Evaluation of electrodeposition synthesis of gold nanodendrite on screen-printed carbon electrode for nonenzymatic ascorbic acid sensor

Gold nanodendrite (AuND) is a type of gold nanoparticles with dendritic or branching structures that offers advantages such as large surface area and high conductivity to improve electrocatalytic performance of electrochemical sensors. AuND structures can be synthesized using electrodeposition method utilizing cysteine as growth directing agent. This method can simultaneously synthesize and integrate the gold nanostructures on the surface of the electrode. We conducted a comprehensive study on the synthesis of AuND on screen-printed carbon electrode (SPCE)-based working electrode, focusing on the optimization of electrodeposition parameters, such as applied potential, precursor solution concentration, and deposition time. The measured surface oxide reduction peak current and electrochemical surface area from cyclic voltammogram were used as the optimization indicators. We confirmed the growth of dendritic gold nanostructures across the carbon electrode surface based on FESEM, EDS, and XRD characterizations. We applied the SPCE/AuND electrode as a nonenzymatic sensor on ascorbic acid (AA) and obtained detection limit of 16.8 μM, quantification limit of 51.0 μM, sensitivity of 0.0629 μA μM-1, and linear range of 180-2700 μM (R2 value = 0.9909). Selectivity test of this electrode against several interferences, such as uric acid, dopamine, glucose, and urea, also shows good response in AA detection.

Gold nanowires-based sensor for quantification of H2O2 released by human airway epithelial cells

Hydrogen peroxide (H2O2) is a biomarker relevant for oxidative stress monitoring. Most chronic airway diseases are characterized by increased oxidative stress. To date, the main methods for the detection of this analyte are expensive and time-consuming laboratory techniques such as fluorometric and colorimetric assays. There is a growing interest in the development of electrochemical sensors for H2O2 detection due to their low cost, ease of use, sensitivity and rapid response. In this work, an electrochemical sensor based on gold nanowire arrays has been developed. Thanks to the catalytic activity of gold against hydrogen peroxide reduction and the high surface area of nanowires, this sensor allows the quantification of this analyte in a fast, efficient and selective way. The sensor was obtained by template electrodeposition and consists of gold nanowires about 5 μm high and with an average diameter of about 200 nm. The high active surface area of this electrode, about 7 times larger than a planar gold electrode, ensured a high sensitivity of the sensor (0.98 μA μM-1cm-2). The sensor allows the quantification of hydrogen peroxide in the range from 10 μM to 10 mM with a limit of detection of 3.2 μM. The sensor has excellent properties in terms of reproducibility, repeatability and selectivity. The sensor was validated by quantifying the hydrogen peroxide released by human airways A549 cells exposed or not to the pro-oxidant compound rotenone. The obtained results were validated by comparing them with those obtained by flow cytometry after staining the cells with the fluorescent superoxide-sensitive Mitosox Red probe giving a very good concordance.

Au-Pt-Ni nanochains as dopamine catalysts: role of elements and their spatial distribution

Multi-element materials can improve biosensing ability as each element can catalyze different steps in a reaction pathway. By combining Pt and Ni on self-assembled 1D gold nanochains and controlling their spatial distribution, a detailed understanding of each element's role in dopamine oxidation is developed. In addition, the developed synthesis process provides a simple way to fabricate multi-element composites for electrocatalytic applications based on electrical double-layer formation on the surface of charged nanoparticles. The performance parameters of the catalyst, such as its sensitivity, limit of detection, and range of operation for dopamine sensing, are optimized by changing the relative ratios of Pt : Ni and the morphology of the Pt and Ni domains, using the developed understanding. The morphology of the domains also affects the oxidation state of Ni, which is crucial to the performance of the electrocatalyst.

