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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]

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]

Abstract This work describes the direct fabrication of Ag nanoparticles on pyramidal silicon using a facile, one-step, electroless deposition process at room temperature with short reaction time (3 min). The resulting device could use for rapid drug detection based on surface-enhanced Raman scattering (SERS). The size of the silicon pyramids controlled by altering the texturing time of the silicon substrate. Spin coating was used to enable the rapid deposition of rhodamine 6G molecules (3 min) on the Ag nanoparticles. The resulting pyramidal silicon decorated with Ag nanoparticles provides large specific area as well as hot spots to promote localized surface plasmon resonance, resulting in notable SERS enhancement and a low 5-fluorouracil detection limit (10−6 M). Highlights • Facile electroless deposition to grow Ag nanoparticles (NPs) on pyramidal silicon. • Room temperature growth of Ag NPs using short (3 min) reaction time. • Surface-enhanced Raman scattering (SERS) tests using rhodamine 6G on Ag NPs/Si pyramids • Size of the silicon pyramids controlled by the texturing time appears to be critical. • Very low detection limit (10−6 M) of the Ag NP-based SERS sensor for 5-fluorouracil. [ABSTRACT FROM AUTHOR]

Abstract In this study, we report a facile replacement reduction method to directly deposit the large-scale Ag nanoparticles on a silicon substrate at the room temperature and short reaction time (3 min). The reaction process is a straightforward wet chemistry approach using silver nitrate and hydrogen fluoride as a silver source and reducing reagent, respectively. The Ag nanoparticles as a surface-enhanced Raman scattering (SERS) substrate present high sensitivity, excellent uniformity, and high stability for rhodamine 6G molecules. Also, Ag nanoparticles are also shown to provide a unique platform for the SERS detection of melamine, 5-fluorouracil, amoxicillin in different aqueous media. The fabrication of Ag nanoparticles is facile, low cost, strong enhancement, low detection limit, high reproducibility, and stability, which is advantageous for the applications of other SERS-based sensors. Highlights • Ag nanoparticles have grown on the Si by a facile a replacement reduction method. • The growth condition is at room temperature and short reaction time (3 min). • Ag nanoparticles revealed high SERS enhancement, uniformity and reusability. • The SERS substrate used to detect toxic chemicals and drugs under the different water-based. • The SERS substrate also exhibited very low detection limit for the detection of toxic chemicals and drugs. [ABSTRACT FROM AUTHOR]

Large-scale ZnO nanoneedle arrays have been grown on four-inch silicon wafers with ZnO seed film by an aqueous chemical growth method at a low growth temperature and short reaction time. The volumes of 1,3 diaminopropane play an important role in controlling the dimension and optical emission properties of ZnO nanoneedle arrays, which exhibit a very prominent green emission and weak UV emission from defect and band gaps in the cathodoluminescence spectrum, respectively. The ZnO nanoneedle arrays with large alignment variations display broadband and omnidirectional antireflection properties from the gradual index profile, and can provide a higher surface-to-volume ratio and stronger defect emission, which results in a peak photocatalytic performance at a light irradiation of 10 W UV. The appropriate Ag sputtering durations on the ZnO nanoneedle arrays have been optimized to yield the greatest surface-enhanced Raman scattering effect in the rhodamine 6G molecule. The ZnO/Ag composite arrays provide a facile, high enhancement, low detection limit and low cost fabrication, which shall be of significant value for practical applications of other SERS sensing systems. [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 paper reports on a facile low-cost electroless deposition method with a short reaction time to directly fabricate Ag nanosheets onto a silicon substrate. Silver nitrate, hydrofluoric acid, and trisodium citrate were used as a silver source, etchant, and capping reagent by a wet chemical approach. The surface morphology of the Ag nanostructures could be controlled by adjusting the difference of reaction conditions (such as concentrations of hydrofluoric acid and trisodium citrate, reaction time). Ag nanosheets provide high corners, anisotropy, and hot spots for enhancing localized surface plasmon resonance with higher surface-enhanced Raman scattering enhancement and lower detection limits, which shall be beneficial in SERS-based chemical sensing. Image 1 • Ag nanosheets have grown on the Si by a facile electroless deposition method. • The growth condition is at room temperature and short reaction time (3 min). • The different reaction conditions can effectively control Ag nanostructures. • Ag nanosheets exhibit a very low detection limit (0.1 nM). [ABSTRACT FROM AUTHOR]

