3D Au Research Articles

Highly Branched Au Superparticles as Efficient Photothermal Transducers for Optical Neuromodulation.

Precise neuromodulation is critical for interrogating cellular communication and treating neurological diseases. Nanoscale transducers have emerged as effective interfaces to exert photothermal effects and modulate neural activities with a high spatiotemporal resolution. Ideal materials for this application should possess strong light absorption, high photothermal conversion efficiency, and great biocompatibility for clinical translation. Here, we show that the structurally designed 3D Au superparticles with a highly branched morphology can be promising candidates for nongenetic and remote neuromodulation. The structure-induced blackbody-like absorption endows Au superparticles with photothermal conversion efficiency over 90%, much higher than that of conventional Au nanorods. With the biocompatible polydopamine ligands, Au superparticles can be readily interfaced with primary mouse hippocampal neurons and other cells and can photostimulate or inhibit their activities in both cell networks or with a single-cell resolution. These findings highlight the importance of structural designs as powerful tools to promote the performance of plasmonic materials in neuromodulation and related research of neuroscience and neuroengineering.

Advanced 3D Micro‐Electrodes for On‐Chip Zinc‐Ion Micro‐Batteries

AbstractThe development of high‐performance planar micro‐batteries featuring safer, cost‐effective systems is crucial for powering smart devices such as medical implants, micro‐robots, micro‐sensors, and the Internet of Things (IoT). However, current on‐chip micro‐batteries suffer from limited energy density within constrained device footprints due to challenges in effectively loading high‐capacity active materials onto micro‐electrodes. Innovative designs for advanced micro‐electrodes are needed for on‐chip micro‐batteries. This work introduces advanced, highly porous 3D gold (Au) scaffold‐based interdigitated electrodes (IDEs) as current collectors, which enable effective loading of active materials (Zn and polyaniline) without compromising overall conductivity and significantly increase active mass loading. These 3D Au scaffold‐based micro‐batteries (3D P‐ZIMB) offer substantially higher energy storage performance (≈135% enhancement) compared to conventional micro‐batteries (C‐ZIMB) when materials loaded onto flat Au IDEs. Furthermore, the 3D P‐ZIMB demonstrates higher areal capacities (≈35 µAh cm−2) and areal energy (≈31.05 µWh cm−2) than most high‐performance on‐chip micro‐batteries, and it delivers a much higher areal power (≈3584.35 µW cm−2) than high‐performance on‐chip micro‐supercapacitors. In‐depth postmortem investigations reveal that the 3D P‐ZIMB avoids issues like material peeling, sluggish electrolyte ion diffusion, and dendrite formation on the anode, while maintaining identical material morphologies and structural characteristics. Therefore, this study presents a smart strategy to enhance the electrochemical performance of planar micro‐batteries and advance the field of on‐chip micro‐battery research.

Composite PEDOT-PSS based highly sensitive electrochemical sensors for sensing glucose from human saliva

Here we report two composites, especially two different 2D materials and Au nanoparticle composite with conducting polymer PEDOT-PSS as electrodes for highly sensitive, cost effective and reliable biosensors. Conducting polymer composite electrodes of AuNP/WS2/PEDOT-PSS and AuNP/GO/PEDOT-PSS were prepared by electrochemical deposition and were studied using various structural and electrochemical techniques. XRD, FTIR and SEM have been used for structural characterization which confirmed the elemental compositions of these composite electrodes. Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) were used to examine the charge transfer kinetics and electroactive properties of the modified electrodes. Impedance spectra analysis had shown the reduced charge transfer resistance and diffusive property of AuNP/WS2/PEDOT-PSS electrodes compared to AuNP/GO/PEDOT-PSS. To demonstrate biosensing advantages of these electrodes, interaction between covalently immobilized glucose oxidase (GlOx) enzyme and D-glucose was monitored via chronoamperometry and CV. GlOx/AuNP/WS2/PEDOT-PSS/ITO yielded wider linear range from 0.74 to 440.67 µM towards the oxidation of glucose with high selectivity and lower limit of detection (LOD) of 1 µM. AuNP/GO/PEDOT-PSS/ITO composite electrode exhibited linearity in the range 3.84–373.33 µM and LOD 2.33 µM. Better sensitivity and wider linear range of GlOx/AuNP/WS2/PEDOT-PSS/ITO has been assigned to special layered structure as sheets formed by incorporation of WS2 to PEDOT-PSS. Validation of the glucose sensors has shown satisfactory results using real saliva samples. Study suggests use of conducting polymer, 2D layered material and metal nanoparticle composite electrodes based sensors offer wider linearity range and higher sensitivity for stable, reliable, cost- effective sensor electrodes which can be used easily in non-clinical diagnostics.