In Situ Deposition of Gold Nanoparticles and L-Cysteine on Screen-Printed Carbon Electrode for Rapid Electrochemical Determination of As(III) in Water and Tea

In this study, a screen-printed carbon electrode (SPCE) based on in situ deposition modification was developed for the sensitive, rapid, easy and convenient determination of As(III) in water and tea by linear sweep anodic stripping voltammetry (LSASV). The screen-printed carbon electrodes were placed in a solution consisting of As(III) solution, chlorauric acid and L-cysteine. Under certain electrical potential, the chloroauric acid was reduced to gold nanoparticles (AuNPs) on the SPCE. L-cysteine was self-assembled onto AuNPs and promoted the enrichment of As(III), thus enhancing the determination specificity and sensitivity of As(III). The method achieved a limit of determination (LOD) of 0.91 ppb (µg L^-1), a linear range of 1~200 µg L^-1, an inter-assay coefficient of variation of 5.3% and good specificity. The developed method was successfully applied to the determination of As(III) in tap water and tea samples, with a recovery rate of 93.8%~105.4%, and further validated by inductively coupled plasma mass spectrometry (ICP-MS). The developed method is rapid, convenient and accurate, holding great promise in the on-site determination of As(III) in tap water and tea leaves, and it can be extended to the detection of other samples.

Detection of a Double-Stranded MGMT Gene Using Electrochemically Reduced Graphene Oxide (ErGO) Electrodes Decorated with AuNPs and Peptide Nucleic Acids (PNA)

The ability to detect double-stranded DNA (dsDNA) as a biomarker without denaturing it to single-stranded DNA (ss-DNA) continues to be a major challenge. In this work, we report a sandwich biosensor for the detection of the ds-methylated MGMT gene, a potential biomarker for brain tumors and breast cancer. The purpose of this biosensor is to achieve simultaneous recognition of the gene sequence, as well as the presence of methylation. The biosensor is based on reduced graphene oxide (rGO) electrodes decorated with gold nanoparticles (AuNPs) and uses Peptide Nucleic Acid (PNA) that binds to the ds-MGMT gene. The reduction of GO was performed in two ways: electrochemically (ErGO) and thermally (TrGO). XPS and Raman spectroscopy, as well as voltammetry techniques, showed that the ErGO was more efficiently reduced, had a higher C/O ratio, showed a smaller crystallite size of the sp2 lattice, and was more stable during measurement. It was also revealed that the electro-deposition of the AuNPs was more successful on the ErGO surface due to the higher At% of Au on the ErGO electrode. Therefore, the ErGO/AuNPs electrode was used to develop biosensors to detect the ds-MGMT gene. PNA, which acts as a bio-recognition element, was used to form a self-assembled monolayer (SAM) on the ErGO/AuNPs surface via the amine-AuNPs interaction, recognizing the ds-MGMT gene sequence by its invasion of the double-stranded DNA and the formation of a triple helix. The methylation was then detected using biotinylated-anti-5mC, which was then measured using the amperometric technique. The selectivity study showed that the proposed biosensor was able to distinguish between blank, non-methylated, non-complementary, and target dsDNA spiked in mouse plasma. The LOD was calculated to be 0.86 pM with a wide linear range of 1 pM to 50 µM. To the best of our knowledge, this is the first report on using PNA to detect ds-methylated DNA. This sandwich design can be modified to detect other methylated genes, making it a promising platform to detect ds-methylated biomarkers.

Nanoscale electrodeposition: Dimension control and 3D conformality

Electrodeposition with a long history has been considered one of the important synthesis techniques for applying various applications. It is a feasible route for fabricating nanostructures using diverse materials due to its simplicity, cost-effectiveness, flexibility, and ease of reaction control. Herein, we mainly focus on the nanoscale electrodeposition with respect to dimension control and three-dimensional (3D) conformality. The principles of electrodeposition, dimensional design of materials, and uniform coatings on various substrates are presented. We introduce that manipulating synthesis parameters such as precursors, applied current/voltage, and additives affect the synthesis reaction, resulting in not only dimensional control of materials from three-dimensional structures to zero-dimensional atomic-level but also conformal coatings on complicated substrates. Various cases regarding morphology control of metal (hydro)oxides, metals, and metal-organic frameworks according to electrodeposition conditions are summarized. Lastly, recent studies of applications such as batteries, photoelectrodes, and electrocatalysts using electrodeposited materials are summarized. This review represents significant advances in the nanoscale design of materials through methodological approaches, which are highly attractive from both academic and commercial aspects.

