Direct Electrochemical Reduction of Single-Layer Graphene Oxide and Subsequent Functionalization with Glucose Oxidase

A direct electrochemical method to reduce single-layer graphene oxide (GO) adsorbed on the 3-aminopropyltriethoxysilane (APTES)-modified conductive electrodes is proposed. The reduced GO adsorbed on glassy carbon electrode was modified with glucose oxidase (GOx) by covalent bonding via a polymer generated by electrografting N-succinimidyl acrylate (NSA). The direct electron transfer between the electrode and GOx molecules was realized. The bioactivity of GOx maintains very well on the electrode. The thus-prepared GOx-modified electrode was successfully used to detect glucose

Facile “Scratching” Method with Common Metal Objects To Generate Large-Scale Catalyst Patterns Used for Growth of Single-Walled Carbon Nanotubes

A facile “scratching” method to pattern a catalyst with commonly used metal objects, such as blade, pen cover, tweezers, watchband, knife, key, clamp, and coin, was developed. The single-walled carbon nanotube (SWCNT) networks and well-aligned SWCNT arrays successfully grew by chemical vapor deposition on the scratched catalyst patterns on Si/SiOx and quartz, respectively. This method provides an extremely simple and nearly zero-cost way to fabricate large-scale catalyst patterns used for controlled growth of SWCNT arrays, which could have potential applications in the fabrication of CNT-based devices

Postchemistry of Organic Particles: When TTF Microparticles Meet TCNQ Microstructures in Aqueous Solution

Postchemistry of Organic Particles: When TTF Microparticles Meet TCNQ Microstructures in Aqueous Solutio

Locally Altering the Electronic Properties of Graphene by Nanoscopically Doping It with Rhodamine 6G

We show that Rhodamine 6G (R6G), patterned by dip-pen nanolithography on graphene, can be used to locally n-dope it in a controlled fashion. In addition, we study the transport and assembly properties of R6G on graphene and show that in general the π–π stacking between the aromatic components of R6G and the underlying graphene drives the assembly of these molecules onto the underlying substrate. However, two distinct transport and assembly behaviors, dependent upon the presence or absence of R6G dimers, have been identified. In particular, at high concentrations of R6G on the tip, dimers are transferred to the substrate and form contiguous and stable lines, while at low concentrations, the R6G is transferred as monomers and forms patchy, unstable, and relatively ill-defined features. Finally, Kelvin probe force microscopy experiments show that the local electrostatic potential of the graphene changes as function of modification with R6G; this behavior is consistent with local molecular doping, highlighting a path for controlling the electronic properties of graphene with nanoscale resolution

A Method for Fabrication of Graphene Oxide Nanoribbons from Graphene Oxide Wrinkles

We report a novel approach for direct fabrication of graphene oxide nanoribbons (GONRs) on the 3-aminopropyltriethoxysilane (APTES)-modified SiOx surface with varied widths and lengths by plasma etching of graphene oxide (GO) wrinkles (GOWs), in which top layers of GOWs are used as sacrificial layers. AFM images show that single- and double-layer GONRs are easily achieved, and also confirm that these GONRs are obtained from GOWs, which normally form during absorption of large GO sheets with a size of at least several micrometers on APTES-modified SiOx substrates. Raman mapping and scanning electron microscopy (SEM) were performed to further confirm the attainment of GONRs by this method. A GONR with a width as narrow as 15 nm was obtained. Reduced graphene oxide nanoribbons (rGONRs) can be readily obtained by chemical reduction of GONRs

Surface-Enhanced Raman Scattering of Ag–Au Nanodisk Heterodimers

We report the fabrication of Ag–Au nanodisk heterodimers based on the modified on-wire lithography method and study their surface-enhanced Raman scattering (SERS) properties experimentally and theoretically. The effects of disk thickness and gap size on SERS are explored. The SERS properties of the optimized heterodimers are compared with those of the respective homodimers and single nanodisks excited at 633 and 488 nm. We found that the enhancement factor (EF) of Ag–Au heterodimers is greater at 633 nm than that at 488 nm, while their EF is between those of the Ag–Ag and Au–Au homodimers. At 488 nm excitation, the calculation indicates that the plasmon energy can be transferred from the Ag disk to the Au disk

