Au Nanoparticles Research Articles

Fabrication and Characterization of Supported Porous Au Nanoparticles

Porous plasmonic nanoparticles offer unique advantages for sensing and catalysis due to their high surface-to-volume ratio and localized electromagnetic field enhancements at nanoscale pores, or “hotspots.” However, current fabrication techniques, which are based on colloidal synthesis, face challenges in achieving precise control over particle size, shape, and porosity. Here, we present a robust nanofabrication method to produce supported arrays of porous Au nanoparticles with excellent dimensional and compositional control. By combining lithographically patterned AuAg alloy nanoparticles and selective dealloying via nitric acid, we achieve particle porosity without compromising particle morphology. Specifically, the method allows fabrication of supported porous nanoparticles with tunable dimension and porosity. Our approach demonstrates precise control of nanoparticle porosity by varying the initial Ag content in the alloy. Optical characterization reveals a blueshift in the extinction peak with increasing porosity, attributed to the reduced effective refractive index from intraparticle voids. Notably, a tunable shift of up to 100 nm in the plasmonic peak is observed, demonstrating the potential for fine-tuning optical properties. This study highlights the versatility of the proposed method in fabricating well-defined porous plasmonic nanoparticles and their ability to modulate optical properties through porosity control. These findings not only expand the toolkit for designing advanced plasmonic materials but also open pathways for applications in plasmon-mediated sensing, catalysis, and photonic devices.

Gold Nanoparticles Decorated CoAl LDH Monolayer: A Peroxidase-Like Nanozyme for Sensitive Colorimetric Detection of Acetylcholinesterase and Inhibitors.

Monitoring acetylcholinesterase (AChE) activity and its inhibitor is crucial yet challenging for the early diagnosis and treatment of neurological diseases. In this study, we present Au nanoparticle decorated CoAl layered double hydroxide monolayer (Au@CoAl-LDH-m) as a peroxidase-like (POD) nanozyme for the sensitive colorimetric detection of AChE and its inhibitor, thiamine pyrophosphate (TPP). Remarkably, the Au@CoAl-LDH-m nanozyme can catalyze the oxidation of chromogenic substrates through its POD-like activity, which is effectively inhibited by thiocholine (TCh, a catalytic product of AChE), thereby enabling detection of AChE and TPP through a visible colorimetric readout. The approach provides a highly sensitive and specificity assay with a broader linear response range (1-100 mU mL-1 for AChE and 1-1000 ng mL-1 for TPP) and a low detection limit (0.092 mU mL-1 for AChE and 0.201 ng mL-1 for TPP), respectively. These results highlight the significant potential of Au@CoAl-LDH-m for advancing colorimetric sensors in detecting small molecules across various biological applications.

Probing Single-Particle Electrocatalytic Stability: Electrogenerated Chemiluminescence Imaging of Nanoparticle Array.

Understanding the stability of single nanoparticles is crucial for optimizing their performance in various applications, including catalysis. In this study, we employed electrochemiluminescence (ECL) imaging to investigate the temporal stability of individual Au and Pt nanoparticles within precisely engineered arrays. Our results reveal significant differences in the stability of Au and Pt NPs. While both exhibit initial decay due to diffusion limitations, Au NPs undergo more rapid degradation, attributed to surface oxidation and detachment. In contrast, Pt NPs demonstrate much better stability with little surface oxidation. This study provides valuable insights into the fundamental behavior of single-NP electrocatalysis and highlights the potential of ECL imaging as a powerful tool for unraveling the complex dynamics of nanoscale systems.

Liquid-Solid Triboelectric Nanogenerator-Based DNA Barcode Detection Biosensor for Species Identification.

