Showing papers by "Fanli Meng published in 2011"

Novel hybridized SWCNT–PCD: synthesis and host–guest inclusion for electrical sensing recognition of persistent organic pollutants

Abstract: Fabrication of a hybridized single-walled carbon nanotube (SWCNT) device based on novel sensing material mono-6-deoxy-6-(p-aminophenylamino)-β-cyclodextrin (PCD) via a facile approach has been reported for the first time; moreover, the hybridized material PCD-decorated SWCNTs (SWCNT–PCD) can be characterized by ultraviolet–visible–near infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, field-emission scanning electron microscopy and high resolution transmission electron microscopy. The PCD-decorated SWCNT devices have been employed to detect Persistent Organic Pollutants (POPs) on the basis of formation of an inclusion complex with guest molecules between SWCNT–PCD and POPs, such as 2,4,5-trichlorobiphenyl (TCB), etc. The significant variation of the electrical conductance of the SWCNT–PCD hybrid corresponding to the presence of several POPs with different adsorption efficiencies on the surface indicates that the hybrid is highly sensitive to some specific POP molecules, implying that hybridized SWCNT–PCD has great potential in application as an environmental monitor. In order to make a quantitative assessment of the inclusion complexation behavior of PCD with these POP molecules, microcalorimetric titration experiments and discussions have been carried out.

Electronic chip based on self-oriented carbon nanotube microelectrode array to enhance the sensitivity of indoor air pollutants capacitive detection

Abstract: Highly sensitive capacitive detection is reported for indoor air pollutants, e.g. formaldehyde, toluene, and ammonia gas, at room temperature using an electronic chip with self-oriented carbon nanotube microelectrode array. A remarkable capacitive response is observed owing to the dense entanglement of CNTs and the highly porous 3D structured CNT network on the surface of gold electrode. Such kind of nanotubes can be considered as extended and oriented electrodes. As compared with the effect of spray-casting MWCNTs, the relative capacitance change of the above-mentioned electronic chip is found to increase from 1.8 to 70 by taking ammonia as an example. A model is proposed to explain qualitatively the sensing mechanism of electronic chip.

Dense doping of indium to coral-like SnO2 nanostructures through a plasma-assisted strategy for sensitive and selective detection of chlorobenzene

Abstract: A plasma-assisted strategy for densely doping indium to SnO2 nanostructures for gas-sensing applications is reported. The morphology, structure, and composition of the as-prepared nanostructures were characterized by field emission scanning electronic microscopy (FESEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectrometry (XPS), respectively. The results show that the densities of hydroxyl and carboxyl groups of the coral-like SnO2/carbonaceous nanocomposites are remarkably improved by using a plasma treatment (PT), which enables them to adsorb a large quantity of indium ions and thereby enhance the doping. In gas-sensing measurements, it is found that the sensor is sensitive to chlorobenzene with a high response and short response and recovery times. Besides, the gas-sensing properties of the sensor based on the In-doped SnO2 with PT are greatly improved compared with sensors based on In-doped SnO2 without PT and pure SnO2. The enhanced doping and the special coral-like structure are demonstrated as the mechanism of improvement. The kinetic processes of gas adsorption and desorption are also investigated. Furthermore, it is revealed that chlorobenzene can be clearly identified from some gas references by using principal component analysis, exhibiting a good selectivity. Our findings not only provide a promising building block for developing a sensitive and selective gas sensor for environmental monitoring, but also demonstrate a novel plasma-assisted strategy which could be potentially developed as a general method for dense doping of nanomaterials.

A novel porous anodic alumina based capacitive sensor towards trace detection of PCBs

Abstract: To detect polychlorinated biphenyls (PCBs), a novel porous anodic alumina (PAA) based capacitive sensor working at room temperature has been developed. The parallel nanopores of PAA not only provide large surface area for PCB adsorption, but also benefit for the enhancement of capacitive response. By dropping the PCB methanol solution on the surface of PAA, it is convenient to load PCB into the nanopores by solvent evaporation. 3,3′,4,4′-tetrachlorobiphenyl (PCB77) was chosen as a typical sample of PCBs to investigate the sensing properties of the capacitive sensor. The capacitance of the PAA membrane shows remarkable enhancement after PCB77 solution was loaded while no significant change can be seen after the pure solvent was loaded. The capacitive sensor also shows good response to PCB77 even in the presence of the interferent of benzene. The sensing mechanism has been qualitatively discussed based on a parallel plate capacitor model. The detection limit is down to 8 × 10 −8 M towards PCB77. The novel PAA based capacitive sensor exhibits great potential for practical application in trace detection of PCBs.

Synthesis of novel layer-packed In 2 O 3 nanostructures and their application in gas sensor for detecting indoor air contaminants

Abstract: A novel layer-packed In 2 O 3 nanostructure and its application in gas sensor for the detection of indoor air contaminants were reported. The special In 2 O 3 nanomaterials were prepared by annealing In 2 S 3 precursors synthesized via a surfactant-assisted assembly route. The influencing factors towards the morphology of In 2 S 3 precursors were also investigated. In gas-sensing measurements, typical indoor air contaminants, including formaldehyde, ammonia, and benzene were employed as target gases. We found that the as-fabricated sensor exhibited a sensitive property to analytes, especially towards formaldehyde. Besides, by using principal component analysis (PCA) and comparison on kinetic processes of gas adsorption-desorption, the gas sensor show a significantly selective performance due to the special layer-packed structure, which enable it to be promisingly applied for environmental monitoring towards indoor air contaminants.