Adsorption Characteristics of Gas Molecules Adsorbed on Graphene Doped with Mn: A First Principle Study.

Herein, the adsorption characteristics of graphene substrates modified through a combined single manganese atom with a vacancy or four nitrogen to CH2O, H2S and HCN, are thoroughly investigated via the density functional theory (DFT) method. The adsorption structural, electronic structures, magnetic properties and adsorption energies of the adsorption system have been completely analyzed. It is found that the adsorption activity of a single vacancy graphene-embedded Mn atom (MnSV-GN) is the largest in the three graphene supports. The adsorption energies have a good correlation with the integrated projected crystal overlap Hamilton population (-IpCOHP) and Fermi softness. The rising height of the Mn atom and Fermi softness could well describe the adsorption activity of the Mn-modified graphene catalyst. Moreover, the projected crystal overlap Hamilton population (-pCOHP) curves were studied and they can be used as the descriptors of the magnetic field. These results can provide guidance for the development and design of graphene-based single-atom catalysts, especially for the support effect.

The Adsorption Behavior of Gas Molecules on Co/N Co-Doped Graphene.

Herein, we have used density functional theory (DFT) to investigate the adsorption behavior of gas molecules on Co/N3 co-doped graphene (Co/N3-gra). We have investigated the geometric stability, electric properties, and magnetic properties comprehensively upon the interaction between Co/N3-gra and gas molecules. The binding energy of Co is -5.13 eV, which is big enough for application in gas adsorption. For the adsorption of C2H4, CO, NO2, and SO2 on Co/N-gra, the molecules may act as donors or acceptors of electrons, which can lead to charge transfer (range from 0.38 to 0.7 e) and eventually change the conductivity of Co/N-gra. The CO adsorbed Co/N3-gra complex exhibits a semiconductor property and the NO2/SO2 adsorption can regulate the magnetic properties of Co/N3-gra. Moreover, the Co/N3-gra system can be applied as a gas sensor of CO and SO2 with high stability. Thus, we assume that our results can pave the way for the further study of gas sensor and spintronic devices.

High Photon Absorptivity of Quantum Dot Infrared Photodetectors Achieved by the Surface Plasmon Effect of Metal Nanohole Array.

With the increasing demand for small-scale photodetector devices, quantum dot-based infrared photodetectors have attracted more and more attention in the past decades. In this work, periodic metal nanohole array structures are introduced to the quantum dot infrared photodetectors to enhance the photon absorptivity performance via the surface plasmon enhancement effect in order to overcome the bottleneck of low optical absorption efficiency that exists in conventional photodetectors. The results demonstrate that the optimized metal nanohole array structures can greatly enhance the photon absorptivity up to 86.47% in the specific photodetectors, which is 1.89 times than that of conventional photodetectors without the metal array structures. The large enhancement of the absorptivity can be attributed to the local coupling surface plasmon effect caused by the metal nanohole array structures. It is believed that the study can provide certain theoretical guidance for high-performance nanoscale quantum dot-based infrared photodetectors.

An ordered mesoporous Ag superstructure synthesized via a template strategy for surface-enhanced Raman spectroscopy.

Surface-enhanced Raman scattering (SERS) substrates with high density and uniformity of nanogaps are proven to enhance the reproducibility and sensitivity of the Raman signal. Up to now, the syntheses of a highly ordered gold or silver superstructure with a controllable nanoparticle size and a well-defined particle gap have been quite limited. Here, we reported an ordered mesoporous silver superstructure replicated by using ordered mesoporous KIT-6 and SAB-15 as templates. By means of a nanocasting process, the ordered mesoporous Ag superstructure was successfully synthesized, which shows uniform distribution of the nanowire diameter (10 nm) and nanogap size (∼2 nm), thus exhibiting a high Raman enhancement of ∼10(9). The finite difference time-domain (FDTD) results indicate that the ordered mesoporous Ag superstructure has a uniform distribution of hot spots. Therefore, the mesoporous silica template strategy presented here could lead to a new class of high quality SERS substrates providing extraordinary potential for diverse applications.

Gold mesoflower arrays with sub-10 nm intraparticle gaps for highly sensitive and repeatable surface enhanced Raman spectroscopy.

Self-assembling Au mesoflower arrays are prepared using a polymethylmethacrylate (PMMA) template on an iron substrate via a combined top-down/bottom-up nanofabrication strategy. The PMMA template with the holes around 300-500 nm in diameter is first fabricated by using polymer blend lithography on iron substrates, and the highly homogeneous Au mesoflower arrays with less than 10 nm intraparticle gaps are subsequently obtained by an in situ galvanic reaction between HAuCl4 solution and the iron substrate under optimal stirring of the solution as well as reaction time. Owing to the unique mesostructures and uniformity, Raman measurements show that the gold mesoflower arrays obtained demonstrated a strong and reproducible surface enhanced Raman scattering (SERS) enhancement on the order of ∼10(7)-10(8). The development of a SERS substrate based on the Au mesoflowers with high spatial density of hot spots, relatively low cost and facial synthesis provides a novel strategy for applications in chemical and biomolecular sensing.

Nanoparticle attachment on silver corrugated-wire nanoantenna for large increases of surface-enhanced Raman scattering.

Using three-dimensional finite-difference time-domain (FDTD) simulation, we described a systematic investigation on the electric field enhancement of the silver corrugated nanowires. The enhancement factor (EF) of surface-enhanced Raman scattering (SERS) for corrugated nanowires can be markedly increased by 1 or 2 orders of magnitude as compared with the smooth nanowires. Moreover, the EF can be further increased with nanoparticle attachment on the corrugated Ag nanowires owing to the coupling between the discrete plasmon state of the nanoparticles and continuum plasmon states of the corrugated nanowire or the crossed corrugated nanowires. The surface plasmonic field distribution of Ag nanowires can be effectively controlled by the polarization of the incident light. Raman spectrum measurements show that the relatively dense corrugated nanowires exhibit a relatively high reproducibility and SERS enhancement attributed to the elimination of polarization-dependent SERS-anisotropic enhancement via the overlapping of randomly distributed Ag nanowires. Such nanostructures as potential nanoantennas offer a route to optimize plasmon coupling for designing miniaturization integration.