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Now showing 1 - 10 of 48

Stimuli-responsive polymer as gate dielectric for organic transistor sensors
(2020-10-01)
Rullyani, Cut
;
Singh, Mriganka
;
Li, Sheng-Han
;
Sung, Chao-Feng
;
Lin, Hong-Cheu
Temperature is a characteristic often correlated with environmental and health issues. This paper presents an organic thin film transistor (OTFT) based temperature sensor having a detection range of 30-45 degrees C, which, therefore, encompasses the human body temperature. The OTFT sensor featured thermosensitive poly(N-iso-propylacrylamide) (PNIPAM) and pentacene as the gate dielectric and semiconductor, respectively. The PNIPAM film possessed a dielectric constant of 4.2 with very low leakage current density. The OTFT exhibited high electrical performance, with a hole mobility (mu) of 0.90 +/- 0.04 cm(2) V-1 s(-1), a threshold voltage (V-th) of -15.4 +/- 1.16 V, and an on/off ratio of 10(4). Significant changes in the drain current and the values of V-th and mu occurred when the temperature of the device was varied within the range 30-45 degrees C at an interval of 0.5 degrees C. The operating principle for this temperature sensor was based on the structural transformation of the PNIPAM dielectric and the enhanced charge transport of the pentacene semiconductor upon varying the temperature. Flexible OTFTs fabricated on polyethylene terephthalate substrate displayed hole mobilities as high as 0.39 +/- 0.01 cm(2) V-1 s(-1), values of V-th of 18.6 +/- 0.45, and on/off ratios of 10(2), and were workable for over 100 bending cycles.
UV-enhanced room-temperature ultrasensitive NO gas sensor with vertical channel nano-porous organic diodes
(2020-10-01)
Madhaiyan, Govindasamy
;
Tung, Ting-Wei
;
Zan, Hsiao-Wen
;
Meng, Hsin-Fei
;
Lu, Chia-Jung
In this work, we successfully proposed an organic semiconductor gas sensor on vertical channel design to exhibit an ultra-sensitive response to nitric oxide gas (10 ppb) at room temperature. The effect of ultra-violet (UV) irradiation (lambda =365 nm) on sensing performance of solution processed vertical organic diode (VOD) has been investigated. After implementing a simple and low-cost UV treatment, the sensing response of PBDTTT-C-T based NO sensor is significantly enhanced from 93 % to 233 % at 1 ppm. In addition, we also introduced a new strategy to tune the selectivity of organic gas sensors by using photochromic molecule and organic semiconductor blends. With the 1 Wt% spiropyran dopant, the sensor response to ammonia can be considerably suppressed, hence the response ratio between NO and ammonia can be improved from 2.9 to 16.0, indicating an improved selectivity. The proposed ultrasensitive and selective NO gas sensor have great potential for exhaled breath detection (asthma patients) and environmental monitoring.
Multi-Stimuli Responsive FRET Processes of Bifluorophoric AlEgens in an Amphiphilic Copolymer and Its Application to Cyanide Detection in Aqueous Media
(2020-03-04)
Nhien, Pham Quoc
;
Chou, Wei-Lun
;
Cuc, Tu Thi Kim
;
Khang, Trang Manh
;
Wu, Chia-Hua
A novel amphiphilic aggregation-induced emission (AIE) copolymer, that is, poly(NIPAM-co-TPE-SP), consisting of N-isopropylacrylamide (NIPAM) as a hydrophilic unit and a tetraphenylethylene-spiropyran monomer (TPE-SP) as a bifluorophoric unit is reported. Upon UV exposure, the close form of non-emissive spiropyran (SP) in poly(NIPAM-co-TPE-SP) can be photo-switched to the open form of emissive merocyanine (MC) in poly(NIPAM-co-TPE-MC) in an aqueous solution, leading to ratiometric fluorescence of AlEgens between green TPE and red MC emissions at 517 and 627 nm, respectively, via Forster resonance energy transfer (FRET). Distinct FRET processes of poly(NIPAM-co-TPE-MC) can be observed under various UV and visible light irradiations, acid-base conditions, thermal treatments, and cyanide ion interactions, which are also confirmed by theoretical studies. The subtle perturbations of environmental factors, such as UV exposure, pH value, temperature, and cyanide ion, can be detected in aqueous media by distinct ratiometric fluorescence changes of the FRET behavior in the amphiphilic poly(NIPAM-co-TPE-MC). Moreover, the first FRET sensor polymer poly(NIPAM-co-TPE-MC) based on dual AlEgens of TPE and MC units is developed to show a very high selectivity and sensitivity with a low detection limit (LOD = 0.26 mu M) toward the cyanide ion in water, which only contain an approximately 1% molar ratio of the bifluorophoric content and can be utilized in cellular bioimaging applications for cyanide detections.
