Gold-silver Core-shell Nanoparticles Research Articles

Portable SERS-Based POCT Kit for Ultrafast and Sensitive Determining Paraquat in Human Gastric Juice and Urine.

Paraquat (PQ) poisoning poses a significant public health concern. Unfortunately, point-of-care testing (POCT) of PQ in biofluids remains challenging. This study developed a portable kit that enables swift and reliable identification and quantification of PQ in human urine and gastric juice. The approach employed the surface-enhanced Raman scattering (SERS) technique, leveraging gold-silver core-shell nanoparticles (Au@Ag NPs) as the substrate. The kit comprised a portable Raman spectrometer and three sealed tubes containing Au@Ag NPs colloid, KI solution, and MgSO4 solution. A discernible correlation was observed between signal intensity and the logarithmic concentration, spanning from 5 to 500 μg/L in urine and 10 μg/L to 1 mg/L in gastric juice. The detection limits, calculated from the characteristic peak at 1648 cm -1, were 1.36 and 4.05 μg/L in human urine and gastric juice, respectively. Notably, this POCT kit obviated the need for pretreatment procedures, and the detection process was accomplished within 1 min, yielding satisfactory recoveries. This expeditious time frame is crucial for clinical diagnosis and rescue operations. Compared to conventional methods, this kit demonstrated real-time determinations in nonlaboratory settings. The simplicity and practicality of this POCT assay suggest its significant potential as an innovative alternative for poisoning detection applications.

Integrating transformer-based machine learning with SERS technology for the analysis of hazardous pesticides in spinach

This study introduces an innovative strategy for the rapid and accurate identification of pesticide residues in agricultural products by combining surface-enhanced Raman spectroscopy (SERS) with a state-of-the-art transformer model, termed SERSFormer. Gold-silver core-shell nanoparticles were synthesized and served as high-performance SERS substrates, which possess well-defined structures, uniform dispersion, and a core-shell composition with an average diameter of 21.44 ± 4.02 nm, as characterized by TEM-EDS. SERSFormer employs sophisticated, task-specific data processing techniques and CNN embedders, powered by an architecture features weight-shared multi-head self-attention transformer encoder layers. The SERSFormer model demonstrated exceptional proficiency in qualitative analysis, successfully classifying six categories, including five pesticides (coumaphos, oxamyl, carbophenothion, thiabendazole, and phosmet) and a control group of spinach data, with 98.4% accuracy. For quantitative analysis, the model accurately predicted pesticide concentrations with a mean absolute error of 0.966, a mean squared error of 1.826, and an R2 score of 0.849. This novel approach, which combines SERS with machine learning and is supported by robust transformer models, showcases the potential for real-time pesticide detection to improve food safety in the agricultural and food industries.

Digital Surface-Enhanced Raman Spectroscopy-Lateral Flow Test Dipstick: Ultrasensitive, Rapid Virus Quantification in Environmental Dust.

This study introduces a novel surface-enhanced Raman spectroscopy (SERS)-based lateral flow test (LFT) dipstick that integrates digital analysis for highly sensitive and rapid viral quantification. The SERS-LFT dipsticks, incorporating gold-silver core-shell nanoparticle probes, enable pixel-based digital analysis of large-area SERS scans. Such an approach enables ultralow-level detection of viruses that readily distinguishes positive signals from background noise at the pixel level. The developed digital SERS-LFTs demonstrate limits of detection (LODs) of 180 fg for SARS-CoV-2 spike protein, 120 fg for nucleocapsid protein, and 7 plaque forming units for intact virus, all within <30 min. Importantly, digital SERS-LFT methods maintain their robustness and their LODs in the presence of indoor dust, thus underscoring their potential for accurate and reliable virus diagnosis and quantification in real-world environmental settings.

