Decorated Au NPs Research Articles

Au nanoparticle decoration of nanoparticular and nanotubular TiO2 using atmospheric pressure cold plasma for photocatalytic applications

In situ formation and direct decoration of Au NPs on TiO2 using an atmospheric pressure DBD plasma torch at low temperature.

Green synthesis of Ag and Au NPs decorated rGO nanocomposite for high impedimetric electrochemical sensor as well as enhanced antimicrobial performance against foodborne pathogens

In the present study, Allium cepa L. leaves extract mediated silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) decorated reduced graphene oxide (Ag/Au/rGO NC’s) were synthesized and demonstrated their biological and electrochemical sensing applications. Interestingly, the synthesis of AgNPs and AuNPs was achieved rapidly within 1 h and 4 h, respectively. Whereas the production of both reduced graphene oxide (rGO) and Ag/Au/rGO NC’s was achieved at 96 h. The achieved results from the UV–Vis spectrum of 432 nm for AgNPs and 550 nm of AuNPs and the shifting of the characteristic GO absorption band of 230 nm into 270 nm as well as an absence of 305 nm confirmed the rGO synthesis. In addition, HR-XRD analyses confirmed the JCPDS file No. 04–0783 and 01–1174 pertaining to Ag and Au NPs. Further, the Raman spectroscopy, FT-IR and EDS analyses confirmed the evidence of nanomaterials biosynthesis. A polydisperse, spherical shaped average size AgNPs of 1 to 30 nm, spherical and triangular shaped AuNPs with an average size of 1 to 120 nm, and silk like appearance of a thin layered graphene sheet in rGO were observed through TEM. Also, the recorded results evident the uniform decoration of Ag and Au NPs into the rGO sheet. The electrochemical properties of as-synthesized materials were studied by electrochemical impedance spectroscopic (EIS) and cyclic voltammetry (CV) techniques. Interestingly, the Ag/Au/rGO NC’s modified electrode exhibited higher electrical conductivity and good electrocatalytic properties towards the electrooxidation of nitrite in a neutral medium than other nanomaterials. Eventually, Ag/Au/rGO NC’s confirmed the enhanced antibacterial against Gram-negative bacteria and dose dependent antifungal inhibitory activities against foodborne fungal pathogens of Fusarium graminearum, Alternaria alternata, and phytopathogenic fungus of Curvularia lunata and Sclerotinia sclerotiorum at the maximum tested conc. of 2 mg/mL, compared to other nanomaterials. From the result of zebrafish embryotoxicity (ZET), the highest toxicity was observed for AgNPs at 0.19 μg/mL. But in the case of Ag/Au/rGO NC’s the reduced toxicity was observed. Hence, the achieved results concluded the Ag/Au/rGO NC’s could be suitable for development of both as biomaterials for biomedical and effective sensors for environmental applications.

Ligand Mediation for Tunable and Oxide Suppressed Surface Gold-Decorated Liquid Metal Nanoparticles.

Gallium-based liquid metal systems hold vast potential in materials science. However, maximizing their possibilities is hindered by gallium's native oxideand interfacial functionalization. In this study, small-molecule ligands are adopted as surfactants to modify the surface of eutectic gallium indium (EGaIn) nanoparticles and suppress oxidation. Different p-aniline derivatives are explored. Next, the reduction of chloroanric acid (HAuCl4 ) onto these p-aniline ligand modified EGaIn nanoparticles is investigated to produce gold-decorated EGaIn nanosystems. It is found that by altering the concentrations of HAuCl4 or the p-aniline ligand, the formation of gold nanoparticles (AuNPs) on EGaIn can be manipulated. The reduction of interfacial oxidation and presence of AuNPs enhances electrical conductivity, plasmonic performance, wettability, stability, and photothermal performance of all the p-aniline derivative modified EGaIn. Of these, EGaIn nanoparticles covered with the ligand of p-aminobenzoic acid offer the most evenly distributed AuNPs decoration and perfect elimination of gallium oxides, resulting in the augmented electrical conductivity, and highest wettability suitable for patterning, enhanced aqueous stability, and favorable photothermal properties. The proof-of-concept application in photothermal therapy of cancer cells demonstrates significantly enhanced photothermal conversion performance along with good biocompatibility. Due to such unique characteristics, the developed gold-decorated EGaIn nanodroplets are expected to offer significant potential in precise medicine.