Liquid crystal dimers containing Cholesteryl and Triazole-containing mesogenic units
(1970-01-01)
Al-shargabi, Arwa
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Yeap, Guan-Yeow
;
Mahmood, Wan Ahmad Kamil
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Han, Chun-Chieh
;
Lin, Hong-Cheu
New liquid crystals categorised as cholesteryl dimers have been successfully synthesised through the reaction between cholesteryl 4-(prop-2-ynyloxy)benzoate moieties with n-azido(cholesteryloxy-carbonyl)alkane. All the dimers display enantiotropic mesophases. Whilst the odd-numbered dimers exhibit chiral nematic (N*), twisted grain boundary (TGB) and chiral smectic C (SmC*) phases, the even-numbered members from the same series show chiral smectic A and C. A detailed inspection on mesophase reveals that the chiral centres and the bent conformation of the odd-numbered members are essential for the induction of TGB phase. However, upon decreasing the temperature, the ratio of the transition temperatures (TSmC*-SmA*/TSmA*-I) is found to be 0.95, which indicate the second order transition according to the McMillan's molecular theory. In addition, the X-ray diffraction study supports the presence of the smectic A phase on the even members rather than the N* by the appearance of the Bragg diffraction peaks at 190 degrees C. A comparison study with the other analogues in which the cholesterol entity is substituted by azobenzene or biphenyl tails has been carried out to assess the relationship between the molecular structure and mesomorphic behaviour. [GRAPHICS] .
Shape and confinement effects of various terminal siloxane groups and C60 on supramolecular interactions of hydrogen-bonded bent-core liquid crystals
(2015-01-01)
Lin, Hong-Cheu
;
Chiang, I-Hung
;
Chuang, Wei-Tsung
;
Lu, Chia-Lin
;
Liao, Chun-Yen
Pyrene-SH functionalized OTFT for detection of Hg2+ ions in aquatic environments
(2019-06-01)
Rullyani, Cut
;
Shellaiah, Muthaiah
;
Ramesh, Mohan
;
Lin, Hong-Cheu
;
Chu, Chih-Wei
Mercury ion (Hg2+) sensor based on bottom gate top contact organic thin film transistor (OTFT) was fabricated. The OTFT channel area was functionalized with pyrene that contain thiol group, which has strong binding affinity toward Hg2+ ion. The OTFT sensor exhibited a charge mobility of 0.28 cm(2) V-1 s(-1), a threshold voltage of -22.3 V and on-to-off ratio 10(3). The sensor shows high selectivity to Hg2+ ion over other two valence metal ions. OTFT sensor exhibited high sensitivity to Hg2+ ion, indicated by increasing of drain current after exposed to different concentration of Hg2+ ion ranging from 1 mM to 0.01 mu M. Moreover, the OTFT sensor capability for practical application was also demonstrated by sensing the present of 25 mu M of Hg2+ ion in tap, drinking and seawater samples.