Inherent Surface Activation of Laser-Scribed Graphene Decorated with Au and Ag Nanoparticles: Simultaneous Electrochemical Behavior toward Uric Acid and Dopamine

Laser-scribed graphene electrodes (LSGEs) have attracted great attention for the development of electrochemical (bio)sensors due to their excellent electronic properties, large surface area, and high porosity, which enhances the electrons' transfer rate. An increasing active surface area and defect sites are the quickest way to amplify the electrochemical sensing attributes of the electrodes. Here, we have found that the activation procedure coupled to the electrodeposition of metal nanoparticles resulted in a significant amplification of the active area and the analytical performance. This preliminary study is supported by the demonstration of the simultaneous electrochemical sensing of dopamine (DA) and uric acid (UA) by the electrochemically activated LSGEs (LSGE*s). Furthermore, the electrodeposition of two different metal nanoparticles, gold (Au) and silver (Ag), was performed in multiple combinations on working and reference electrodes to investigate the enhancement in the electrochemical response of LSGE*s. Current enhancements of 32, 27, and 35% were observed from LSGE* with WE:Au/RE:LSG/CE:LSGE, WE:Au/RE:Au/CE:LSGE, and WE:Au/RE:Ag/CE:LSGE, compared to the same combinations of LSGEs without any surface activation. A homemade and practical potentiostat, KAUSTat, was used in these electrochemical depositions in this study. Among all of the combinations, the surface area was increased 1.6-, 2.0-, and 1.2-fold for WE:Au/RE:LSG/CE:LSGE, WE:Au/RE:Au/CE:LSGE, and WE:Au/RE:Ag/CE:LSGE prepared from LSGE*s, respectively. To evaluate the analytical performance, DA and UA were detected simultaneously in the presence of ascorbic acid. The LODs of DA and UA are calculated to be ∼0.8 and ∼0.6 μM, respectively. Hence, this study has the potential to open new insights into new surface activation strategies with a combination of one-step nanostructured metal depositions by a custom-made potentiostat. This novel strategy could be an excellent and straightforward method to enhance the electrochemical transducer sensitivity for various electrochemical sensing applications.

Glucose Biosensor Based on Dendritic Gold Nanostructures Electrodeposited on Graphite Electrode by Different Electrochemical Methods

In this research, we have demonstrated a one-step electrochemical deposition of dendritic gold nanostructures (DGNs) on a graphite rod (GR) electrode without any template, seeds, surfactants, or stabilizers. Three electrochemical methods, namely, constant potential amperometry (CPA), pulse amperometry, and differential pulse voltammetry, were used for DGN synthesis on GR electrode and further application in enzymatic glucose biosensors. Formed gold nanostructures, including DGNs, were characterized by a field emission scanning electron microscopy. The optimal concentration of HAuCl4 (6.0 mmol L−1), duration of DGNs synthesis (400 s), electrodeposition potential (−0.4 V), and the best electrochemical method (CPA) were determined experimentally. Then the enzyme, glucose oxidase, was adsorbed on the surface of DGNs and covalently cross-linked with glutaraldehyde vapor. The enzymatic glucose biosensor based on DGNs electrodeposited at optimal conditions and modified with glucose oxidase showed a quick response (less than 3 s), a high saturation current (291 μA), appropriate linear range (up to 9.97 mmol L−1 of glucose, R2 = 0.9994), good repeatability (RSD 2.4, 2.2 and 1.5% for 2, 30, 97 mmol L−1 of glucose), low limit of detection (0.059 mmol L−1, S/N = 3) and good stability. Additionally, this biosensor could be successfully applied for glucose determination in real samples with good accuracy. These results proved the principle of enzymatic glucose biosensor development based on DGNs as the basis for further investigations.

Improved Hardness and Thermal Stability of Nanocrystalline Nickel Electrodeposited with the Addition of Cysteine

Experiments were conducted for the study of the effect of cysteine addition on the microstructure of nanocrystalline Ni films electrodeposited from a nickel sulfate-based bath. Furthermore, the thermal stability of the nanostructure of Ni layers processed with cysteine addition was also investigated. It was found that with increasing cysteine content in the bath, the grain size decreased, while the dislocation density and the twin fault probability increased. Simultaneously, the hardness increased due to cysteine addition through various effects. Saturation in the microstructure and hardness was achieved at cysteine contents of 0.3-0.4 g/L. Moreover, the texture changed from (220) to (200) with increasing the concentration of cysteine. The hardness of the Ni films processed with the addition of 0.4 g/L cysteine (∼6800 MPa) was higher than the values obtained for other additives in the literature (<6000 MPa). This hardness was further enhanced to ∼8400 MPa when the Ni film was heated up to 500 K. It was revealed that the hardness remained as high as 6000 MPa even after heating up to 750 K, while for other additives, the hardness decreased below 3000 MPa at the same temperature.

