One-pot Preparation of Creatinine-functionalized Gold Nanoparticles for Colorimetric Detection of Silver Ions

Creatinine-functionalized AuNPs (CreAuNPs) were prepared via a facile one-pot reaction of sodium borohydride and the mixture solution of gold(III) chloride trihydrate and creatinine. The morphology and surface state of as-prepared CreAuNPs were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. All the results demonstrated that CreAuNPs were spherical with an average diameter of about 4.2 nm, and creatinine existed on the surface of AuNPs via Au-N interaction. The as-prepared CreAuNPs exhibited a weak surface plasmon resonance (SPR) absorption owing to their small size, while the addition of Ag⁺ could induce the aggregation of spherical CreAuNPs, producing a strong SPR absorption and apparent color change from colorless to purple owing to the surface plasmon coupling. On this basis, a colorimetric assay for Ag⁺ was established. The assay could selectively detect Ag⁺ as low as 1 μM with a good linearity in the range of 5–40 μM. Additionally, the assay was successfully applied to the determination of Ag⁺ in tap water, lake water, and river water samples.

     

Immunohistochemistry of IL-1β, IL-6 and TNF-α in spleens of mice treated with gold nanoparticles

Gold nanoparticles (AuNPs) possess considerable biocompatibility and therefore gaining more attention for their biomedical applications. Previous studies have shown the transient increase in pro-inflammatory cytokines expression in different organs of rats and mice exposed to AuNPs. Structural changes in the spleen of mice treated with AuNPs have also been reported. This investigation was aimed to study the immunostaining of IL-1β, IL-6 and TNF-α in mice treated with different sizes of AuNPs. The animals were divided into 7 groups of 4 animals in each group. One group received saline and served as control. Two sets of three groups were treated with 5 nm, 20 nm and 50 nm diameter AuNPs. One set was sacrificed on day 1 and the other on day 7 following the AuNPs injections. Spleens were dissected out and promptly fixed in formalin for 3 days and then processed for IL-1β, IL-6 and TNF-α immunostaining using target-specific antibodies. The immunoreactivities of IL-1β and IL-6 were increased with the increase of AuNP size. The immunostaining of IL-1β in spleen of 20 nm AuNP treated mice was subsequently decreased on day 7 whereas it persisted in 50 nm AuNP group. The increase in the immunoreactivity of IL-6 on day 1 was decreased on day 7 in the spleens of mice treated with 20 nm or 50 nm AuNPs. The immunostaining of TNF-α was found to be negative in all the treatment groups. In conclusion, the size of AuNPs plays an important role in the expression of proinflammatory cytokines in mouse spleen; small size (5 nm) AuNPs caused minimal effect, whereas larger (50 nm) AuNPs produced intense immunostaining.     

A deep learning approach to gold nanoparticle quantification in computed tomography

IntroductionDeep learning (DL) is used to classify, detect, and quantify gold nanoparticles (AuNPs) in a human-sized phantom with a clinical MDCT scanner.MethodsAuNPs were imaged at concentrations between 0.0274 and 200 mgAu/mL in a 33 cm phantom. 1 mm-thick CT image slices were acquired at 120 kVp with a CTDI_vol of 23.6 mGy. A convolutional neural network (CNN) was trained on 544 images to classify 17 different tissue types and AuNP concentrations. A second set of 544 images was then used for testing.ResultsAuNPs were classified with 95% accuracy at 0.1095 mgAu/mL and 97% accuracy at 0.2189 mgAu/mL. Both these concentrations are lower than what humans can visually perceive (0.3–1.4 mgAu/mL). AuNP concentrations were also classified with 95% accuracy at 150 and 200 mgAu/mL. These high concentrations result in CT numbers that are at or above the 12-bit limit for CT’s dynamic range where extended Hounsfield scales are otherwise required for measuring differences in contrast.ConclusionsWe have shown that DL can be used to detect AuNPs at concentrations lower than what humans can visually perceive and can also quantify very high AuNP concentrations that exceed the typical 12-bit dynamic range of clinical MDCT scanners. This second finding is possible due to inhomogeneous AuNP distributions and characteristic streak artifacts. It may even be possible to extend this approach beyond AuNP imaging in CT for quantifying high density objects without extended Hounsfield scales.     

