Au Nanodots Research Articles

Formation of tunable diamond micro- and nanopillars for field effect enhancement applications

We developed a process for the fabrication of tunable single crystal diamond micro- and nanopillars, with tip widths ranging from 40 to 460 nm, densities ranging from 0.5 to 53.5 pillars/μm2, and heights greater than 4.5 μm. A self-assembled Au nanodot ensemble etch mask was formed from an annealed Au thin film. The nanodot diameter and density can be tuned using the initial film thickness. The pillars were etched from the nanodot mask using an RIE O2 plasma, which has infinite selectivity for the diamond when applied at low RF powers (50 W). Finally, the pillars can be sharpened to ∼40 nm tip widths by annealing in air at 650 °C. These pillars can be used for applications such as field effect enhancement of diamond photocathode devices, enhancement of optical emission from N-V centers, and antireflective coatings.

Functionalization of ZnO Nanorods with Au Nanodots via In Situ Reduction for High-Performance Detection of Ethyl Acetate.

Ethyl acetate is a critical medical indicator for detecting certain types of cancer. However, at present, available sensitive materials often exhibit drawbacks, such as high operating temperatures and poor responses to low concentrations of ethyl acetate. In this study, a ZnO nanorod sensing material was prepared using high-temperature annealing and a hydrothermally synthesized metal-organic framework (MOF) as a template. Au nanodots (AuNDs) were subsequently modified on the ZnO nanorods using an in situ ion reduction, which provided a better dispersion of Au nanodots compared with that obtained using the common reductant method. A variety of characterization methods indicate that the highly dispersed AuNDs, which possess a high catalytic activity, were loaded onto the surface as active centers, leading to a significant augmentation in the adsorption of oxygen on the surface compared with the original ZnO material. Consequently, the AuND@ZnO material exhibited heightened responsiveness to ethyl acetate at a lower operating temperature. The Au@ZnO-based sensor has a response rate (Ra/Rg) of 41.8 to 20 ppm ethyl acetate gas at 140 °C, marking a 17.4-fold increase compared with that of the original material. Due to its low power consumption and high responsiveness, AuND@ZnO is a promising candidate for the detection of ethyl acetate gas in medical applications.

Heteronanotrimers by Selective Photodeposition of Gold Nanodots on Janus-Type Cu2‒ xS/CuInS2 Heteronanocrystals.

This study focuses on the development of environmentally friendly Au-Cu2-xS/CuInS2 heteronanotrimers. The chosen strategy relies on the laser photodeposition of a single gold nanodot (ND) onto Janus Cu2- xS/CuInS2 heteronanocrystals (HNCs). This method offers precise control over the number, location, and size (5 to 8nm) of the Au NDs by adjusting laser power for the career production, concentration of hole scavenger for charge equilibration in redox reactions, and gold precursor concentration, and exposure time for the final ND size. The photoreduction of gold ions onto HNCs starts systematically at the Cu2- xS tip. The Au deposition then depends on the CuInS2 segment length. For short HNCs, stable Au-Cu2- xS/CuInS2 heteronanotrimers form, while long HNCs undergo a secondary photo-induced step: the initial Au ND is progressively oxidized, with concomitant deposition of a second gold ND on the CuInS2 side, to yield Au2S-Cu2- xS/CuInS2-Au heteronanotrimers. Results are rationalized by quantitative comparison with a model that describes the growth kinetics of NDs and Au-Cu2- xS transformation and emphasizes the importance of charge separation in predicting selective deposition in heteronanotrimer production. The key parameter controlling Au-Cu2‒ xS/CuInS2 HNCs is the photoinduced electric field gradient generated by charge separation, which is tailored by controlling the CuInS2 segment size.