Plasma-assisted synthesis of gold-silver core-shell nanoparticles and their enhanced catalytic dye degradation and surface enhanced Raman spectroscopy performance

The plasma-liquid interaction (PLI) technique has been employed as a green approach for the synthesis of gold-silver core-shell nanoparticles (Au@AgNPs) using a two-step method. In the first step, the Au seed particles were grown by the PLI technique. Subsequently, the formation of Ag shell was achieved by adding AgNO3 to the solution containing Au seeds and placing it under the atmospheric pressure plasma. The growth of Ag shell on Au seeds was optimized and secondary nucleation was avoided by tuning the discharge current, precursor concentration, and stabilizer (d-fructose) concentration. The shell thickness of Ag was also changed by changing the concentration of AgNO3 in the solution. UV-Vis spectroscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy were used to analyze the synthesized nanoparticles. Furthermore, the particles were employed for catalysis and surface enhanced Raman spectroscopy (SERS)-based molecular trace detection. The catalytic efficiency of the NPs was investigated for the reduction of four molecules, i.e., 4-nitrophenol, methyl orange, Congo red, and rhodamine B. The SERS-based trace detection was studied for rhodamine 6G using the substrates of synthesized NPs. In both cases, core-shell nanoparticles showed far superior performance compared to the seed Au nanoparticles.

Electrochemical Sensors based on Gold-Silver Core-Shell Nanoparticles Combined with a Graphene/PEDOT:PSS Composite Modified Glassy Carbon Electrode for Paraoxon-ethyl Detection.

Herein, a nonenzymatic detection of paraoxon-ethyl was developed by modifying a glassy carbon electrode (GCE) with gold-silver core-shell (Au-Ag) nanoparticles combined with the composite of graphene with poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS). These core-shell nanoparticles (Au-Ag) were synthesized using a seed-growth method and characterized using UV-vis spectroscopy and high-resolution transmission electron microscopy (HR-TEM) techniques. Meanwhile, the structural properties, surface morphology and topography, and electrochemical characterization of the composite of Au-Ag core-shell/graphene/PEDOT:PSS were analyzed using infrared spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS) techniques. Moreover, the proposed sensor for paraoxon-ethyl detection based on Au-Ag core-shell/graphene/PEDOT:PSS modified GCE demonstrates good electrochemical and electroanalytical performance when investigated with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry techniques. It was found that the synergistic effect between Au-Ag core-shell nanoparticles and the composite of graphene/PEDOT:PSS provides a higher conductivity and enhanced electrocatalytic activity for paraoxon-ethyl detection at an optimum pH of 7. At pH 7, the proposed sensor for paraoxon-ethyl detection shows a linear range of concentrations from 0.2 to 100 μM with a limit of detection of 10 nM and high sensitivity of 3.24 μA μM-1 cm-2. In addition, the proposed sensor for paraoxon-ethyl confirmed good reproducibility, with the possibility of being further developed as a disposable electrode. This sensor also displayed good selectivity in the presence of several interfering species such as diazinon, carbaryl, ascorbic acid, glucose, nitrite, sodium bicarbonate, and magnesium sulfate. For practical applications, this proposed sensor was employed for the determination of paraoxon-ethyl in real samples (fruits and vegetables) and showed no significant difference from the standard spectrophotometric technique. In conclusion, this proposed sensor might have a potential to be developed as a platform of electrochemical sensors for pesticide detection.

“On-site” analysis of pesticide residues in complex sample matrix by plasmonic SERS nanostructure hybridized hydrogel

BackgroundSurface-enhanced Raman spectroscopy (SERS) has been extensively used in biomedical and food safety detection due to its advantages of label-free, in situ and fingerprint spectrum. However, it is challenging to develop an excellent SERS substrate that possesses all three of these characteristics including sensitivity, repeatability and stability. ResultsIn this work, a specific sodium alginate hydrogel flexible SERS substrate encapsulated gold-silver core-shell nanoparticles (Au@Ag NPs) was developed to address the aforementioned issue. The Au@Ag NPs with SERS “hot spot” structure were evenly dispersed in the hydrogel, which achieved the direct and high efficiency detection of the pesticide residues from complex sample matrix. Taking thiram as objective, this SERS substrates exhibit high sensitivity (detection limit of approximately 1 × 10−10 mol/L), excellent stability (maintain above 78.35 % of SERS activity after 7 weeks) and outstanding repeatability (RSD in one substrate as low as 3.56 %). Furthermore, the flexible hydrogel SERS substrates can be used to analyze a variety of small molecules in real samples (juices, vegetables and fruits), without the need for a laborious pretreatment process. SignificanceIn light of the aforementioned benefits, the functional flexible hydrogel SERS substrates present a reliable platform for the accurate and on-site measurement of chemical contaminants from complex samples.

