Search

A multi-step procedure was effectively employed to synthesize innovative three-dimensional (3D) heterostructures encompassing sodium titanate (Na2Ti3O7) nanowire cores, an intermediate resorcinol–formaldehyde (RF) layer, and outer silver (Ag) nanoparticle sheaths, referred to as Na2Ti3O7@RF@Ag heterostructures. Initially, a one-step hydrothermal technique facilitated the direct growth of single-crystal Na2Ti3O7 nanowires onto a flexible Ti foil. Subsequently, a two-step wet chemical process facilitated the sequential deposition of an RF layer and Ag nanoparticles onto the Na2Ti3O7 nanowires at a low reaction temperature. Optimal concentrations of silver nitrate and L-ascorbic acid can lead to the cultivation of Na2Ti3O7@RF@Ag heterostructures exhibiting heightened surface-enhanced Raman scattering (SERS), which is particularly beneficial for the detection of rhodamine B (RhB) molecules. This phenomenon can be ascribed to the distinctive geometry of the Na2Ti3O7@RF@Ag heterostructures, which offer an increased number of hot spots and surface-active sites, thereby showcasing notable SERS enhancement, commendable reproducibility, and enduring stability over the long term. Furthermore, the Na2Ti3O7@RF@Ag heterostructures demonstrate remarkable follow-up as first-order chemical kinetic and recyclable photocatalysts for the photodecomposition of an RhB solution under UV light irradiation. This result can be attributed to the enhanced inhibition of electron–hole pair recombination and increased surface-active sites. [ABSTRACT FROM AUTHOR]

Vertically aligned ZnO: Ga nanotowers can be directly synthesized on a glass substrate with a ZnO seed film via the chemical bath method. A novel heterostructure of ZnO: Ga@ITO@Ag nanotowers was subsequently deposited in the ITO layer and Ag nanoparticles via the facile two-step ion-sputtering processes on the ZnO: Ga nanotowers. The appropriate ion-sputtering times of the ITO layer and Ag nanoparticles can benefit the fabrication of ZnO: Ga@ITO@Ag nanotowers with higher surface-enhanced Raman scattering (SERS) enhancement in detecting rhodamine 6G (R6G) molecules. Compared with ZnO: Ga@Ag nanotowers, ZnO: Ga@ITO@Ag nanotowers exhibited a high SERS enhancement factor of 2.25 × 108 and a lower detection limit (10−14 M) for detecting R6G molecules. In addition, the ITO layer used as an intermediate layer between ZnO: Ga nanotowers and Ag nanoparticles can improve SERS enhancement, sensitivity, uniformity, reusability, detection limit, and stability for detecting amoxicillin molecules. This phenomenon shall be ascribed to the ITO layer exhibiting a synergistic Raman enhancement effect through interfacial charge transfer for enhancing SERS activity. As a result, ZnO: Ga@ITO@Ag nanotowers can construct a three-dimensional SERS substrate for potential applications in environmentally friendly and cost-effective chemical or drug detection. [ABSTRACT FROM AUTHOR]

Vertical-aligned CuO nanowires have been directly fabricated on Cu foil through a facile thermal oxidation process by a hotplate at 550 °C for 6 h under ambient conditions. The intermediate layer of resorcinol–formaldehyde (RF) and silver (Ag) nanoparticles can be sequentially deposited on Cu nanowires to form CuO@RF@Ag core-shell nanowires by a two-step wet chemical approach. The appropriate resorcinol weight and silver nitrate concentration can be favorable to grow the CuO@RF@Ag nanowires with higher surface-enhanced Raman scattering (SERS) enhancement for detecting rhodamine 6G (R6G) molecules. Compared with CuO@Ag nanowires grown by ion sputtering, CuO@RF@Ag nanowires exhibited a higher SERS enhancement factor of 5.33 × 108 and a lower detection limit (10−12 M) for detecting R6G molecules. This result is ascribed to the CuO@RF@Ag nanowires with higher-density hot spots and surface-active sites for enhanced high SERS enhancement, good reproducibility, and uniformity. Furthermore, the CuO@RF@Ag nanowires can also reveal a high-sensitivity SERS-active substrate for detecting amoxicillin (10−10 M) and 5-fluorouracil (10−7 M). CuO@RF@Ag nanowires exhibit a simple fabrication process, high SERS sensitivity, high reproducibility, high uniformity, and low detection limit, which are helpful for the practical application of SERS in different fields. [ABSTRACT FROM AUTHOR]

This study used a rapid and simple microwave-assisted synthesis method to grow ZnO nanoneedle arrays on the silicon substrate with the ZnO seed layer. The effects of reaction temperature and time on the lengths of ZnO nanoneedle arrays were investigated. The appropriate temperature programming step can grow the longer ZnO nanoneedle arrays at the same reaction time (25 min), which is 2.08 times higher than without the temperature programming step. The geometry of the ZnO nanoneedle arrays features a gradual decrease from the Si substrate to the surface, which provides an excellent progressive refractive index between Si and air, resulting in excellent antireflection properties over an extensive wavelength range. In addition, the ZnO nanoneedle arrays exhibit a suitable structure for uniform deposition of Ag nanoparticles, which can provide three-dimensional hot spots and surface active sites, resulting in higher surface-enhanced Raman scattering (SERS) enhancement, high uniformity, high reusability, and low detection limit for R6G molecule. The ZnO/Ag nanoneedle arrays can also reveal a superior SERS-active substrate detecting amoxicillin (10−8 M). These results are promising for applying the SERS technique for rapid low-concentration determination in different fields. [ABSTRACT FROM AUTHOR]

