticles (AuNPs@MoS2-rGO) was prepared and used for voltammetric detection of hydroquinone (HQ), catechol (CC) or resorcinol (RC). The composition and structure of the hybrid were characterized in detail. The electrochemical behaviors of a glassy carbon electrode (GCE) modified with the hybrid towards the oxidation of HQ, CC, and RC were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results revealed 3D MoS2 is active for the catalytic oxidation of these isomers. Additional integration with rGO and AuNPs further improves catalysis due to their synergistic interaction. The enhanced catalysis leads to oxidation of HQ, CC and RC at 0.074V, 0.178V, and 0.527V (vs. Ag/AgCl; by CV) with reduced overpotential (20-100mV) and 8-fold or 3-fold increased peak current compared to those obtained on MoS2/GCE, or MoS2-rGO/GCE, respectively. Selective detection of one isomer in the presence of the other two was realized by DPV. The linear ranges are 0.1-950μM, 3-560μM, and 40-960μM for HQ, CC, and RC, and the detection limits are 0.04μM, 0.95μM, and 14.6μM, respectively. The sensor also shows good selectivity and displays satisfactory recovery for real sample analysis. Graphical abstract Schematic illustration of the preparation of AuNPs@MoS2-rGO hybrid by hydrothermal growth of MoS2-rGO and subsequent electrodeposition of gold nanoparticles (AuNPs), and its application for selective detection of hydroquinone, catechol and resorcinol by voltammetry.

Flexible gold nanoparticles/rGO and thin film/rGO papers: novel electrocatalysts for hydrogen evolution reaction

AbstractBACKGROUNDFabrication of cost‐effective and durable materials for efficient hydrogen production in splitting water (hydrogen evolution reaction) is of importance for the successful utilization of hydrogen‐based green energy technologies. Therefore, electrocatalytic materials have been designed with a simple approach using electrodeposition of gold nanoparticles (AuNPs) and thin film (AuTF) directly on reduced graphene oxide (rGO) paper. As‐prepared paper electrocatalysts (AuNPs/rGO and AuTF/rGO) were characterized by X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM).RESULTSFree‐standing and flexible AuNPs/rGO and AuTF/rGO electrocatalysts have exhibited excellent performances on HER with low Tafel slopes (88 and 112 mV dec−1), low onset potentials (−47 and −55 mV), small overpotentials of only −176 and −204 mV to drive 10 mA cm−2, respectively, and high durability even with the rolled design. The outstanding performance of these two electrocatalysts can be attributed to the uniform distribution of 20‐nm‐sized AuNPs and the deposition of well‐ordered AuTF on rGO paper, providing an increment in the surface area and an enhancement of the electron density.CONCLUSIONThe controllable design of AuNPs/rGO and AuTF/rGO electrocatalysts, together with their high flexibility, good stability and promising results, suggest potential use in future applications of H2 production in splitting water. © 2019 Society of Chemical Industry

Electrodeposition of gold nanoparticles on ZnO nanorods for improved performance of enzymatic glucose sensors

Well-arranged ZnO nanorods were hydrothermally grown on reduced graphene oxide coated indium tin oxide electrode, and subsequently gold nanoparticles (AuNPs) were electrodeposited on these nanorods. Glucose sensors were constructed with glucose oxidase (GOx) loaded on the AuNPs decorated ZnO nanorods via electrostatic interaction, and during the electrochemical measurements were stimulated with UV irradiation. The results indicate that the AuNPs simultaneously increase the yield and transfer rate of electrons. On the one hand, the AuNPs accelerate the electrons to transfer from the redox centers of GOx to the ZnO nanorods and hence, the transfer rate of the electrons is obviously increased. On the other hand, together with UV irradiation, the AuNPs effectively facilitate the separation of the photoinduced charges within the ZnO nanorods, and further enable more quantity of holes to participate in the oxidation of GOx(FADH2) to GOx(FAD) during the redox reaction. Therefore, the yield of the electrons is also raised. In comparison to the glucose sensor without the AuNPs, the sensitivity of the glucose sensor with the AuNPs is increased 4.8 times and the low detection limit (signal-to-noise of 3) is decreased 5 times. Besides, the other performance of the glucose sensor with the AuNPs, such as the detection range, selectivity, stability, and the detection accuracy to serum glucose concentration, is also improved accordingly. Therefore, it is an effective method to functionalize ZnO nanorods with AuNPs to enhance the electrochemical and photoelectrochemical performance of enzymatic glucose sensors.