Interfacing Nanomaterials with Biology through Ligand Engineering.

Nanoparticles (NPs) have incredible potential in biology and biomedicine. Gold nanoparticles (AuNPs) have become a cornerstone of the nanomedicine revolution due to their ease of synthesis, inertness, and versatility. The widespread use of AuNPs can be traced to the development of accessible, bottom-up wet synthesis methods that emphasized the role of ligands in controlling the size, dispersity, and stability of colloids in solution. Decoration of AuNPs with organic ligands can be used to dictate the interactions of these nanomaterials with biosystems on multiple scales. The tunability of the AuNP ligand monolayer via covalent and noncovalent approaches allows the use of AuNPs in a broad range of biomedical fields.In this Account, we describe our use of AuNPs to answer a central question in the ligand engineering of colloidal nanoparticles: can we fabricate NPs that are nontoxic, modular, and functional in biological environments? We explored spherical AuNPs of different sizes and ligand structures, empirically exploring the AuNP-biomolecule interaction. We show here how the atom-by-atom control provided by organic synthesis can be used to create engineered ligands. Presenting these ligands on the surface of AuNPs creates multivalent constructs with unique and useful properties. Ligand design is a key feature of these AuNPs. We have developed ligands that have three distinct structural segments: 1) a hydrophobic alkanethiol interior that imparts stability; 2) a tetra(ethylene glycol) segment that creates a noninteracting tabula rasa surface; and 3) ligand headgroups that dictate how the AuNP interacts with the outside world. Our research into the design principles of ligands on AuNPs and their interactions with biological systems can be translated to other nanoparticle systems.This Account also summarizes the trajectory of ligand engineering in our laboratory and further afield. At the outset, experimental and theoretical fundamental studies were focused on the interactions between AuNPs and cellular components, such as proteins and lipid membranes. Understanding these behaviors provided the direction for investigating how ligands mediate the interface of AuNPs with mammalian and bacterial cells. In these experiments, it was particularly noteworthy that the ligand hydrophobicity and charge play a significant role in the uptake and toxicity of AuNPs. These revelations formed a basis for translating AuNPs to physiological environments. We present how we have integrated our synthetic abilities to construct AuNPs for biomedical applications, including delivery, bioorthogonal catalysis, antimicrobial and antitumor therapeutics, and biosensing.Overall, we hope that this Account will give the reader insight into how our research has evolved, changing AuNPs from synthetic curiosities into functional nanoplatforms for nanomedicine, all through the power of ligand design and synthesis.

Terahertz emission enhancement of GaAs-based photoconductive antennas via the nanodecoration of their surface by means of pulsed-laser-deposition of gold nanoparticles

We report a systematic study of free-space terahertz (THz) emission from photoconductive antennas (PCAs) nanodecorated with gold nanoparticles (Au-NPs) deposited by using the pulsed laser deposition (PLD) technique. H-shaped dipole micro-structured PCAs fabricated on semi-insulating GaAs substrates were decorated under various PLD conditions. Thus, by increasing the number of laser ablation pulses (NLP) of the Au target, both the average size of Au-NPs and the surface loading of PCAs increase. Compared with non-decorated PCAs, those decorated with Au-NPs exhibit significant enhancement in the radiated THz pulse amplitude. A maximum enhancement of ∼2.3 was achieved at NLP = 1250. Under this optimal NLP condition, not only is the average Au-NP size (of ∼15 nm) favorable for light absorption via localized surface plasmons, but also the inter-distance between NPs, the light reflectance, and facilitated transport of photocarriers, all combine to yield a stronger THz field emission. For higher NLP (≥2000), NPs coalesce and tend to form continuous film NPs, which not only significantly limits the light scattering toward the GaAs underlying substrate, but also electrically shorts the PCA. Finally, the Au-NP decoration of GaAs PCAs was also found to improve their overall thermal conductivity, making them much more thermally stable than their non-decorated counterparts.