DNA barcode detection method is widely applied for species identification, which is imperative to evaluate the effect of human economic activities on the biodiversity of ecosystem. However, the wide utilization of existing detection biosensors is limited by bulky and expensive instruments, such as Raman spectroscopy and electrochemical station. Herein, a liquid-solid triboelectric nanogenerator (TENG)-based DNA barcode detection biosensor is proposed, which consists of water flow, fluid channel, and PDMS film attached by specifically designed capture probe. Through sequentially combining capture probe, targeted DNA barcode, and signal probe with Au nanoparticles (NPs), the surface charge density of friction layer of TENG decreases under the effect of AuNPs, verified by the density functional theory (DFT) method. Consequently, the peak value of output current spike signal for targeted DNA is smaller than that for other DNA, which is the working mechanism of the present TENG-based biosensor. Such biosensor successfully recognizes Alvinocaris muricola among different types of Alvinocarididae shrimps, and its low limit detection can reach 1×10-12m. The present work provides a paradigm-shift way to develop an inexpensive and accurate technique to detect DNA barcode for species identification, and paves a novel way for the application of liquid-solid TENG.

Probing electronic-structure pH-dependency of Au nanoparticles through X-ray Absorption Spectroscopy

Research on gold nanoparticles (Au NPs) remains a field of intense activity due to their broad range of applications in diverse fields like catalysis, renewable energy, environmental science, and medicine. Herein, the morphological and electronic structures investigation of Au NPs prepared at different pH values is reported. The dependence of the localized surface plasmon resonance wavelength and electronic structure with size was determined by combining transmission electron microscopy, and various spectroscopic methods led by X-ray absorption spectroscopy. The X-ray absorption experiments evidenced that the citrate-stabilized Au NPs bulk electronic structure remains intact over a broad range of pHs, and changes were detected resulting from differences in NPs surface terminations.

Potential Energy as Descriptor for Nanoparticle Coalescence

AbstractCoalescence is a fundamental process in gas‐phase synthesis of nanoparticles (NPs), affecting their structure and resultant properties. Various metrics are currently used to measure the degree of coalescence in atomistic simulation studies, such as the radius of the neck formed between the NPs’ centers of mass, gyration radii, sphericity, and surface area changes. A common characteristic of such metrics is that they typically require additional, often painstaking, data manipulation. Here, a new descriptor is introduced, the Overall Reduced Change in Potential Energy (ORCiPE) between initially uncoalesced and coalesced configurations. To benchmark the descriptor, its definition is analogous to that of the Overall Change in Surface Area, a common and dependable metric. When no phase transition occurred, comparison with other metrics confirms the reliability of ORCiPE in coalescing Au NPs. Considering that potential energy is a standard output property in atomistic simulations, ORCiPE is proposed as a valuable and facile coalescence metric.

Application of Laser‐Generated Au‐Ag/Al2O3 Nanoparticle Catalysts for the Selective Catalytic Oxidation of 5‐(Hydroxymethyl) Furfural to 2,5‐Furan‐Dicarboxylic Acid

AbstractConversion of lignocellulosic biomass‐derived 5‐(Hydroxymethyl) furfural (HMF) into 2,5‐Furandicarboxylic acid (FDCA) has a high potential to replace petroleum‐based feedstocks for the production of plastics. In this study, a green synthesis strategy for the selective oxidation of HMF to FDCA is reported by using laser‐generated and specifically designed bimetallic AuAg nanoparticle catalysts supported on Al2O3 using molecular oxygen as oxidant and water as a solvent. Although supported AuAg catalysts are already known as suitable catalysts for this reaction, the optimal reaction conditions (type of base, reaction temperature, oxygen pressure), Au : Ag composition, role of metal‐support effects and origin of the active site still remain under debate. Interestingly, an Au9Ag1/Al2O3 catalyst exhibited the highest activity with a FDCA yield of up to 66 % at 80 % HMF conversion. Hereby, NaHCO3 (instead of NaOH) as a smoother base in 2 : 1 base:HMF ratio, low oxygen pressures of 5 bar, and a mild temperature of 150 °C were found optimal. The yield remained fairly stable on reuse of the catalyst for 3 cycles without hints of catalyst sintering or leaching. The titration of surficial hydroxyls on the AuxAgy/Al2O3 surface showed the highest density of acidic hydroxyls for the most active Au9Ag1/Al2O3 catalyst. The respective hydroxyls potentially originate from metal‐support interactions between the AuAg nanoparticles with the alumina support and act as Lewis acidic sites that oxidize the alcohol moiety of HMF to form FDCA with high selectively. In summary, this study shows that the catalytic activity of AuAg catalysts in HMF oxidation is not just linked to an alloying effect but also to a metal‐support effect where the AuAg nanoparticles appear to directly affect the local acidity of the support.

