Search Results (19)

FKBP12 is a peptidyl––prolyl cis–trans isomerase that was recently proposed as a candidate biomarker for cancer, for neurodegenerations and for anti–rejection therapy after organ transplant. We designed and fabricated a nanosensor platform for the rapid and efficient determination of FKBP12 concentration in biological fluids exploiting anisotropic silver nanoparticles (AgNps) to enhance the capabilities of Quartz Crystal Microbalance (QCM) detection. To this end, the QCM sensor was coated with a compact array of AgNPs that were further functionalized with a Self–Assembled–Monolayer containing a synthetic receptor, GPS–SH1, designed and synthesized specifically to selectively bind FKBP12. Silver nanoflowers, AgNFs, and silver dendrites, AgNDs, were prepared by electrodeposition and characterized by means of UV–Vis spectroscopy, Scanning Electron Microscopy (SEM), QCM and water contact angle (CA). The AgNPs@Au/GPS–SH1–functionalized QCM sensors were used to detect increasing concentrations of FKBP12 in solution; the results showed that the use of AgNDs significantly enhanced the sensitivity of the sensor with respect to flat Ag sensor chips, allowing the detection of FKBP12 at sub–picomolar concentrations. Full article

The visualization of the spatial distributions of gases from various sources is essential to understanding the composition, localization, and behavior of these gases. In this study, an inkjet-printed localized surface plasmon resonance (LSPR) subpixel gas sensor array was developed to visualize the spatial distributions of gases and to differentiate between acetic acid, geraniol, pentadecane, and cis-jasmone. The sensor array, which integrates gold nanoparticles (AuNPs), silver nanoparticles (AgNPs), and fluorescent pigments, was positioned 3 cm above the gas source. Hyperspectral imaging was used to capture the LSPR spectra across the sensor array, and these spectra were then used to construct gas information matrices. Principal component analysis (PCA) enabled effective classification of the gases and localization of their sources based on observed spectral differences. Heat maps that visualized the gas concentrations were generated using the mean squared error (MSE) between the sensor responses and reference spectra. The array identified and visualized the four gas sources successfully, thus demonstrating its potential for gas localization and detection applications. The study highlights a straightforward, cost-effective approach to gas sensing and visualization, and in future work, we intend to refine the sensor fabrication process and enhance the detection of complex gas mixtures. Full article

Weak doping can broaden, shift, and quench plasmon peaks in nanoparticles, but the mechanistic intricacies of the diverse responses to doping remain unclear. In this study, we used the time-dependent density functional theory (TD-DFT) to compute the excitation properties of transition-metal Pd- or Pt-doped gold and silver atomic arrays and investigate the evolution characteristics and response mechanisms of their plasmon peaks. The results demonstrated that the Pd or Pt doping of the off-centered 10 × 2 atomic arrays broadened or shifted the plasmon peaks to varying degrees. In particular, for Pd-doped 10 × 2 Au atomic arrays, the broadened plasmon peak significantly blueshifted, whereas a slight red shift was observed for Pt-doped arrays. For the 10 × 2 Ag atomic arrays, Pd doping caused almost no shift in the plasmon peak, whereas Pt doping caused a substantial red shift in the broadened plasmon peak. The analysis revealed that the diversity in these doping responses was related to the energy positions of the d electrons in the gold and silver atomic clusters and the positions of the doping atomic orbitals in the energy bands. The introduction of doping atoms altered the symmetry and gap size of the occupied and unoccupied orbitals, so multiple modes of single-particle transitions were involved in the excitation. An electron transfer analysis indicated a close correlation between excitation energy and the electron transfer of doping atoms. Finally, the differences in the symmetrically centered 11 × 2 doped atomic array were discussed using electron transfer analysis to validate the reliability of this analytical method. These findings elucidate the microscopic mechanisms of the evolution of plasmon peaks in doped atomic clusters and provide new insights into the rational control and application of plasmons in low-dimensional nanostructures. Full article

Functionalized Au and Ag nanoparticles (NPs) with ascorbic and tannic acid, respectively, were used as SERS substrates (SS). Several SS were fabricated with different loads of metal NPs deposited on silicon wafers. We focused on the thyroxine (T4) band at 1044 cm⁻¹ and tracked its intensity and position at concentrations from 10 pM to 1 mM. For all SS, the band intensity decreased as the T4 concentration decreased. Additionally, the band shifted to larger wavenumbers as the NP loads increased. In the case of Au, the SS with the highest load of NPs, the minimum concentration detected was 1 μM. The same load of the Ag NP SS showed a better performance detecting a concentration of 10 pM, an outcome from a SERS-EF of 10⁹. The NP spatial distribution includes mainly isolated NPs, quasi-spherical clusters, and semi-linear arrays of NPs in random orientations. From the numerical simulations, we conclude that the hot spots at the interparticle gaps in a linear array of three NPs are the most intense. The Ag NP SS demonstrated good sensitivity, to allow the detection of pM concentrations. Therefore, its complementation to any immunoassay technique provides an interesting alternative for point-of-care implementations, such as test strips. Full article