Electrochemical dual-aptamer biosensors based on nanostructured multielectrode arrays for the detection of neuronal biomarkers

Multielectrode arrays (MEAs) have been increasingly used for the development of biosensors due to their capability to record signals from multiple channels, fast mass transfer rates, and high spatial resolution. Alzheimer's disease (AD) is often associated with mitochondrial dysfunction, which is closely related to reduced levels of adenosine triphosphate (ATP). Therefore, simultaneous detection of ATP together with amyloid-β oligomers (AβO), a reliable biomarker for AD, can potentially advance the early detection of Alzheimer's disease. In this work, a dual-aptamer modified MEA chip was developed that consists of microelectrodes modified with electrodeposited 3D nanostructures (3D-GMEs). Electrodeposition methods, deposition potential, and deposition time were systematically altered and the active surface areas as well as the electrode morphologies were characterized by cyclic voltammetry and scanning electron microscopy. The nanostructured microelectrodes were sequentially modified with AβO and ATP specific aptamer receptors. To achieve the modification of different aptamer receptors at different 3D-GMEs of the same MEA chip, electrochemical cleaning was applied to individual 3D-GMEs. Ferrocene labels were attached to the aptamer receptors to enable amperometric signaling after target-aptamer binding. The developed aptasensor showed a linear detection range from 1 pM to 200 nM for the detection of AβO and from 0.01 nM to 1000 nM for the detection of ATP. Finally, ATP and AβO were detected simultaneously in the same analyte solution by the same sensor chip, which could support the early detection of AD, provide comprehensive information about the health status of the patient, and be helpful for pathological studies of neurodegenerative diseases.

Spontaneous and field-induced crystallographic reorientation of metal electrodeposits at battery anodes

The propensity of metal anodes of contemporary interest (e.g., Li, Al, Na, and Zn) to form non-planar, dendritic morphologies during battery charging is a fundamental barrier to achievement of full reversibility. We experimentally investigate the origins of dendritic electrodeposition of Zn, Cu, and Li in a three-electrode electrochemical cell bounded at one end by a rotating disc electrode. We find that the classical picture of ion depletion-induced growth of dendrites is valid in dilute electrolytes but is essentially irrelevant in the concentrated (≥1 M) electrolytes typically used in rechargeable batteries. Using Zn as an example, we find that ion depletion at the mass transport limit may be overcome by spontaneous reorientation of Zn crystallites from orientations parallel to the electrode surface to dominantly homeotropic orientations, which appear to facilitate contact with cations outside the depletion layer. This chemotaxis-like process causes obvious texturing and increases the porosity of metal electrodeposits.

Seed-mediated Electrochemically Developed Au Nanostructures with Boosted Sensing Properties: An Implication for Non-enzymatic Glucose Detection

A new approach has been developed to improve sensing performances of electrochemically grown Au nanostructures (AuNSs) based on the pre-seeding of the electrode. The pre-seeding modification is simply carried out by vacuum thermal deposition of 5 nm thin film of Au on the substrate followed by thermal annealing at 500 °C. The electrochemical growth of AuNSs on the pre-seeded substrates leads to impressive electrochemical responses of the electrode owing to the seeding modification. The dependence of the morphology and the electrochemical properties of the AuNSs on various deposition potentials and times have been investigated. For the positive potentials, the pre-seeding leads to the growth of porous and hole-possess networks of AuNSs on the surface. For the negative potentials, AuNSs with carved stone ball shapes are produced. The superior electrode was achieved from AuNSs developed at 0.1 V for 900 s with pre-seeding modification. The sensing properties of the superior electrode toward glucose detection show a high sensitivity of 184.9 µA mM⁻¹ cm⁻², with a remarkable detection limit of 0.32 µM and a wide range of linearity. The excellent selectivity and reproducibility of the sensors propose the current approach as a large-scale production route for non-enzymatic glucose detection.

