Co-reporter:Huan Yuan;Huiling Tai;Xiao Yang;Ming Xu
RSC Advances (2011-Present) 2017 vol. 7(Issue 52) pp:32749-32756
Publication Date(Web):2017/06/23
DOI:10.1039/C7RA03271D
This work presents the investigation of reduced graphene oxide (RGO) as a new type of stationary phase for gas chromatographic separation on a microcolumn which is fabricated on a silicon wafer by the application of microelectromechanical system (MEMS) techniques. A ZnO film synthesized by a sol–gel method is utilized as a supporting material between RGO and the column wall for inwall roughening to form a stable RGO stationary phase and increase gas-stationary phase interaction. The RGO/ZnO grafted on the column wall was characterized by SEM and FT-IR spectra. The experimental results demonstrate that good separations for mixtures of a wide range of organic compounds including alkanes and esters are achieved by the microcolumn coated with bilayer film. And the maximum column efficiency of 11 363 theoretical plates per meter for n-dodecane is obtained, which is higher than any previously reported values for chromatography columns coated with graphene and their analogs to the best of our knowledge. However, the RGO stationary phase shows obvious peak tailings for polar alcohols, which mainly originate from its specific π–π stacking interaction as well as the hydrophobic effect between analytes and the π-electron on the high surface area of reduced graphene oxide. This work greatly favors RGO coated chip columns for gas chromatographic separation in achieving micro-total analytical systems.
Co-reporter:Huan Yuan;Yi Li;Xulan Zhao;Ming Xu
Journal of Separation Science 2016 Volume 39( Issue 7) pp:1295-1299
Publication Date(Web):
DOI:10.1002/jssc.201501138
A two-channel gas chromatography column and a single-channel column were made by deep reactive-ion etching technology. The two short columns were coated with different stationary phases, and then linked without a modulator. This is to aim at increasing the sample capacity and achieving a higher separation efficiency in complex environments. The results show that the capacity of the connected column is approximately 4 and 1.5 times larger than that of the single- and two-channel columns, respectively. The linked column was utilized to separate a six-component mixture, composed of three simulants of nerve and blister agents and three interfering vapors. The results demonstrate that the combined column has a remarkably higher separation efficiency than the individual columns, and an acceptable resolution is achieved although the total length of the linked column is only 1.5 m.
Co-reporter:Huan Yuan, Xiaosong Du, Ming Xu
Physica E: Low-dimensional Systems and Nanostructures 2016 Volume 79() pp:119-126
Publication Date(Web):May 2016
DOI:10.1016/j.physe.2015.12.028
•Cobalt/copper-codoped ZnO films show Cu valence from +2 to +1 as the Co concentration level exceeds 1% by XPS.•The optical bandgap of Zn0.95−xCoxCu0.05O films shows a blue-shift from 3.01 to 3.13 eV with increasing Co concentration.•The ferromagnetism of Zn0.95−xCoxCu0.05O films is correlated with the valence state of the Cu ions and oxygen vacancies.Cobalt/copper-codoped ZnO nanoparticles, synthesized with different Co concentrations by a sol–gel method using ethanol as solvent, were studied via XPS. Hexagonal wurtzite structure was found in all samples, with no evidence of any secondary phase. The average crystallite size of the samples was around 20–30 nm, altered significantly with increasing Co concentration. Copper ions and Cobalt ions are indeed substituted into the ZnO lattice at the Zn2+ site, as shown by XRD and XPS. Further studies showed dramatic changes of Cu valence from +2 to +1 as the Co concentration level exceeds 1%, accompanied by a blue-shift of the optical bandgap from 3.01 to 3.13 eV. Ferromagnetism of the Co-doped Zn0.95Cu0.05O thin films was observed and found to be tunable – a phenomenon associated with the valence state of the Cu ions and the existence of some defects like oxygen vacancies in the films.
Co-reporter:Huan Yuan, Li Zhang, Ming Xu, Xiaosong Du
Journal of Alloys and Compounds 2015 Volume 651() pp:571-577
Publication Date(Web):5 December 2015
DOI:10.1016/j.jallcom.2015.08.172
•Cobalt-iron-codoped ZnO films were synthesized with different precursor sol pHs by a sol–gel method.•The bandgap energy of the ZnO films increases from 3.15 eV (pH = 5) to 3.24 eV (pH = 9).•Enhanced room-temperature ferromagnetism is observed for the (Co, Fe)-codoped ZnO films at sol pHs lower than 8.Cobalt-iron-codoped ZnO films were synthesized with different precursor sol pHs by a sol–gel method. All the samples possess hexagonal wurtzite structure, with no evidence of secondary phases. The average crystallite size of the samples was in the range of 10–40 nm, accompanying significant differences with the increase of the H+ ion level. The Co/Fe ions are indeed substituted at the Zn2+ site into the ZnO lattice, as shown by XRD and XPS. Strong ultraviolet emission, blue double emission and weak green emission peaks are observed in the photoluminescence spectra of all samples at room temperature. Further studies reveal that the bandgap energy of the ZnO films increases from 3.15 eV (pH = 5) to 3.24 eV (pH = 9). Enhanced room-temperature ferromagnetism is observed for the (Co, Fe)-codoped ZnO films at sol pHs lower than 8. Our work clearly establishes that the origin of room-temperature ferromagnetism in the (Co,Fe)-codoped ZnO films is linked to O vacancies, tunable by the sol pH.Optical energy gap (a) and magnetic properties (b) for the Zn0.95Co0.025Fe0.025O films deposited from the varied sol pH.