In this study, we fabricated Er-doped ZnO/CuS/Au core-shell nanowires using two-step wet chemical methods and an ion-sputtering method on a glass substrate as a bifunctional photocatalytic and surface-enhanced Raman scattering (SERS) substrate. The characteristic properties of as-prepared photocatalysts were confirmed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, DR/UV-Vis spectroscopy, and photoluminescence spectroscopy. Compared with Er-doped ZnO nanowires and Er-doped ZnO/CuS core-shell nanowires, Er-doped ZnO/CuS/Au core-shell nanowires exhibited remarkably photocatalytic activity to degrade acid orange 7 solutions under blue LED light. These results ascribed to the Er-doped ZnO/CuS/Au core-shell nanowires can enhance the visible-light absorbance and the separation efficiency of photogenerated electron-hole pairs, inducing their higher photocatalytic activity under blue LED light. In addition, Er-doped ZnO/CuS/Au core-shell nanowires exhibit high sensitivity, a low detection limit (10−6 M), uniformity, recyclability, and stability of SERS performance for detected acid orange 7. [ABSTRACT FROM AUTHOR]

This study demonstrates a simple method to fabricate the silicon pyramid on the silicon substrate via a chemical etching method. The chemical etching process with different reaction conditions plays an essential role in controlling the growth of uniform and large silicon pyramids. The silicon pyramid can provide suitable geometric structures to deposit silver nanoparticles with better anti-aggregation stability to apply surface-enhanced Raman spectroscopy (SERS) substrates via the ion-sputtering method. The appropriate silicon pyramid and silver nanoparticles sizes were optimized to produce the most significant SERS effect in the rhodamine 6G molecule. The silicon pyramid exhibited better morphology for the deposition of uniform-sized silver nanoparticles, facilitating the fabrication of high-performance SERS substrate to detect different drugs. The fabrication of silver nanoparticles decorated on the silicon pyramid is facile, of high reproducibility, which shall be advantageous in applications for detecting other molecules via SERS. [Display omitted] • Different reaction conditions play an essential role in controlling the growth of uniform silicon pyramids. • Silicon pyramids can provide a larger surface area and anti-reflective properties rather than flat silicon. • Silicon pyramids provided better geometry for the deposition of uniform-sized silver nanoparticles. • Silicon pyramid/Ag heterostructures can detect R6G with high sensitivity, uniformity, and low detection limits. • The SERS substrate exhibited a very low detection limit for the detection of 5-FU and amoxicillin solutions. [ABSTRACT FROM AUTHOR]

• Ag nanoparticles-Ga-doped ZnO nanoneedles-pyramidal silicon hybrids were prepared as SERS substrates. • The hybrids exhibited excellent SERS performance with good uniformity and stability. • SERS signal enhancement of up to 6.52 × 108 was observed in the detection of R6G. • Ag/Ga-doped ZnO/pyramidal silicon substrate can be facilely self-cleaned using UV light. • Ag/Ga-doped ZnO/pyramidal silicon substrate can use to detect different types of drugs with low detection limits. [Display omitted] High-performance surface-enhanced Raman scattering (SERS)-active substrate can be fabricated by deposited silver (Ag) nanoparticles on the pyramidal silicon with Ga-doped zinc oxide (ZnO) nanoneedles. Properly manufacturing a ZnO seed layer on pyramidal silicon may be beneficial to grow vertically aligned Ga-doped ZnO nanoneedles to deposit silver nanoparticles uniformly. Suitable silver sputtering duration on the Ga-doped ZnO nanoneedles has been upgraded to produce the most remarkable SERS effect in rhodamine 6G (R6G) molecules. SERS results show that Ag/Ga doped ZnO/pyramidal silicon is better than Ag/pyramidal silicon and Ag/silicon substrates. This phenomenon is attributed to Ag/Ga-doped ZnO/pyramidal silicon geometry, providing more hot spots and surface-active sites to exhibit high SERS enhancement, good reproducibility, and long-term stability. Ag/Ga doped ZnO/pyramidal silicon can also provide excellent SERS active substrates for detecting different types of drugs with low detection limits, such as amoxicillin (10−10 M) and irinotecan (10−7 M). [ABSTRACT FROM AUTHOR]

In this study, we report a feasible aqueous chemical method to synthesize Au core–Ag shell nanoparticles (NPs) by seeding growth approach. The concentration of Au NPs plays an important role in growing the different thicknesses of Ag shells. The design of signaling aptamer utilizes the target-induced switching between an aptamer/DNA duplex and an aptamer/target complex. The surface enhanced Raman scattering (SERS) signal was enhanced upon the hybridization of the Raman reporter-labeled DNA released from the target-induced displacement with the captured DNA immobilized on the silicon substrate with Au–Ag core–shell NPs. This substrate with 12.4 nm Ag shell shows high reproducibility, strong enhancement, and a low detection limit (1 nM). The enhancement in DNA-based adenosine detection properties shall be advantageous in applications for other aptamer sensing systems. [ABSTRACT FROM AUTHOR]