In Situ Modification of Three-Dimensional Polyphenylene Dendrimer-Templated CuO Rice-Shaped Architectures with Electron Beam Irradiation

In this study, the high-energy electron beam of the transmission electron microscope (TEM) is utilized as an external force to in situ modify the polyphenylene dendrimer (G2Td(COOH)16) templated CuO rice-shaped architecture (RSA). By virtue of the nanoscale precision of this approach, the electron beam-modified RSA retains its rice shape while the internal primary CuO nanoparticles are converted to the Cu2O nanoparticles with increased size. Detailed investigation using a time-lapse TEM technique reveals that such a modification process is mainly constituted by two stages, involving the arrangement of the primary CuO nanoparticles and the transformation of the primary CuO into Cu2O nanoparticles. Within the modification process, the high-energy electron beam of TEM serves as the external driving force and energy resource to improve the orientation and increase the crystallinity of the single-phase CuO nanoparticles and subsequently transfer the nanoparticle phase from CuO to Cu2O. This study highlights a facile in situ way to finely tune the nanoscale morphology and chemical composition of nanoparticles and nanoparticle-based assembled structures

Local Refractive Index Sensing Based on Edge Gold-Coated Silver Nanoprisms

Bulk and surface refractive index sensitivity for localized surface plasmon resonance (LSPR) sensing based on edge gold-coated silver nanoprisms (GSNPs) and gold nanospheres was investigated and compared with conventional surface plasmon resonance (SPR) sensing based on propagating surface plasmons. The hybrid GSNPs benefit from an improved stability since the gold frame protecting the unstable silver facets located at the silver nanoprisms (SNPs) edges and tips prevents truncation or rounding of their sharp tips or edges, maintaining a high refractive index sensitivity even under harsh conditions. By using layer-by-layer deposition of polyelectrolytes and protein adsorption, we found that GSNPs exhibit 4-fold higher local refractive index sensitivity in close proximity (<10 nm) to the surface compared to a flat gold film in the conventional SPR setup. Moreover, the sensitivity was 8-fold higher with GSNPs than with gold nanospheres. This shows that relatively simple plasmonic nanostructures for LSPR-based sensing can be engineered to outperform conventional SPR, which is particularly interesting in the context of detecting low molecular weight compounds where a small sensing volume, reducing bulk signals, is desired

Centimeter-Long and Large-Scale Micropatterns of Reduced Graphene Oxide Films: Fabrication and Sensing Applications

Recently, the field-effect transistors (FETs) with graphene as the conducting channels have been used as a promising chemical and biological sensors. However, the lack of low cost and reliable and large-scale preparation of graphene films limits their applications. In this contribution, we report the fabrication of centimeter-long, ultrathin (1−3 nm), and electrically continuous micropatterns of highly uniform parallel arrays of reduced graphene oxide (rGO) films on various substrates including the flexible polyethylene terephthalate (PET) films by using the micromolding in capillary method. Compared to other methods for the fabrication of graphene patterns, our method is fast, facile, and substrate independent. In addition, we demonstrate that the nanoelectronic FETs based on our rGO patterns are able to label-freely detect the hormonal catecholamine molecules and their dynamic secretion from living cells

Photochemically Controlled Synthesis of Anisotropic Au Nanostructures: Platelet-like Au Nanorods and Six-Star Au Nanoparticles

We report the shape-controlled synthesis of anisotropic Au nanostructures through TiO2-assisted photochemical reduction of HAuCl4. By using this method, we have successfully synthesized the platelet-like Au nanorods and six-star Au nanoparticles. Importantly, the platelet Au nanorod exhibits the unique asymmetric five-twinned structure. The colloidal TiO2 sols were used as both the photocatalyst to initiate the reaction and the stabilizing agent for the produced Au nanostructures. Significantly, in this photochemical process, the tunable irradiation intensity allows us to kinetically control the crystal evolution at various growth stages, leading to the shape difference of ultimate gold nanostructures. Our synthetic method shows a great potential as an alternative or supplement to the other wet chemical approaches for the shape-control of metallic nanostructures