Recent advancement in the electrocatalytic synthesis of ammonia

Ammonia can not only be used as an active nitrogen component of nitrogen fertilizers, fibers, explosives, etc., but also provides a high energy density and carbon free energy carrier. Currently, ammonia is industrially synthesized by the Haber Bosch process at high temperature and high pressure, which results in high energy loss and a serious greenhouse effect. The electrocatalytic nitrogen reduction reaction (NRR) is a sustainable and environmentally friendly strategy for the synthesis of ammonia. Although lots of electrocatalysts have been developed for this reaction, further breakthroughs are needed in catalytic activity, selectivity and Faraday efficiency to meet the large-scale commercial demand. In this review, the recent advance in NRR electrocatalysis is thoroughly commented on. Different kinds of electrocatalysts used in ammonia synthesis (including single atom catalysts, metal oxide catalysts, nanocomposite catalysts, and metal free catalysts) are introduced. The reaction mechanism of the NRR is discussed in detail. The structure-function relationship and efficient strategies to improve the ammonia yield are clearly discussed. The effect of the electronic structure and morphology of catalysts on the selectivity of the NRR is highlighted. The research directions and perspectives on the further development of more efficient electrocatalysts for the NRR are provided.

Electrochemical nano-genosensor for highly sensitive detection of miR-21 biomarker based on SWCNT-grafted dendritic Au nanostructure for early detection of prostate cancer

MicroRNAs (miRNAs) appear as a novel reliable candidate in biomarkers for early diagnosis of cancer. Due to their roles in various types of cancer, their potential as a diagnostic biomarker is getting more attention. Here, a novel electrochemical biosensor for detection of miR-21 was demonstrated, through combining the advantages of electrochemical methods and nanomaterials with the selectivity of oligonucleotides, based on thiolated receptor probe-functionalized dendritic gold nanostructures (den-Au) via the self-assembly monolayer (SAM) process which grafted on the single-wall carbon nanotubes (SWCNTs) platform on the surface of the fluorine-doped tin oxide (FTO) electrode. Cadmium ions (Cd²⁺) were used as signal units and also signal amplification substance which labeled before on miR-21 target. The oxidation signal of Cd²⁺ as a signal unit was measured by differential pulse voltammetry (DPV) technique that had a very wide linear relationship with the concentration of miR-21 target (0.01 fmol L^-1 to 1 μmol L^-1) and low experimental detection limit of 0.01 fmol L^-1. Furthermore, fabricated biosensor showed acceptable performance in human serum samples and also good selectivity indiscriminate between the complementary target and non-complementary one, so this nano-genosensor can clinically be used for prostate cancer diagnosis through the detection of miR-21 in human serum samples.

Formation of 3-Dimensional Gold, Copper and Palladium Microelectrode Arrays for Enhanced Electrochemical Sensing Applications

Microelectrodes offer higher current density and lower ohmic drop due to increased radial diffusion. They are beneficial for electroanalytical applications, particularly for the detection of analytes at trace concentrations. Microelectrodes can be fabricated as arrays to improve the current response, but are presently only commercially available with gold or platinum electrode surfaces, thus limiting the sensing of analytes that are more electroactive on other surfaces. In this work, gold (Au), copper (Cu), and palladium (Pd) are electrodeposited at two different potentials into the recessed holes of commercial microelectrode arrays to produce 3-dimensional (3D) spiky, dendritic or coral-like structures. The rough fractal structures that are produced afford enhanced electroactive surface area and increased radial diffusion due to the 3D nature, which drastically improves the sensitivity. 2,4,6-trinitrotoluene (TNT), carbon dioxide gas (CO₂), and hydrogen gas (H₂) were chosen as model analytes in room temperature ionic liquid solvents, to demonstrate improvements in the sensitivity of the modified microelectrode arrays, and, in some cases (e.g., for CO₂ and H₂), enhancements in the electrocatalytic ability. With the deposition of different materials, we have demonstrated enhanced sensitivity and electrocatalytic behaviour towards the chosen analytes.