Rational design of Au-Bi bimetallic nanozyme for NIR-II laser mediated multifunctional combined tumor therapy

To maximize the therapeutic effects and minimize the adverse effects of synergistic tumor therapies, a multifunctional nanozyme Au-Bi/ZIF-8@DOX@HA (ABZ@DOX@HA) was designed and synthesized through the Au and Bi bimetallic doping of ZIF-8, loading of the DOX, and modifying with hyaluronic acid (HA). The ABZ@DOX@HA nanoparticles (NPs) could simulate the enzymatic activities of glucose oxidase (GOx) and peroxidase (POD). Upon irradiated by near-infrared region (NIR-II) laser, the strong synergism of the photothermal abilities of the loaded Au and Bi nanodots accelerated the collapse of the ABZ structure at the tumor site considerably and released Au, Bi nanodots and DOX. The results in vitro and in vivo proved that ABZ@DOX@HA nanozyme could effectively exert the combined tumor therapy of starvation treatment, photothermal therapy (PTT), chemodynamic therapy (CDT) and chemotherapy. The current research provides a new strategy to address the inherent challenges of easy clearance and short blood circulation of small-sized NPs during the treatment of tumors with nanomedicine, as well as the aggregation and oxidation of inorganic nanodots.

Drug Evaluation of Parkinson's Disease Patient-Derived Midbrain Organoids Using Mesoporous Au Nanodot-Patterned 3D Concave Electrode.

Brain organoids are being recognized as valuable tools for drug evaluation in neurodegenerative diseases due to their similarity to the human brain's structure and function. However, a critical challenge is the lack of selective and sensitive electrochemical sensing platforms to detect the response of brain organoids, particularly changes in the neurotransmitter concentration upon drug treatment. This study introduces a 3D concave electrode patterned with a mesoporous Au nanodot for the detection of electrochemical signals of dopamine in response to drugs in brain organoids for the first time. The mesoporous Au nanodot-patterned film was fabricated using laser interference lithography and electrochemical deposition. Then, the film was attached to a polymer-based 3D concave mold to obtain a 3D concave electrode. Midbrain organoids generated from Parkinson's disease (PD) patient-derived iPSCs with gene mutations (named as PD midbrain organoid) or normal midbrain organoids were positioned on the developed 3D concave electrode. The 3D concave electrode showed a 1.4 times higher electrochemical signal of dopamine compared to the bare gold electrode. And the dopamine secreted from normal midbrain organoids or PD midbrain organoids on the 3D concave electrode could be detected electrochemically. After the treatment of PD midbrain organoids with levodopa, the drug for PD, the increase in dopamine level was detected due to the activation of dopaminergic neurons by the drug. The results suggest the potential of the proposed 3D concave electrode combined with brain organoids as a useful tool for assessing drug efficacy. This sensing system can be applied to a variety of organoids for a comprehensive drug evaluation.

High Amplitude Spike Generator in Au Nanodot-Incorporated NbOx Mott Memristor.

NbOx-based Mott memristors exhibit fast threshold switching behaviors, making them suitable for spike generators in neuromorphic computing and stochastic clock generators in security devices. In these applications, a high output spike amplitude is necessary for threshold level control and accurate signal detection. Here, we propose a materialwise solution to obtain the high amplitude spikes by inserting Au nanodots into the NbOx device. The Au nanodots enable increasing the threshold voltage by modulating the oxygen contents at the electrode-oxide interface, providing a higher ON current compared to nanodot-free NbOx devices. Also, the reduction of the local switching region volume decreases the thermal capacitance of the system, allowing the maximum spike amplitude generation. Consequently, the Au nanodot incorporation increases the spike amplitude of the NbOx device by 6 times, without any additional external circuit elements. The results are systematically supported by both a numerical model and a finite-element-method-based multiphysics model.

