The surface-enhanced Raman scattering detection of N-nitrosodimethylamine and N-nitrosodiethylamine via gold nanorod arrays with a chemical linkage of zwitterionic copolymer.

Due to the emerging issue of the contamination of sartan medicines and drinking water with N-nitrosodimethylamine (NDMA) and/or N-nitrosodiethylamine (NDEA), the detection of NDMA/NDEA has become an important theme. In this study, we utilized the focused ion beam (FIB) technique to fabricate gold nanorods (Au NRs) and Surface-enhanced Raman Scattering (SERS) substrates and modified them with 1,2-ethanedithiol to quench the high luminescence excitation background signals derived from the high density of localized surface plasmon resonance. To improve the surface hydrophilicity, zwitterionic copolymer PGMA-r-PSBMA was grafted onto the nanosurface of Au NRs, which was confirmed by contact angle analysis and AFM. Raman spectra of the copolymer were observed to confirm the successful grafting of Au NRs, which was also corroborated by TEM and SEM. The Au NRs could easily trap the small polar NDMA and NDEA molecules in aqueous solution due to strong zwitterionic hydrophilicity. Furthermore, the self-association of the anions and cations of the polymeric chain grafted in the hot spot zone assisted in trapping the NDMA/NDEA polar molecules. The Raman scattering cross-section of NDMA/NDEA molecules could be enhanced through the chemical linkage of 1,2-ethanedithiol and the self-association behavior of the zwitterionic copolymer. Accordingly, for the first time, we detected the characteristic peaks of NDMA/NDEA through SERS with detection limit of 10-8 M for both molecules.

Chitosan production from Paecilomyces saturatus using three monosaccharides via mixture design.

In this study, we demonstrate that chitosan is produced from Paecilomyces saturatus fungi using ternary monosaccharide carbon sources liquid cultivation via mixture design strategy. Sixteen experiments were carried out to obtain regression equations of fungal dry mycelial biomass (W), chitosan ratio (R), and deacetylation degree (DD) for plotting contour lines. Contour lines reveal that the maximum W, R, and DD can be simultaneously obtained in cultivated media containing 20% glucose, 60% fructose and 20% mannitol rather than pure monosaccharide cultivation. Three additional confirmation experiments based on the maximum FuCS deacetylation degree had been performed to confirm to be 92.3% via Fourier-transform infrared spectra. Accordingly, FuCS possessed much better anti-microbial activity on E. coli than commercial chitosan (CrCS). Meanwhile, X-ray diffraction results confirmed that FuCS possessed both α and γ crystalline peaks while CrCS possessed only α crystalline peak, being collaborated with thermogravimetric analysis results. The superior FuCS was obtained by using ternary monosaccharides system in fungal culture via mixture design for the first time. This study provides a new approach to produce chitosan from fungal cultivation by using the mixture design strategy.

Surfactant-Enriched ZnO Surface via Sol-Gel Process for the Efficient Inverted Polymer Solar Cell.

In this study, we demonstrate that the top surface is enriched by surfactants, tetraoctylammonium bromide, and cetylpyridinium bromide (CPB), in the sol-gel ZnO, being evidenced by the Br depth profile of electron spectroscopy for chemical analysis data. X-ray photoelectron spectroscopy results showed the formation of Zn-Br bonding due to the oxygen defects occupied by Br at the surfactant-enriched ZnO surface. The surfactant-enriched ZnO surface possessed a smoother surface and more hydrophobicity than the pristine ZnO from the experimental results of atomic force microscopy and contact angle, respectively. On the basis of ultraviolet photoelectron spectroscopy data, the work function slightly reduced due to the dipole built-up by the electrostatic force between Br- and N+ to enhance the electron extraction ability. The improved properties benefited the power conversion efficiency (PCE) of bulk-heterojunction polymer solar cells (PSCs) by spin-coating the active layer on the surfactant-enriched ZnO surface. The inverted PSCs with the surfactant-enriched ZnO surface showed the highest PCE of 9.55% for the CPB case, in comparison with the pristine ZnO surface (8.08% PCE). This study discloses that turning the ZnO surface is easily achieved by the addition of surfactants with different molecular structures in the sol-gel ZnO for high performance polymer solar cells.

An anti-fouling nanoplasmonic SERS substrate for trapping and releasing a cationic fluorescent tag from human blood solution.

In bioenvironmental detection, surface-enhanced Raman scattering (SERS) signals are greatly affected by anti-specific biomolecule adsorption, which generates strong background noise, reducing detection sensitivity and selectivity. It is thus necessary to modify the SERS substrate surface to make it anti-fouling to maintain excellent SERS signals. Herein, we propose a zwitterionic copolymer, namely poly(glycidyl methacrylate-co-sulfobetaine methacrylate) (poly(GMA-co-SBMA)), for the surface modification of SERS substrates, which were fabricated and characterized spectroscopically. The copolymer was grafted onto Ag nanocubes (NCs) on an Ag surface with massive nanogaps via 1,2-ethanedithiol, which acted as a metal-insulator-metal (MIM) substrate. The high density of poly(GMA-co-SBMA) grafted near NCs favored the formation of connections between adjacent NCs, causing strong surface plasmon resonance at these junctions. With the zwitterionic-copolymer-modified surface, the adhesion of large biomolecules in platelet-rich plasma (PRP) solution can be effectively resisted, as determined from immunoassay and fibrinogen adsorption results. The SERS signals for malachite green (MG) in PRP solution (10-6 M) were effectively distinguished using the copolymer-grafted MIM substrate. MG was deposited on adjacent copolymer-grafted NCs, which amplified the SERS signals. Moreover, the copolymer connected adjacent NCs, inducing the electromagnetic effect at copolymer-grafted surfaces, which improved the SERS mechanism. The hydration process restructured the MG-trapped copolymer-grafted surface, decreasing the number of MG characteristic peak regions and increasing that of the copolymer regions. These results reveal that grafting a copolymer onto an MIM substrate allows MG to be easily trapped and released in complex biomatrices and increases surface reproducibility due to anti-fouling, leading to high SERS enhancement.