Co-reporter:Huan Yuan, Ming Xu, Xiaosong Du
Materials Letters 2015 Volume 154() pp:94-97
Publication Date(Web):1 September 2015
DOI:10.1016/j.matlet.2015.04.069
•Oxygen vacancies in the Zn0.95Cu0.05O films increase with the Co doping level.•The introduction of Co ions causes Cu2+ to Cu+ as the Co concentration level exceeds 1%.•The Eg of Zn0.95Cu0.05O films shows a blue shift with increasing Co doping level.Effects of Co doping concentration on the microstructure and the photoluminescent properties of Zn0.95Cu0.05O thin films synthesized by a sol–gel method were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, room-temperature photoluminescence, UV transmission spectrometer. An analysis of the O 1s peak of ZnO film showed that the concentration of oxygen vacancies increases with the Co doping level. We also revealed that the introduction of Co ions causes the valence state of Cu to change from +2 to +1 as the Co concentration level exceeds 1%. The Eg of Zn0.95Cu0.05O films shows a blueshift from 3.01 to 3.14 eV with increasing Co doping level.
Co-reporter:Yi Li, Xiaosong Du, Yang Wang, Huiling Tai, Dong Qiu, Qinghao Lin and Yadong Jiang
RSC Advances 2014 vol. 4(Issue 8) pp:3742-3747
Publication Date(Web):03 Dec 2013
DOI:10.1039/C3RA44255A
In this paper, micro gas chromatography columns were fabricated through the micro-electro-mechanical system (MEMS) technique. Two types of columns were designed, namely, open-tube and semi-packed columns. By comparing different structures, column efficiency was improved by embedding square posts in the channel to form a semi-packed column. The result showed that column efficiency of the semi-packed column reached 55366 plates per m. This study was the first to report based on experimentation that MEMS-based columns can reach a plate number this high. The plate number was five times higher than the value previously reported. In addition, a 30 m-long Agilent HP-5 commercial capillary column was used to compare the results with findings obtained using a MEMS-based semi-packed column. The analytes were perfectly separated in both columns. The column efficiency of the HP-5 capillary column was 5490 plates per m, which was 10 times lower than that of the micro-fabricated, semi-packed column.
Co-reporter:Yang Wang, Xiaosong Du, Yin Long, Xianzhong Tang, Huiling Tai and Yadong Jiang
Analytical Methods 2014 vol. 6(Issue 6) pp:1951-1955
Publication Date(Web):08 Jan 2014
DOI:10.1039/C3AY42214C
A hydrogen-bond acidic (HBA) polymer, poly{methyl[3-(2-hydroxyl, 4,6-bistrifluoromethyl)phenyl]propylsiloxane}(DKAP), was coated on a 434 MHz surface acoustic wave (SAW) device, and subsequently tested against sarin (GB) and soman (GD) vapour along with dimethyl methyl phosphonate (DMMP) at concentrations below 10 mg m−3. The direct detection of GB and GD in the sub mg m−3 range, indicated the high sensitivity of the sensor, and was demonstrated by the corresponding sensor which showed high reproducibility as well. However, the response of the sensor to the real agents was relatively smaller and slower than to the simulant DMMP. Towards the real agents, the time to reach an adsorption equilibrium was considerable (∼16 min) and a time-dependent linear response was observed in the initial >3 min for both the adsorption and the desorption processes. The sensor was also compared with other HBA polymers coated SAW sensors in terms of response characteristics, with emphasis on the kinetic response behaviour. The slow adsorption and desorption property of the DKAP sensor towards the real chemical agents was attributed to the effect of the size of the analytes and to the strength of hydrogen-bonding, respectively.