Tuning the plasmon resonance of Au-Ag core-shell nanoparticles: The influence on the visible light emission for inorganic fluorophores application

In this study, the gold and gold-silver (Au-Ag) core-shell nanoparticles were synthesized via chemical reduction method at different types and quantities of precursor materials. Initially, the gold nanoparticles were prepared with different reducing agents (i.e., sodium borohydride, sodium citrate, and ascorbic acid) and their composites. The optical absorbance, morphology, and size distribution of gold nanoparticles were analyzed to observe the best deposition conditions, used for the Au-Ag core-shell synthesis. Then, the Au-Ag core-shell nanoparticles were grown at four different quantities (i.e., 175 µL, 200 µL, 225 µL, and 250 µL) of silver nitrate precursor to study their effects on the fluorescence property. Optical absorbance, transmission electron microscopy, and laser scanning confocal microscopy were used to characterize the as-synthesized Au-Ag core-shell nanoparticles. From the results of optical absorbance, a single peak is seen for gold nanoparticles while two peaks (major and minor peaks) are observed for Au-Ag core-shell nanoparticles. The sizes of gold and core-shell particles observed from TEM measurement are less than 10 nm, which is typically used in fluorescence applications. The CoSh-2 sample showed a better fluorescence property compared to other core-shell samples. With a rise in exposure time in a laser with a specific wavelength of 405 nm, the intensity of fluorescence declined more for the filter having shorter wavelengths than larger wavelengths. Analyzing these results can be useful to understand the perspective applications of Au-Ag core-shell nanoparticles like synthetic fluorophores application.

Gold-Silver Core-Shell Nanoparticle Crosslinking Mediated by Protease Activity for Colorimetric Enzyme Detection.

Plasmonic nanoparticles produce a localized surface plasmon resonance (LSPR) under optical excitation. The LSPR of nanoparticles can shift in response to changes in the local dielectric environment and produce a color change. This color change can be observed by the naked eye due to the exceptionally large extinction coefficients (108-1011 M-1 cm-1) of plasmonic nanoparticles. Herein, we investigate the optical shifts (i.e., color change) of three unique gold-silver core-shell nanoparticle structures in response to changes in their dielectric environment upon nanoparticle aggregation. Aggregation is induced by a cysteine-containing peptide that has a sulfhydryl near its N and C termini, which crosslinks nanoparticles. Furthermore, we demonstrate that adding proline spacers between the cysteines impacts the degree of aggregation and, ultimately, the color response. Using this information, we construct a colorimetric enzyme assay, where the signal produced from nanoparticle aggregation is modulated by proteolysis. The degree of aggregation and the resulting optical shift can be correlated with enzyme concentration with high linearity (R2 = 0.998). Overall, this study explores the optical properties of gold-silver core-shell nanoparticles in a dispersed vs aggregated state and leverages that information to develop an enzyme sensor with a spectral LOD of 0.47 ± 0.09 nM.

Label-Free and Bioluminescence-Based Nano-Biosensor for ATP Detection.