Facile and in situ production of reduced graphene oxide nanosheets paste electrode via electrochemical exfoliation of carbon paste electrode for fabricating a VEGF165 tumor marker aptasensor

The sensitive detection of trace amounts of vascular endothelial growth factor (VEGF165) in samples holds significant potential for clinical cancer diagnosis across various cancer types. This work introduces a simple, quick, and economical electrochemical method for exfoliating a graphite paste electrode (CPE) to directly synthesize a reduced graphene oxide nanosheet paste electrode (r-GONPE) for the determination of VEGF165. Thionine (Th) was used as a redox probe due to its strong interaction with the graphene surface. The functionalization of r-GONPE by thionine improves its stability while preserving the intrinsic properties of r-GONPE. Au nanoparticles were electrodeposited on the r-GONPE/Th electrode to stabilize the SH-aptamer by self-assembly for selective interaction and to enhance the speed of electron transfer. FESEM images confirmed the formation of a fixed, stable, very thin, and large few-layer reduced graphene oxide nanosheet on the outer surface of the CPE. The surface area of the bare CPE increased significantly after electrochemical exfoliation of the surface graphite layers (from 0.059 cm2 for CPE to 0.281 cm2 for r-GONPE). Electrical characterization showed that the conversion of graphite to graphene resulted in a five-fold increase in peak height and a decrease in peak separation by nearly 30 mV. The selective interaction of the VEGF165 with the r-GONPE/Th/nano-Au electrode modified with SH-aptamer reduced the oxidation peak current of thionine in the DPV signal. Thus, a wide linear calibration ranges from 5.0 pM to 320 pM and a low LOD of 1.03 pM (using the 3σ/S equation) were obtained. The aptasensor demonstrated consistent stability and strong selectivity against typical interferences when detecting picomolar concentrations of VEGF165. It also showed high accuracy and speed in detecting VEGF165 in human serum samples. Additionally, this aptasensor is advantageous due to its cost-effectiveness and simple fabrication process compared to traditional methods that use complex nanocomposites for signal enhancement.

Ultrasensitive detection of thiamethoxam by an aptasensor modified with reduced graphene oxide and Au nanoparticles

Ultrasensitive detection of thiamethoxam by an aptasensor modified with reduced graphene oxide and Au nanoparticles

Rapid dual-modal detection of two types of pesticides in fruits using SERS-based immunoassay

Pesticide residue is a harmful chemical residue produced in agricultural production, posing a threat to human health. To detect mixed pesticide residues in food rapidly and simultaneously, we present a dual-channel dual-modal test strip immunoassay. According to the standard colorimetric bar, the naked-eye test can achieve semi-quantitative detection. By collecting the Raman spectra of the signal probes, surface-enhanced Raman scattering (SERS) detection can achieve accurate quantification of pesticide residues. Specifically, a double-layer 4-mercaptobenzoic acid (4-MBA) molecule-labeled bimetallic core-shell material (AuMBA@AgMBA) was conjugated with target antibodies to obtain signal probes. Here, antibody bonding was achieved by the dehydrated condensation of its amino group with the carboxyl group of the outer 4-MBA. In addition, the Au nanoparticles were connected to rabbit IgG by electrostatic adsorption as indicating probes to ensure the normal operation of the test strips. Under the optimal parameters, the detection ranges of acetamiprid and carbendazim were 0.3 - 2μg/kg and 3 - 30μg/kg, respectively. Furthermore, the recovery experiments showed that the results of the SERS method matched well with the high-performance liquid chromatography method. The SERS immunoassay is characterized by high sensitivity, rapidity and reliability, which has potential to simultaneously detect mixed pesticides in the field.

