Active Gold Nanoparticles Research Articles

High-Performance Flexible Near-Infrared-II Phototransistor Realized by Combining the Optimized Charge-Transfer-Complex/Organic Heterojunction Active Layer and Gold Nanoparticle Modification

High-Performance Flexible Near-Infrared-II Phototransistor Realized by Combining the Optimized Charge-Transfer-Complex/Organic Heterojunction Active Layer and Gold Nanoparticle Modification

Multi-signal aptasensor for thrombin detection based on catalytically active gold nanoparticles and fluorescent silicon quantum dots.

A multi-signal aptasensor for thrombin determination isproposed based on catalytically active gold nanoparticles (AuNPs) and fluorescent silicon quantum dots (SiQDs). Yellow 4-Nitrophenol (4-NP) could be converted to colorless 4-Aminophenol (4-AP) by catalytically active aptamer-modified AuNPs (S1-AuNPs). The SiQDs emitted strong blue fluorescence at 455nm at the excitation wavelength of 367nm. When thrombin was absent, S1-AuNPs could catalytically reduce yellow 4-NP to colorless 4-AP. When thrombin was added, the aptamer could be transformed into a G-quadruplex structure, which masked the surface-active catalytic sites of AuNPs and restrained the reduction of 4-NP. Thus, the fluorescence of SiQDs was greatly quenched by 4-NP through the inner filter effect (IFE), and the solution color remained yellow. As the concentration of thrombin increased, the catalytic activity of S1-AuNPs decreased. The concentration of 4-NP that was converted to 4-AP declined and the unconverted 4-NP increased. In this process, the absorption peak of 4-NP at 400nm increased while the fluorescence emission of SiQDs at 455nm decreased. The linear ranges of the fluorometric and colorimetric aptasensor were 0.5-30nM and 0.3-30nM, respectively. The limits of detection (LOD) for the two modes were 0.15nM and 0.13nM. Furthermore, a portable sensing platform was constructed by combining the smartphone-based device with the software ImageJ for the determination of thrombin. With the advantages of cost-effectiveness, simplicity of operation and broad applicability, this aptasensor provided a new perspective for on-site determinationof thrombin in the clinical field.

Ultrasensitive Nonenzymatic Real-Time Hydrogen Peroxide Monitoring Using Gold Nanoparticle-Decorated Titanium Dioxide Nanotube Electrodes.

An amperometric enzyme-free hydrogen peroxide (H2O2) sensor was developed by catalytically stabilizing active gold nanoparticles (Au NPs) of 4-5 nm on a porous titanium dioxide nanotube (TiO2 NTs) electrode. The Au NPs were homogeneously distributed on anatase TiO2 NTs with an outer diameter of ~102 nm, an inner diameter of ~60 nm, and a wall of thickness of ~40 nm. The cyclic voltammogram of the composite electrode showed a pair of redox peaks characterizing the electrocatalytic reduction of H2O2. The entrapping of Au NPs on TiO2 NTs prevented aggregation and facilitated good electrical conductivity and electron transfer rate, thus generating a wide linear range, a low detection limit of ~104 nM, and high sensitivity of ~519 µA/mM, as well as excellent selectivity, reproducibility, repeatability, and stability over 60 days. Furthermore, excellent recovery and relative standard deviation (RSD) were achieved in real samples, which were tap water, milk, and Lactobacillus plantarum bacteria, thereby verifying the accuracy and potentiality of the developed nonenzymatic sensor.

Alveoli-Like Multifunctional Scaffolds for Optical and Electrochemical In Situ Monitoring of Cellular Responses from Type II Pneumocytes.