Electrochemical detection of lipopolysaccharide based on rolling circle amplification assisted formation of copper nanoparticles for enhanced resistance generation

In this work, a novel sandwich-type impedimetric biosensor was fabricated for highly sensitive and selective detection of lipopolysaccharide (LPS) from E. coli O55:B5. LPS aptamer I was immobilized onto electrodeposited gold nanoparticles (Au) modified electrode for capturing LPS in buffer and serum. LPS aptamer II and rolling circle amplification (RCA) primer were conjugated with gold nanoparticles (AuNPs) to use as signal tags. LPS was sandwiched between AuNPs/primer/aptamer II bioconjugates and aptamer I. This was followed by extension of RCA, which resulted in long poly-thymine (T) single strand (ssDNA) sequences to adsorb copper ions (Cu2+) into the skeleton of poly-T sequences. Thus, poly-T ssDNA directly served as the specific template for copper nanoparticles (CuNPs) formation with the aid of ascorbic acid (VC). Finally, the formed CuNPs@ssDNA complex promoted the oxidation of pyrocatechol violet (PCV) to insoluble bulky oligomer (precipitation) in the presence of H2O2. The reaction significantly enhanced the resistance signal of LPS quantitative determination. The impedimetric aptasensor exhibited a wide dynamic working range of 0.01 pg/mL ˜ 100 ng/mL with a detection limit of 4.8 fg/mL. This method also showed good selectivity and reproducibility, and demonstrated the applicability of LPS detection in human serum samples, offering a promising avenue for sensitive LPS detection.

Ketjen black/ferrocene dual-doped MOFs and aptamer-coupling gold nanoparticles used as a novel ratiometric electrochemical aptasensor for vanillin detection

In this work, a facile ratiometric electrochemical aptasensor was developed towards sensitive and selective detection of vanillin, based on Ketjen black/ferrocene dual-doped zeolite-like MOFs (Fc-KB/ZIF-8) and electrodeposited gold nanoparticles (AuNPs) coupling with DNA aptamer. Fc-KB/ZIF-8 composites were prepared via one-pot solvothermal reaction and drop-coated on glassy carbon electrode (GCE) surface to form Fc-KB/ZIF-8@GCE. AuNPs were in-situ electro-deposited on the modified GCE. 5′-SH terminated aptamer of vanillin was combined with AuNPs via Au-S coupling to form aptamer-AuNPs/Fc-KB/ZIF-8@GCE as a new sensing platform. Under optimal conditions, electrochemical (square wave voltammetry) curves of this sensing platform were measured in electrolyte solutions containing vanillin. With increase of vanillin concentration (Cvan), vanillin had an increased peak current intensity (Ivan, as response signal). Fc doped into ZIF-8 had slight changes in its peak current intensity (IFc, as reference signal). There is a well plotting linear relationship between Ivan/IFc and the logarithm of Cvan ranging from 10 nM to 0.2 mM, with a low limit of detection of 3 nM. The aptamer-AuNPs/Fc-KB/ZIF-8@GCE was applied as a ratiometric electrochemical aptasensor of vanillin. This aptasensor had sensitive and selective electrochemical signal responses on vanillin, over potential interferents. This aptasensor enabled vanillin detection in real food samples, showing high detection performance. Experimental results testified that this aptasensor had high reliability and practicability for vanillin determination in real samples.

