M.J. Yang

Humidity sensors using in situ synthesized sodium polystyrenesulfonate/ZnO nanocomposites.

Thin film humidity sensors have been prepared using in situ synthesized inorganic/organic nanocomposites of sodium polystyrenesulfonate (NaPSS) and ZnO. Its humidity sensing characteristics and the sensing mechanism have been investigated by measuring the complex impedance spectra of the sensor at different humidities. The logarithm of the impedance of sensor based on composite film changes linearly by four-orders of magnitude over almost whole humidity range (11-97% RH). Furthermore, the sensor exhibits a quick response (absorption: 2s, desorption: 2s) and small hysteresis (less than 2% RH). The composite film shows better sensing properties than NaPSS film, such as better linearity, quicker response. Explanation to the improvement is attempted by taking into account of the composition and structure of the nanocomposites.

Humidity sensors based on polymer solid electrolytes: investigation on the capacitive and resistive devices construction

Abstract Resistive and capacitive sensors were prepared by using polymer solid electrolytes. Monolayer and bilayer devices were prepared by filming polymer electrolytes or blends of polymer electrolytes on interdigitated gold electrodes. By working at low frequency, humidity sensors with fast response and operating over a wide range of RH% were obtained.

Polymer electrolytes as humidity sensors: progress in improving an impedance device

Impedance humidity sensors based on a blend of sodium sulphonated polystyrene and a cellulose-based polymer electrolyte, have been improved by carefully refining the construction details. Enhanced performances have been attained with a close investigation on the electrical characteristics of the device as a function of humidity. The best results have been achieved by choosing both exciting frequency and the distance between the electrodes so that electrode redox processes are avoided.

A novel highly reversible humidity sensor based on poly(2-propyn-2-furoate)

Thin film humidity sensors were prepared with salt-doped poly(2-propyn-2-furoate) (PPF). The humidity sensitive properties of the sensors have been investigated by measuring the complex impedance spectroscopy at different relative humidities (RHs). Both impedance and capacitance of the sensors change 3–4 orders of magnitude from 33 to 97% RH, and no hysteresis is observed. In addition, the capacitance responses exhibit good linearity for PPF doped with LiCl (R2=0.9995) and FeCl3 (R2=0.9996) over a wide humidity range. It is proposed that the highly reversible impedance and capacitance responses are related to the furan ring in PPF.

Bilayer thin film humidity sensors based on sodium polystyrenesulfonate and substituted polyacetylenes

Bilayer thin film humidity sensors based on sodium polystyrenesulfonate (NaPSS) and substituted polyacetylenes (poly(propiolic acid) (PPA), poly(p-diethynylbenzene) (PDEB) and poly(propiolic acid-co-propargyl alcohol) (PA-co-OHP)) have been prepared, and their humidity sensitive properties have been investigated over a wide range of relative humidity (10–95% RH). The bilayer sensors exhibit different humidity response depending on the sensing properties of the outer layers of polyacetylenes. Of all the bilayer sensors, the sensor based on NaPSS and PA-co-OHP doped with FeCl3 shows the best sensing properties. Its impedance changes linearly with relative humidity for approximately four orders of magnitude in a wide range of 10–85% RH, showing high sensitivity and quick response in both adsorption and desorption processes. In addition, its capacitance shows a highly sensitive and quick response to humidity variation.

Humidity sensitive properties of a novel soluble conjugated copolymer: ethynylbenzene-co-propargyl alcohol

Abstract A novel soluble conjugated copolymer, ethynylbenzene-co-propargyl alcohol (EB-co-OHP), was homogeneously doped with different salts and investigated as a humidity sensitive material for the first time. Thin films of the doped polymer were deposited on interdigital gold electrodes to prepare sensors. The doping agents affect the sensing behavior of the sensors, and the LiCl-doped copolymer shows better response, in which great changes of about three orders of magnitude in both impedance and capacitance variation was observed when relative humidity was varied from 33 to 97% RH. Moreover, the logarithm of capacitance of the copolymer varied linearly with RH% in the tested humidity range and exhibited little hysteresis and high sensitivity. The impedance spectra of doped copolymers at different humidities were measured and compared, and their sensing mechanism was also investigated.

Ion conductivity in poly(p-diethynylbenzene-co-propargyl alcohol) films doped with iron trichloride: dependence on temperature

Abstract The ionic conductivity of the film of poly( p -diethynylbenzene- co -propargylalcohol) (DEB- co -OHP) doped with iron trichloride has been investigated in the temperature range 25–60°C at a fixed value of the relative humidity (RH) (100%). Both the film conductance and capacitance have been found to be dependent on temperature. An equation valid for ion solutions, the Onsager-modified equation, has been satisfactorily used to describe the conductance trend with temperature.

Optical behaviors and electroluminescence of a new polyimide

A novel diphenylfluorene-based cardo polyimide (PI) containing acridine units in the backbone was firstly synthesized. Its optical behaviors in film and in solution were studied. Using this polyimide as luminescent material, single-layer device of the structure as ITO/PI/Al was fabricated, yellow-orange electroluminescence was observed from this device.

Humidity sensors using in-situ synthesized sodium polystyrenesulfonate/ZnO nanocomposites

Thin film humidity sensor has been prepared using in-situ synthesized inorganic/organic nanocomposites of sodium polystyrenesulfonate (NaPSS) and ZnO. Its humidity sensing characteristics and the sensing mechanism have been investigated by measuring the complex impedance spectra of the sensor at different humidities. The logarithm of the impedance of sensor based on composite film changes linearly by 4 orders of magnitude over almost the whole humidity range (11%/spl sim/97%RH). Furthermore, the sensor exhibits a quick response (absorption: 2 sec., desorption: 2 sec.) and small hysteresis (less than 2%RH). The composite film shows better sensing properties than NaPSS film, such as better linearity, quicker response. Explanation of the improvement is attempted by taking into account the composition and structure of the nanocomposites.

Narrow emission from polyimide light-emitting diodes

Novel organic light-emitting diodes (OLEDs) using polymidy, fluorene-based cardo perylere polyimide (PFB5) were fabricated. EL properties of single-layer light-emitting diodes (LED) of indium-tin-oxide (ITO)/PFB5+/Al and ITO/PFB5+PBD/Al and multi-layer devices of ITO/PFB5/PBD/Al,ITO/PFB5/Alq/Al were characterized. In the pure PFB5 single layer device, the EL spectrum has a broad band and the peak wavelenght at 420nm, 450nm, and 545nm respectively. However, the EL emission fromthe single layer deviec of PFB5 blend PBD or multi-layer devices has the greatly narrow band and the peak wavelength at 545nm. Furthermore, the EL efficiency is improved significantly in these EL devices.