Multifunctional nanoprobe for multi-mode imaging and diagnosis of metastatic prostate cancer

The high incidence and complex subtypes of prostate cancer put forward higher requirements for accurate diagnosis. Furthermore, advanced prostate cancer is prone to metastasis. Single biological imaging mode faces a challenge of sensitive and fast bioimaging of metastasic prostate cancer. Thus, exploring a nanoprobe with multi-mode imaging function has an important impact on preoperative imaging and intraoperative visualization guide of metastatic prostate cancer. Herein, based on the optical properties and X-ray attenuation capability of Au nanodots as well as the slow electronic relaxation of Gd3+, we designed and fabricated the multifunctional nanoprobe Au/Gd nanodots for multi-mode imaging and accurate diagnosis of bone metastatic prostate cancer. The results showed that multiple imaging modes complement each other to achieve high-precision of metastasic prostate cancer detection and accurately guide treatment. In addition, in vitro/vivo experiments showed that Au/Gd nanodots had good biocompatibility and biosafety. Therefore, the prepared multifunctional nanoprobe may provide new strategies and insights for precise diagnosis of metastatic prostate cancer in clinical practice.

Fabrication of gold nanodots decorated on 2D tungsten sulfide (Au-WS2) photoanode for simultaneous oxidation of phenol and arsenic (III) from industrial wastewater

Two dimensional (2D) photoelectrocatalysts with a tunable band gap and a large surface area have emerged in recent years for advanced oxidation processes that remove toxic compounds from wastewater. In this study, ultra-thin 2D tungsten sulfide (2D WS2) photoelectrocatalysts have been fabricated using organosulfur sources, and the resulting 2D WS2 has high chemical stability and visible light band edges. Additionally, citrate stabilized Au nanodots were successfully incorporated into the 2D WS2 nanosheets in order to reduces the charge carrier recombination. The morphology, composition, chemical state, and optical properties of the Au-WS2 photoanodes have been systematically investigated. An Au-WS2 photoanode is successfully assembled in a photoelectrochemical cell (PEC) for removing phenol and oxidizing toxic As(III) into non-toxic As(V) under visible light. The studies show that the Au-WS2 photoanode had an oxidation efficiency of 99% for phenol and 95% for As(III) under visible light illumination. Furthermore, X-ray photoelectron spectroscopy (XPS) and theoretical analyses were used to investigate the oxidation pathways of phenol and As(III). A reachability study was carried out to demonstrate that mixed synthetic wastewater containing phenol and arsenite could be used for extended periods in a practical manner. In this study, Au-WS2 photoanodes were demonstrated to be highly effective in enhancing environmental remediation using advanced oxidation methods.

Defect-engineered plasmonic Z-scheme heterostructures for superior photoelectrochemical water oxidation

The Z-scheme photoelectrochemical (PEC) catalytic system that mimics natural photosynthesis is considered an encouraging method to improve the catalytic activities of the catalysts and finally address the global energy crisis. Herein, a plasmon-enhanced Z-Scheme heterostructure is synthesized via interface-structure-designing and defect-engineering. The optimized TiO2/Au/ZnIn2S4OS exhibits an excellent PEC catalytic activity with a photocurrent density of 3.80 mA/cm2 at 1.23 V (vs RHE), which is 2.1 times higher than that of TiO2 nanorod arrays. The density functional theory (DFT) calculation results demonstrate that the synergy of O, S-defects can tailor the charge density distribution and electronic structure of ZnIn2S4, which effectively improves the electrical conductivity of the photocatalyst. The kinetic and thermodynamic behavior investigation, as well as theoretical simulations, indicate that the successful construction of the Z-scheme system can significantly improve the redox capacity and photo-excited electron-hole separation efficiency of the catalysts, thereby promoting the water oxidation activity. Furthermore, the Au nanodots sandwiched between TiO2 and ZnIn2S4OS are found to play multifunctional roles in boosting the PEC catalytic performance. This work provides a valuable approach to constructing defects-dominated Z-scheme systems at the atomic scale and sheds light on new insight into the LSPR effect for improving the catalytic performance in Z-scheme systems.