Construction of efficient bioelectrochemical devices: Improved electricity production from cyanobacteria (Leptolyngbia sp.) based on π-conjugated conducting polymer/gold nanoparticle composite interfaces

In this study, gold electrodes (GE) were coated with conducting polymers to obtain a high photocurrent using cyanobacteria from a novel bioelectrochemical fuel cell. For this purpose, 4-(4H-ditiheno[3,2-b:2',3'-d]pyrol-4-yl) aniline and 5-(4H-dithieno[3,2-b:2',3'-d]pyrol-4-yl) napthtalane-1-amine monomers were coated on GE by performing an electropolymerization process. After that, gold nanoparticles (AuNP) were specifically modified by 2-mercaptoethane sulfonic acid and p-aminothiophenol to attach to the electrode surface. The conducting polymers GE coat was modified with functionalized AuNP using a cross-linker. The resulting electrode structures were characterized by cyclic voltammetry and chronoamperometry under on-off illumination using a fiber optic light source. Cyanobacteria Leptolyngbia sp. was added to the GE/conducting polymer/AuNP electrode surface and stabilized by using a cellulose membrane. During the illumination, water was oxidized by the photosynthesis, and oxygen was released. The released oxygen was electrocatalytically reduced at the cathode surface and a 25 nA/cm ² photocurrent was observed in GE/ Leptolyngbia sp. After the electrode modifications, a significant improvement in the photocurrent up to 630 nA/cm ² was achieved.     

Fungal surface protein mediated one-pot synthesis of stable and hemocompatible gold nanoparticles

Despite their large secretome and wide applications in bioprocesses, fungi remain underexplored in metal nanoparticles (MNP) biosynthesis. Previous studies have shown that cell surface proteins of Rhizopus oryzae play a crucial role in biomineralization of Au(III) to produce gold nanoparticles (AuNPs). Therefore, it is hypothesized that purified cell surface protein may produce in vitro AuNPs with narrow size distribution for biomedical and biocatalytic applications. However, different protein extraction methods might affect protein stability and the AuNP biosynthesis process. Herein, we have explored the extraction of cell surface proteins from R. oryzae using common detergents and reducing agent (sodium dodecyl sulfate (SDS) Triton X-100, and 1,4-dithiothreitol (DTT)) and their effect on the size and shape of the biosynthetic AuNPs. The surface proteins extracted with reducing agent (DTT) and non-ionic detergent (Triton X-100) produce spherical AuNPs with a mean particle size of 16 ± 7 nm, and 19 ± 4 nm, respectively, while the AuNPs produced by the surface protein extracted by ionic detergent (SDS) are flower-like AuNPs with broader size distribution of 43 ± 19 nm. This synthetic approach does not require use of any harsh chemicals, multistep preparation and separation process, favouring environmental sustainability. The biosynthetic AuNPs thus formed, are stable in different physiological buffers and hemocompatible, making them suitable for biomedical applications.     

Use of Coupled Al-Ag Bimetallic Cylindrical Nanoparticles to Improve the Photocurrent of a Thin-Film Silicon Solar Cell

In this paper, cylindrical shape coupled bimetallic plasmonic nanoparticles (NPs) were used to improve the performance of a thin-film silicon solar cell. Our design is based on the appropriate selection of the composition and morphology of the NPs to reach a cell with excellent optical properties. The specific interaction between the incident light and bimetallic NPs helps us to design better solar absorbers. Here, the FDTD method was used to evaluate the effect of cylindrical Al-Ag bimetallic NPs on the surface of a thin silicon absorber. At first, a unit cell with Al-Al paired nano-cylinders at the surface was evaluated and a photocurrent of 14.65 mA/cm² was obtained. In the case of a cell with paired Al-Ag bimetallic nano-cylinders, the photocurrent was increased to 16.15 mA/cm². This value was increased to 16.57 mA/cm² when paired polymetallic NPs were used. According to the results of this work, bimetallic and polymetallic nanoparticles can significantly improve the photocurrent of an ultra-thin silicon solar cell. The results of this work can be used to design better plasmonic-based light trapping systems for thin-film solar cells.