Investigating SERS performance of controllable fabricated Ag periodic nanostructures with morphologies of nanoclaws and nanocones in detecting SARS-CoV-2 S protein

Surface-enhanced Raman scattering (SERS) spectroscopy plays an important role in enabling high-precision detection and non-invasive diagnostics. Periodic metallic nanostructures with strong electromagnetic fields and tunable localized surface plasmon resonance can achieve high SERS sensitivity, but fabricating such nanostructures remains a challenge. In this work, the anodic aluminum oxide (AAO) nanocavity template-assisted process of fabricating periodic nanostructures with modulating morphologies from Ag nanoclaws (AgNCWs) to Ag nanocones (AgNCEs) is proposed. The morphologies-related SERS performances of nanostructures are analyzed by using rhodamine 6 g (R6G) as a probe molecule and the optimized AgNCEs possess a limit of detection (LOD) of 1 × 10−9 M. A sandwich strategy is applied to detect SARS-CoV-2 S protein in phosphate-buffered saline (PBS) and pharyngeal swab solution (PSS). The ACE2-modified AgNCEs (ACE2/AgNCEs) structure is applied to bind to the SARS-CoV-2 S protein. The 4-MBA and SARS-CoV-2 S antibody functionalized Au nanoparticles (AuNPs) are used as nanotags. By forming the ACE2/AgNCEs-SARS-CoV-2 S protein-nanotags sandwich structure, characteristic peak intensities of 1580 cm−1 are used as the report signal, and the LOD for SARS-CoV-2 S protein in PBS and PSS solution are 10 fg/mL.

Entropy-driven DNA nanomachine with magnetic assistance manipulating the aggregation of Au nanoparticles for label-free photothermal Aptasensing

Photothermal sensing has attracted increasing attention as a fast and portable detection method. However, photothermal sensors with excellent comprehensive performance still face challenges. Herein, a unique photothermal biosensor for bisphenol A as a model target is successfully constructed based on aptamer recognition coupled with the programmable entropy-driven DNA nanomachine cascaded strand displacement manipulating the aggregation of gold nanoparticles. In this protocol, the exposed bases of two DNA probes released from the DNA amplification network can anchor gold nanoparticles by van der Waals attraction. This allows gold nanoparticles to resist aggregation induced by a certain concentration of sodium chloride. Based on this exclusive mechanism, target-induced visual detection can be achieved by reading temperature changes. The two probes that are fully utilized to improve the atomic economy of the reaction and enhance the detection sensitivity. Also, label-free gold nanoparticles save time in the fabrication of the photothermal sensor. Moreover, visualized photothermal sensors with multi-color gradients enable self-verification of detection results, increasing sensor reliability. In particular, the splitting mode of magnetic-assisted extraction gives the designed photothermal sensor excellent specificity, which can meet the needs of real sample detection with high background noise. Additionally, this programmable and robust photothermal sensor has advantages of portability, replicability, rapid response, and simple operation.

Tapered optical fiber LRSPR biosensor based on gold nanoparticle amplification for label-free BSA detection

Surface plasmon resonance (SPR)-based fiber optic sensors are widely used in biosensing and associated analysis of biomolecular interactions. However, the limited penetration depths of conventional SPR (CSPR, <300 nm) and localized SPR (LSPR, <200 nm) restrict their applications in specific biosensing as the surface immobilized biomolecules, i. e. antibody or aptamer, will shield the plasma wave from the target. To solve the problem, an optical fiber long range SPR (LRSPR) biosensor based on Au nanoparticles (AuNPs) amplification is developed for bovine serum albumin (BSA) detection. The single mode fiber spliced between two multimode fibers is firstly tapered for the enhancement of evanescent field, then deposited with Al2O3-Ag-Au multilayers to stimulate LRSPR and realize micron-scale larger penetration depth, finally modified with the BSA antibody by covalent bonding to specifically recognize the target biomolecule. AuNPs are introduced to improve the sensitivity after the BSA antigen-antibody combination is accomplished, taking advantage of the plasma hybridization with LRSPR and their high mass ratio. A good log-linear spectral response is obtained at the BSA concentration range of 1 ng/mL-10 mg/mL, with high sensitivity of 19.46 nm/log(ng/mL) and low limit of detection (LOD) of 0.3 ng/mL. The sensitivity of LRSPR is improved 5.6-fold and the minimum detectable BSA concentration is reduced 4 orders of magnitude by introducing AuNPs amplification. Moreover, the designed sensor shows the merits of high specificity, good stability and fast response, making it of great potential for trace biosensing applications.