Controlled Electroplating of Noble Metals on III-V Semiconductor Nanotemplates Fabricated by Anodic Etching of Bulk Substrates

Porous templates are widely used for the preparation of various metallic nanostructures. Semiconductor templates have the advantage of controlled electrical conductivity. Site-selective deposition of noble metal formations, such as Pt and Au nanodots and nanotubes, was demonstrated in this paper for porous InP templates prepared by the anodization of InP wafers. Metal deposition was performed by pulsed electroplating. The produced hybrid nanomaterials were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It was shown that uniform deposition of the metal along the pore length could be obtained with optimized pulse parameters. The obtained results are discussed in terms of the optimum conditions for effective electrolyte refreshing and avoiding its depletion in pores during the electroplating process. It was demonstrated that the proposed technology could also be applied for the preparation of metal nanostructures on porous oxide templates, when it is combined with thermal treatment for the oxidation of the porous semiconductor skeleton.

Facile Fabrication of Flexible Polymeric Membranes with Micro and Nano Apertures over Large Areas.

Freestanding, flexible and open through-hole polymeric micro- and nanostructured membranes were successfully fabricated over large areas (>16 cm2) via solvent removal of sacrificial scaffolds filled with polymer resin by spontaneous capillary flow. Most of the polymeric membranes were obtained through a rapid UV curing processes via cationic or free radical UV polymerisation. Free standing microstructured membranes were fabricated across a range of curable polymer materials, including: EBECRYL3708 (radical UV polymerisation), CUVR1534 (cationic UV polymerisation) UV lacquer, fluorinated perfluoropolyether urethane methacrylate UV resin (MD700), optical adhesive UV resin with high refractive index (NOA84) and medical adhesive UV resin (1161-M). The present method was also extended to make a thermal set polydimethylsiloxane (PDMS) membranes. The pore sizes for the as-fabricated membranes ranged from 100 µm down to 200 nm and membrane thickness could be varied from 100 µm down to 10 µm. Aspect ratios as high as 16.7 were achieved for the 100 µm thick membranes for pore diameters of approximately 6 µm. Wide-area and uniform, open through-hole 30 µm thick membranes with 15 µm pore size were fabricated over 44 × 44 mm2 areas. As an application example, arrays of Au nanodots and Pd nanodots, as small as 130 nm, were deposited on Si substrates using a nanoaperture polymer through-hole membrane as a stencil.

Enzyme-Powered Hollow Nanorobots for Active Microsampling Enabled by Thermoresponsive Polymer Gating.

Achieving molecular sample capture at micro/nanoscales while integrating functions of controllable loading and real-time monitoring of cargo molecules is of great significance in the development of intelligent micro/nanorobots. Herein, we prepare a temperature-responsive microsampling nanorobot by encapsulating metal (Au) nanodots inside hollow mesoporous silica nanoparticles and grafting a temperature-responsive polymer, poly(N-isopropylacrylamide), on their external surface. The molecular gate of nanochannels accessing the internal hollow reservoir can be switched between "open" and "closed" states by regulating the temperature, allowing on-demand loading and releasing of small molecules. The internally embedded surface-enhanced Raman scattering hotspots of gold nanodots can serve as sensing probes for real-time detection of the molecular cargo load inside the hollow nanorobots. Furthermore, we demonstrate temperature-dependent self-propulsion behavior of the nanorobots driven by enzymatic reactions. The active motion behavior can favorably regulate the loading efficiency of molecular cargos. In addition, by further introducing the magnetic component Ni, the nanorobots can accomplish effective transportation of cargo molecules by magnetic guidance under real-time Raman monitoring. The current strategy is expected to provide a manipulable nanorobot platform for precise biomedical sampling, which holds promising potential for disease diagnosis or controlled drug delivery in precision medicine.

Better colloidal lithography: Tilt-rotate evaporation overcomes the limits of plasma etching

Colloidal lithography (CL) is a promising method for large-area fabrication of nanohole and nanodot arrays with applications in optical biosensing, separations, and magnetic data storage. However, reducing the diameter of the polystyrene sphere mask by plasma etching unavoidably increases their coefficient of variation (CV) and deforms their shape, thereby limiting the pitch-to-hole-diameter ratio of the resulting nanohole array to less than 3:1 and the minimum hole size to 200 nm with a 10% or better CV. We show that tilt-rotate evaporation colloidal lithography (TRE-CL) breaks the trade-off between hole diameter and polydispersity by leveraging glancing angle evaporation, not plasma etching, to adjust the hole size. TRE-CL allows pitch-to-hole-diameter ratios as high as 7:1 and nanohole diameters down to 60 nm while maintaining a nearly constant CV below 10% and hole circularity above 91%. We transfer these hole arrays into ultrathin Si3N4 films to form nearly-monodisperse microsieves for separation applications. Furthermore, we extend TRE-CL to fabricate adhesion-layer-free plasmonic Au nanodot arrays down to 70 nm in diameter with 10% CV.