     

A label-free optical sensor based on nanoporous gold arrays for the detection of oligodeoxynucleotides

Interest in using nanoporous materials for sensing applications has increased. The present study reports a method of preparing well-ordered nanoporous gold arrays using a porous silicon (PSi) template. Gold nanolayer could be electrodeposited on the surface of the PSi template at low electrolysis currents in low concentration of chloroauric acid (HAuCl₄) solution. Surface morphology characterizations and optical measurements revealed that a PSi-templated nanoporous gold (Au–PSi) array well replicated the nanoporous structure and retained the optical properties of PSi. Fourier transform reflectometric interference spectra showed that a characteristic blue-shifted effective optical thickness (EOT) was observed due to the low refractive index of the gold film. An optical DNA biosensor was then fabricated via the self-assembly of single-stranded DNA (ssDNA) with a specific sequence on the surface of Au–PSi. The attachment of ssDNA and its hybridization with target oligonucleotides (ODNs) persistently caused the blue shift of the EOT. Consequently, a relationship between the EOT shift and the ODN concentration was established. The mechanism of the optical response caused by DNA hybridization on the Au–PSi surface was qualitatively explained by the electromagnetic theory and electrochemical impedance spectroscopy (EIS). The lowest detection limit for target ODNs was estimated at around 10⁻¹⁴ mol L⁻¹, when the baseline noise, a variation in the value of EOT is around 5 nm. The fabricated Au–PSi based optical biosensor has potential use in the discovery of new ODN drugs because it will be able to detect the binding event between ODNs and the target DNA.     

Preparation of sulfonated poly(ether–ether–ketone) functionalized ternary graphene/AuNPs/chitosan nanocomposite for efficient glucose biosensor

A facile method of preparing water-dispersible sulfonated graphene (SPG) using sulfonated poly(ether–ether–ketone) organic polymer as a modifier was realized. A glucose biosensor was fabricated by immobilizing glucose oxidase (GO_x) on the surface of AuNPs used to modify SPG and chitosan (CH) deposited on an indium tin-oxide (ITO) glass electrode by a solution casting method. Morphological and structural characterizations confirm that the AuNPs can be efficiently applied to the SPG–CH matrix. The amperometric response of the GO_x/SPG–AuNPs–CH/ITO bioelectrode shows a broad linear range of 0.5 to 22.2 mM, with a limit of detection of 0.13 mM and a high sensitivity of 6.51 μA/(mM cm²). The excellent performance of the constructed biosensor is attributed to the large surface-to-volume ratio and electron transfer ability of SPG, the high catalytic activity of the AuNPs, and the good biocompatibility of CH. In addition, the sensor has important advantages, such as its simple preparation, fast response time (10 s), good stability (70 days), and high reproducibility. Favorable results upon examining the electrochemical response for the determination of glucose in human blood serum were obtained, without the assistance of a negligible effect of interfering bio-analytes. The results of studies show that the ternary SPG–AuNPs–CH nanocomposite may offer a new approach for developing novel types of highly sensitive and stable electrochemical biosensors.     