Co-reporter:Yang Wang;Yin Long;Huiling Tai;Yadong Jiang
Science Bulletin 2014 Volume 59( Issue 21) pp:2608-2612
Publication Date(Web):2014 July
DOI:10.1007/s11434-014-0257-y
A strong hydrogen-bond acidic (HBA) polymer linear fluoroalcoholic polysiloxane (PLF), synthesized by one-step hydrosilylation, was introduced for 2,4-dinitrotoluene (2,4-DNT) detection using surface acoustic wave (SAW) devices. FT-IR spectra and 1H NMR spectra characterizations confirmed its molecular structure. Then, PLF was dissolved in chloroform, and spray coated onto a 434 MHz SAW device. And subsequently, the sensitivity and selectivity of the fabricated sensor were studied based on a SAW test platform. To 2,4-DNT of 1 ppm and 100 ppb (for DNT, 1 ppm = 8.1 mg/m3; 1 ppb = 8.1 μg/m3), the responses of the sensor rose 7.7 and 1.5 kHz, respectively. Furthermore, compared with some common interference vapors at 10 mg/m3, the response of the sensor to 2,4-DNT at 1 ppm was 5 times stronger. The sensitive property was attributed to the hydrogen bond interaction between the hexafluoroisopropanol (HFIP) group in PLF and the basic lone electron pairs of nitro-groups in 2,4-DNT. Comparison between the PLF sensor and hydroxyl group functionalized polymer (carbowax and MOBCD)-coated sensors was investigated, and the results showed that the PLF sensor exhibited better sensitivity. In a word, the PLF sensor exhibited fast response, negligible baseline drifts and excellent reversibility, indicating good candidates of HFIP group functionalized HBA polymers for practical nitroaromatic explosives detection.
Co-reporter:Yang Wang;Yi Li;Yin Long;Dong Qiu;Huiling Tai;Xianzhong Tang ;Yadong Jiang
Journal of Applied Polymer Science 2013 Volume 130( Issue 6) pp:4516-4520
Publication Date(Web):
DOI:10.1002/app.39724
ABSTRACT
Hexafluoroisopropanol (HFIP) was the most widely used functional group for nerve agents detection. However, to incorporate HFIP group into a polymer backbone, highly toxic hexafluoroacetone gas was needed in a conventional synthetic route. In this article, a new route with low toxicity was proposed to synthesize a strong hydrogen-bond acidic (HBA) siloxane polymer by using 2-vinylhexfluoroisopropanol as the raw material in the hydrosilylation reaction. The synthesized fluoroalcoholic linear polysiloxane (LSFA) was characterized by FT-IR, confirming its molecular structure was much similar to SXFA, a well-established HBA polymer synthesized by the conventional route. TGA data verified the adduct's thermal stability. The dimethyl methylphosphonate (DMMP) sensing properties of LSFA and SXFA, along with PLF, were compared basing on the surface acoustic wave (SAW) platform. The results demonstrated that the conventional synthetic route was somewhat difficult to handle and control, while the new route was simpler, easier and was an effective and promising alternative. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4516–4520, 2013
Co-reporter:Xiaosong Du, Zhihua Ying, Yadong Jiang, Zhongxiang Liu, Taojun Yang, Guangzhong Xie
Sensors and Actuators B: Chemical 2008 Volume 134(Issue 2) pp:409-413
Publication Date(Web):25 September 2008
DOI:10.1016/j.snb.2008.05.016
A new polysiloxane material, polymethyl[3-(2-hydroxy)phenyl] siloxane (PMPS), was synthesized. The PMPS is a linear polysiloxane polymer functionalized with o-allyl phenol group. The chemoselective polymer was spin-coated on a 434 MHz surface acoustic wave (SAW) device for detection of dimethyl methylphosphonate (DMMP) vapor ranging from 5 to 40 ppm. It was found that the frequency shifts were linear to the vapor concentrations with a high sensitivity of 3 kHz/ppm. Fast response of 30 s and good reproducibility were achieved as well. The influence of humidity on the sensor response was also examined. The results showed that the sensitivity decreased about 1/2 when tested in 70% RH wet air than in dry nitrogen.
Co-reporter:
Analytical Methods (2009-Present) 2014 - vol. 6(Issue 6) pp:NaN1955-1955
Publication Date(Web):2014/01/08
DOI:10.1039/C3AY42214C
A hydrogen-bond acidic (HBA) polymer, poly{methyl[3-(2-hydroxyl, 4,6-bistrifluoromethyl)phenyl]propylsiloxane}(DKAP), was coated on a 434 MHz surface acoustic wave (SAW) device, and subsequently tested against sarin (GB) and soman (GD) vapour along with dimethyl methyl phosphonate (DMMP) at concentrations below 10 mg m−3. The direct detection of GB and GD in the sub mg m−3 range, indicated the high sensitivity of the sensor, and was demonstrated by the corresponding sensor which showed high reproducibility as well. However, the response of the sensor to the real agents was relatively smaller and slower than to the simulant DMMP. Towards the real agents, the time to reach an adsorption equilibrium was considerable (∼16 min) and a time-dependent linear response was observed in the initial >3 min for both the adsorption and the desorption processes. The sensor was also compared with other HBA polymers coated SAW sensors in terms of response characteristics, with emphasis on the kinetic response behaviour. The slow adsorption and desorption property of the DKAP sensor towards the real chemical agents was attributed to the effect of the size of the analytes and to the strength of hydrogen-bonding, respectively.