While breathing, alveoli are exposed to external irritants, which contribute to the pathogenesis of lung disease. Therefore, in situ monitoring of alveolar responses to stimuli of toxicants under in vivo environments is important to understand lung disease. For this purpose, 3D cell cultures are recently employed for examining cellular responses of pulmonary systems exposed to irritants; however, most of them have used ex situ assays requiring cell lysis and fluorescent labeling. Here, an alveoli-like multifunctional scaffold is demonstrated for optical and electrochemical monitoring of cellular responses of pneumocytes. Porous foam with dimensions like the alveoli structure is used as a backbone for the scaffold, wherein electroactive metal-organic framework crystals, optically active gold nanoparticles, and biocompatible hyaluronic acid are integrated. The fabricated multifunctional scaffold allows for label-free detection and real-time monitoring of oxidative stress released in pneumocytes under toxic-conditions via redox-active amperometry and nanospectroscopy. Moreover, cellular behavior can be statistically classified based on fingerprint Raman signals collected from the cells on the scaffold. The developed scaffold is expected to serve as a promising platform to investigate cellular responses and disease pathogenesis, owing to its versatility in monitoring electrical and optical signals from cells in situ in the 3D microenvironments.

Water-soluble ionic carbon nitride as unconventional stabilizer for highly catalytically active ultrafine gold nanoparticles.

Ultrafine metal nanoparticles (NPs) hold promise for applications in many fields, including catalysis. However, ultrasmall NPs are typically prone to aggregation, which often leads to performance losses, such as severe deactivation in catalysis. Conventional stabilization strategies (e.g., immobilization, embedding, or surface modification by capping agents) are typically only partly effective and often lead to loss of catalytic activity. Herein, a novel type of stabilizers based on water-soluble ionic (K+ and Na+ containing) polymeric carbon nitride (i.e., K,Na-poly(heptazine imide) = K,Na-PHI) is reported that enables effective stabilization of highly catalytically active ultrafine (size of ∼2-3 nm) gold NPs. Experimental and theoretical comparative studies using different structural units of K,Na-PHI (i.e., cyanurate, melonate, cyamelurate) indicate that the presence of functionalized heptazine moieties is crucial for the synthesis and stabilization of small Au NPs. The K,Na-PHI-stabilized Au NPs exhibit remarkable dispersibility and outstanding stability even in solutions of high ionic strength, which is ascribed to more effective charge delocalization in the large heptazine units, resulting in more effective electrostatic stabilization of Au NPs. The outstanding catalytic performance of Au NPs stabilized by K,Na-PHI is demonstrated using the selective reduction of 4-nitrophenol to 4-aminophenol by NaBH4 as a model reaction, in which they outperform even the benchmark "naked" Au NPs electrostatically stabilized by excess NaBH4. This work thus establishes ionic carbon nitrides (PHI) as alternative capping agents enabling effective stabilization without compromising surface catalysis, and opens up a route for further developments in utilizing PHI-based stabilizers for the synthesis of high-performance nanocatalysts.

Facile preparation of highly active zirconia-supported gold nanoparticle catalyst

Au/insulating ZrO2 prepared by a modified deposition precipitation (DP) method with a pre-step of long-time stirring of ZrO2 NPs in HAuCl4 solution shows catalytic activity for two electron-oxygen reduction much higher than Au/semiconducting metal oxides prepared by the normal DP method.

Gold Nanoparticles Supported on Triazole-Functionalized Biochar as Nanocatalyst for Hydrogen Evolution from Aqueous Solution

Biochar is a material of great ecological interest obtained from the carbonization of biomass. Its structure is composed of graphene-like aggregates, and it contains useful functional groups such as carboxyl. Using these groups, biochar functionalization with triazole groups that improve support characteristics has been achieved to anchor and stabilize catalytically active gold nanoparticles (Au NPs). The Au NPs obtained were homogeneously distributed under biochar, with a size of 7.7 ± 3.5 nm. The efficiency of the nanomaterial was shown in nanogold-catalyzed hydrogen evolution from an aqueous solution containing B2(OH)4, with a maximum hydrogen generation of 715 mLH2 g-1 min-1 under optimized conditions (0.070 mmol of Au NPs and 0.300 mol L-1 of NaOH). This nanomaterial showed excellent efficiency in four successive catalytic cycles.