Field electron emission behavior of pristine and Au nanoparticles decorated Sb2Te3-rGO heterostructure emitters

A facile one-pot hydrothermal method was used to synthesize pristine Sb2Te3 and its heterostructure with reduced graphene oxide (rGO). A novel approach dealing with high energy (6 MeV) electron irradiation has been efficiently used for synthesis of gold nanoparticles (Au- NPs) and their in-situ decoration on Sb2Te3-rGO heterostructure. From an application point of view, we have investigated the field electron emission characteristics of pristine Sb2Te3 and Sb2Te3-rGO heterostructures, with and without Au-NPs decoration. The Au-NPs decorated Sb2Te3-rGO heterostructure emitter showed enhanced electron emission behavior in terms of reduced value of turn-on field, delivery of large emission current density (∼1171 µA/cm2) at relatively lower applied field (∼3.1 V/µm), and excellent emission stability. The improvement in emission characteristics upon decoration of Au-NPs is attributed to noticeable increase in the number of emission sites, higher value of field enhancement factor (β = 4562), and betterment in the electronic properties due to Au-NPs-Sb2Te3-rGO interface effects. The obtained results suggest that Au-NPs decorated Sb2Te3-rGO heterostructure emitter has potential towards practical applications in various vacuum microelectronic devices. Furthermore, the present approach dealing with high energy electron irradiation for synthesis and in-situ decoration of nanoparticles can extended to other inorganic heterostructures towards improving their functionality.

Au nanoparticles decorated nanographene oxide-based platform: Synthesis, functionalization and assessment of photothermal activity

A novel hybrid nanocomposite formed of carboxylated Nano Graphene Oxide (c-NGO), highly densely decorated by monodisperse citrate-coated Au nanoparticles (c-NGO/Au NPs), is synthesized and thoroughly characterized for photothermal applications. A systematic investigation of the role played by the synthetic parameters on the Au NPs decoration of the c-NGO platform is performed, comprehensively studying spectroscopic and morphological characteristics of the achieved nanostructures, thus elucidating their still not univocally explained synthesis mechanism.Remarkably, the Au NPs coating density of the c-NGO sheets is much higher than state-of-the-art systems with analogous composition prepared with different approaches, along with a higher NPs size dispersion. A novel theoretical approach for estimating the average number of NPs per sheet, combining DLS and TEM results, is developed. The assessment of the c-NGO/Au NPs photothermal activity is performed under continuous wave (CW) laser irradiation, at 532 nm and 800 nm, before and after functionalization with PEG-SH. c-NGO/Au NPs composite behaves as efficient photothermal agent, with a light into heat conversion ability higher than that of the single components. The c-NGO/Au NPs compatibility for photothermal therapy is assessed by in vitro cell viability tests, which show no significant effects of c-NGO/Au NPs, as neat and PEGylated, on cell metabolic activity under the investigated conditions. These results demonstrate the great potential held by the prepared hybrid nanocomposite for photothermal conversion technologies, indicating it as particularly promising platform for photothermal ablation of cancer cells.

Decorated Au NPs on lignin coated magnetic nanoparticles: Investigation of its catalytic application in the reduction of aromatic nitro compounds and its performance against human lung cancer

In the recent years, bio-functionalized noble metal doped advanced magnetics nanocomposite materials has been materialized as potential featured catalysts in diverse applications. In this connection, we report herein a novel biogenic lignin driven Au nanoparticle supported Fe3O4 composite material. The procedure is free from any harsh reducing or stabilizing agent. Morphology and structural features were assessed following different physicochemical methodologies like FT-IR, FE-SEM, TEM, EDS, XRD, VSM and ICP-OES techniques. Thereafter, the [Fe3O4/Lignin/Au] material was successfully employed in the efficient reduction of different nitroarenes in aqueous medium. The process was monitored over UV–Vis spectroscopic study. Excellent yields were achieved with a range of diverse functionalized nitroarenes within 10–45 min of reaction. The nanocatalyst was recycled 10 times without any significant loss of catalytic activity. Distinctiveness of the material's activity was validated by comparing the results in the reduction of 4-nitrophenol. Furthermore, the prepared [Fe3O4/Lignin/Au] nanocomposite system exhibited outstanding antioxidant and anticancer effects against five lung cancer cell lines, such as, BICR 3, BICR 78, CALU 1, ChaGo-K-1, and A549. Cytotoxicity assay was determined in terms of % cell viability following MTT protocol. The corresponding IC50 values were obtained as 47, 31, 19, 25, and 31 μg/mL respectively.