Biosensor Applications of Electrodeposited Nanostructures

The development of biosensors for a range of analytes from small molecules to proteins to oligonucleotides is an intensely active field. Detection methods based on electrochemistry or on localized surface plasmon responses have advanced through using nanostructured electrodes prepared by electrodeposition, which is capable of preparing a wide range of different structures. Supported nanoparticles can be prepared by electrodeposition through applying fixed potentials, cycling potentials, and fixed current methods. Nanoparticle sizes, shapes, and surface densities can be controlled, and regular structures can be prepared by electrodeposition through templates. The incorporation of multiple nanomaterials into composite films can take advantage of the superior and potentially synergistic properties of each component. Nanostructured electrodes can provide supports for enzymes, antibodies, or oligonucleotides for creating sensors against many targets in areas such as genomic analysis, the detection of protein antigens, or the detection of small molecule metabolites. Detection can also be performed using electrochemical methods, and the nanostructured electrodes can greatly enhance electrochemical responses by carefully designed schemes. Biosensors based on electrodeposited nanostructures can contribute to the advancement of many goals in bioanalytical and clinical chemistry.

Liquid Cell Transmission Electron Microscopy Sheds Light on The Mechanism of Palladium Electrodeposition

Electrodeposition is widely used to fabricate tunable nanostructured materials in applications ranging from biosensing to energy conversion. A model based on 3D island growth is widely accepted in the explanation of the initial stages of nucleation and growth in electrodeposition. However, there are regions in the electrodeposition parameter space where this model becomes inapplicable. We use liquid cell transmission electron microscopy along with post situ scanning electron microscopy to investigate electrodeposition in this parameter space, focusing on the effect of the supporting electrolyte, and to shed light on the nucleation and growth of palladium. Using a collection of electron microscopy images and current time transients recorded during electrodeposition, we discover that electrochemical aggregative growth, rather than 3D island growth, best describes the electrodeposition process. We then use this model to explain the change in the morphology of palladium electrodeposits from spherical to open clusters with nonspherical morphology when HCl is added to the electrolyte solution. The enhanced understanding of the early stages of palladium nucleation and growth and the role of electrolyte in this process provides a systematic route toward the electrochemical fabrication of nanostructured materials.

Ambient Electrochemical Synthesis of Ammonia from Nitrogen and Water Catalyzed by Flower-Like Gold Microstructures

Electrochemical nitrogen reduction to ammonia is proposed as a promising alternative to the Haber-Bosch process because it can be driven by renewable electricity at ambient conditions. Currently, the development of such a process is hampered by the lack of efficient electrocatalysts for the nitrogen reduction reaction (NRR). Herein, we report a super-rapid approach for the synthesis of flower-like Au microstructures (Au flowers) within 5 s. The obtained Au structures are assembled by staggered nanoplates as building blocks, which provide abundant electrocatalytically active sites for the NRR. The Au flowers achieve a high performance (NH₃ yield: 25.57 μg h^-1  mg_cat. ^-1 ; faradaic efficiency: 6.05 %), 100 % selectivity (no N₂ H₄ production), and long-term durability toward the electrochemical ammonia production. The work is highly valuable for the rapid synthesis of active catalysts for the NRR.

Aminosilane-Assisted Electrodeposition of Gold Nanodendrites and Their Catalytic Properties

A promising alternative route for the synthesis of three-dimensional Au dendrites was developed by direct electrodeposition from a solution of HAuCl4 containing 3-aminopropyltriethoxysilane (APTS). Ultraviolet-visible spectroscopy, fourier transform infrared spectroscopy and isothermal titration calorimetry were used to study the interaction of APTS in electrolyte. The effect of APTS on the formation of the hierarchical structure of Au dendrites was investigated by cyclic voltammetry, rotating disk electrode, electrochemical impedance spectroscopy and quartz crystal microbalance. The growth directions of the trunks and branches of the Au dendrites can be controlled by sweep-potential electrodeposition to obtain more regular structures. The efficacy of as-synthesised Au dendrites was demonstrated in the enhanced electro-catalytic activity to methanol electro-oxidation and the high sensitivity of glucose detection, which have potential applications in direct-methanol fuel cells and non-enzymatic electrochemical glucose biosensors, respectively.

Surface-plasmon-induced azo coupling reaction between nitro compounds on dendritic silver monitored by surface-enhanced Raman spectroscopy

Azo coupling reactions with a 4-NTP-functionalized Ag-Ds/GCE composites.

Controlled synthesis of dendritic gold nanostructures by graphene oxide and their morphology-dependent performance for iron detection in coastal waters

Dendritic gold nanostructures were controllably synthesized by graphene oxide for voltammetric determination of Fe(iii) in coastal waters.