Enabling Ab Initio Molecular Dynamics under Bias: The CP2K+SMEAGOL Interface for Integrating Density Functional Theory and Non-Equilibrium Green Functions.

Density functional theory (DFT) combined with non-equilibrium Green's functions (NEGF) is a powerful approach to model quantum transport under external bias potentials at reasonable computational cost. In this work, we present a new interface between the popular mixed Gaussian/plane waves electronic structure package, CP2K, and the NEGF, code SMEAGOL, the most feature-rich implementation of DFT-NEGF available for CP2K to date. The CP2K+SMEAGOL interface includes the implementation of current induced forces. We verify this implementation for a variety of systems: an infinite 1D Au wire, a parallel-plate capacitor, and a Au-H2-Au junction. We find good agreement with SMEAGOL calculations performed with SIESTA for the same systems and with the example of a solvated Au wire demonstrating for the first time that DFT-NEGF can be used to perform molecular dynamics simulations under bias of large-scale condensed phase systems under realistic operating conditions.

Au NPs modified Ni-B nanosheets/graphene oxide three-dimensional network as label-free electrochemical immunosensor for the detection of diethylstilbestrol

Three-dimensional (3D) network provide a promising platform for construction of high sensitive electrochemical immunosensor due to the benefits of high specific surface area and electron mobility. Herein, a sensitive label-free electrochemical immunosensor based on Au nanoparticles modified Ni-B nanosheets/graphene matrix was constructed to detect diethylstilbestrol (DES). The 3D network not only could increase the electron transport rate and surface area, but also could provide confinement area, which is conducive to increases the collision frequency with the active site. Moreover, Au NPs also have good biocompatibility, which is beneficial for ligating antibodies. Benefiting from the 3D network structure and Au collective effect, the electrochemical immunosensor possess sterling detection ability with wide linear response range (0.00038–150 ng/mL) and low detection limit (31.62 fg/mL). Moreover, the constructed immunosensor can also be extend to detect DES in Tap-water and river water. This work may provide a novel material model for the construction of high sensitive immunosensor.

Carbon dots as reductants to fabricate three-dimensional Au mesoflowers as SERS substrates

Abstract Reductive carbon dots (CDs) were obtained by a hydrothermal method using citric acid and diethylenetriamine as carbon sources. Three-dimensional Au mesoflowers (3D Au MFs) could be fabricated by directly mixing HAuCl4 and CD solution without using any extra reductant and morphology-directing reagent. The as-obtained 3D Au MFs exhibited high surface-enhanced Raman spectroscopy (SERS) activity in detection of methylene blue.

Stabilization of 2D Raft Structures of Au Nanoclusters with up to 60 Atoms by a Carbon Support

Herein, the stabilization of 2D single‐atom high gold rafts containing up to ≈60 Au atoms on amorphous carbon, fabricated by sputtering of atoms and imaged by aberration‐corrected scanning transmission electron microscopy, is demonstrated. These rafts deviate from the established cluster transition from 2D to 3D Au structural motifs in free clusters, which occurs in the region of 10–14 atoms. The experimental findings by performing explicit ab initio calculations of Aun (n = 3–147) clusters on graphene are supported and the role of cluster–surface interactions in the stabilization of the 2D single‐atom high Au cluster rafts on graphene is revealed. The transition from equilibrium 2D–3D structures is delayed to n = 19, while metastable 2D single‐atom high rafts compete with 3D structures up to about n = 60 atoms. The catalytic activity of supported nanoclusters depends strongly on their structure (and carbon‐based supports are used for a number of reactions); therefore these results are relevant to the catalytic performance of nanocluster‐based catalysts.

Surface lattice resonance in an asymmetric air environment of 2D Au near-spherical nanoparticle arrays: impact of nanoparticle size and its sensitivity

2D Au nanoparticle (NP) arrays with larger NP size displayed an obvious surface lattice resonance (SLR) peak in an asymmetric air environment, indicating that, if the NP size was large enough, index-matching was not necessary for forming SLR.

