Surface-Enhanced Raman Scattering Quantitative Analysis of Ethanol Drop-Coating Silver Nanocubes on Gold Film

Surface-enhanced Raman scattering (SERS) has been a sensitive tool for the accurate detection and analysis of a wide range of molecules. In the present study, a simple and repeatable approach is developed for the fabrication of a silver nanocubes/polyelectrolyte/gold film (Ag nanocubes/PE/Au film) sandwich structure as SERS substrate. An ethanol-water mixture, instead of pure water, is used as solvent to reduce the coffee ring effect by the drop coating deposition method, such that Ag nanocubes are distributed evenly on the gold film surface with polyelectrolyte as the middle layer. In 15 repeated measurements of a 10-7 M rhodamine 6G solution, the intensity of the Raman peak at 609 cm-1 exhibits a relative standard deviation less than 20%. Significantly, the sandwich substrate exhibits excellent point-to-point repeatability and sample to sample reproducibility, and may be used for real-life quantitative analysis, as demonstrated by the rapid diagnosis of dual analytes of rhodamine 6G and crystal violet.

Physiological Homeostasis Alteration and Cellular Structure Damage of Chlorella Vulgaris Exposed to Silver Nanoparticles with Various Microstructure Morphologies

The toxicity of silver nanoparticles (AgNPs) with single morphology exposed to aquatic organisms had been well revealed in the past decade, but few studies have been carried out to evaluate the toxicity differences between AgNPs with various microstructure morphologies, especially to algae. In this work, Chlorella vulgaris was used as the tested organism to illustrate the differences of toxic effects between silver nanospheres (AgNSs), silver nanocubes (AgNCs) and silver nanoplates (AgPLs) with concentration of 0.5, 1.0, 2.0, 5.0 mg⸳L-1, based on the algae’s growth (72h), chlorophyll-a content, antioxidant enzyme activity, lipid peroxidation and cell apoptosis (48h). The results showed that the toxicity level exposed to Chlorella vulgaris was in the order of AgPLs> AgNCs> AgNSs. The difference shown indicated that the potential toxicity of AgNPs is primarily depended on their microstructure morphologies. This current study initially revealed the structure-effects of AgNPs on Chlorella vulgaris, provided a scientific basis for aquatic environmental risk assessment.

Development of a Tri-Functional Nanoprobe for Background-Free SERS Detection of Sialic Acid on the Cell Surface

Sialic acid (SA) on the surface of cells is indispensable in numerous physiological and pathological processes, and sensitive and reproducible detection of SA is crucial for diagnosis and therapy in many diseases. Here, we developed a tri-functional nanoprobe as a sensitive and straightforward surface-enhanced Raman spectroscopy (SERS) nanoprobe for sialoglycan detection on cell surfaces. The reporter was designed to provide three key functionalities that make it ideal for SA detection. First, we employed two recognition groups, phenylboronic acid and an ammonium group, that enhance SA recognition and capture efficiency. Second, we used cyano as the Raman reporter because it emits in the cellular Raman silent region. Finally, thiol acted as an anchoring agent to conjugate the reporter to silver nanocubes to provide SERS enhancement. Our molecular nanoprobe design demonstrated the ability to detect SA on the cell surface with high sensitivity and spatial resolution, opening up new routes to cellular diagnostics.

Naked-Eye Detection of Mercury Ions from Morphological Transition of Silver Nanocubes: Tuning Sensitivity Using Co-Staining Agent

A simple, low-cost and highly selective nanosensor was developed for naked-eye detection of mercury ions (Hg2+) based on Eosin/silver nanocubes (Eosin/AgNCbs). Silver nanocubes (AgNCbs) were synthesized by polyol assisted chemical method. HR-TEM result shows the formed AgNCbs have a mean diameter of 84±0.005 nM (diagonally measured) and edge length of 55±0.01 nM. XRD result confirms that the AgNCbs are single crystalline in nature with a phase structure of face centered cubic (FCC) of silver. On interaction of Hg2+, AgNCbs exhibits a color change from gray to black up to 16.67 μM of Hg2+ owed to the formation of solid like bimetallic complex of Ag/Hg amalgam. The selectivity of AgNCbs was evaluated with several other toxic metal ions including, Mg2+, Ba2+, Ca4+, Pb2+, Cd4+, Zn2+, Co2+, Cu2+, K+ and Ni2+ and found good selectivity towards Hg2+. The sensitivity of the AgNCbs sensor system was tuned by using Eosin as a co-staining agent. The Eosin/AgNCbs showed a limit of detection of 60±0.050 nM with the color change from orange to purple. The results suggests that the Eosin/AgNCbs nanosensor exhibits good selectivity, sensitivity, repeatability and rapid response, which could be explored for real-time detection of Hg2+ in environmental and biological samples.