Transport of Au–Ag Nanoparticles in Dense Carbon Dioxide Fluid of the Middle Crust

Individual fluid inclusions with dense carbon dioxide hosted in quartz from the gold-bearing interval penetrated by the SD-3 Kola Superdeep Borehole were studied using modern techniques. The composition and density of the carbon dioxide fluid were determined by Raman spectroscopy and microthermometry. The density of the fluid is 0.37–1.14 g/cm3 and contains minor admixtures of nitrogen (0.3–1.8 mol %) and water (0.1–0.4 mol %). LA-ICP-MS data indicate that the carbon dioxide fluid inclusions contain high concentrations of Au (1–2611 ppm) and Ag (1–4389 ppm), and high-precision optical data indicate that the high-density CO2 fluid of the inclusions contains Au–Ag nanoparticles. Evidently, gold and silver were transported from the Earth’s mantle to the crust by high-density carbon dioxide fluid in the form of nanoparticles.

Dual-Enhanced Nanohybrids for Synergistic Photothermal and Photodynamic Therapy in Cancer Treatment with Immune Checkpoint Inhibitors.

This study presents a nanohybrid that simultaneously improves both photothermal (PT) and photodynamic (PD) effects for cancer therapy. The conjugated polymer nanoparticle (CPN) comprises of p-type conjugated polymer as a photosensitizer, charge donor, and PT agent, n-type conjugated polymer as a charge acceptor and PD agent, and Au nanoparticles (NPs) as a PT agent. This nanohybrid is assembled through a film dispersion process using a hydrophobically modified phospholipid, producing a high yield of uniform hybrid NPs in a short timeframe, and displays exceptional photothermal and photodynamic effects, when activated at a single near-infrared wavelength. Photophysical analysis indicates that the inclusion of AuNPsenhances nonradiative exciton relaxation, while the incorporation of a n-type conjugated polymer boosts photoinduced charge transfer and potentially contributes to the charge-recombination mediated triplet-state formation for an enhanced generation of reactive oxygen species. During phototherapy, the nanohybrid demonstrates the most effective suppression of primary tumor growth and significantly boosts anti-tumor immune responses owing to its simultaneous photothermal and photodynamic effects. Furthermore, when combined with immune checkpoint inhibitors, nanohybrid treatment minimizes tumor sizes while maximizing survival rates in mice. Thus, the nanohybrid represents a promising nanoplatform for combination phototherapy in cancer treatment.

Copper nanocluster based cascade amplified DNA electrochemical detection combining with bio-barcode assay and surface-initiated enzyme polymerization

Early cancer diagnosis is paramount for enhancing treatment efficacy, extending patient survival, and improving the quality of life. We developed a highly sensitive electrochemical biosensor for the detection of target DNA (tDNA) associated with gastric cancer. This advancement integrates dual signal amplification strategies: bio-barcode amplification (BCA) and surface-initiated enzyme polymerization (SIEP), with copper nanoclusters (CuNCs) serving as signal labels. Silica nanoparticles (SiO2) were covalently linked with polythymine (poly T) and complementary DNA to create bio-barcode probes. These probes, through hybridization, were immobilized on the reduced graphene oxide and Au nanoparticle (rGO-AuNPs) modified interface and marking the first amplification of the electrical signal. Subsequently, the extended poly T prompted by SIEP bound additional CuNCs through the combination of T-Cu2+, leading to a second round of signal amplification. The biosensor demonstrated a minimum detection limit of 0.13 fmol/L over a linear response range from 1 fmol/L to 1 nmol/L. It also showcased excellent specificity, repeatability, and stability, making it a promising tool for the sensitive detection of gastric cancer biomarkers.

