S.Z. Jiang

Direct synthesis of graphene on SiO2 substrates by chemical vapor deposition

Continuous and uniform graphene films were directly grown on SiO2 substrates using a chemical vapor deposition system with two-temperature zones assembled. The carbon species from the high temperature zone nucleate in the low temperature zone, initiating the growing process of graphene. The films are predominantly single-layer graphene, with a small percentage of the area having a few layers, whose optical transmittance and electrical conductivity can be comparable with transferred metal-catalyzed graphene. This method avoids the need for either a metal catalyst or a complicated and skilled post growth transfer process and favors the application of graphene as a transparent electrode.

Direct synthesis of graphene on any nonmetallic substrate based on KrF laser ablation of ordered pyrolytic graphite

We present a method for few-layer graphene growth on nonmetallic substrates using excimer KrF laser ablation of ordered pyrolytic graphite. The graphene is scalable and its thickness is controllable. It can be deposited on virtually any nonmetallic substrates at a relative low temperature of 750??C. This laser-based method is highly efficient and the whole growing process takes less than 100?s. Raman spectroscopy confirms the formation of sp2-bonded carbon with a grain size of about 40?nm. The optical transmittance and conductivity of the graphene films are comparable with exfoliated or metal-catalyzed graphene. This work demonstrates a promising laser-based, transfer-free technique for synthesis of graphene.

Sapphire-based graphene saturable absorber for long-time working femtosecond lasers

We report a long-time working femtosecond laser using metal-free sapphire-based graphene as a saturable absorber (SA). The sapphire-based graphene yielded excellent nonlinear saturable absorption properties and was demonstrated to be suitable as an SA for an ultrafast solid-state laser. Stable mode-locked pulses of 325 fs were obtained at a central wavelength of 1032 nm with a repetition rate of 66.3 MHz. At pump power of 8.23 W the average output power was 1.78 W and the highest pulse energy reached 26.8 nJ with a peak power of 72.6 kW. Our work opens up a facile route for making reliable graphene SA in the mode-locking technique and also displays an exciting prospect in making low-cost and ultrafast lasers.

Low-temperature facile synthesis of graphene and graphene-carbon nanotubes hybrid on dielectric surfaces

Various carbon based nanostructures (graphene, graphene-CNTs hybrid and three-dimensional (3D) carbon network) have been grown separately on low-temperature (600 ?C) substrates by using a chemical vapor deposition system with a two-heating reactor. The two-heating reactor is utilized to offer sufficient, well-proportioned floating C atoms and provide a simple method for low-temperature deposition. Morphology and electrical properties of the carbon based nanostructures can be controlled by the substrate surfaces. A relatively flat surface is beneficial for the synthesis of graphene and surfaces with nanodots are required to directly grow graphene-carbon nanotube hybrids. A chemical vapor deposition mechanism dependent on the temperature gradient is proposed, suggesting that the transfer-free carbon nanostructures can be deposited on different substrates. These results open an easy way for direct and high-efficiency deposition of various carbon nanostructures on the low-temperature dielectric substrates.

An optical fiber SERS sensor based on GO/AgNPs/rGO sandwich structure hybrid films

In this work, we present a novel optical fiber SERS (OF-SERS) sensor based on a sandwich structure of GO/AgNPs/rGO. Rhodamine 6G (R6G) was selected as the probe molecule to compare the SERS ability of different films composed of the bare optical fiber, GO, AgNPs, rGO/AgNPs, GO/AgNPs and GO/AgNPs/rGO. Raman spectra, scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were performed to characterize the sandwich structure hybrid films. Besides, the stability of GO/AgNPs and GO/AgNPs/rGO was compared on the optical fiber end face. The OF-SERS sensor based GO/AgNPs/rGO hybrid films had stable SERS performance even when exposed to ambient conditions for a prolonged time of 30 days. This work may provide a new strategy for an efficient stable OF-SERS sensor due to its simplicity, low-cost and long-term stability.