Biogenic amines (BAs) were presented as significant markers for the evaluation of the spoilage of meat and meat products. In this work, a colorimetric sensor array was developed for the discrimination and detection of spermine (SP), spermidine (SD), histamine (HS), and tryptamine (TP) as important BAs in food assessment. For this aim, two important spherical plasmonic nanoparticles, namely gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs), were utilized as the sensing elements of the probes. The cross-reactive interaction of the target biogenic amines and the plasmonic nanoparticles caused the aggregation-induced UV–Vis spectra changes, which were accompanied by visual color variation in the solution. The collected responses were analyzed by principal component analysis-linear discrimination analysis (PCA-LDA) to classify the four BAs. This colorimetric sensor array can also discriminate between the individual BAs and their mixture accurately. Partial least squares regression (PLS-R) was also utilized for quantitative analysis of the BAs. The wide linear concentration ranges of 0.1–10.0 µM for the four BAs and desirable figures of merits (FOMs) showed the potential of the developed sensor for quantitative detection of the BAs. Finally, the practical ability of the developed probe was studied by the determination of the BAs in the meat samples, which successfully proved the potential of the colorimetric sensor array in a food sample. Full article

Although the fabrication of controllable three-dimensional (3D) microstructures on substrates has been proposed as an effective solution for SERS, there remains a gap in the detection and manufacturability of 3D substrates with high performance. In this study, photolithography is adopted to obtain a pyramid-like array on a patterned sapphire substrate (PSS), with Al₂O₃ as the dielectric layer. In addition, silver nanoparticles (AgNPs) are used to decorate Au films to obtain mass-producible 3D SRES substrates. In the case of low fluorescence, the substrate realizes the coupling of localized surface plasmon polaritons (LSPs) and surface plasmon polaritons (SPPs), which is consistent with the simulation results obtained using the finite element method. The performance of the SERS substrate is evaluated using rhodamine 6G (R6G) and toluidine blue (TB) as probe molecules with detection limits of 10⁻¹¹ M and 10⁻⁹ M, respectively. The substrate exhibits high hydrophobicity and excellent light-capturing capability. Moreover, it shows self-cleaning ability and long-term stability in practical applications. Allowing for the consistency of the composite substrate in the preparation process and the high reproducibility of the test results, it is considered to be promising for mass production. Full article

A freely available “in vitro dosimetry” web application is presented enabling users to predict the concentration of nanomaterials reaching the cell surface, and therefore available for attachment and internalization, from initial dispersion concentrations. The web application is based on the distorted grid (DG) model for the dispersion of engineered nanoparticles (NPs) in culture medium used for in vitro cellular experiments, in accordance with previously published protocols for cellular dosimetry determination. A series of in vitro experiments for six different NPs, with Ag and Au cores, are performed to demonstrate the convenience of the web application for calculation of exposure concentrations of NPs. Our results show that the exposure concentrations at the cell surface can be more than 30 times higher compared to the nominal or dispersed concentrations, depending on the NPs’ properties and their behavior in the cell culture medium. Therefore, the importance of calculating the exposure concentration at the bottom of the cell culture wells used for in vitro arrays, i.e., the particle concentration at the cell surface, is clearly presented, and the tool introduced here allows users easy access to such calculations. Widespread application of this web tool will increase the reliability of subsequent toxicity data, allowing improved correlation of the real exposure concentration with the observed toxicity, enabling the hazard potentials of different NPs to be compared on a more robust basis. Full article

Metallic nanoparticles (MNPs) and metallic nanostructures are both commonly used, independently, as SERS substrates due to their enhanced plasmonic activity. In this work, we introduce and investigate a hybrid nanostructure with strong SERS activity that benefits from the collective plasmonic response of the combination of MNPs and flow-through nanohole arrays (NHAs). The electric field distribution and electromagnetic enhancement factor of hybrid structures composed of silver NPs on both silver and gold NHAs are investigated via finite-difference time-domain (FDTD) analyses. This computational approach is used to find optimal spatial configurations of the nanoparticle positions relative to the nanoapertures and investigate the difference between Ag-NP-on-Ag-NHAs and Ag-NP-on-Au-NHAs hybrid structures. A maximum G_SERS value of 6.8 × 10⁹ is achieved with the all-silver structure when the NP is located 0.5 nm away from the rim of the NHA, while the maximum of 4.7 × 10¹⁰ is obtained when the nanoparticle is in full contact with the NHA for the gold-silver hybrid structure. These results demonstrate that the hybrid nanostructures enable hotspot formation with strong SERS activity and plasmonic enhancement compatible with SERS-based sensing applications. Full article

