Liyuan Song

Chlorine doped graphene quantum dots: Preparation, properties, and photovoltaic detectors

Graphene quantum dots (GQDs) are becoming one of the hottest advanced functional materials because of the opening of the bandgap due to quantum confinement effect, which shows unique optical and electrical properties. The chlorine doped GQDs (Cl-GQDs) have been fabricated by chemical exfoliation of HCl treated carbon fibers (CFs), which were prepared from degreasing cotton through an annealing process at 1000 °C for 30 min. Raman study shows that both G and 2D peaks of GQDs may be redshifted (softened) by chlorine doping, leading to an n-type doping. The first vertical (Cl)-GQDs based photovoltaic detectors have been demonstrated, both the light absorbing and electron-accepting roles for (Cl)-GQDs in photodetection have been found, resulting in an exceptionally big ratio of photocurrent to dark current as high as ∼105 at room temperature using a 405 nm laser irradiation under the reverse bias voltage. The study expands the application of (Cl)-GQDs to the important optoelectronic detection devices.

The preparation of organic infrared semiconductor phthalocyanine gadolinium (III) and its optical and structural characterizations

In order to increase the species of organic infrared semiconductor, we synthesized organic infrared semiconductor phthalocyanine gadolinium by using o-phthalodinitrile and GdCl3 as reactants, ammonium molybdate as catalyzer. Under light and dark field modes of microscope, the translucency emerald-like powder of phthalocyanine gadolinium has been observed, the size of the small grain for the sample is around 5μm in diameter, the size of larger grain may reach to several tens of microns. The main vibrational peaks in FT-IR spectrum and Raman spectrum have been assigned. Elementary analysis shows that the experimental data of phthalocyanine gadolinium in the main agree with those of calculated data. The UV-Vis absorption spectrum of the sample indicates the sandwich-like structure of phthalocyanine gadolinium. The organic infrared semiconductor phthalocyanine gadolinium thin film on quartz substrate has been prepared with our synthesized powdered sample by using solution method. The characterizations of XRD and UV-Vis-NIR absorption have been carried out for the phthalocyanine gadolinium thin film on quartz substrate, XRD shows that phthalocyanine gadolinium diffractions occur at 2θ=6.851,8.290 and 8.820 degrees, the corresponding plane spacings (d) for the diffraction peaks are 12.8921, 10.6570, and 10.0176Å.The diffraction peaks locate at low diffraction angle, suggesting that the molecular size of the phthalocyanine gadolinium is big that causes the large spacing of crystal planes. The UV-Vis-NIR absorption of phthalocyanine gadolinium thin film on quartz substrate implies that within near infrared band there is a absorption in the 1.3~2.0μm wavelength range peaked at ca. 1.75μm, indicating the important potential application value of phthalocyanine gadolinium in the field of organic infrared optoelectronics.