(Invited) To Prepare 2D Au Nanoplates and Its Controlled Molecular Self-Assembly (MS) Mechanism

It is very important to prepare 2D noble-metal nanomaterials, but very little is known about their chemical synthesis at molecular level. In this paper, we found the classic citric (CA) reduction method can prepare 2D Au nanoplates with a large range for 2D size (3-150nm). Furthermore, these 2D Au nanoplates exhibit thin thickness (8-20nm), along with two kinds of single crystal structure as 2D Au (110) –dominated and Au (111) –dominated nanoplates. To explore their preparation, we adjusted the CA reduction kinetic as CA additive→ acetone dicarboxylic acid (DCA) →acetone, revealing the intermediate species of DCA is crucial for nanoplate formation. Our DFT (Density-Functional-Theory) model further clarifies that the DCA has molecular interaction, preferentially transferring 2D clusters (Au3-Au7) towards Au(111) facets though accompanying with some Au (100) facets. These soft-hard interaction help us establish two kinds of controlled MS mechanisms towards (111) –dominated nanoplates and Au (110) –dominated nanoplates, revealing the cluster origination and its essential 2D growth process in nucleation-growth process. Consequently, our preparation for 2D Au nanoplates and controlled MS mechanisms open a gate towards nucleation-growth process, thus having great significance and broad impact for future studies.

3D nanocake-like Au-MXene/Au pallet structure-based label-free electrochemical aptasensor for paraquat determination.

3D nanocake-like Au-MXene and Au pallet (Au-MXene/AuP) nanocomposite-modified screen-printed carbon electrodes (SPCEs) were utilized to construct an ultrasensitive label-free electrochemical aptasensor through a self-assembly procedure for trace paraquat (PQ) residue detection. Benefiting from the excellent electrochemical (EC) performances (e.g., high conductivity and large surface area) of Au-MXene nanocomposites and AuP substrate, the developed Apt/Au-MXene/AuP/SPCE-based EC aptasensor displayed excellent specificity and anti-interference ability, good repeatability, and stability. A linear relationship between the log value of the change in current intensity [lg (ΔI)] and the log value of the concentration of PQ [lg (CPQ)] was obtained in the range 0.05-1000 ng/mL. The limit of detection was 0.028 ng/mL, and thesensitivity was 255.5 μA/(μM·cm2). Practical applications in malt and mint samples confirmed the accuracy of the EC aptasensor in complex matrices for PQ detection, providing a universal analytical tool for othertrace pesticides in differentfood samples by simply replacing the corresponding aptamers.

3D Au Targeting using Machine Learning with Different Sample Combination and Return-Risk Analysis in the Sanshandao-Cangshang District, Shandong Province, China

3D Au Targeting using Machine Learning with Different Sample Combination and Return-Risk Analysis in the Sanshandao-Cangshang District, Shandong Province, China

Realizing tunneling electroresistance effect in the Au/h-BN/In2Se3/Au vertical ferroelectric tunnel junction.

Two-dimensional (2D) ferroelectric tunnel junctions (FTJs) have great potential in the design of non-volatile memory devices due to the tunneling electroresistance (TER) effect and the fact that it is not constrained by critical thickness. Incorporation of 2D ferroelectric materials in realistic FTJs inevitably involves the contacts to the traditional three-dimensional (3D) metals. However, how to design the FTJs by combining the 2D ferroelectric materials with the 3D metals still needs to be studied. In this work, we design a vertical 3D FTJ by adopting the 3D metal Au as the left and right electrodes and the 2D ferroelectric material In2Se3 together with h-BN as the central scattering region. By density functional theory combined with the non-equilibrium Green's function (NEGF) method, we demonstrate that the h-BN intercalation with a large bandgap plays the role of good "insulator," which breaks the symmetry of the left and right electrodes. As a result, we obtain the TER ratio of about 170%, and it can be further improved to about 1200% if two layers of In2Se3 (2L-In2Se3) are adopted as the tunneling barrier layer. Our results provide another way for the design and application of ferroelectric memory devices based on 2D ferroelectric materials.

Slippery Au Nanosphere Monolayers with Analyte Enrichment and SERS Enhancement Functions.

Slippery surfaces can enrich analytes from solutions into tiny dots after solvent evaporation for surface-enhanced Raman scattering (SERS) detection. Here, we make the self-assembled Au nanosphere monolayers slippery, which can not only behave as SERS substrates but also enrich the analytes during solvent evaporation. A thin silica shell was used to wrap the Au nanosphere monolayer to allow the functionalization of a slippery polydimethylsiloxane brush monolayer onto it. These slippery Au nanosphere monolayers could be easily cleaned and reused many times. When Au nanospheres were introduced into the analyte solution droplet on the slippery Au nanosphere monolayer, a 3D Au nanoparticle/analyte aggregate was formed after solvent evaporation. Both the Au nanoparticle aggregate and the underneath slippery Au nanosphere monolayer could contribute to SERS enhancement. We endow the self-assembled Au nanosphere monolayer SERS substrates with an analyte enrichment function, greatly strengthening their SERS enhancement.