Photochemical synthesis of pink silver and its use for monitoring peptide nitration via surface enhanced Raman spectroscopy (SERS)

Oxidative stress may cause extended tyrosine posttranslational modifications of peptides and proteins. The 3-nitro-L-tyrosine (Nit), which is typically formed, affects protein behavior during neurodegenerative processes, such as Alzheimer’s and Parkinson’s diseases. Such metabolic products may be conveniently detected at very low concentrations by surface enhanced Raman spectroscopy (SERS). Previously, we have explored the SERS detection of the Nit NO₂ bending vibrational bands in a presence of hydrogen chloride (Niederhafner et al., Amino Acids 53:517–532, 2021, ibid). In this article, we describe performance of a new SERS substrate, “pink silver”, synthesized photochemically. It provides SERS even without the HCl induction, and the acid further decreases the detection limit about 9 times. Strong SERS bands were observed in the asymmetric (1550–1475 cm^?1) and symmetric (1360–1290 cm^?1) NO stretching in the NO₂ group. The bending vibration was relatively weak, but appeared stronger when HCl was added. The band assignments were supported by density functional theory modeling.

     

Transmission Surface Plasmon Resonance Signal Enhancement via Growth of Gold Nanoparticles on a Gold Grating Surface

We developed a novel technique for increasing the sensitivity of transmission surface plasmon resonance (T-SPR) signals. T-SPR spectroscopy was performed by irradiating, with white light, a gold grating substrate whose surface was nanostructured by growing gold nanoparticles (AuNPs). AuNPs were grown directly on the substrate surface by alcohol reduction and their growth was observed at various stages by UV–visible spectroscopy and standard Kretschmann-type SPR spectroscopy. For comparison, normal gold film with smooth surface was examined under similar condition. The T-SPR results show a possibility of hybrid excitation of both localized and propagating surface plasmon. Significantly, T-SPR spectra of the gold grating substrate obtained during AuNP growth show stronger and narrower peaks in the range 650–800 nm. The maximum T-SPR excitation was at an incident angle of 35°. A layer-by-layer system of 5,10,15,20-tetrakis (1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) molecules and sodium copper chlorophyllin molecules was used to verify the enhancement of the developed system. We believe that the AuNPs/Au grating for T-SPR devices will provide enhanced signals for detecting nanometer order materials and for high-sensitive sensor applications.     

Larvicidal potential of gold and silver nanoparticles synthesized using Acalypha fruticosa leaf extracts against Culex pipiens (Culicidae: Diptera)

Plant secondary metabolites have been recently used for the synthesis of different nanoparticles. The present investigation aimed at evaluating the effect of gold (AuNPs) and silver (AgNPs) nanoparticles synthesized using Acalypha fruticosa leaf extracts to control the mosquito Culex pipiens. The A. fruticosa AuNPs and AgNPs spectra displayed their maximum absorption at 550 nm and 440 nm, respectively. The infrared spectra revealed different functional groups related to different chemical compounds. The larval mortality of aqueous leaf extract of A. fruticosa was 499.54 ppm (LC₅₀) and 1734.06 ppm (LC₉₀) after 24 h of treatment. This study revealed that AuNP (LC₅₀, 30.2 and LC₉₀, 104.83 ppm) and AgNP (LC₅₀, 52.86 and LC₉₀, 157.227 ppm) preparations were highly effective compared to the A. fruticosa extract alone and also more affordable, as a smaller amount was required. The present findings show the potential larvicidal effect of the synthesized AuNPs and AgNPs for the control of mosquito-mediated disease transmission.     

Identifying Metal Nanoparticle Size Effect on Sensing Common Human Plasma Protein by Counting the Sensitivity of Optical Absorption Spectra Damping