Gold nanodots-decoration stabilizes and activates metastable metallic phase MoS2 nanosheets for efficient hydrogen evolution reaction

Hydrogen evolution reaction (HER), an efficient and sustainable method for clean hydrogen energy producing, has been impeded by scarcity and costly of precious metals electrocatalysts. Two-dimensional (2D) metallic phase MoS2 (M-MoS2) nanosheets (NSs) have been identified as cost-effective and efficient alternative electrocatalysts for HER. However, the practical applications of M-MoS2 NSs are often limited by the metastable property of their metallic phase. Here, we demonstrate both the metallic phase stability and the electrocatalytic activity of the M-MoS2 NSs can be dramatically improved by gold (Au) nanodots (NDs) decoration. The obtained Au NDs decorated M-MoS2 NSs (namely, Au NDs@M-MoS2 NSs) maintain well their metallic phase even after about 100 days storage, while the M-MoS2 NSs have already transferred to dominant 2H phase one for about 2 weeks. The results of first-principles density functional theory (DFT) calculation also indicate that the Au NDs modification can stabilize the metastable metallic phase of M-MoS2 NSs. Moreover, the as-prepared Au NDs@M-MoS2 NSs also show remarkable enhanced electrocatalytic activity toward HER. These findings may open up an ideal approach to stabilize and activate the metastable metallic phase 2D transition metal dichalcogenides-based electrocatalysts for various promising applications.

A lab-on-injector device with Au nanodots confined in carbon nanofibers for in situ electrochemical BPA sensing in beverages

Bisphenol A (BPA) as the most common endocrine disruptor used in food containers and packaging is causing adverse effects for human beings. Accordingly, in situ detection of BPA is of practical importance for food safety. However, the complicated operations of existed methods and interference of various impurities in food matrix restrict the realization of real-time in situ BPA sensing in food samples. We report here a portable and fully-integrated electrochemical sensing device with an injector as the reaction vessel which assembled with screen printed electrodes (SPEs) as sensing electrodes and a detachable filter unit to filter impurities. This device, namely lab-on-injector, reduces the sampling, pretreatment and detection to a simple on-step operation, making in situ detection of BPA in real samples much easier and more feasible. Moreover, extra-small Au nanodots confined in carbon nanofibers ([email protected]) were synthesized by in situ carbothermic reduction of Au3+ absorbed on cellulose, and were used to modified SPEs surface to greatly enhance detection performance of the lab-on-injector. Using this [email protected] based lab-on-injector, BPA in food matrix was detected directly with recoveries from 93.14% to 94.25%, demonstrating a reliable platform for in situ detection of BPA, and opening a new way for the development of smart devices in electroanalysis.

Multifunctional theragnostic ultrasmall gold nanodot-encapsuled perfluorocarbon nanodroplets for laser-focused ultrasound sequence irradiation (LFSI)-based enhanced tumor ablation.

Despite the substantial potential of focused ultrasound therapy, its efficacy in cancer therapy has been limited due to the high cavitation threshold and safety concerns regarding the use of high-intensity energy pulses. Here, ultrasmall Au nanodot-loaded PEG-modified perfluorocarbon nanodroplets (Au-PFCnDs) were prepared and used as a therapeutic enhancer. A LFSI method was designed to achieve enhanced tumor ablation at a mild focused ultrasound (FUS) energy pulse with the assistance of the instinct photothermal effect of intratumor-permeable ultrasmall Au nanodots under 808 nm NIR laser irradiation. In addition to their therapeutic function, Au-PFCnDs can also generate multimodal images to provide information for tumor surveillance and treatment guidance. The experimental results also showed that the cRGD-targeted Au-PFCnDs could be more efficiently delivered into the tumor and selectively destroy tumors with no observable side effects on normal tissue under LFSI treatment.

