Plasmon-enhanced Raman spectroscopy of two-dimensional semiconductors

A semiconductor SERS sensor of corrosion-resistant PPy/GO composite film by electrochemical growth for detecting crystal violet residues in fresh fish tissue

Crystal violet (CV) residues in Marine food have produced a severe health threat in human life. In this study, we proposed a semiconductor surface-enhanced Raman scattering (SERS) sensor of corrosion-resistant Polyaniline/Graphene oxide (PPy/GO) film by electrochemical growth method to detect CV residues in fresh fish tissue. A PPy/GO dispersion solution was one-step deposited on a stainless steel sheet surface by electrochemical polymerization process to form a PPy/GO composite film acting as a semiconductor SERS substrate. Since the substrate of PPy/GO film was mainly composed of GO sheet without other metals, it had a good corrosion resistance. The SERS enhancement factor and charge transfer intensity PCT of PPy/Go SERS substrate for CV molecules were up to 1.18 × 106 and 0.903, respectively. Furthermore, the limit of detection (LOD) of PPy/GO SERS substrate could reach 1.58 nM. In addition, SERS sensor of PPy/GO film could identify CV residues in fresh fish tissues, and its recovery rate was 91.8 %-107 %. This preparing method and detecting method we proposed PPy/GO SERS substrate provide a new pathway for detecting CV residues in Marine food.

Covalently-Bonded Laminar Assembly of Van der Waals Semiconductors with Polymers: Toward High-Performance Flexible Devices

Van der Waals semiconductors (vdWS) offer superior mechanical and electrical properties and are promising for flexible microelectronics when combined with polymer substrates. However, the self-passivated vdWS surfaces and their weak adhesion to polymers tend to cause interfacial sliding and wrinkling, and thus, are still challenging the reliability of vdWS-based flexible devices. Here, an effective covalent vdWS-polymer lamination method with high stretch tolerance and excellent electronic performance is reported. Using molybdenum disulfide (MoS2 )and polydimethylsiloxane (PDMS) as a case study, gold-chalcogen bonding and mercapto silane bridges are leveraged. The resulting composite structures exhibit more uniform and stronger interfacial adhesion. This enhanced coupling also enables the observation of a theoretically predicted tension-induced band structure transition in MoS2 . Moreover, no obvious degradation in the devices' structural and electrical properties is identified after numerous mechanical cycle tests. This high-quality lamination enhances the reliability of vdWS-based flexible microelectronics, accelerating their practical applications in biomedical research and consumer electronics.

Green-Lighting the Sub-Band Gap Excitation in Two-Dimensional Zinc Oxide

Solar spectrum and sensitivity of human eyes peak at green wavelength range of visible light, and the materials that can respond to a larger part of the visible spectrum are highly sought after. Two-dimensional graphene-like zinc oxide (gZnO) is a wide band gap semiconductor, but photogeneration of electron-hole pairs in it at visible wavelengths has not been achieved so far. Here, the sub-band gap excitation in 2D zinc oxide layers covered with gold nanoparticles is reported. The sub-band gap excitation and corresponding emission are correlated with oxygen interstitials introduced by AuNP deposition in the gZnO lattice. Attachment of AuNPs on gZnO also leads to increased electron availability at oxygen sites of the gZnO lattice, which translates into greater electron availability for sub-band gap excitation. The plasmonically enhanced trap level to conduction band transition constitutes sub-band gap excitation and manifests itself in local surface potential measurements carried out using a Kelvin probe force microscope.