Colloidal nanoparticles (NPs) interact with biological fluids such as human plasma to form a protein coating (corona) on the surface of NPs (NP-protein complex). However, the impact of size and type of NPs on binding of the hard corona to the surface of NPs as well as damping of their optical spectra has not been systematically explored. To elucidate the interaction between biological environment (human plasma) and NPs, a photophysical measurement was conducted to quantify the interaction of two different types of NPs (gold (Au) and silver (Ag)) with common human plasma proteins. The colloidal AuNPs and AgNPs were electrostatically stabilized and varied in diameter from 10 to 80 nm in the presence of common human plasma. The sizes of the NPs were determined using transmission electron microscopy (TEM). Optical absorption spectra were obtained for the complexes. Dynamic light scattering (DLS) measurement and zeta potential were used to characterize the sizes, hydrodynamic diameters, and surface charges of the protein-NPs complexes. Protein separation was performed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to isolate and identify the protein bands. The absorption of proteins to the NPs was found to be strongly dependent on the size and type of NPs. The distance between surface of NPs by absorbed protein bound to the NPs gradually increased with size of NPs, particularly for AgNPs with primary diameter of < 50 nm. The chi-square test proved that AgNPs are a good candidate in sensing the protein complex in human plasma compared with AuNPs mainly for the AgNPs with diameter sized 50 nm.

     

Hydrothermal synthesis, characterization, and KOH activation of carbon spheres from glucose

Carbon spheres (CSs) with controllable sizes and rich in oxygen-containing groups were fabricated using a simple hydrothermal treatment of glucose. The effects of the hydrothermal parameters, including the concentration of glucose, reaction temperature, duration, and the second hydrothermal treatment were investigated. The obtained CSs were then activated using KOH for the eventual preparation of porous carbon spheres. A scanning electron microscope was used to characterize the morphology and size of the CSs. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to analyze the functional surface groups. N₂ adsorption–desorption isotherms were used to analyze the porous structure of the CS. The results revealed that the morphologies and size distribution of the CSs can be controlled by adjusting the experimental parameters. A hydrothermal temperature between 180 and 190 °C over 4–5 h was suitable for CS formation. Under these conditions, the size of the CS increased with the concentration of glucose. Mono-dispersed CSs with good morphologies and large numbers of oxygen-containing functional groups (primarily –OH and CO) can be obtained using a 0.3 mol/L glucose solution that is hydrothermally treated at 190 °C for 4 h. The resulting CSs sizes were about 350 nm in diameter. After a second hydrothermal treatment, the sizes of CSs grew nearly 250 nm without damage to its morphology or broadening of their size distribution. Porous CSs with perfectly spherical shapes and fully developed structures (S_BET = 1282.8 m²/g, V_micro = 0.44 cm³/g) could then be obtained via KOH activation.     

Enhanced immobilization of hexa-arginine-tagged esterase on gold nanoparticles using mixed self-assembled monolayers

Mixed self-assembled monolayers (MSAMs) composed of diverse ligands offer a mechanism for the specific binding of biomolecules onto solid surfaces. In this study, we examined the formation of MSAMs on gold nanoparticles (AuNPs) and the immobilization of hexa-arginine-tagged esterase (Arg₆-esterase) on the surfaces of the resulting particles. The functionalization of AuNPs with MSAMs was achieved by introducing a mixture of tethering and shielding ligands into an AuNP solution. The formation of self-assembled monolayers (SAMs) on the AuNP surface was characterized by UV/visible spectroscopy, transmission electron microscopy, and Fourier-transform infrared spectroscopy. Arg₆-esterase was immobilized in a highly specific manner onto AuNPs treated with mixed SAMs (MSAM–AuNPs) by providing a shielding ligand which reduce the non-specific adsorption of enzymes caused by hydrophobic interaction compared to AuNPs treated with single-component SAMs (SSAM–AuNPs). Moreover, Arg₆-esterase immobilized on MSAM–AuNPs showed substantially enhanced catalytic activity up to an original activity compared to that on SSAM–AuNPs (58%).     