Successively enhanced photoelectrochemical performance from plasmonic Au nanoparticles decorated Ta3N5-TiO2 heterostructure

Semiconductor-based photocatalysts innovation and heterojunction design incorporating novel materials have shed light on the enhancement of the photoelectrochemical performances concerning energy fields, among which the plasmonic metal/semiconductor nanostructure raised extensive research attentions due to further PEC performance enhancement. In this work, an innovatively sandwiched structure composed of Ta3N5 nanorods/ultrathin TiO2/Au nanoparticles was designed with successive PEC enhancement. The successful combination between the Ta3N5 nanorods and the dielectric TiO2 layer represented carriers’ migration, in addition with the heterojunction between TiO2 and Au NPs contributed to the synergistically suppression of the charge carriers’ recombination. Au NPs could further serve as the plasmonic absorber underlying their localized surface plasma resonance effect, expanding the light absorption over the whole visible range, and inducing hot electrons injection to the TiO2 layer effectively. The hierarchical performance improvement via surface plasmon enhanced photoelectrochemical activity in the well-designed heterostructure propose strong potential for the development of novel photocatalysts.

Magnetically-assembled multifunctional Fe3O4@SiO2@Au particles for SERS detection of low-concentration dye molecules

Abstract Surface-enhanced Raman scattering (SERS) is a sensitive spectroscopic method to detect low concentration-low volume analytes. Owing to this, there has been a rising interest in developing improved as well as novel nanostructured substrates for SERS applications. For SERS applications, it is desirable to have large-scale assemblies of such nanostructures that can sustain multiple electromagnetic ‘hotspots’ for improved sensitivity. In this work, we use magnetic-field aided large-scale assembly of multifunctional magnetic-plasmonic particles to generate a large area SERS substrate. The particles, composed of a Fe3O4 core with a thin silica coating followed by Au nanoparticles (Fe3O4@SiO2@Au), were synthesized by simple chemical methods. The multifunctional particles were characterized using powder x-ray diffraction, transmission electron microscopy, Raman spectroscopy, and SQUID magnetometer. Magnetic assembly of the composite particles, carried out using a bi-electromagnet setup, was used for SERS detection of organic dyes such as rhodamine B and methylene blue. Using this scheme, it was possible to detect ultra-low concentrations (up to 1fM) of the dye molecules. This method is promising for applications such as chemical sensors, biomolecular detection, cancer detection, and hyperthermia treatment, forensic investigations, and drug delivery.

Fabrication of Periodically Ordered MnO2 Arrays Decorated with Au Nanoparticles for Interference Enhanced SPR-Mediated Visible-Light Responsive Photocatalysis

Fabrication of Periodically Ordered MnO2 Arrays Decorated with Au Nanoparticles for Interference Enhanced SPR-Mediated Visible-Light Responsive Photocatalysis

Utilizing DNA Logic Device for Precise Detection of Circulating Tumor Cells via High Catalytic Activity Au Nanoparticle Anchoring.

As medical advancements turn most cancers into manageable chronic diseases, new challenges arise in cancer recurrence monitoring. Detecting circulating tumor cells (CTCs) is crucial for monitoring cancer recurrence, but the current methods are cumbersome and costly. This study developed a new CTC detection system combining DNA aptamer recognition, hybridization chain reaction (HCR) technology, and DNA logic devices, enabling the one-step recognition of CTCs by identifying multiple membrane proteins. After catalytically active Au nanoparticles were attached through reduction synthesis in situ onto the DNA hybridization strands of the CTCs surface, a 3,3',5,5'-tetramethylbenzidine (TMB) colorimetric reaction was used to detect CTCs concentration via peroxidase-like catalysis. With this CTCs detection reporting system, we achieved an LOD of 4 cells/mL using an ultraviolet-visible (UV-vis) spectrophotometer. At certain concentrations, CTCs could even be detected visually without the need for an instrument. The development of this CTCs detection reporting system provided a convenient, reliable, and cost-effective detection strategy for widespread CTCs-based cancer recurrence monitoring.