Zhenle Qin,Yansheng Liu,Xiaobo Jia,Jin Zhou,Hongli Li,Xiaohong Wang,Shaohui Zhang,Haixin Chang,Guofu Wang
The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in widespread disease transmission, challenging the stability of global healthcare systems. Surface-enhanced Raman scattering (SERS) as an easy operation, fast, and low-cost technology illustrates a good potential in detecting SARS-CoV-2. In the study, one-step fabrication of gold-silver alloy nanoparticles (AuAgNPs) with adjustable metal proportions and diameters is employed as SERS substrates. The angiotensin-converting enzyme 2 (ACE2) functionalized AuAgNPs are applied as sensor surfaces to detect SARS-CoV-2 S protein. By optimizing the SERS substrates, ACE2/Au 35 Ag 65 NPs illustrate higher performance in detecting the SARS-CoV-2 S protein with a limit of detection (LOD) of 10 fg/mL in both phosphate-buffered saline (PBS) and pharyngeal swabs solution (PSS). It also provides excellent reproducibility with a relative standard deviation (RSD) of 7.7 % and 7.9 %, respectively. This easily preparable and highly reproducible SERS substrate has good potential in the practical application of detecting SARS-CoV-2.
A colorful surface plasmon resonance imaging (SPRi) sensor with the hue-based enhanced sensitivity has been developed by using sputtered AuAg alloy thin film as the sensing layer. The condition for optimizing the hue-based sensitivity of the SPRi sensor was achieved, that is, the initial resonance wavelength is in the range from 595 to 610 nm. Under this condition, the hue-based refractive index sensitivity of the SPRi sensor was measured as high as Δhue/Δnc=29879/RIU. This sensitivity is 8 times higher than that obtained with a gold-layer SPRi sensor (Δhue/Δnc=3658/RIU) and 7.7 times as high in magnitude as the spectral sensitivity of the same sensor (ΔλR/Δnc=3897.6 nm/RIU). After functionalization of the AuAg alloy film with the monoclonal antibody, the sensor was used for quantitative immunodetection of highly carcinogenic benzo[a]pyrene (BaP) in water. According to the experimental results, the average hue of the SPR color image (300 pixels×300 pixels) experiences an initial rapid increase and then stabilizes 15 min after exposure of the functionalized AuAg alloy film to an aqueous BaP solution sample. The variation of average hue obtained at the equilibrium of surface immunoreaction is a linear function of BaP concentration with the slope being Δhue/Δc=132.2/(μg·L−1). A cooled CCD camera is able to distinguish a change of Δhue=1, offering the colorful SPRi sensor the BaP detection limit of 0.01 μg·L−1. The comparative measurements of the sensor’s responses indicate that the hue variation obtained with 0.1 μg·L−1 of BaP is equal to that obtained either with 5 μg·L−1 of benzanthracene or with 5 μg·L−1 of benzofluoranthene, revealing the sensor’s excellent specificity to BaP. The work demonstrated that the AuAg alloy film-based colorful SPRi sensor can be used not only for visualized analysis of molecular interaction at the surface but also for quantitative trace detection of small-molecule analytes.
Zhen-Ming Shen,Jie Liu,Kun-Peng Wang,Xi-Hao Zhang,Lan Chen,Zhigang Zhou,Tian-Song Deng
Hollow core-shell noble metallic nanoparticles have garnered significant attention due to their plasmonic properties, which are markedly enhanced by the hollow structure. However, precisely controlling the size and shape of the shell and cavity in such structures remains a challenge. Here, a novel strategy is reported that eliminates the need for etchants, utilizing monodispersed gold nanorods (AuNRs) as templates to synthesize hollow Au@AuAg core-shell nanostructures. By precisely regulating the CTAB/CTAC and Au/Ag ratios during the co-deposition of Au and Ag atoms onto the AuNRs, uniform bimetallic hollow shells are achieved without the use of corrosive etching agents. High-resolution TEM and EDS characterizations confirm the formation of crystalline AuAg alloy shells surrounding the AuNRs cores, with well-defined cavities. Compared to pure silver shells, the AuAg alloy shells exhibit superior stability. Furthermore, the resulting Au@AuAg nanostructures with hollow shells demonstrate significantly enhanced refractive index sensitivity and surface-enhanced Raman scattering (SERS) activity relative to pristine AuNRs, making them highly promising for biomedical applications such as biosensing and bioimaging.
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