Ligand-assisted deposition of ultra-small Au nanodots on Fe2O3/reduced graphene oxide for flexible gas sensors.

The development of flexible room-temperature gas sensors is important in environmental monitoring and protection. In this contribution, by using 1-octadecanethiol (ODT) as a surface ligand, Au nanodots (NDs) with ultra-small size of ∼1.7 nm were deposited on the surface of α-Fe2O3/reduced graphene oxide (rGO). The Au ND–ODT/α-Fe2O3/rGO composite was fabricated into flexible gas sensors, which could detect NO2 gas down to 200 ppb at room temperature. Compared with α-Fe2O3/rGO, Au ND–ODT/α-Fe2O3/rGO showed enhanced sensing performance because of the beneficial effects of Au NDs, including facilitating the adsorption of NO2 molecules and forming ohmic-like contact with rGO and α-Fe2O3. In addition, the sensing performance of the composite was also influenced by the surface ligands of the Au NDs. Ligands with less polar terminal groups were found to be beneficial to charge transfer in the sensing film. Moreover, Au ND–ODT/α-Fe2O3/rGO-based flexible sensors showed negligible performance deterioration under moderately bent conditions, suggesting their potential to be used in portable and wearable devices.

Enhanced high-temperature energy storage properties of polymer composites by interlayered metal nanodots

The PC-Au nanodots-PC heterojunction film with merely 0.0035 vol% of Au nanodots exhibited a superior Ue (6.25 J cm−3) and η (86.6%) at 150 °C, far surpassing those of the reported advanced polymers and nanocomposite dielectrics.

Surface-Tailored InP Nanowires via Self-Assembled Au Nanodots for Efficient and Stable Photoelectrochemical Hydrogen Evolution.

With a band gap close to the Shockley-Quiesser limit and excellent conduction band alignment with the water reduction potential, InP is an ideal photocathode material for photoelectrochemical (PEC) water reduction. Here, we develop facile self-assembled Au nanodots based on dewetting phenomena as a masking technique to fabricate wafer-scale InP nanowires (NWs) via a top-down approach. In addition, we report dual-function wet treatment using sulfur-dissolved oleylamine (S-OA) to remove a plasma-damaged surface in a controlled manner and stabilize InP NWs against surface corrosion in harsh electrolyte solutions. The resulting InP NW photocathodes exhibit an excellent photocurrent density of 33 mA/cm2 under 1 sun illumination in 1 M HCl with a highly stabilized performance without needing additional protection layers. Our approach combining large-area NW fabrication and surface engineering synergistically enhances light harvesting and PEC performance and stability, thereby providing a pathway for the development of efficient and durable InP photoelectrodes in a scalable manner.

Gold nanodot assembly within a cobalt chalcogenide nanoshell: Promotion of electrocatalytic activity

The assembly of functional nanoparticles within materials with unique architectures can improve the interfacial surfaces, defects, and active sites, which are key factors for the designing novel nanocatalysts. Nano metal–organic framework (NMOF) can be employed to fabricate nanodots-confined nanohybrids for use in electrocatalytic processes. Herein, we report a controlled synthesis of gold nanodot assembly within cobalt chalcogenide nanoshell (dots-in-shell Au/CoxSy nanohybrids). A cobalt-based NMOF (the cobalt-based zeolite imidazole framework, ZIF-67) is used as a versatile sacrificial template to yield dots-in-shell Au/CoxSy nanohybrids. Due to the synergistic effect of the well-dispersed Au nanodots and the thin CoxSy nanoshell, the obtained dots-in-shell Au/CoxSy nanohybrids exhibit enhanced performance for the oxygen evolution reaction (OER) with low overpotential values at a current density of 10 mA cm−2 and a small Tafel slope (343 mV and 62 mV dec−1, respectively).