Ag Nanoparticles Decorated CuO@RF Core-Shell Nanowires for High-Performance Surface-Enhanced Raman Spectroscopy Application

Abstract

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.

Na2Ti3O7@RF@Ag Heterostructures as Efficient Substrates for SERS and Photocatalytic Applications

“…Figure 1 presents a schematic representation of the fabrication process for cultivating Na 2 Ti 3 O 7 @RF@Ag heterostructures. Initially, a straightforward hydrothermal technique was utilized to nurture Na 2 Ti 3 O 7 nanowires on a Ti foil at 220 °C for 5 h. Subsequently, a self-assembled APTMS ((3-Aminopropyl)trimethoxysilane) monolayer was employed to enhance the hydrophilic properties of Na 2 Ti 3 O 7 nanowires, allowing for the uniform decoration of the RF layer [ 47 ]. Lastly, Na 2 Ti 3 O 7 nanowires coated with an RF layer, in conjunction with L-ascorbic acid, facilitated the reduction of Ag + to Ag, culminating in the formation of Na 2 Ti 3 O 7 @RF@Ag heterostructures.…”

“…The uniformity and reusability of SERS substrates are crucial factors in real-world SERS applications [ 25 , 47 ]. In order to assess the uniformity of the Na 2 Ti 3 O 7 @RF@Ag heterostructures, ten random spots were chosen on the substrate loaded with RhB solution (10 −6 M) for an SERS analysis.…”

“…Molecules 2024, 29, x FOR PEER REVIEW 3 of 16 decoration of the RF layer [47]. Lastly, Na2Ti3O7 nanowires coated with an RF layer, in conjunction with L-ascorbic acid, facilitated the reduction of Ag + to Ag, culminating in the formation of Na2Ti3O7@RF@Ag heterostructures.…”

“…These methods can effectively produce high-performance SERS substrates but fall short regarding energy savings and carbon reduction [ 45 ]. Moreover, the literature dedicated to the development of SERS substrates on one-dimensional semiconductor nanostructures through the application of a resorcinol–formaldehyde (RF) resin layer, a strategy aimed at diminishing the reliance on noble metal nanoparticles, has been relatively scant [ 46 , 47 ]. In earlier studies, resorcinol exhibited versatility by serving as a critical reactant in forming the RF layer and playing an essential role in passivating the surfaces of metal nanoparticles to prevent agglomeration [ 48 , 49 ].…”

Fabrication of Three-Dimensional ZnO: Ga@ITO@Ag SERS-Active Substrate for Sensitive and Repeatable Detectability

“…Figure 6 a shows the SERS spectra of ZnO: Ga nanotowers with different Ag ion-sputtering times that were immersed in 1 × 10 −6 M R6G solution for 1 h and then dried with air purge. The main vibrational mode for the characteristic peaks of the R6G molecule is C−H in-plane bending (1127 and 1186 cm −1 ), C−O−C in-plane bending (1311 cm −1 ), and aromatic C−C stretch (1362, 1421, 1510, 1572, and 1649 cm −1 ), respectively [ 38 , 39 ]. The SERS activities gradually improved with the ion-sputtering time, ranging from 15 to 60 s, but decreased when further increasing the ion-sputtering time to 90 and 120 s. Therefore, it can be obtained that the strongest SERS activity is at an ion-sputtering time of 60 s.…”