Nanostructural dimension and oxygen vacancy synergistically induced photoactivity across high surface area monodispersed AuNPs/ZnO nanorods heterojunction

Inhibiting the electron-hole recombination by adequate surface modification is a significant challenge for developing highly efficient photoanodes. This report envisions a structural synergism between a surface oxygen vacancy and metal/semiconductor contact area to significantly boost up the charge separation and injection efficiency of ZnO nanorods (NRs) in photoelectrochemical (PEC) performance. A three-dimensional photoanode is designed by vertically aligning the ZnO NRs and tuned their dimension by varying the annealing temperature and time followed by their decoration with AuNPs. Different stages of heat treatment created high oxygen vacancy, which is a key factor in tailoring the PEC activity. The ZnO NRs-A offered 75.5% average contact area for hosting the 16 nm diameter AuNPs, whereas, the ZnO NRs-B delivered 47.8%. The ZnO NRs-B with high oxygen defects exhibits a similar photoactivity shown by large dimensional ZnO NRs-A. After decorating with AuNPs, the AuNPs/ZnO NRs-A delivered ~3-fold increases in photocurrent than AuNPs/ZnO NRs-B, suggesting the photoactivity enhancement is mainly contributed from the effective charge transfer across the heterojunction between the electron mediating AuNPs and ZnO NRs, which reduces the electron-hole pair recombination. Besides, having higher oxygen vacancies, the AuNPs/ZnO NRs-B exhibited substantial photoactivity similar with AuNPs/ZnO NRs-A. The comparison of the incident photon-to-current and the applied bias photon-to-current efficiencies of the AuNPs/ZnO NRs with the reported photoanodes further authenticated the enhanced PEC performance of AuNPs/ZnO NRs. This work opens up a potential approach to metal-semiconductor heterojunction design by reduction of electron-hole recombination in PEC water splitting and solar energy conversion applications. A three-dimensional (3-D) photoanode was designed based on vertically aligned ZnO nanorods followed by their homogeneous decoration with AuNPs and their defects versus metal/semiconductor heterojunction induced photoelectrochemical behavior was investigated. • The PEC performance of ZnO nanorods was improved by the decoration of AuNPs nanocomposite on SrTiO 3 substrate. • Different approaches were employed for tuning the dimension of ZnO NRs by varying the annealing temperature and time. • Decoration of AuNPs enhances the oxygen vacancy of ZnO NRs and hence the electron-hole pair recombination was evaded . • The ZnO NRs-B exhibited oxygen defects induced PEC performance than ZnO NRs-A in visible light region. • The AuNPs/ZnO NRs-A delivered plasmonic and metal/semiconductor contact area induced PEC performance .

Ultrasonic-assisted decoration of AuNPs on carbon nano-onions as robust electrochemical scaffold for sensing of carcinogenic hydrazine in industrial effluents

This paper describes the decoration of AuNPs on carbon nano-onions (CNO) followed by its fabrication on electrode surface for the sensitive determination of environmental pollutant hydrazine (HZ). A green ultrasonication approach was employed to decorate the AuNPs on CNOs and it follows electroless deposition. HR-TEM results reveal that spherical 10 nm-sized AuNPs were well dispersed on 30 nm-sized CNOs. The obtained 3.7 eV spin–orbit coupling in the XPS Au4f region suggests the successful decoration of Au(0) on CNO. The Au@CNO nanostructure was then directly attached on GC electrode surface by simple immersion and achieved through π–π stacking interaction and the resultant electrode exhibited high electroactive surface area and lower resistivity when compared to the CNO fabricated electrode. The Au@CNO electrode was utilized to determine HZ in effluent samples and delivered higher electrocatalytic activity by showing lower onset potential than the bare and CNO fabricated electrodes. The increased electroactive area and high electronic conductivity of Au@CNO nanostructure are attributed to the offered lowest detection limit of 12 × 10−9 M (S/N = 3) and larger sensitivity of 485.7 µA/mM cm−2. The green and environmentally benign approached Au@CNO nanostructure leads to their successful implementation in the determination of HZ in effluent samples.