Inactivation of food pathogen Bacillus cereus by photosensitization in vitro and on the surface of packaging material

Aims: The study was focused on the possibility to inactivate food pathogen Bacillus cereus by 5‐aminolevulinic acid (ALA) – based photosensitization in vitro and after adhesion on the surface of packaging material. Methods and Results: Bacillus cereus was incubated with ALA (3–7·5 mmol l^?1) for 5–60 min in different environment (PBS, packaging material and wheat grains) and afterwards illuminated with visible light. The light source used for illumination emitted light at λ = 400 nm with energy density at the position of the cells, 20 mW cm^?2. The illumination time varied from 0 to 20 min, and subsequently a total energy dose was between 0 and 24 J cm^?2. The obtained results indicate that B. cereus after the incubation with 3–7·5 mmol l^?1 ALA produces suitable amounts of endogenous photosensitizers. Following illumination, micro‐organism inactivated even by 6·3 log. The inactivation of B. cereus after adhesion on the surface of food packaging by photosensitization reached 4 log. It is important to note that spores of B. cereus were susceptible to this treatment as well; 3·7‐log inactivation in vitro and 2·7‐log inactivation on the surface of packaging material were achieved at certain experimental conditions. Conclusions: Vegetative cells and spores of Gram‐positive food pathogen B. cereus were effectively inactivated by ALA‐based photosensitization in vitro. Moreover, the significant inactivation of B. cereus adhered on the surface of packaging material was observed. It was shown that photosensitization‐based inactivation of B. cereus depended on the total light dose (illumination time) as well as on the amount of endogenous porphyrins (initial ALA concentration, time of incubation with ALA). Significance and Impact of the Study: Our previous data, as well as the one obtained in this study, support the idea that photosensitization with its high selectivity, antimicrobial efficiency and nonthermal nature could serve in the future for the development of completely safe, nonthermal surface decontamination and food preservation techniques.     

Development of Novel Glucose oxidase Immobilization on Graphene/Gold nanoparticles/Poly Neutral red modified electrode

Glucose oxidase (GOx) was immobilized onto glassy carbon electrode (GCE) that modified by reduced graphene oxide-gold nanoparticles- poly neutral red (RGO/AuNPs/PNR) nanocomposite. The composite was analyzed by scanning electron microscope (SEM), energy dispersive x-ray (EDX) spectroscopy, atomic force microscopy (AFM), attenuated total reflectance (ATR), cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). SEM/EDX analysis showed the morphological of the nanocomposite. AFM results showed the morphology and structure of the RGO/AuNPs and RGO surfaces. The covalent bonding between glucose oxidase and composite was confirmed by ATR technique. The electrochemical experiments were done in 100 mM phosphate buffer at pH 7 and temperature of 25 °C with three electrodes including Ag/AgCl, platinum wire and the modified GCE as the reference electrode, the auxiliary electrode and working electrode respectively. The electrochemical results confirmed the activity and direct electron transfer of immobilized enzyme. The immobilized electroactive GOx concentration was estimated 3.06 × 10⁻¹¹ mol cm⁻². The results showed the immobilized enzyme had a good stability and maintained 90% of its performance after two weeks. The nanocomposite bioanode in an air-birthing biofuel cell and 100 mM glucose concentration showed 176 μWcm⁻² Power density. This strategy could be used for GOx-based biofuel cells.     

Glucose biosensor based on glucose oxidase immobilized at gold nanoparticles decorated graphene-carbon nanotubes

Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV–vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of −0.40 V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5 × 10⁻¹⁰ mol cm⁻² and 3.36 s⁻¹, respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10 μM – 2 mM with LOD of 4.1 μM, (2) 2 mM – 5.2 mM with LOD of 0.95 mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible.     

In Vivo Study of Spherical Gold Nanoparticles: Inflammatory Effects and Distribution in Mice

Objectives

Gold nanoparticles (AuNPs) of 21 nm have been previously well characterized in vitro for their capacity to target macrophages via active uptake. However, the short-term impact of such AuNPs on physiological systems, in particular resident macrophages located in fat tissue in vivo, is largely unknown. This project investigated the distribution, organ toxicity and changes in inflammatory cytokines within the adipose tissue after mice were exposed to AuNPs.