This present study used a simple aqueous chemical growth method to synthesize Al-doped ZnO (ZnO: Al) nanoneedles on ZnO seeds/glass substrates. The surface morphology and length of ZnO: Al nanostructures can suitably control by the concentration of aluminum sulfate. The surface-enhanced Raman scattering (SERS) effect of Ag sputtering durations on the ZnO: Al nanoneedles and the concentration of aluminum sulfate on the ZnO: Al/Ag heterostructures systematically investigated. The ZnO: Al/Ag heterostructures (2 mM aluminum sulfate and 60 s sputtering time) exhibited a more substantial enhancement, a lower detection limit (10−10 M), excellent uniformity, high reusability and stability for the SERS detection of rhodamine 6G molecule. The ZnO: Al/Ag heterostructures can also use to detect the lower concentration of melamine (10−9 M) and 5-fluorouracil (10−7 M). ZnO: Al/Ag heterostructures can provide a low-cost and straightforward manufacturing method with high enhancement, low detection limit, excellent uniformity, and reusability for the SERS applications in areas of chemical and medicine. Image 1 • A facile aqueous chemical growth method can use to grow ZnO: Al nanostructures on the ZnO seeds/glass substrates. • The morphology and length of ZnO: Al nanostructures can suitably control by the concentration of aluminum sulfate. • ZnO: Al/Ag heterostructures exhibited excellent SERS performance in the detection of rhodamine 6G molecule. • ZnO: Al/Ag heterostructures can use to detect the lower concentration of melamine (10−9 M) and 5-fluorouracil (10−7 M). [ABSTRACT FROM AUTHOR]

• H 2 Ti 3 O 7 nanowires have directly synthesized on the Ti foil by simple hydrothermal and ion‐exchange processes. • H 2 Ti 3 O 7 nanowires revealed very prominent blue emission from surface oxygen vacancies. • H 2 Ti 3 O 7 nanowires exhibited high efficient and reusable photocatalysts under visible-light irradiation. • Holes and hydroxyl radicals played central roles in rhodamine 6G photodegradation. • H 2 Ti 3 O 7 @Ag heterostructures can provide an excellent SERS-active substrate. In the present work, we reported one kind of photocatalytic and surface-enhanced Raman scattering substrate, H 2 Ti 3 O 7 nanowires, which prepared on the Ti foil by the hydrothermal and ion‐exchange methods. The morphologies, crystal structures, chemical compositions, optical properties of the as-prepared substrates investigated via the different kinds of characterization techniques. H 2 Ti 3 O 7 nanowires revealed remarkably enhanced visible-light photocatalytic activity for the degradation of rhodamine 6 G solution compared to Na 2 Ti 3 O 7 nanowires, TiO 2 nanowires, and commercial photocatalysts (TiO 2 and ZnO nanoparticles). These results attributed to the H 2 Ti 3 O 7 nanowires with a higher concentration of oxygen vacancies can enhance the visible-light absorbance, resulting in the higher photocatalytic activity under the visible-light irradiation. The radical-trapping test shows that holes and hydroxyl radicals played central roles in rhodamine 6 G photodegradation. The deposition of Ag nanoparticles on the H 2 Ti 3 O 7 nanowires can also use as a highly sensitive surface-enhanced Raman scattering substrate for detecting rhodamine 6 G solution with a concentration as low as 10−9 M by the ion-sputtering system. [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]