Quantifying Radiosensitization of PSMA-Targeted Gold Nanoparticles on Prostate Cancer Cells at Megavoltage Radiation Energies by Monte Carlo Simulation and Local Effect Model.

Active targeting gold nanoparticles (AuNPs) are a very promising avenue for cancer treatment with many publications on AuNP mediated radiosensitization at kilovoltage (kV) photon energies. However, uncertainty on the effectiveness of AuNPs under clinically relevant megavoltage (MV) radiation energies hinders the clinical translation of AuNP-assisted radiation therapy (RT) paradigm. The aim of this study was to investigate radiosensitization mediated by PSMA-targeted AuNPs irradiated by a 6 MV radiation beam at different depths to explore feasibility of AuNP-assisted prostate cancer RT under clinically relevant conditions. PSMA-targeted AuNPs (PSMA-AuNPs) were synthesized by conjugating PSMA antibodies onto PEGylated AuNPs through EDC/NHS chemistry. Confocal fluorescence microscopy was used to verify the active targeting of the developed PSMA-AuNPs. Transmission electron microscopy (TEM) was used to demonstrate the intracellular biodistribution of PSMA-AuNPs. LNCaP prostate cancer cells treated with PSMA-AuNPs were irradiated on a Varian 6 MV LINAC under varying depths (2.5 cm, 10 cm, 20 cm, 30 cm) of solid water. Clonogenic assays were carried out to determine the in vitro cell survival fractions. A Monte Carlo (MC) model developed on TOPAS platform was then employed to determine the nano-scale radial dose distribution around AuNPs, which was subsequently used to predict the radiation dose response of LNCaP cells treated with AuNPs. Two different cell models, with AuNPs located within the whole cell or only in the cytoplasm, were used to assess how the intracellular PSMA-AuNP biodistribution impacts the prostate cancer radiosensitization. Then, MC-based microdosimetry was combined with the local effect model (LEM) to calculate cell survival fraction, which was benchmarked against the in vitro clonogenic assays at different depths. In vitro clonogenic assay of LNCaP cells demonstrated the depth dependence of AuNP radiosensitization under clinical megavoltage beams, with sensitization enhancement ratio (SER) of 1.14 ± 0.03 and 1.55 ± 0.05 at 2.5 cm depth and 30 cm depth, respectively. The MC microdosimetry model showed the elevated percent of low-energy photons in the MV beams at greater depth, consequently resulting in increased dose enhancement ratio (DER) of AuNPs with depth. The AuNP-induced DER reached ~5.7 and ~8.1 at depths of 2.5 cm and 30 cm, respectively. Microdosimetry based LEM accurately predicted the cell survival under 6 MV beams at different depths, for the cell model with AuNPs placed only in the cell cytoplasm. TEM results demonstrated the distribution of PSMA-AuNPs in the cytoplasm, confirming the accuracy of MC microdosimetry based LEM with modelled AuNPs distributed within the cytoplasm. We conclude that AuNP radiosensitization can be achieved under megavoltage clinical radiotherapy energies with a dependence on tumor depth. Furthermore, the combination of Monte Carlo microdosimetry and LEM will be a valuable tool to assist with developing AuNP-aided radiotherapy paradigm and drive clinical translation.

Methylene blue biosorption and antibacterial active gold nanoparticle synthesis using microwave-treated structurally modified water hyacinth biomass

Methylene blue biosorption and antibacterial active gold nanoparticle synthesis using microwave-treated structurally modified water hyacinth biomass

A surface‐enhanced Raman sensor for trace identification and analysis of high‐priority drugs of abuse with portable and handheld Raman devices