A bioluminescence-based assay for ATP can measure cell viability. Higher ATP concentration indicates a higher number of living cells. Thus, it is necessary to design an ATP sensor that is low-cost and easy to use. Gold nanoparticles provide excellent biocompatibility for enzyme immobilization. We investigated the effect of luciferase proximity with citrate-coated gold, silver, and gold-silver core-shell nanoparticles, gold nanorods, and BSA-Au nanoclusters. The effect of metal nanoparticles on the activity of luciferases was recorded by the luminescence assay, which was 3-5 times higher than free enzyme. The results showed that the signal stability in presence of nanoparticles improved and was reliable up to 6 h for analytes measurements. It has been suggested that energy is mutually transferred from luciferase bioluminescence spectra to metal nanoparticle surface plasmons. In addition, we herein report the 27-base DNA aptamer for adenosine-5'-triphosphate (ATP) as a suitable probe for the ATP biosensor based on firefly luciferase activity and AuNPs. Due to ATP application in the firefly luciferase reaction, the increase in luciferase activity and improved detection limits may indicate more stability or accessibility of ATP in the presence of nanoparticles. The bioluminescence intensity increased with the ATP concentration up to 600 µM with a detection limit of 5 µM for ATP.

Potential use of gold-silver core-shell nanoparticles derived from Garcinia mangostana peel for anticancer compound, protocatechuic acid delivery.

Colorectal cancer is one of the most killing cancers and this has become a global problem. Current treatment and anticancer drugs cannot specifically target the cancerous cells, thus causing toxicity towards surrounding non-cancer cells. Hence, there is an urgent need to discover a more target-specific therapeutic agent to overcome this problem. Core-shell nanoparticles have emerged as good candidate for anticancer treatment. This study aimed to synthesize core-shell nanoparticles via green method which utilised crude peels extract of Garcinia mangostana as reducing and stabilising agents for drug delivery. Gold-silver core-shell nanoparticles (Au-AgNPs) were synthesized through seed germination process in which gold nanoparticles acted as the seed. A complete coating was observed through transmission electron microscopy (TEM) when the ratio of AuNPs and AgNPs was 1:9. The size of Au-AgNPs was 38.22 ± 8.41 nm and was mostly spherical in shape. Plant-based drug, protocatechuic acid (PCA) was loaded on the Au-AgNPs to investigate their anticancer activity. In HCT116 colon cancer cells, PCA-loaded Au-AgNPs (IC50 = 10.78 μg/ml) showed higher inhibitory action than the free PCA (IC50= 148.09 μg/ml) and Au-AgNPs alone (IC50= 24.36 μg/ml). Up to 80% inhibition of HCT116 cells was observed after the treatment of PCA-loaded Au-AgNPs at 15.63 μg/ml. The PCA-loaded Au-AgNPs also showed a better selectivity towards HCT116 compared to CCD112 colon normal cells when tested at the same concentrations. These findings suggest that Au-AgNPs system can be used as a potent nanocarrier to combat cancerous cells by offering additional anticancer properties to the loaded drug.

Plasmonic Sensing of Glucose Based on Gold–Silver Core–Shell Nanoparticles

Developing a simple and convenient approach for glucose sensing is crucially important in disease diagnosis and health monitoring. In this work, a glucose sensor based on plasmonic nanostructures was developed using gold–silver core–shell nanoparticles as the sensing platform. Based on the oxidative etching of the silver shell, the concentration of hydrogen peroxide and glucose could be determined quantitatively via the spectral change. This spectral change could also be observed with the naked eye or with a phone camera, realizing colorimetric sensing. To demonstrate this, glucose solutions at different concentrations were quantitatively detected in a wide concentration range of 0–1.0 mM using this colorimetric sensor. Importantly, shell thickness could significantly affect the sensitivity of our colorimetric sensor. This work provides a deeper understanding of the plasmonic sensing of glucose, which will help to realize its real applications. Based on this strategy, the non-invasive sensing of metabolites may be realized for disease diagnosis and health monitoring.