Triple amplified ultrasensitive electrochemical immunosensor for alpha fetoprotein detection based on MoS2@Cu2O-Au nanoparticles

Recently, alpha fetoprotein (AFP), a tumour marker to identify adult primary liver cancer, has attracted increasingly widespread attention. In this work, an ultrasensitive sandwich-type electrochemical biosensor was fabricated for AFP detection. Electrodeposited gold nanoparticles (D-Au NPs) modified on glassy carbon electrodes (GCE) were used as antibody carriers and sensing platforms. Furthermore, a molybdenum disulfide @ cuprous oxide hybrid (MoS2@Cu2O) was prepared to combine gold nanoparticles (Au NPs) as a strategy for achieving signal amplification. The experimental results revealed that molybdenum disulfide @ cuprous oxide-gold nanoparticles (MoS2@Cu2O-Au) showed superb tri-amplification electrochemical signals when catalyzing hydrogen peroxide (H2O2) reduction. This method was demonstrated as a novel tool for the highly reliable separation and quantification of AFP. Under the most suitable experimental conditions, the proposed method exhibits a linear range from 0.1 pg/mL to 50 ng/mL and a low detection limit of 0.037 pg/mL (S/N = 3). The ultrasensitive electrochemical immunosensor has been tested for human serum, and satisfactory recoveries were obtained, indicating that the proposed method is promising for practical applications in the clinical diagnosis of AFP detection.

Amperometric Detection of Tryptophane and Pyridoxine on a Dual Screen-Printed Electrode Modified by Gold Nanoparticles in a Flow-Injection System

A method is developed for the flow-injection amperometric determination of tryptophane and pyridoxine on a screen-printed electrode with electrodeposited gold nanoparticles. The dependence of the analytical signal on the concentrations of tryptophane and pyridoxine on the logarithmic coordinates is linear in the ranges from 5 × 10−7 to 5 × 10−3 and from 5 × 10−8× to 5 × 10–3 M, respectively. A possibility of the simultaneous amperometric determination of tryptophane and pyridoxine on a dual screen-printed electrode modified by gold nanoparticles in a flow-injection system is shown. The developed method is approved in the determination of tryptophane and pyridoxine in medicinal preparations.

Controlled Electrodeposition of Gold on Graphene: Maximization of the Defect-Enhanced Raman Scattering Response.

A reliable method to prepare a surface-enhanced Raman scattering (SERS) active substrate is developed herein, by electrodeposition of gold nanoparticles (Au NPs) on defect-engineered, large area chemical vapour deposition graphene (GR). A plasma treatment strategy is used in order to engineer the structural defects on the basal plane of large area single-layer graphene. This defect-engineered Au functionalized GR, offers reproducible SERS signals over the large area GR surface. The Raman data, along with X-ray photoelectron spectroscopy and analysis of the water contact angle are used to rationalize the functionalization of the graphene layer. It is found that Au NPs functionalization of the "defect-engineered" graphene substrates permits detection of concentrations as low as 10-16 m for the probe molecule Rhodamine B, which offers an outstanding molecular sensing ability. Interestingly, a Raman signal enhancement of up to ≈108 is achieved. Moreover, it is observed that GR effectively quenches the fluorescence background from the Au NPs and molecules due to the strong resonance energy transfer between Au NPs and GR. The results presented offer significant direction for the design and fabrication of ultra-sensitive SERS platforms, and also open up possibilities for novel applications of defect engineered graphene in biosensors, catalysis, and optoelectronic devices.

Hierarchically porous Zr-MOFs labelled methylene blue as signal tags for electrochemical patulin aptasensor based on ZnO nano flower

In this work, the feasibility of a novel sensitive electrochemistry aptasensor for the detection of patulin (PAT) using hierarchically porous metal organic framework@methylene blue connection aptamer as signal tags was demonstrated. The substrate electrode of the aptasensor was prepared by electrodeposited gold nanoparticles (AuNPs) on chitosan-zinc oxide nano flower-modified electrode. Subsequently, the complementary single-stranded DNA was attached to the surface of the modified electrode by Au-S bond. Signal tags self-assemble on the surface of modified electrodes by aptamer-cDNA binding, while methylene blue as mediator for electrochemical detection. Thanks to the large specific surface area provided by zinc oxide nano flower, the electrode can load more signal tags and AuNPs to achieve signal amplification. In presence of PAT, Apt preferentially binds to PAT, causing dissociation of some Apt-cDNA and releasing some signal tags leading, resulting in decreased electrical signals. Under optimal conditions, the change in electrochemical signal was proportional to the logarithm of PAT concentration, from 5 × 10−8-5 × 10-1 μg mL−1, and the detection limit was estimated to be 1.46 × 10-8 μg mL-1. The aptasensor exhibited aceptable reproducibility, renewability, long-term stability and specificity. Moreover, aptasensor was reliable in determination of PAT in spiked apple juice samples.