AbstractSurface‐enhanced Raman spectroscopy (SERS) is a rapidly emerging technology that offers a fast, extremely sensitive, and quantitative approach to trace chemical detection. Such a technique incorporated into a portable device is attractive to law enforcement and emergency room personnel for rapid accurate on‐site screening of illicit and abused drugs. Toward this, we are developing an analyzer in a hand‐held unit, based on SERS that is integrated with a capillary sensor embedded with activated gold nanoparticles in a porous glass matrix. In this preliminary study, we have used this gold sol–gel capillary to measure aqueous solutions of 14 high‐priority drugs to define sensitivity (lowest measured concentration [LMC] and estimated limit of detection [LOD]), determine concentration dependence and quantification capabilities by constructing calibration curves, examine effects of pH at 3, 7, and 11 on SERS measurements, and perform multicomponent analysis of fentanyl laced drug mixtures and spectral identification on our portable and handheld units. Of particular significance, fentanyl was detected with an LMC of 1 ng/ml and estimated LOD at 0.11 ng/ml, while other representative drugs such as cocaine and phenylcyclidine produced LMCs and LODs at 5.0 and 0.77 ng/ml, and 10.0 and 0.62 ng/ml, respectively. These sub‐nanogram per milliliter detection limits are comparable or lower than previously reported and confirm that this gold sol–gel has the potential to meet the sensitivity requirements for saliva analysis. Most importantly, these sensors can be manufactured easily and cheaply and when integrated with our portable Raman units produce high‐quality spectra and accurate identification within 1.2 s.

Colorimetric Kit for Rapid Porcine Circovirus 2 (PCV-2) Diagnosis.

The aim of the current study is to present a low-cost and easy-to-interpret colorimetric kit used to diagnose porcine circovirus 2 (PCV-2) to the naked eye, without any specific equipment. The aforementioned kit used as base hybrid nanoparticles resulting from the merge of surface active maghemite nanoparticles and gold nanoparticles, based on the deposition of specific PCV-2 antibodies on their surface through covalent bonds. In total, 10 negative and 40 positive samples (≥102 DNA copies/µL of serum) confirmed by qPCR technique were tested. PCV-1 virus, adenovirus, and parvovirus samples were tested as interferents to rule out likely false-positive results. Positive samples showed purple color when they were added to the complex, whereas negative samples showed red color; they were visible to the naked eye. The entire color-change process took place approximately 1 min after the analyzed samples were added to the complex. They were tested at different dilutions, namely pure, 1:10, 1:100, 1:1000, and 1:10,000. Localized surface plasmon resonance (LSPR) and transmission electron microscopy (TEM) images were generated to validate the experiment. This new real-time PCV-2 diagnostic methodology emerged as simple and economic alternative to traditional tests since the final price of the kit is USD 4.00.

Low Temperature CO Oxidation Over Highly Active Gold Nanoparticles Supported on Reduced Graphene Oxide@Mg-BTC Nanocomposite

Low Temperature CO Oxidation Over Highly Active Gold Nanoparticles Supported on Reduced Graphene Oxide@Mg-BTC Nanocomposite

Part-Per-Billion Level Chemical Sensing with a Gold-Based SERS-Active Substrate.

We used surface-enhanced Raman spectroscopy (SERS) for the rapid and sensitive detection and quantification of caffeine in solution. Such a technique incorporated into a portable device is finding wide applications in trace chemical analysis in various fields, including law enforcement, medicine, environmental monitoring, and food quality control. To realize such applications, we are currently developing portable and handheld trace chemical analyzers based on SERS, which are integrated with a sensor embedded with activated gold nanoparticles in a porous glass matrix. In this study, we used this gold SERS-active substrate to measure aqueous solutions of the drug caffeine as a test chemical to benchmark sensor performance by defining sensitivity (lowest measured concentration (LMC) and estimated limit of detection (LOD)), determining concentration dependence and quantification capabilities by constructing calibration curves; by evaluating the effects of pH values of 3, 7, and 11; and by examining the reproducibility of the SERS measurements. The results demonstrate that the SERS sensor is sensitive, with caffeine detected at an LMC of 50 parts per billion (ppb) with an LOD of 0.63 ppb. The results further show that the sensor is very stable and can be used to make reproducible measurements, even under extremely acidic to basic pH conditions. Vibrational assignments of all observed SERS peaks are made and reported for the first time for caffeine on a gold substrate.