Sheetlike gold nanostructures/graphene oxide composites via a one-pot green fabrication protocol and their interesting two-stage catalytic behaviors

Au nanoplate/GO composites are facilely synthesized via a one-pot green protocol. The composites display a fascinating two-stage catalytic behavior, where the catalytic reactivity of the latter stage increases substantially by a factor of 9 times.

On-Electrode Synthesis of Shape-Controlled Hierarchical Flower-Like Gold Nanostructures for Efficient Interfacial DNA Assembly and Sensitive Electrochemical Sensing of MicroRNA

The performance for biomolecular detection is closely associated with the interfacial structure of a biosensor, which profoundly affects both thermodynamics and kinetics of the assembly, binding and signal transduction of biomolecules. Herein, it is reported on a one-step and template-free on-electrode synthesis method for making shape-controlled gold nanostructures on indium tin oxide substrates, which provide an electrochemical sensing platform for ultrasensitive detection of nucleic acids. Thus-prepared hierarchical flower-like gold nanostructures (HFGNs) possess large surface area that can readily accommodate the assembly of DNA probes for subsequent hybridization detection. It is found that the sensitivity for electrochemical DNA sensing is critically dependent on the morphology of HFGNs. By using this new strategy, a highly sensitive electrochemical biosensor is developed for label-free detection of microRNA-21 (miRNA-21), a biomarker for lung cancers. Importantly, it is demonstrated that this biosensor can be employed to measure the miRNA-21 expression level from human lung cancer cell (A549) lysates and worked well in 100% serum, suggesting its potential for applications in clinical diagnosis and a wide range of bioanalysis.

Tuning photothermal properties of gold nanodendrites for in vivo cancer therapy within a wide near infrared range by simply controlling their degree of branching

Although dendritic nanoparticles have been prepared by many different methods, control over their degree of branching (DB) is still impossible, preventing us from understanding the effect of the DB on the properties of the nanodendrites as cancer therapeutics. Herein, we developed a novel seed-mediated method to prepare gold nanodendrites (AuNDs) in an organic solvent using long chain amines as a structural directing agent. We discovered that the DB could be tuned facilely by simply adjusting synthetic parameters, such as the solvent type, the type and concentration of the long chain amines. We found that DB tuning resulted in dramatic tunability in the optical properties in the near infrared (NIR) range, which led to significantly different performance in the photothermal cancer therapy. Our in vitro and in vivo studies revealed that AuNDs with a higher DB were more efficient in photothermal tumor destruction under a lower wavelength NIR irradiation. In contrast, those with a lower DB performed better in tumor destruction under a higher wavelength NIR irradiation, indicating that AuNDs of even lower DB should have even better photothermal cancer therapy efficiency within the second NIR window. Thus, the tunable optical properties of AuNDs in the NIR range allow us to selectively determine a suitable laser wavelength for the best cancer therapeutic performance.

Electrochemically fabricated gold dendrites with underpotential deposited silver monolayers for a bimetallic SERS-active substrate

SERS of Ag-covered Au-dendrites (Ag–Au-Ds) outperforms that of Au-Ds at a specific 633 nm laser excitation, and is attributed to improved chemical mechanism (CM) SERS with the Ag–p-NTP bonding and the p-NTP molecular architecture.

Pulse reverse electrodeposited NiCo2S4 nanostructures as efficient counter electrodes for dye-sensitized solar cells

Dendrite nanostructures of NiCo₂S₄ fabricated by a simple and cost effective electrodeposition method and its performance as a counter electrode in dye-sensitized solar cells.

Anisotropic growth and structure-dependent photoresponse activity of multi-level one-dimensional PbS nano-architectures

PbS nanostructures with three-fold hierarchy in 〈111〉 directions for designing optoelectronic devices.

Sharp-interface model of electrodeposition and ramified growth

We present a sharp-interface model of two-dimensional ramified growth during quasisteady electrodeposition. Our model differs from previous modeling methods in that it includes the important effects of extended space-charge regions and nonlinear electrode reactions. The electrokinetics is described by a continuum model, but the discrete nature of the ions is taken into account by adding a random noise term to the electrode current. The model is validated by comparing its behavior in the initial stage with the predictions of a linear stability analysis. The main limitations of the model are the restriction to two dimensions and the assumption of quasisteady transport.