Pei-Ying Lin

Eco-friendly synthesis of shrimp egg-derived carbon dots for fluorescent bioimaging

Developing synthetic methods to produce carbon dots (CDs) using natural biomass or other readily available carbon sources are currently being explored. We describe a simple and green synthetic method for preparing fluorescent CDs by water extraction from heat-treated shrimp eggs (SE-CDs). The SE-CDs appeared spherical with an average size of 3.25 ± 1.06 nm. Elemental analysis indicate that the SE-CDs have functional groups such as C-OH, C-O-C, CO, and C-H on the surface which give rise to a series of emissive traps between π-π* states. SE-CDs also showed a broad emission range with excellent quantum yield of 18.5 ± 2.6%. In addition, when compared with commonly used traditional CdSe and CdTe nanocrystals, SE-CDs were bio-tolerable to cell at high doses (200 μgml(-1)) in MTT assay. Thus, SE-CDs are very promising alternatives to semiconductor-based quantum dots for in vitro and in vivo bioimaging applications.

Silanization of solid surfaces via mercaptopropylsilatrane: a new approach of constructing gold colloid monolayers

Mercaptopropylsilatrane (MPS) was investigated as a novel self-assembled film on silica surfaces and also as a novel adhesive layer for the construction of a gold colloid monolayer on silica surfaces. We compare the preparation procedure and film quality of the MPS films to those of (3-mercaptopropyl)trimethoxysilane (MPTMS), which is commonly used for anchoring of gold nanoparticles on silica surfaces. The films were characterized by Fourier transform infrared spectroscopy, contact angle measurements, X-ray photoelectron spectroscopy, atomic force microscopy, and Ellmans reagent to determine surface mercaptan concentration. The process in preparing the MPS films involves more environmentally friendly aqueous or polar organic solvents, takes significantly shorter time (<30 min), and results in more uniform and reproducible films due to its insensitivity to moisture. The MPS films also have higher mercaptan surface density than that of the MPTMS films, resulting in higher saturation coverage of the gold colloid monolayers on the MPS-coated substrates. The higher ambient stability of the MPS films as compared to the MPTMS films is important for applications where sufficient durability of the self-assembled films under ambient conditions is required. Thus, mercaptosilatrane may have the potential to replace mercaptosilane for surface modification and as an adhesive layer for the construction of a noble metal colloid monolayer on oxide surfaces.

Improved surface-enhanced Raman scattering of insulin fibril templated colloidal gold nanoparticles on silicon

Insulin fibrils were used as a biotemplate to attach gold nanoparticles to silicon wafer surfaces for application as surface-enhanced Raman scattering (SERS) substrates. Gold nano- particles (NP) attach to the insulin fibrils through electrostatic interactions forming chains of discreet NPs. A combination of 4-aminothiophenol and 4-Mercaptobenzoic acid were used as probe molecules to evaluate the Raman signal enhancement that was 10 4 to 10 6 . The SERS signal was strongly enhanced on these surfaces due to the close inter-particle spacing of the patterned gold NPs.

Aqueous self-assembly and surface-functionalized nanodots for live cell imaging and labeling

AbstractNanoparticles have enormous potential for bioimaging and biolabeling applications, in which conventional organically based fluorescent labels degrade and fail to provide long-term tracking. Thus, the development of approaches to make fluorescent probes water soluble and label cells efficient is desirable for most biological applications. Here, we report on the fabrication and characterization of self-assembled nanodots (SANDs) from 3-aminopropyltriethoxysilane (APTES) as a probe for protein labeling. We show that fluorescent SAND probes exhibit both bright photoluminescence and biocompatibility in an aqueous environment. Selective in vitro imaging using protein and carbohydrate labeling of hepatoma cell lines are demonstrated using biocompatible SANDs conjugated with avidin and galactose, respectively. Cytotoxicity tests show that conjugated SAND particles have negligible effects on cell proliferation. Unlike other synthetic systems that require multistep treatments to achieve robust surface functionalization and to develop flexible bioconjugation strategies, our results demonstrate the versatility of this one-step SAND fabrication method for creating multicolor fluorescent probes with the tailored functionalities, efficient emission, as well as excellent biocompatibility, required for broad biological use.

Porosity‐Controlled Eggshell Membrane as 3D SERS‐Active Substrate

We report on the fabrication of a surface-enhanced Raman scattering (SERS) platform, comprised of a three-dimensional (3D) porous eggshell membrane (ESM) scaffold decorated with Ag nanoparticles (NPs). Both native and treated ESM were used, where the treated ESM pore size and fiber crossing density was controlled by timed exposure to hydrogen peroxide (H2O2). Ag NPs were synthesized in situ by reduction of silver nitrate with ascorbic acid. Our results demonstrate that H2O2-treated Ag-ESM provides a more densely packed 3D network of active material, which leads to consistently higher SERS enhancement than untreated Ag-ESM substrates.

Rapid and Sensitive SERS Detection of Bisphenol A Using Self-assembled Graphitic Substrates

We have prepared and tested a new surface enhanced Raman scattering (SERS) substrate based on self-assembled graphitic sheets to detect bisphenol A (BPA) in plastic consumer goods. Transmission electron microscopy (TEM) and atomic-force microscopy (AFM) were used to characterize the structure of the graphitic sheets and showed a lattice spacing of 0.24 nm and layer height of 0.34 nm. These values were comparable to single monolayer graphene. The effective SERS detection limit of this method is 1 μM BPA, which is lower than the European Union specific migration limit for BPA of 0.6 mg/kg (2.6 μM). When used in salt solutions, graphitic sheets exhibited ultra-sensitivity toward BPA of 0.025 M to 2 M, which was broader than physiological ionic strength (0.14 M) and urinary NaCl (0.17 M). Our results demonstrated that this graphitic sheet based SERS detection platform can be used to determine BPA levels leached from commercial polycarbonate plastic products and for on-site rapid analysis with good results.