Core-shell SERS nanotags-based western blot

Western blot (WB) is the most commonly used scheme for protein identification in life science, but it still faces great challenges in the accurate quantitative detection of low-abundance proteins. Here, we proposed a novel surface-enhanced Raman scattering-based Western blot (SERS-WB) to solve this challenge. SERS nanotags were used as quantitative labels of proteins, which were composed of gold-silver core-shell nanoparticles, and Nile blue A (NBA) molecules were anchored on the interface of the core and shell. The results show that the SERS-WB possessed excellent sensitivity with detection limit of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein of 0.15 pg, as well as wide linear dynamic range (LDR) of 382 fg to 382 ng. In addition, the target protein on nitrocellulose (NC) membrane could be directly identified by colorimetric signal due to the aggregation effect of nanoparticles, which greatly simplifies the procedure. This as-proposed strategy will bring new thoughts to technological innovation of WB.

Acoustic Vibration Modes of Gold–Silver Core–Shell Nanoparticles

Bimetallic Au/Ag core–shell cuboid nanoparticles (NPs) exhibit a complex plasmonic response dominated by a dipolar longitudinal mode and higher-order transverse modes in the near-UV, which may be exploited for a range of applications. In this paper, we take advantage of the strong signature of these modes in the NP ultrafast transient optical response, measured by pump-probe transient absorption (TA) spectroscopy, to explore the NP vibrational landscape. The fast Fourier transform analysis of the TA dynamics reveals specific vibration modes in the frequency range 15–150 GHz, further studied by numerical simulations based on the finite element method. While bare Au nanorods exhibit extensional and breathing modes, the bimetallic NPs undergo more complex motions, involving the displacement of facets, edges and corners. The amplitude and frequency of these modes are shown to depend on the Ag shell thickness, as the silver load modifies the NP aspect ratio and mass. Moreover, the contributions of the vibrational modes to the experimental TA spectra are shown to vary with the probe laser wavelength at which the signal is monitored. Using the combined simulations of the NP elastic and optical properties, we elucidate this influence by analyzing the effect of the mechanisms involved in the acousto-plasmonic coupling.

Influence of Size and Composition on the Transformation Mechanics of Gold–Silver Core–Shell Nanoparticles

Influence of Size and Composition on the Transformation Mechanics of Gold–Silver Core–Shell Nanoparticles

A novel electrochemical aptasensor based on layer-by-layer assembly of DNA-Au@Ag conjugates for rapid detection of aflatoxin M1 in milk samples

Aflatoxin M1 (AFM1) is a common toxin in dairy products that causes acute and chronic human health disorders. Thus, the development of a rapid and accurate AFM1 detection method is of vital importance for food safety monitoring. This work was to develop a novel electrochemical aptasensor for sensitive and specific determination of AFM1. The dendritic-like nanostructure was formed on the gold electrode surface by layer-by-layer assembly of gold-silver core-shell nanoparticles modified with DNA conjugates. In the presence of AFM1, the specific recognition between AFM1 and Apt caused the disassociation of the DNA controlled dual Au@Ag conjugates from the surface of the electrode, causing less methylene blue to bind to the surface and weakening the electrochemical signal. The more AFM1 there is, the weaker the electrochemical signal. Transmission electron microscope results showed that the successfully synthesized Au@Ag nanoparticles exhibited a core-shell structure with Au as core and Ag as shell, and their average diameter was about 30 nm. Under optimal conditions, the electrochemical aptasensor showed a wide detection ranging from 0.05 ng mL-1 to 200 ng mL-1, and a low detection limit of 0.02 ng mL-1. Moreover, the proposed strategy has been successfully applied to the detection of AFM1 in cow, goat, and sheep milk samples with satisfactory recoveries ranging from 91.10% to 104.05%. This work can provide a novel rapid detection method for AFM1, and also provide a new sensing platform for the detection of other toxins.