Investigating the Production of Antimicrobial Nanoparticles by Chlorella vulgaris and the Link to Its Loss of Viability.

Chlorella vulgaris from Al-Ahsa, KSA was proved to be an active silver and gold nanoparticle producer. Nanogold and nanosilver particles were characterized using UV-visible spectroscopy, Fourier-transform infrared spectroscopy, and scanning electronmicroscopy. Both nanoparticles were used in the antimicrobial bioassay. The two nanoparticles showed antibacterial activities, with the silver nanoparticles being the most effective. To investigate the argumentative nature of their biosynthesis (i.e., whether it is a biotic or abiotic process), we isolated total ribonucleic acid RNA as an indicator of vitality. RNA was completely absent in samples taken after one week of incubation with silver nitrate and even after one or two days. However, successful extraction was only achievable in samples taken after incubation for one and four hours with silver nitrate. Most importantly, the gel image showed recognizable shearing of the nucleic acid after 4 h as compared to the control. An assumption can be drawn that the synthesis of nanoparticles may start biotically by the action of enzyme(s) and abiotically by action of reducing entities. Nonetheless, with prolonged incubation, excessive nanoparticle accumulation can be deadly. Hence, their synthesis continues abiotically. From the RNA banding profile, we suggest that nanosilver production starts both biotically and abiotically in the first few hours of incubation and then continues abiotically. Nanosilver particles proved to have more of an antimicrobial impact than nanogold and hence are recommended for different applications as antibacterial agents.

A Manuscript for Journal of Catalysissimple Preparation of Highly Active Zirconia-Supported Gold Nanoparticle Catalyst

A Manuscript for Journal of Catalysissimple Preparation of Highly Active Zirconia-Supported Gold Nanoparticle Catalyst

Gold decorated on anodic aluminium oxide and its unique catalytic activity

Highly active gold nanoparticles (Au NPs) on anodic aluminium oxide (AAO) were successfully fabricated via the deposition–precipitation (DP) method for the reduction of p-nitrophenol (p-NP). The effect of Au precursor (HAuCl4) concentration from 0.04 until 8.00 mM was studied. The highest rate constant (k) value of 0.846 min−1 was achieved for Au-AAO prepared at 4.0 mM Au concentration. Scanning electron microscopy (SEM) shows a clear image of Au NPs on AAO with an average of 8.67 ± 2.39 nm and 0.853 wt% Au loadings by Inductive Couple Plasma (ICP) analysis. The Au on CNTs/AAO was further prepared to study the effect of second support; carbon nanotubes (CNTs) towards p-NP reduction. Significant enhancement of the k value up to 1.041 min−1 was demonstrated with Au loadings of 2.32 wt%. This result shows the combination of two supports (CNTs/AAO) improved the deposition and distribution of Au (as viewed by SEM) and subsequently enhanced the catalytic activity.

A coordination cage hosting ultrafine and highly catalytically active gold nanoparticles.

Ultrafine metal nanoparticles (MNPs) with size <2 nm are of great interest due to their superior catalytic capabilities. Herein, we report the size-controlled synthesis of gold nanoparticles (Au NPs) by using a thiacalixarene-based coordination cage CIAC-108 as a confined host or stabilizer. The Au NPs encapsulated within the cavity of CIAC-108 (Au@CIAC-108) show smaller size (∼1.3 nm) than the ones (∼4.7 nm) anchored on the surface of CIAC-108 (Au/CIAC-108). The cage-embedded Au NPs can be used as a homogeneous catalyst in a mixture of methanol and dichloromethane while as a heterogeneous catalyst in methanol. The homogeneous catalyst Au@CIAC-108-homo exhibits significantly enhanced catalytic activities toward nitroarene reduction and organic dye decomposition, as compared with its larger counterpart Au/CIAC-108-homo and its heterogeneous counterpart Au@CIAC-108-hetero. More importantly, the as-prepared Au@CIAC-108-homo possesses remarkable stability and durability.