Highly sensitive and reproducible surface-enhanced Raman scattering (SERS) substrates are the main challenge for practical applications. In this work, an ordered and hierarchical Ag nanoparticles (Ag-NPs)-decorated Au nanotubes (Au-NTs) array was achieved based on a funnel-shaped pore anodic aluminum oxide (AAO) template-assisted strategy. First, funnel-pore-AAO templates were fabricated by further oxidation of conical-pore-AAO templates achieved by multistep anodization and etching. Then physical sputtering was used to assemble the Au-NTs and Ag-NPs using the as-prepared funnel-pore-AAO as sacrificial templates. SEM revealed abundant sub-10 nm neighboring gaps and sub-10 nm nanocavities at the bottom of the nanotubes because of the special shape of the AAO template, which resulted in abundant strong “hot spots” contributing to the sensitive SERS detection. The resultant hierarchical substrates manifested a SERS enhancement factor of 1.8 × 10⁷ and reproducible response to 10⁻¹¹ M rhodamine 6G and 10⁻⁸ M methyl parathion, showing potential in SERS-based rapid detection of trace pollutants in the environment. Full article

Disease diagnosis through breath analysis has attracted significant attention in recent years due to its noninvasive nature, rapid testing ability, and applicability for patients of all ages. More than 1000 volatile organic components (VOCs) exist in human breath, but only selected VOCs are associated with specific diseases. Selective identification of those disease marker VOCs using an array of multiple sensors are highly desirable in the current scenario. The use of efficient sensors and the use of suitable classification algorithms is essential for the selective and reliable detection of those disease markers in complex breath. In the current study, we fabricated a noble metal (Au, Pd and Pt) nanoparticle-functionalized MoS₂ (Chalcogenides, Sigma Aldrich, St. Louis, MO, USA)-based sensor array for the selective identification of different VOCs. Four sensors, i.e., pure MoS₂, Au/MoS₂, Pd/MoS₂, and Pt/MoS₂ were tested under exposure to different VOCs, such as acetone, benzene, ethanol, xylene, 2-propenol, methanol and toluene, at 50 °C. Initially, principal component analysis (PCA) and linear discriminant analysis (LDA) were used to discriminate those seven VOCs. As compared to the PCA, LDA was able to discriminate well between the seven VOCs. Four different machine learning algorithms such as k-nearest neighbors (kNN), decision tree, random forest, and multinomial logistic regression were used to further identify those VOCs. The classification accuracy of those seven VOCs using KNN, decision tree, random forest, and multinomial logistic regression was 97.14%, 92.43%, 84.1%, and 98.97%, respectively. These results authenticated that multinomial logistic regression performed best between the four machine learning algorithms to discriminate and differentiate the multiple VOCs that generally exist in human breath. Full article

Recent investigations into cardiac or nervous tissues call for systems that are able to electrically record in 3D as opposed to 2D. Typically, challenging microfabrication steps are required to produce 3D microelectrode arrays capable of recording at the desired position within the tissue of interest. As an alternative, additive manufacturing is becoming a versatile platform for rapidly prototyping novel sensors with flexible geometric design. In this work, 3D MEAs for cell-culture applications were fabricated using a piezoelectric inkjet printer. The aspect ratio and height of the printed 3D electrodes were user-defined by adjusting the number of deposited droplets of silver nanoparticle ink along with a continuous printing method and an appropriate drop-to-drop delay. The Ag 3D MEAs were later electroplated with Au and Pt in order to reduce leakage of potentially cytotoxic silver ions into the cellular medium. The functionality of the array was confirmed using impedance spectroscopy, cyclic voltammetry, and recordings of extracellular potentials from cardiomyocyte-like HL-1 cells. Full article