Portable smartphone‐based microfluidic electrochemical immunosensor for ultrasensitive detection of alpha‐fetoprotein in human serum

AbstractRapid and accurate tracing of biomarkers is essential for early detecting and diagnosing of cancer. Therefore, a valid and convenient strategy needs to be developed for efficient monitoring of cancer biomarkers. Herein, we constructed a portable microfluidic electrochemical immunosensor based on three‐dimensional reduced graphene oxide (3D rGO) doped with gold nanoparticles (Au NPs) for ultrasensitive determination of alpha‐fetoprotein (AFP). The designed microfluidic chip, with the advantages of small injection volume, detachable structure and high integration, was fabricated by 3D printing, which only needed 9 μL of reagent to realize the high sensitivity detection. In addition, the 3D Au NPs‐rGO composites with high specific surface area and electrons transfer capacity can effectively increase electroactive sites and enhance electrochemical signals. Benefiting from these features, the 3D Au NPs‐rGO microfluidic electrochemical immunochip showed a wide detection range between 0.1 pg/mL–200 ng/mL and a best detection limit of 0.045 pg/mL with the high sensitivity of 175.008 μA (ng/mL)−1 cm−2. Meanwhile, the proposed immunosensor exhibited reliable AFP detection in human serum samples, which demonstrated that this portable smartphone‐based microfluidic electrochemical immunosensor hold great promises in clinical detection and huge potential in personalized healthcare.

Regulation on the electrical and optical properties of two-dimensional stacked graphene quantum dots/gold quantum dots/tungsten sulfide heterostructures

Two-dimensional (2D) transition metal dichalcogenides (TMDCs), like WS2, have been particularly promising in the application of solar energy conversion. Nevertheless, how to enhance the absorption capacity and photogenerated dcharge transfer is yet challenging. Herein, 2D stacked heterostructures were firstly constructed by 2D Au quantum dots (QDs), graphene quantum dots (GQDs) and WS2 monolayer. Compared with WS2 monolayer, the absorption abilities of the Au QDs/WS2 heterostructures in visible-near infrared light region of 450–2300 nm increase evidently. Simultaneously, charge redistribution occurs at the WS2–Au interfaces and generates the built-in electric field with the direction from Au QDs to the WS2 monolayer. This built-in electric field is conducive to boosting photo-induced charge separation and transfer. Notably, more obvious charge transfer and stronger built-in electric field can be achieved in WS2–Au6 interface after introducing the GQDs. Therefore, this work provides unique insights for designing new WS2-based heterostructures to improve the solar energy conversion.

A high-energy/power and ultra-stable aqueous ammonium ion microbattery based on amorphous/crystalline dual-phase layered metal oxides

The prosperity of microelectronic systems stimulates fast development of high-performance power sources with micro/nano sizes. Considering the defects of conventional lithium-ion microbatteries, i.e. high cost, severe safety concerns as well as the unsatisfactory power delivery due to the sluggish ion transport of the organic electrolytes, novel energy storage microdevices are worth looking forward to. Here, we assemble an aqueous ammonium-ion microbattery using 2D (NH4)xV2O5 with amorphous/crystalline dual-phase nanostructure deposits on 3D nanoporous Au as anode while nanoporous Au/δ-MnO2 composite as cathode. As a result of the superb electronic/ionic conductivities as well as the large voltage window, the resultant NP Au/ac-(NH4)xV2O5//NP Au/δ-MnO2 aqueous ammonium-ion microbattery exhibits ultrahigh energy density of 0.126 Wh cm−3 with electrical powers ∼280-fold higher than commercial lithium thin-film batteries, in addition to excellent rate capability (∼84.2% capacity retention at 5–50 mV s−1 scan rates) and cycling stability (retains ∼93.3% of the initial value after 10,000 cycles at 500 mV s−1). The superb performance endows it to be promising candidate as monolithic micropower source for micro/nano portable/wearable electronics with high energy storage and power delivery demands.

Renal Clearable Catalytic 2D Au-Porphyrin Coordination Polymer Augmented Photothermal-Gas Synergistic Cancer Therapy.