Influence of reducing agents on in situ synthesis of gold nanoparticles and scaffold conductivity with emphasis on neural differentiation

BackgroundRecorded advancements in nerve tissue regeneration have still not provided satisfactory results, and complete physiological recovery is not assured. The engineering of nanofibrous scaffolds provides a suitable platform for stem cell transplantation by controlling cell proliferation and differentiation to replace lost cells. In this study, a conductive scaffold was fabricated by in situ synthesis of gold nanoparticles (Au-NPs) on electrospun polycaprolactone/chitosan nanofibrous scaffolds and its effect on neural differentiation of mesenchymal stem cells was investigated. MethodThe conductive scaffold was prepared using polycaprolactone/chitosan solution containing soluble Au ions by electrospinning approach. In situ synthesis of Au-NPs was conducted using two reducing agents, Tetrakis(hydroxymethyl)phosphonium chloride (THPC) as an organophosphorus compound and formaldehyde, and also different reduction times. Morphology and distribution of the Au-NPs on the nanofibrous scaffolds were assessed using field emission scanning electron microscopy (FE-SEM) and energy dispersed X-ray spectroscopy (EDX). The hydrophilicity and biocompatibility of the scaffolds were determined by water contact angle and MTT assays respectively. The characterization of the scaffolds was proceeded by testing the porosity, tensile strength and electrical conductivity. Also, the scaffold's ability to support neural differentiation of mesenchymal stem cells was evaluated by immune-staining/blotting of Beta tubulin III. Results & conclusionFE-SEM and EDX results demonstrated the uniform distribution of Au-NPs on electrospun nanofibers made of a combination of polycaprolactone and chitosan (PCL/CS). We found that electrical conductivity of the scaffolds fabricated using THPC for 4 days and formaldehyde for 7 days was in the range of electrical conductivity of the scaffolds suitable for nerve regeneration. Contact angle measurements showed the effect of Au-NPs on the hydrophilic properties of the scaffolds, where the scaffold showed the porosity of 50% in the presence of Au-NPs. Au-NPs decoration on the scaffold decreased the mechanical properties with the ultimate strength of 14 (MPa). In vitro assessment demonstrated the potential of the fabricated conductive scaffold to enhance the attachment and proliferation of fibroblast cells, and differentiation potential of mesenchymal stem cells toward neuron-like cells. This designed scaffold holds promise as a future carrier and delivery platform in nerve tissue engineering.

Synthesis of AuNPs decorated multi-valent Cu-Ni oxide nanoplates for electrochemical oxidation of methanol

Cu-Ni oxide nanocomposite was synthesized via solvothermal method with nickel (II) nitrate and copper nitrate as Ni and Cu resource respectively. AuNPs/oxide nanocomposite was obtained by dispersing the oxide into the pre-synthesized Au colloid. Transmission electron microscope (TEM) shows that the synthesized oxides are nanoplate morphology. Interplanar distance from the high resolution TEM (HRTEM) image shows that the Ni and Cu in the oxide are multivalent state. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization further proves that the Ni and Cu are multivalent state, and the Au is Au0 form in the nanocomposte. EDS-mapping images confirm large numbers of AuNPs are uniformly absorbed onto the ultra-thin multivalent Cu-Ni oxide nanoplate. The electrochemical properties of multivalent oxide (m-v oxide) with or without AuNPs decoration are investigated in 0.1 M potassium chloride electrolyte with 2.0 mM Ferri/Ferro-Cyanide. When employed for the electrochemical catalysis in methanol oxidation reaction (MOR), the AuNPs/m-v oxide exhibits better electrochemistry performance than m-v oxide. The current density of AuNPs/m-v oxide (21.1 mA/cm2) is 3.4 times bigger than that of m-v oxide/GCE (6.2 mA/cm2). What’s more, it shows good electrochemical stability and lower slope of the Tafel plot (41.87 mV/dec).

Decoration of Au NPs on hollow structured BiOBr with surface oxygen vacancies for enhanced visible light photocatalytic H2O2 evolution

Photocatalytic H2O2 evolution is a sustainable and safe method with O2 and H2O as sources. In this study, Au nanoparticles anchored on hollow BiOBr with rich oxygen vacancies were prepared; the obtained hollow OVs-BiOBr-Au exhibited a highest H2O2 evolution of 317.65 ​μM in 150 ​min. It was shown that the combination of 3D hollow structure, Au nanoparticles and oxygen vacancies can narrow the bandgap and improve charge separation efficiency. Further, rotating disk electrode measurements reveal H2O2 is obtained mainly by two electron reduction of O2 (H2O2 evolution), and density functional theory calculations indicating that oxygen vacancies promote the absorptions and activations of O2. This work provides a new and promising process for the development of high efficiency H2O2 evolution.

