Hongyi Qin

Highly Sensitive and Selective Gas Sensor Using Hydrophilic and Hydrophobic Graphenes

New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor.

A conductive copolymer of graphene oxide/poly(1-(3-aminopropyl)pyrrole) and the adsorption of metal ions

Graphene oxide (GO) was covalently functionalized by a 1-(3-aminopropyl)pyrrole monomer by an esterification reaction between carboxyl and amino groups. In addition, a GO/poly(1-(3-aminopropyl)pyrrole) copolymer material was prepared by an in situ polymerization. The composite was characterized using several measurements to demonstrate that the polymer monomer was successfully grafted on the surface of GO. The poly(GO–APP) copolymer was a conductive material. The swelling of poly(GO–APP) and the adsorption of metal ions were investigated by both experiments and theoretic fitting, which showed that the poly(GO–APP) had enhanced swelling and adsorption properties.

A Conductive Copolymer Based on Graphene Oxide and Poly (amidoxime-pyrrole) for Adsorption of Uranium (VI)

A novel conducting copolymer based on amidoxime groups, polypyrrole and graphene oxide was synthesized by in situ copolymerization by usin g two monomers. The monomer, amidoxime-pyrrole, was synthesized by amidoximation of 1-(2-cyanoethyl) pyrrole. The other monomer, GO-pyrrole, was prepared via esterification between –COOH of GO and –NH2 of 1-(3-aminopropyl) pyrrole. The conductive ability of the copolymer was based on conductive π-conjugated system of polypyrrole backbone. The copolymer was able to be used as an effective sorption material for the preconcentration and recovery of uranium. The maximum of adsorption capacity for uranyl ion is as high as 149.57mg/g.

A simple and economical method using graphene oxide for the fabrication of water/oil separation papers

We present a facile method using graphene oxide for the preparation of water/oil separation papers. We coated regular paper with graphene oxide by spraying or soaking, and performed thermal annealing at 180 °C for 1–3 hours. The thermal treatment transforms the paper from hydrophilic to hydrophobic due to the thermal reduction of graphene oxide, and thus water can hardly permeate through the separation paper. In contrast, low polarity organic solvents and oil can easily pass through the separation paper. The water/oil separation papers have very good reusable stability. The separation selectivity is above 99% for different mixtures of oily solvents and water.

Note: Evaluation of slurry particle size analyzers for chemical mechanical planarization process

In the chemical mechanical planarization (CMP) process, slurry particle size is important because large particles can cause defects. Hence, selection of an appropriate particle measuring system is necessary in the CMP process. In this study, a scanning mobility particle sizer (SMPS) and dynamic light scattering (DLS) were compared for particle size distribution (PSD) measurements. In addition, the actual particle size and shape were confirmed by transmission electron microscope (TEM) results. SMPS classifies the particle size according to the electrical mobility, and measures the particle concentration (single particle measurement). On the other hand, the DLS measures the particle size distribution by analyzing scattered light from multiple particles (multiple particle measurement). For the slurry particles selected for evaluation, it is observed that SMPS shows bi-modal particle sizes 30 nm and 80 nm, which closely matches with the TEM measurements, whereas DLS shows only single mode distribution in the range of 90 nm to 100 nm and showing incapability of measuring small particles. Hence, SMPS can be a better choice for the evaluation of CMP slurry particle size and concentration measurements.

High-Purity Amino-Functionalized Graphene Quantum Dots Derived from Graphene Hydrogel

The unique properties of graphene quantum dots (GQDs) make them interesting candidate materials for innovative applications. Herein, we report a facile method to synthesize amino-functionalized graphene quantum dots (AF-GQDs) by a hydrothermal reaction. Graphene oxide (GO) was synthesized by Hummer’s method where ultra-small GO sheets were obtained by a prolonged oxidation process followed by sonication using an ultrasonic probe. Subsequently, graphene hydrogel (GH) was also obtained by a hydrothermal synthesis method. Proper care was taken during synthesis to avoid contamination from water soluble impurities, which are present in the precursor, GO solution. Following the treatment of GH in ammonia, ultra-small amino-functionalized graphene fragments (AF-GQDs) were formed, which detached from the GH to eventually disperse evenly in the water without agglomerating. This modified synthesis process enables the formation of high-purity AF-GQDs (99.14%) while avoiding time-consuming synthesis procedures. Our finding shows that AF-GQDs with sizes less than 5nm were well dispersed. A strong photoluminescence (PL) emission at ∼410nm with 10% PL quantum yield was also observed. These AF-GQDs can be used in many bio applications in view of their low cytotoxicity and strong fluorescence that can be applied to cell imaging.

Characteristic of pad cut rate as conditioner structure

The purpose of this paper is to investigate the effect of diamond grit during chemical mechanical polishing (CMP) process. CMP is the most important for planarization of wafer surface in semiconductor manufacturing. During polishing process, the wafer surface and the pad are contacted with the slurry. There are various contact area, which are wafer-pad aperture and conditioner-pad aperture, and so on. Between diamond grits and pad, those contacts can affect wafer polishing process. Conditioner of CMP dresses pad surface to maintain CMP pad surface constant. Otherwise, CMP pad will be degraded out quickly after several wafer process. Shape of diamond pattern and their effect on pad property were reported, but there are no researchers related novel diamond conditioner. In this study, we experiment CMP process by using different conditioners and analyze wafer polishing property as conditions.