Selective recognition and determination of malachite green in fish muscles via surface-enhanced Raman scattering coupled with molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) were incorporated with surface-enhanced Raman scattering (SERS) for selective recognition and rapid detection of malachite green in fish muscles. Among four functional monomers, methacrylic acid was selected as the suitable one for MIPs synthesis based upon computational simulation. The optimized MIP exhibited a higher adsorption efficiency for malachite green than that of nonimprinted polymers. The 74 nm gold-silver core-shell nanoparticles (Au@Ag NPs) provided stronger SERS signals for malachite green than those of other eleven gold nanoparticles and Au@Ag NPs. The use of selected MIP with Au@Ag NPs enabled to detect as low as 0.5–1 ng/g of malachite green in fish muscles from three different species, which was similar to that of 0.5 μg/L for malachite green standard solutions. The limit of detection was 0.37–0.64 ng/g in different fish muscles. This study provided a rapid, selective, and sensitive approach for SERS analysis of malachite green in aquatic products. • Surface-enhanced Raman scattering (SERS) used for malachite green (MG) detection. • Molecularly imprinted polymers (MIPs) designed to capture MG via computer simulation. • From 12 metallic colloid, Au@Ag (dia. 74 nm, seed 43 nm) chosen as a SERS substrate. • As low as 0.5–1 ppb MG in fish muscles detected with MIP-SERS hybrid method. • Interference of sample matrix effects minimized via MIP for SERS detection of MG.

Sensitivity Enhancement in the Colorimetric/Spectroscopic Determination of Lysozyme Concentration in Nanomolar Level with Colloidal Citrat e Capped Au@Ag Core-shell Nanoparticles

Background: Lysozyme level in body fluids is a significant indicator of various diseases. Cheap and simple colorimetric detection of lysozyme, in biological sample, by gold and silver nanoparticles is a field of interest of nanoparticle research for more than a decade. Objective: We report here an attempt to improve the sensitivity part of the colorimetric lysozyme detection process by using citrate capped gold-silver core-shell nanoparticles without any functionalization. Methods: Performance of gold-silver core-shell nanoparticles in determining of lysozyme concentration in water is done using colorimetric/spectroscopic technique. Gold nanoparticles, silver nanoparticles and mixed colloidal suspension of gold and silver nanoparticles, for comparison have also been studied. Selectivity study has been performed through spectroscopic analysis, red-greenblue colour component analysis and fractal dimension analysis of the nanoparticles interacted with several low and high isoelectric point proteins. Results: Gold-silver core-shell nanoparticles showed higher sensitivity for a wider range of lysozyme concentration compared to gold and silver nanoparticles prepared by us or reported in literature. Gold nanoparticles showed higher sensitivity compared to the core-shell nanoparticles, but for a narrow concentration range of lysozyme. For silver nanoparticles and the mixed nanoparticle system, both sensitivity and range of determination of lysozyme concentration were much smaller compared to the core-shell nanoparticles. Core-shell nanoparticles showed better selectivity compared to gold nanoparticles in identifying aquatic solution of lysozyme from that of other proteins. Conclusion: Gold-silver core-shell nanoparticles have higher sensitivity in determining wide range of lysozyme concentration in water compared to gold and silver nanoparticles reported in literature.

Production of biodiesel from oleaginous fungal lipid using highly catalytic bimetallic gold-silver core-shell nanoparticle.

This study aims to synthesize, characterize and apply gold-silver core-shell nanoparticles (Au@Ag NPs), a nanocatalyst, to maximize biodiesel production from fungal isolate Fusarium solani (FS12) via a transesterification one-step reaction. The Au@Ag NPs structure was examined by UV-vis spectrophotometer, transmission electron microscopy, X-ray diffraction and Fourier transform infrared (FTIR). All devices were used to characterize Au@Ag NPs and confirmed successful synthesis of nanoparticles. Fungal lipid was quantitatively determined by sulfo-phospho-vanillin colorimetric method. Among 15 F. solani isolates obtained from rhizospheric soils of the date palm, F. solani (AF12) was chosen as the highly significant producer that accumulates above 20% lipid. The maximum biodiesel yield was 91.28±0.19%, obtained under the optimum reaction conditions of 3% Au@Ag NPs as nanocatalyst concentration, and 1:20 oil to methanol molar ratio at 70℃ for 30min. HPLC method was applied for monitoring in situ transesterification reaction. FTIR spectroscopy was used in qualitative analysis of biodiesel by verifying the presence of unique characteristic peaks of diagnostic significance. The quality of the biodiesel produced was confirmed by the high purity of fatty acid methyl esters analysis content up to >99%. These findings propose the applicability of F. solani (FS12) as a promising isolate to accumulate lipids and biodiesel production as a feedstock. The link between nanotechnology and fungi. Au@Ag NPs were synthesized at room temperature, which displayed high catalytic activity for in situ transesterification reaction. Catalytic activity appeared at low temperature, mole ratio and short reaction time. Oleaginous fungi are described as easily grown, have short life cycle, are cost-effective, and they utilized various sources of carbon up to waste and a simplified process to develop scale-up production as well, economic value, opposite the usage of vegetable oils which need for large agricultural areas.