This work investigates the influence of an Ag nanoparticle addition on the microstructure, microhardness, creep, temperature-dependent elastic properties, damping capacity, and shear strength of an environmentally friendly eutectic Sn-9Zn (wt.%) material. A microstructure analysis confirmed that adding Ag nanoparticles significantly altered the morphologies of the Zn-rich phase, which includes the size and shape in the presence of fine spherical-shaped AgZn₃ intermetallic compound (IMC) particles in the β-Sn matrix. These fine microstructures positively impact on microhardness, creep, damping capacity, and temperature-dependent elastic properties. Furthermore, in the electronic interconnection on an Au/Ni-plated-Cu pad ball grid array (BGA) substrate, adding Ag nanoparticles generates an additional AgZn₃ IMC layer at the top surface of the AuZn₃ IMC layer. It also significantly improves the oxidation resistance of Sn-Zn material due to the formation of fine AgZn₃ IMC particles. Moreover, the interfacial shear strength value of the Sn-Zn material doped with Ag nanoparticles on the Au/Ni-Cu pad BGA substrate increased about 12% as compared to the reference material after five minutes of reaction in the presence of a fine Zn-rich phase and AgZn₃ IMC particles, which acted as second phase dispersion strengthening mechanism. Adding Ag nanoparticles also altered the fracture mode to a typical ductile failure with rough dimpled surfaces of the Sn-Zn material. Full article

The use of biomolecules in nanomaterial synthesis has received increasing attention, because they can function as a medium to produce inorganic materials in ambient conditions. Short peptides are putative ligands that interact with metallic surfaces, as they have the potential to control the synthesis of nanoscale materials. Silver nanoparticle (AgNP) mineralization using peptides has been investigated; however, further comprehensive analysis must be carried out, because the design of peptide mediated-AgNP properties is still highly challenging. Herein, we employed an array comprising 200 spot synthesis-based peptides, which were previously isolated as gold nanoparticle (AuNP)-binding and/or mineralization peptides, and the AgNP mineralization activity of each peptide was broadly evaluated. Among 10 peptides showing the highest AgNP-synthesis activity (TOP10), nine showed the presence of EE and E[X]E (E: glutamic acid, and X: any amino acid), whereas none of these motifs were found in the WORST25 (25 peptides showing the lowest AgNP synthesis activity) peptides. The size and morphology of the particles synthesized by TOP3 peptides were dependent on their sequences. These results suggested not only that array-based techniques are effective for the peptide screening of AgNP mineralization, but also that AgNP mineralization regulated by peptides has the potential for the synthesis of AgNPs, with controlled morphology in environmentally friendly conditions. Full article

Controlling chemical reactions by plasma is expected to be a new method for improving the structural properties of substrates. An Au nanojar array was prepared when Au was deposited onto a 2D polystyrene (PS) array. The site-selective chemical growth of Ag nanoparticle rings was realized around the Au nanojar necks by a local surface plasmon resonance (LSPR)-assisted chemical reaction. The catalytic hotspots in the nanostructure array could be controlled by both etching the nanojars and Au or TiO₂ sputtering onto the nanojars, which were confirmed by the growth sites of the Ag nanoparticle in the LSPR-assisted chemical reaction. The structure of the nanojars and the electric field distributions of the growing nanoparticles were simulated and analyzed using Finite-Difference Time-Domain. FDTD simulations showed that the changes in the nanojar shape led to the changed hotspot distributions. At the same time, tracking the hotspot shifts in the process of structural change was also achieved by the observation of Ag growth. Nanoarray structure prepared by LSPR-assisted chemical reaction is one of the hot fields in current research and is also of great significance for the application of Surface-Enhanced Raman Scattering. Full article

Two-dimensional (2D) periodic micro/nanostructured arrays as SERS substrates have attracted intense attention due to their excellent uniformity and good stability. In this work, periodic hierarchical SiO₂ nanopillar arrays decorated with Ag nanoparticles (NPs) with clean surface were prepared on a wafer-scale using monolayer Au NP arrays as masks, followed by reactive ion etching (RIE), depositing Ag layer and annealing. For the prepared SiO₂ nanopillar arrays decorated with Ag NPs, the size of Ag NPs was tuned from ca. 24 to 126 nanometers by controlling the deposition thickness of Ag film. Importantly, the SiO₂ nanopillar arrays decorated with Ag NPs could be used as highly sensitive SERS substrate for the detection of 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) due to the high loading of Ag NPs and a very uniform morphology. With a deposition thickness of Ag layer of 30 nm, the SiO₂ nanopillar arrays decorated with Ag NPs exhibited the best sensitive SERS activity. The excellent SERS performance of this substrate is mainly attributed to high-density “hotspots” derived from nanogaps between Ag NPs. Furthermore, this strategy might be extended to synthesize other nanostructured arrays with a large area, which are difficult to be prepared only via conventional wet-chemical or physical methods. Full article