Metal coordination induced SERS nanoprobe for sensitive and selective detection of histamine in serum

Sensitivity and credibility detecting histamine (HA) as an important neurotransmitter in biofluids is of importance in analytical science and physiology. Surface-enhanced Raman spectroscopy (SERS) is able to realize the high sensitivity with single molecules level, but providing the high sensitivity for HA with a small cross section remains a challenge. Here we develop the metal complex-based SERS nanoprobe nitrilotriacetic acid-Ni2+ (NTA-Ni2+) combined with self-assemble Au NPs active substrates for sensitive detection of HA. The NTA-Ni2+ can capture the HA molecules close to Au NPs substrates and then amplify the Raman signals of HA owing to the formation of a complex of NTA-Ni2+-HA. The self-assemble Au film through the evaporation-driven method can provide the high-density hot spots substrate with high stability and reproducibility. The NTA-Ni2+ decorated Au NPs as nanoprobe responds to HA with 1 μM level of sensitivity. More importantly, the developed SERS nanoprobe composing of NTA-Ni2+ and self-assemble Au NPs can be utilized to detect and monitor the HA spiked into serum, indicating the potential prospect in analysis of HA in complex specimen.

Three-dimensional gold nanoparticles-modified graphene hydrogel for high-sensitive NO2 and NH3 detection with enhanced resistance to humidity

A one-step, facile hydrothermal approach was developed to synthesize gold nanoparticles (Au NPs) modified reduced graphene oxide hydrogel (Au-RGOH) with three-dimensional (3D) porous microstructures for sensitive NO2 and NH3 monitoring. It was found that the Au-RGOH displayed an order of magnitude higher sensitivity and much lower limit of detections (LODs) than the unmodified RGOH counterpart, demonstrating the remarkable role of Au NPs in boosting the responsivity toward NO2 and NH3. To address the disturbance of humidity on gas sensing, an integrated microheater platform was exploited to quench the response to humidity without impairing the response to target gas, enhancing the resistance to humidity. The mechanisms of Au NPs decoration effect and temperature-assisted screening effect were elucidated by molecular dynamics and density functional theory simulations for the first time. It revealed that Au NPs were active adsorption sites for NO2 molecules, and the strong and weak dependence of the adsorption of H2O and NO2 molecules on temperature, respectively, providing theoretical evidences for experimental results. Benefiting from the chemical sensitization effect of Au NPs, 3D porous structure, and localized temperature modulation, the Au-RGOH gas sensor exhibited high sensitivity, low LODs (1.16 NO2 and 55.3 ppb NH3), excellent selectivity, reversibility, fast recovery speed, etc. This study offers a facile and practical solution to boost the gas sensing performance by engineering the surface, structure and operation temperature of transducing materials, as well as understand the sensing behaviors via theoretical simulations.

In situ decoration of Au NPs over polydopamine encapsulated GO/Fe3O4 nanoparticles as a recyclable nanocatalyst for the reduction of nitroarenes

A new and efficient catalyst has been designed and prepared via in situ immobilization of Au NPs fabricated polydopamine (PDA)-shelled Fe3O4 nanoparticle anchored over graphene oxide (GO) (GO/Fe3O4@PDA/Au). This novel, architecturally interesting magnetic nanocomposite was fully characterized using different analytical techniques such as Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, elemental mapping, Transmission Electron Microscopy, Fourier Transformed Infrared Spectroscopy, X-ray Diffraction and Inductively Coupled Plasma-Atomic Electron Spectroscopy. Catalytic activity of this material was successfully explored in the reduction of nitroarenes to their corresponding substituted anilines, using NaBH4 as reducing agent at ambient conditions. The most significant merits for this protocol were smooth and clean catalysis at room temperature with excellent productivity, sustainable conditions, ease of separation of catalyst from the reaction mixture by using a magnetic bar and most importantly reusability of the catalyst at least 8 times without any pre-activation, minimum loss of activity and considerable leaching.