Methods

Male C57BL/6 mice were injected intraperitoneally (IP) with a single dose of AuNPs (7.85 μg AuNPs/g). Body weight and energy intake were recorded daily. Tissues were collected at 1 h, 24 h and 72 h post-injection to test for organ toxicity. AuNP distribution was examined using electron microscopy. Proinflammatory cytokine expression and macrophage number within the abdominal fat pad were determined using real-time PCR.

Results

At 72 hours post AuNP injection, daily energy intake and body weight were found to be similar between Control and AuNP treated mice. However, fat mass was significantly smaller in AuNP-treated mice. Following IP injection, AuNPs rapidly accumulated within the abdominal fat tissue and some were seen in the liver. A reduction in TNFα and IL-6 mRNA levels in the fat were observed from 1 h to 72 h post AuNP injection, with no observable changes in macrophage number. There was no detectable toxicity to vital organs (liver and kidney).

Conclusion

Our 21 nm spherical AuNPs caused no measurable organ or cell toxicity in mice, but were correlated with significant fat loss and inhibition of inflammatory effects. With the growing incidence of obesity and obesity-related diseases, our findings offer a new avenue for the potential development of gold nanoparticles as a therapeutic agent in the treatment of such disorders.     

A simple gold nanoplasmonic SERS method for trace Hg2+ based on aptamer‐regulating graphene oxide catalysis

The as‐prepared graphene oxide (GO) exhibited a strong catalytic effect on reduction of HAuCl₄ by trisodium citrate to form gold nanoplasmons (AuNPs) with a strong surface‐enhanced Raman scattering (SERS) effect at 1615 cm^?1 in the presence of molecular probe Victoria blue 4R (VB4r). SERS intensity increased with nanocatalyst GO concentration due to the formation of more AuNP substrates. The aptamer (Apt) of Hg²⁺ can bind to GO to form Apt–GO complexes, which can strongly inhibit nanocatalysis. When target Hg²⁺ is present, the formed stable Hg²⁺–Apt complexes are separated from the GO surface, which leads to GO catalysis recovery. The enhanced SERS signal was linear to Hg²⁺ concentration in the range 0.25–10 nmol/L, with a detection limit of 0.08 nmol/L Hg²⁺. Thus, a new gold nanoplasmon molecular spectral analysis platform was established for detecting Hg²⁺, based on Apt regulation of GO nanocatalysis.     

Hierarchically Multiscale Vertically Oriented NiFeCo Nanoflakes for Efficient Electrochemical Oxygen Evolution at High Current Densities

Crucial advancements in versatile catalyst systems capable of achieving high current densities under industrial conditions, bridging the gap between fundamental understanding and practical applications, are pivotal to propel the hydrogen economy forward. In this study, vertically oriented hierarchically multiscale nanoflakes of NiFeCo electrocatalysts are presented, developed by surface modification of a porous substrate with nano-structured nickel. The resulting electrodes achieve remarkably low overpotentials of 139 mV at 10 mAcm⁻² and 248 mV at 500 mAcm⁻². Further, scaled-up electrodes are implemented in a water-splitting electrolyser device exhibiting a stable voltage of 1.82 V to deliver a constant current density of 500 mA cm⁻² for over 17 days. Moreover, the role of the unique structures on electrochemical activity is systematically investigated by fractal analysis, involving computation of structure factors such as Minkowski connectivity, fractal dimension, and porosity using scanning electron microscope images. It is found that such structures offer higher surface area than typical layered double hydroxide structures due to morphological coherence that results in a superhydrophilic surface, while the base Ni layer boosts the charge transfer. This study demonstrates a Ni/NiFeCo(OH)_x heterostructure with highly porous morphology, a key to unlocking extremely efficient oxygen evolution reaction activity with exceptional stability. Moreover, fractal analysis is presented as a valuable tool to evaluate the electrochemical performance of catalysts for their structured morphology.