Weina Wang

Development of chitosan-coated gold nanoflowers as SERS-active probes

Surface-enhanced Raman scattering (SERS) has been intensely researched for many years as a potential technique for highly sensitive detection. This work, through the reduction of HAuCl(4) with pyrrole in aqueous solutions, investigated a facile one-pot synthesis of flower-like Au nanoparticles with rough surfaces. The formation process of the Au nanoflowers (AuNFs) was carefully studied, and a spontaneous assembly mechanism was proposed based on the time-course experimental results. The key synthesis strategy was to use pyrrole as a weak particle stabilizing and reducing agent to confine crystal growth in the limited ligand protection region. The nanometer-scale surface roughness of AuNFs provided several hot spots on a single particle, which significantly increased SERS enhancement. Good biocompatible stable Raman-active probes were synthesized by coating AuNFs with chitosan. The conservation of the SERS effects in living cells suggested that the chitosan-capped AuNFs could be suitable for highly sensitive detection and have potential for targeting of tumors in vivo.

Synthesis of fluorescent carbon nanoparticles from polyacrylamide for fast cellular endocytosis

Fluorescent carbon nanoparticles (CNPs) with different core sizes (5, 20, 50 nm) were synthesized in one step by hydrothermal treatment of polyacrylamide. It showed CNPs underwent fast endocytosis into the LnCaP cells. The CNPs had a marked size effect on cellular imaging and the optimal size was about 20 nm.

Synthesis of stable Au-SiO2 composite nanospheres with good catalytic activity and SERS effect

For improving stability and efficiency of noble metal nanomaterials, a straightforward one-step method was developed to synthesize Au-SiO2 composite nanospheres. Monodisperse hybrid silica nanospheres that had anilino-methyl on the surfaces were prepared first. The as-prepared hybrid silica nanospheres were then used to obtain Au nanocrystal through the redox reaction of HAuCl4 and anilino-methyl. This approach led to a better utilization of Au. By adjusting the surface morphologies and the particle sizes, the functional nanospheres displayed different surface-enhanced Raman scattering effects of Rhodamine 6G. The composite nanospheres showed high catalytic activity and good reusability in catalytic reduction of 4-nitrophenol because of their active gold surface.

A novel Au-Pt@PPy(polypyrrole) coral-like structure: Facile synthesis, high SERS effect, and good electro catalytic activity

The Au-Pt@PPy(polypyrrole) with a novel three-dimensional structure was synthesized by a facile one-pot reaction. Raman spectra, transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-vis spectroscopy (UV-vis), and cyclic voltammograms (CV) were employed to characterize the complex. TEM and SEM results indicated that the products had novel three-dimensional (3D) multi-branch structures, which were controllable by simply adjusting the ratios of HAuCl4 to H2PtCl6 added. Raman characterization proved that the products had significant surface-enhanced Raman effect with the aid of long-range effect of the enhanced electromagnetic (EM) field and roughness in nanometer-scale. CV results showed that the Au-Pt@PPy with coral-like structure had high catalytic efficiency for methanol oxidation.

A novel biosensor based on a gold nanoflowers/hemoglobin/carbon nanotubes modified electrode

Well-oriented 3D gold flower-like nanoparticles were successfully synthesized by a facile one-pot method, and the gold nanoflowers (AuNFs) were mixed with hemoglobin (Hb) to form a gold nanoflowers/hemoglobin composite. The composite was further combined with multiwalled carbon nanotubes on a glassy carbon electrode (GCE) to fabricate a novel biosensor. The sensor has high stability and bioactivity, and was studied by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The hemoglobin/gold nanoflowers/multiwalled carbon nanotubes glassy carbon electrode (Hb/AuNFs/CNTs/GCE) either retained the Hb in similar native conformations or promoted direct electron transfer. Moreover, the sensor exhibited remarkable catalytic activity toward H2O2 and trichloroacetic acid (TCA). The linear relationship for the determination is in the range of 1.0–60 μM for H2O2 and 0.06–28 mM for TCA. The detection limits were 0.08 μM and 7.3 μM (S/N = 3), respectively.

Preparation of disk-like particles with micro/nano hierarchical structures

A facile, reproductive method has been successfully developed to produce disk-like microparticles self-assembled from monodispersed hybrid silica nanoparticles under certain circumstance. The disk-like microparticles with micro/nano hierarchical structures could be obtained in large amount under a mild condition and further used to biomimetic design of the superhydrophobic surface of lotus leaf. After traditional surface modification with dodecyltrichlorosiliane, the static contact angle of water on the surface with micro/nano hierarchical structure could reach 168.8°. The method of surface modification could be further simplified by click reaction with the introduction of thiol groups under mild condition. The present strategy for constructing the surface with micro/nano hierarchical structures offers the advantage of simple and large area fabrication, which enables a variety of superhydrophobic applications.