As a gasotransmitter, carbon monoxide (CO) possesses antitumor activity by reversing the Warburg effect at higher concentrations. The targeted delivery of carbon monoxide-releasing molecules (CORMs) using nanomaterials is an appealing option for CO administration, but how to maintain CO above the threshold concentration in tumor tissue remains a challenge. Herein, a nanozyme-catalyzed cascade reaction is proposed to promote CO release for high-efficacy photothermal therapy (PTT)-combined CO therapy of cancer. A gold-based porphyrinic coordination polymer nanosheet (Au0 -Por) is synthesized to serve as a carrier for CORM. It also possesses excellent glucose oxygenase-like activity owing to ultrasmall zero-valent gold atoms on the nanosheet. The catalytically generated H2 O2 can efficiently catalyze CORM decomposition, which enables in situ generation of sufficient CO for gas therapy. In vivo, the Au0 -Por nanosheets-enhanced photoacoustic imaging (PAI) and fluorescence imaging collectively demonstrate high tumor-targeting efficiency and nanomaterial retention. Proven to have augmented therapeutic efficacy, the nanoplatform can also be easily degraded and excreted through the kidney, indicating good biocompatibility. Thus, the application of rational designed Au0 -Por nanosheet with facile approach and biodegradable property to PAI-guided synergistic gas therapy can provide a strategy for the development of biocompatible and highly effective gaseous nanomedicine.

Субмонослойные покрытия натрия на поверхности золотой пленки

n situ photoelectron spectroscopy studies have been carried out in ultrahigh vacuum of the electronic structure of a 2D Au film deposited on a surface W with a natural oxide, before and after adsorption of Na atoms. The spectra of photoemission from the valence band and core levels of Au 4f, W 4f and Na 2p were studied under synchrotron excitation in the photon energy range of 120-300 eV. The investigated 2D Au film with a thickness of 0.83 nm has a valence band close to the valence band of the massive sample. The diffusion of Na atoms deep into the gold film was not detected, which indicates the layered growth of the 2D Au film. Two states have been found: Nadelta+ and Na+, which exist even with a 0.15 sodium coating of the monolayer, which indicates the formation of Na islands and single adsorption of Na atoms. The density functional method is used to calculate the electronic structure of a 2D Au layer without and with adsorbed Na. It is established that the adsorption of Na atoms in the pit or bridge position is preferable. It is found that the adsorption of Na leads to the reconstruction of the surface.

An unexpected interfacial Mo-rich phase in 2D molybdenum disulfide and 3D gold heterojunctions.

The interface engineering of two-dimensional transition metal dichalcogenides (2D-TMDs) and metals has been regarded as a promising strategy to modulate their outstanding electrical and optoelectronic properties. Chemical Vapour Deposition (CVD) is an effective strategy to regulate the contact interface between TMDs and metals via directly growing 2D TMDs on a 3D metal substrate. Nevertheless, the underlying mechanisms of interfacial phase formation and evolution during TMD growth on a metallic substrate are less known. In this work, we found a 2D non-van der Waals (vdW) Mo-rich phase (MoNSN+1) during thermal sulfidation of a Mo-Au surface alloy to molybdenum disulfide (MoS2) in a S-poor environment. Systematic atomic-scale observations reveal that the periodic Mo and S atomic layers are arranged separating from each other in the non-vdW Mo-rich phase, and the Mo-rich phase preferentially nucleates between outmost 2D MoS2 and a 3D nanostructured Au substrate which possesses copious surface steps and kinks. Theoretical calculations demonstrate that the appearance of the Mo-rich phase with a unique metallic nature causes an n-type contact interface with an ultralow transition energy barrier height. This study may help understand the formation mechanism of the interfacial second phase during the epitaxial growth of 2D-TMDs on 3D nanostructured metals, and provide a new approach to tune the Schottky barrier height by the design of the interfacial phase structure at the heterojunction.

Formation and Characterization of 2D Closely Packed Arrays of Bare Gold Nanoparticles without Aggregation.

Uniform 2D arrays of metal nanoparticles (NPs) have received significant attention in the field of molecular sensing using localized surface plasmon resonance. Generally, metal NPs bear organic surface-modifying molecules to prevent aggregation and form 2D metal NP arrays. However, surface-modifying molecules negatively affect molecular sensing. Previously, we developed a technique for forming a 2D bare metal NP array, denoted the sandwich (SW) technique. However, the formation mechanism of these 2D metal NP arrays remains unknown and therefore the experimental conditions of the SW technique are not optimized. Here, we observed the formation of a 2D Au NP (d: 60 nm) array using the SW technique with an optical microscope. Moderate drying conditions of the colloidal droplets sandwiched between two parallel substrates were necessary for forming 2D Au NP arrays. We then optimized the drying conditions and obtained a 2D Au NP array. This array was uniform, and the Au NPs were arranged at distances of 4.5 nm with hexagonal periodicity, without aggregation. Further, the 2D Au NP arrays exhibited excellent spot-to-spot reproducibility in surface-enhanced Raman scattering.