Facile sol-gel method derived Au nanoparticles decoration nickel ferrites thin films: Effect on optical and magnetic properties

Noble metal Au nanoparticles (Au NPs) decoration nickel ferrite (hereafter abbreviated as NFA-x, x = 0, 0.04, 0.08 and 0.12) thin films were synthesized on quartz and Pt/Ti/SiO2/Si substrates by a facile sol-gel method. The structural, optical and magnetic performances of NFA-x thin films have been investigated. The XRD patterns revealed the formation of cubic spinel ferrite structure. The SEM analysis indicated that NFA-x thin films were dense and uniform, which also confirm that crystalline size decreased with increasing of Au content. A remarkable surface plasmon resonance (SPR) features has been observed in NFA-0.12 films. The optical band gap of NFA-x thin films decreased with increasing Au concentration. In addition, our results revealed that the magnetism was highly depending on the Au concentration. The saturation magnetization remarkable decreased then sharply increased with increasing of Au content, which is attributed to Au NPs decoration effect. However, the coercive field and squareness ration showed increasing trend with increasing of Au concentration. Our work suggests that Au nanoparticles decoration nickel ferrites thin films have promising applications in multifunctional materials field.

Decorated Au NPs on agar modified Fe3O4 NPs: Investigation of its catalytic performance in the degradation of methylene orange, and anti-human breast carcinoma properties

This work describes an eco-friendly approach for in situ immobilization of Au nanoparticles on the surface of Fe3O4 nanoparticles, with help of Agar and ultrasound irradiations, without using any toxic reducing and capping agents. The structure, morphology, and physicochemical properties were characterized by various analytical techniques such as Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), inductively coupled plasma (ICP) and vibrating sample magnetometer (VSM). The desired catalyst showed great efficiency in the reductive degradation of methylene orange (MO) dye over NaBH4 at room temperature. The MO was fully reduced in only 70 s and achieved rate constant of 9.6 × 10−2 s−1. The catalyst was reused for 10 runs without significant loss in catalytic activity. Cell viability of Fe3O4/agar/Au NPs was very low against breast adenocarcinoma (MCF7), breast carcinoma (Hs 578Bst), infiltrating ductal cell carcinoma (Hs 319.T), and metastatic carcinoma (MDA-MB-453) cell lines without any cytotoxicity on the normal cell line. According to the above findings, the Fe3O4/agar/Au NPs may be administrated for the treatment of several types of human breast carcinoma in humans.

Strict DNA Valence Control in Ultrasmall Thiolate-Protected Near-Infrared-Emitting Gold Nanoparticles.

Realizing robust DNA functionalization with strict valence control in the sub-2-nm thiolate-protected luminescent gold nanoparticles (AuNPs) is highly demanded but remains unsolved due to their unique Au(0) core and Au(I)-S shell structures. Herein, we report a facile strategy using phosphorothioates (ps)-modified DNA (psDNA) as a template for in situ growth of near-infrared (NIR)-emitting AuNPs with precisely controlled DNA valence. In addition, the particle size could be finely tuned in ultrasmall ranges from 1.3 to 2.6 nm with regulation of the ps length of psDNA. The ultrasmall NIR-emitting AuNPs bearing strict DNA valence are also demonstrated to be as powerful building block for well-organized one-dimensional assembly and optical probe for targeted cellular imaging. Such a facile strategy in decoration of luminescent AuNPs with strict DNA valence provides a new pathway for development of surface-functionalizable ultrasmall metal nanoplatforms toward various downstream applications.

Au-Nanoplasmonics-Mediated Surface Plasmon-Enhanced GaN Nanostructured UV Photodetectors.

The nanoplasmonic impact of chemically synthesized Au nanoparticles (Au NPs) on the performance of GaN nanostructure-based ultraviolet (UV) photodetectors is analyzed. The devices with uniformly distributed Au NPs on GaN nanostructures (nanoislands and nanoflowers) prominently respond toward UV illumination (325 nm) in both self-powered as well as photoconductive modes of operation and have shown fast and stable time-correlated response with significant enhancement in the performance parameters. A comprehensive analysis of the device design, laser power, and bias-dependent responsivity and response time is presented. The fabricated Au NP/GaN nanoflower-based device yields the highest photoresponsivity of ∼ 380 mA/W, detectivity of ∼ 1010 jones, reduced noise equivalent power of ∼ 5.5 × 10–13 W Hz–1/2, quantum efficiency of ∼ 145%, and fast response/recovery time of ∼40 ms. The report illustrates the mechanism where light interacts with the chemically synthesized nanoparticles guided by the surface plasmon to effectively enhance the device performance. It is observed that the Au NP-stimulated local surface plasmon resonance effect and reduced channel resistance contribute to the augmented performance of the devices. Further, the decoration of low-dimensional Au NPs on GaN nanostructures acts as a detection enhancer with a fast recovery time and paves the way toward the realization of energy-efficient optoelectronic device applications.