Controlled Growth of Metal Nanoparticles on Multi-Walled Carbon Nanotubes for Chemical Sensing Applications

We have grown nanoparticles of gold, silver, copper, cobalt and nickel on the surface of carbon nanotubes which are deposited by CVD on gold wires bearing a nickel catalyst layer. A study of the CVD reaction as a function of time revealed that one-minute and ten-minute deposition times yielded qualitatively similar coatings. Metal nanoparticles were grown from electroplating solutions by using the nanotube-coated wire as the working electrode and running a galvanostatic, electrochemical deposition. For gold depositions, we were able to show that varying the conditions of current, plating bath concentration and deposition time allowed control of the size of the deposited nanoparticles within the range of 10 – 150 nm. The morphology of the gold nanoparticles was approximately spherical, except under unique conditions where spiked spheroids, also known as nano-urchins, were observed. By using the gold nanoparticle-decorated CNT electrode as one plate in a parallel-plate capacitor, we were able to show a change in electrical properties, such as capacitance, by comparing voltammograms before and after exposure of the electrode to a dilute solution of organic thiols. This demonstrates the potential utility of the electrode structure as a chemical detector. The two SEM images below show typical results. On the left, CVD carbon nanotube growth prior to electrodeposition of metal nanoparticles; note the presence of nickel catalyst particles at nanotube tips. On the right, carbon nanotube sample after electrodeposition of gold nanoparticles. Figure 1

A novel sensitive laccase biosensor using gold nanoparticles and poly L-arginine to detect catechol in natural water.

In this study, the simple, green, and fast layer-by-layer modification of the glassy carbon electrode was mainly performed by electrodeposition of gold nanoparticles and then, poly-l-arginine, and finally, laccase was covalently bonded to poly-l-arginine using glutaraldehyde. This type of fabrication is used for the first time for catechol detection, which provides a bioelectrocatalytic cycle for electron transport in the presence of laccase that results in sensitive and fast detection of catechol. The scanning electron microscopy, Fourier-transform infrared spectroscopy, and electrochemical studies were performed to confirm successful immobilization of the enzyme. The biosensor response was linear in a wide range of catechol trace concentrations, 24.90-274.00nM, with the detection limit of 18.00nM. Values of Km , α, n, and Ks for the immobilized enzyme were calculated to be 1.25×10-2 µM, 0.56, 3.19, and 0.28Sec-1 , respectively. It was examined in real sample successfully confirming it is capable of measuring catechol in natural water.

Surface engineering of commercial Ni foams for stable Li metal anodes

The short life span of lithium metal anodes (LMAs) due to dendrite growth and low coulombic efficiency (CE) has been regarded as the bottleneck in developing next-generation high-energy-density lithium metal based secondary batteries. Employing three-dimensional (3D) current collectors is one approach to reduce the effective current density and delay dendrite growth. Commercial Ni foam, in spite of its high electronic conductivity and 3D topology, has not been considered for this application due to its low specific surface area and lithiophobic nature. In this study, we develop a surface engineering strategy to uniformly coat lithiophilic AuLi3 particles on Ni foam skeletons through lithiation of electrodeposited gold nanoparticles. In comparison with the bare Ni foam, the AuLi3@Ni foam is more lithiophilic, significantly lowering the nucleation energy barrier and enhancing the uniformity for Li deposition. Such a structure results in effective suppression of Li dendrite growth in the void space of the foam. As a result, the AuLi3@Ni foam current collector based LMAs can run for 740 h without cell failure in a symmetric cell. Furthermore, the Li-AuLi3@Ni foam|LiFePO4 full cell shows an excellent capacity retention of 43.8% with a high CE of 99.2% at 1C for 500 cycles. This work further illustrates the critical importance of surface lithiophilicity in guiding lithium cycling and suggests engineering the skeleton surface of commercial metal foam current collectors is important to improve 3D structured LMAs.