Evaluation of the Sorption Capacity of a Maleic Acid Copolymer Towards Gold(III) Ions and Production of Catalytically Active Gold Nanoparticles on Its Base

Two spectrophotometric approaches are suggested for the assessment of the concentration of gold(III) cations in an aqueous solution: direct recording of the optical density of gold cations and galvanic substitution of silver atoms in polymer-stabilized silver nanoparticles with gold cations. The sorption capacity of a maleic acid copolymer towards gold cations is estimated. A colloidal composite containing gold nanoparticles is obtained from the polymeric gold salt. The catalytic properties of the resulting polymer-stabilized nanogold are studied in the aerobic oxidation of glucose to gluconic acid.

Role of tannic acid in desiging of electrically active and magnetic gold nanoparticles and enhanced photovoltaic performance of gold@titania photoanode in DSSC

We describe here in significance of tannic acid in obtaining size dependent electrochemically active and magnetic gold nanoparticles (GNPs). In this account, two types of GNPs (SCGNPs and SC-TAGNPs) were synthesized by using sodium citrate and sodium citrate-tannic acid as reducing agents, respectively. Highly monodispersed, uniformly distributed and small size GNPs were produced when tannic acid was used together with sodium citrate. SC-TAGNPs exhibited room temperature ferromagnetism while SCGNPs revealed diamagnetism. With higher anodic peak current and lower charge transfer resistance, the SC-TAGNPs exhibited better conductivity and electron transfer ability than SCGNPs. Mott-Schottky analysis revealed n-type semiconducting behavior of GC/SCGNPs & GC/SC-TAGNPs and showed positive shift in flat-band potential of GC/SC-TAGNPs compared to GC/SCGNPs suggesting better conductivity of SC-TAGNPs. Subsequently, SCGNPs and SC-TAGNPs were added to TiO2 nanoparticles to fabricate modified titania photoanodes (SCGNPs@TiO2 and SC-TAGNPs@TiO2) for dye-sensitized solar cells (DSSCs) application. With the use of TiO2, SCGNPs@TiO2 and SC-TAGNPs@TiO2 photoanodes, the short-circuit current density (JSC) was observed to be 2.18, 4.50 and 6.68 mA/cm2, while energy conversion efficiency (η) was found to be 0.75, 1.74 and 2.50%, respectively. The TiO2 photoanode employing SC-TAGNPs exhibited remarkably increased JSC and η by ∼48 and ∼44%, respectively, then SCGNPs modified photoanode.

Active Targeting Gold Nanoparticle for Chemotherapy Drug Delivery: A Review

Objective Active targeting strategy in chemotherapy drug delivery aims to improve the therapeutic outcomes and minimise the side effects of chemotherapeutics. This review discusses utilising ligands attached to gold nanoparticles (AuNPs) along with several specific ligands attached to AuNPs for active targeting in chemotherapy drug delivery. Key finding Antibodies, peptides, vitamins, DNA, polysaccharides, aptamers, and hormones showed active-targeting abilities as ligands attached to AuNPs. Active-targeting AuNPs enhanced cellular uptake and cytotoxicity in a specific cancer cell in vitro while reducing tumor growth in vivo by improving the photothermal, photodynamic and chemotherapy effects. Active-targeting ligands increased the internalization of AuNPs loaded onto the specific tumour site and minimised the accumulation in the normal site. Conclusion AuNPs with active-targeting ligands such as antibodies, peptides, vitamins, DNA polysaccharides, aptamers, and hormones can improve the therapeutic outcomes of chemotherapeutics and can attenuate the toxicity effect in normal cells. For further research and development, researchers should be addressing AuNP characterization, drug–ligand disposition, active-targeting AuNP quantification, and target-AuNPs pertinence concerning the desired therapeutic outcomes.