Molybdenum disulfide (MoS 2 ) with excellent properties has been widely reported in recent years. However, it is a great challenge to achieve p-type conductivity in MoS 2 because of its native stubborn n-type conductivity. Substitutional transition metal doping has been proved to be an effective approach to tune their intrinsic properties and enhance device performance. Herein, we report the growth of Nb-doping large-area monolayer MoS 2 by a one-step salt-assisted chemical vapor deposition method. Electrical measurements indicate that Nb doping suppresses ntype conductivity in MoS 2 and shows an ambipolar transport behavior after annealing under the sulfur atmosphere, which highlights the p-type doping effect via Nb, corresponding to the density functional theory calculations with Fermi-level shifting to valence band maximum. This work provides a promising approach of two-dimensional materials in electronic and optoelectronic applications.

This paper describes a new strategy for fabricating continuous gold films based on the self-assembly of the gold colloid monolayer on a poly(diallyldimethylammonium chloride)-modified glass slide, followed by electroless plating. Hydroxylamine-mediated reduction was proven as an excellent route to enlargement of immobilized nanoparticles on polymer-coated glass substrates in comparison to formaldehyde-mediated reduction. Au colloidal surface-catalyzed reduction of Au3+ by hydroxylamine exhibited very fast kinetics as monitored and confirmed by UV−vis spectroscopy in real time. The nanoscale morphology of the gold film was dependent on the initial coverage of gold nanoparticles and thermal annealing. Atomic force micrographs further revealed that enlarged particles were neither spherical nor cyclindrical, but highly complex in shape. The gold film thickness and its corresponding surface roughness could be easily controlled by setting the electroless deposition time. X-ray diffraction certified uniformity of deposits with the Au(111) crystallographic structure as the predominant one. No organic contamination during the course of electroless plating was observed as confirmed by both X-ray photoelectron spectroscopy and contact angle measurements. The stable and continuous gold films were used as electrodes for electrochemical experiments.

We report and discuss how gold nanoparticles were synthesized by the reduction of hydrogen tetrachloroaurate(III) trihydrate by sodium citrate in the presence of unmodified α-cyclodextrin (CD), β-CD, and γ-CD. Gold nanoparticles were immobilized on poly(diallyldimethylammonium) chloride (PDDA) modified glass slides to enable AFM measurements. The particle size was dependent upon the type and concentration of cyclodextrin used as well as the sodium citrate concentration. An increase in the cyclodextrin concentration effected a shift of the particle size range from 12−15 to 4−6 nm with uniform particle size distribution. The homogeneity of the synthesized gold nanoparticles was also evident from transmission electron micrographs (TEMs). Synthesis of gold nanoparticles by the reduction of hydrogen tetrachloroaurate(III) trihydrate by sodium borohydride in the presence of cyclodextrins also reduced the particle size from 6−8 to 2−4 nm. The consecutive particle growth due to the mutual coalescence between nanoclusters and their neighboring free gold atoms was limited in the presence of CDs. FT-Raman, FT-IR spectroscopy, and mass spectrometry (MS) indicated that the synthesis procedure exhibited no effect on the cyclodextrins. There was no evidence that gold nanoparticles were included in the CD cavities.