Aggregation triggered aflatoxin B1 determination in foodstuff employing 5-aminotetramethylrhodamine decorated gold–silver core–shell nanoparticles in surface enhanced Raman scattering

The current study examines aflatoxin B1 (AFB1) as the indicator of the total aflatoxins in wheat with a 5-aminotetramethylrhodamine (NH2-Rh)-decorated gold–silver core–shell nanoparticles ([email protected] CSNPs) sensor based surface enhanced Raman scattering (SERS) strategy, using Hg(II) as the media. The principle of the work was based on the selective interaction of Hg(Ⅱ) media with AFB1 via carbonyl oxygen atoms to inhibit the aggregation of NH2[email protected] CSNPs sensor. Due to the nanogap effect induced by sensors aggregation, the quenching in SERS intensity was an indication for AFB1 selective quantification. Under the optimized experimental conditions, a detection limit of 0.03 ng·mL−1 was obtained with a correlation coefficient R2 = 0.9895 within the dynamic range of 0.1–5.0 ng·mL−1. This quantification of AFB1 was further coupled with solid-phase extraction in real wheat, hazelnut, and peanut oil samples. The strategy was validated by standard HPLC-FLD approach and was in a good agreement. The proposed detective system offers a promising platform for the rapid determination of traces AFB1 residue in foodstuff with high selectivity and economical efficiency.

Evaluating the total gold concentration in metallic nanoparticles with a high content of organic matter through microwave-assisted decomposition platform and plasma-based spectrometric techniques (ICP-MS and ICP OES)

We report a complete set of strategies for characterization and an accurate determination of gold in metallic nanoparticles. For this, gold nanorods (AuNR) were synthesized by using the surfactant hexadecyltrimethylammonium bromide (CTAB) as the stabilizer and shape-directing agent. The surfactant CTAB forms a bilayer structure around the nanoparticles and became a challenge for the development of the microwave-assisted decomposition of the AuNR colloid. The bilayer structure of CTAB prevents the Au3+ release for the acidic media during the decomposition procedure. To overcome this limitation, a combination of low sample volume consumption (only 200 μL), an acidic mixture of reverse aqua regia (1:3 v/v, HCl:HNO3), and sulfuric acid, and a microwave program was used. The gold quantification by ICP-MS and checked through the ICP OES, demonstrated that the seed-mediated growth method used for the AuNR synthesis has a high yield, presenting ca. 100% of gold content (ca. 100 mg L−1 of gold concentration) in the post-synthesis colloid (AuNR-total) as well as in the colloid after a washing step (AuNR-res). The microwave-assisted decomposition procedure also demonstrated to be efficient in the acidic decomposition of the gold-silver core-shell nanoparticle (Au@AgNR), which presents a high content of polyvinylpyrrolidone (PVP) (Mw ~55000 g mol−1) acting as a stabilizer, in addition to the matrix with CTAB. The results demonstrated an accurate recovery of ca. 100% of gold content for the Au@AgNR regarding the gold nanorod before the growth of the silver shell (AuNR_Core). The proposed microwave-assisted decomposition platform demonstrated to be an efficient, reliable, and robust characterization tool for the gold quantification in metallic nanoparticles, presenting no interference of the complex matrix with high organic content.