A 0.05 V driven ammonia gas sensor based on an organic diode with a top porous layered electrode and an air-stable sensing film
(2019-06-07)
Madhaiyan, Govindasamy
;
Chen, Chao-Hsuan
;
Wu, Yi-Chu
;
Horng, Sheng-Fu
;
Zan, Hsiao-Wen
In this work, we successfully demonstrated an extremely-low-voltage (0.05 V) gas sensor based on a vertical organic diode with work-function-matched electrodes. With the designed electrodes (MoO3/Al vs. Al), the built-in field in the vertical diode is greatly reduced and hence the diode can be turned on at a very low voltage. By producing nanometer pores in the top electrode, the diode becomes a very sensitive gas sensor to detect ammonia in parts-per-billion (ppb) concentrations. Upon reducing the voltage from 5 V to 0.05 V, this sensor device shows an over 5-times enhancement in the sensitivity. The air-stable sensing film also exhibits a lifetime of 30 days in air. Finally, by connecting with an organic photovoltaic (OPV) device, the gas sensor can be directly powered and switched on by irradiating light on the OPV.
Facile synthesis of composite tin oxide nanostructures for high-performance planar perovskite solar cells
(2019-06-01)
Singh, Mriganka
;
Ng, Annie
;
Ren, Zhiwei
;
Hu, Hanlin
;
Lin, Hong-Cheu
Metal oxide carrier transporting layers have been investigated widely in organic/inorganic lead halide perovskite solar cells (PSCs). Tin oxide (SnO2) is a promising alternative to the titanium dioxide commonly used in the electron transporting layer (ETL), due to its tunable carrier concentration, high electron mobility, amenability to low-temperature annealing processing, and large energy bandgap. In this study, a facile method was developed for the preparation of a room-temperature-processed SnO2 electron transporting material that provided a high-quality ETL, leading to PSCs displaying high power conversion efficiency (PCE) and stability. A novel physical ball milling method was first employed to prepare chemically pure ground SnO2 nanoparticles (G-SnO2), and a sol-gel process was used to prepare a compact SnO2 (C-SnO2) layer. The effects of various types of ETLs (C-SnO2, G-SnO2, composite G-SnO2/C-SnO2) on the performance of the PSCs are investigated. The composite SnO2 nanostructure formed a robust ETL having efficient carrier transport properties; accordingly, carrier recombination between the ETL and mixed perovskite was inhibited. PSCs incorporating C-SnO2, G-SnO2, and GSnO(2)/C-SnO2 as ETLs provided PCEs of 16.46, 17.92, and 21.09%, respectively. In addition to their high efficiency, the devices featuring the composite SnO2 (G-SnO2/C-SnO2) nanostructures possessed excellent long-term stability-they maintained 89% (with encapsulation) and 83% (without encapsulation) of their initial PCEs after 105 days ( > 2500 h) and 60 days ( > 1400 h), respectively, when stored under dry ambient air (20 +/- 5 RH %).
Self-assembled 1,2-bis[4-(4-(10-decyloxy)phenylazo)]benzoylhydrazine dimer and its hydrogen-bonded complexes
(2013-07-01)
Yeap, Guan-Yeow
;
Balamurugan, Subramanian
;
Rakesh, Samikannu
;
Han, Chun-Chieh
;
Lin, Hong-Cheu
We report the synthesis and investigation of a new self-assembled benzoylhydrazine-based compound, namely 1,2-bis[4-(4-(10-decyloxy)phenylazo)]benzoylhydrazine and their hydrogen-bonded complexes with different carboxylic acid derivatives, of which some exhibit liquid crystalline properties and some are non-mesogens. The conversion of the non-liquid crystalline target compound that is free from carboxylic acid to liquid crystalline complexes containing various carboxylic acids can probably be rationalised through the breaking of intermolecular hydrogen bonding within the supramolecular assembly by carboxylic acid dopants. The enhancement of liquid crystalline properties of benzoylhydrazine compounds with respect to various carboxylic dopants is documented. Other salient features can be exemplified by the formation of discotic columnar phase as shown by the azo-linkage containing 4-(4-(10-decyloxy)phenylazo)benzoic acid-doped complex.
DOPANT EFFECTS OF PHOTOREACTIVE ZnO NANOPARTICLES ON FAST RESPONSE LC MATERIALS IN OPTICAL COMPENSATED BEND (OCB) MODE LIQUID CRYSTAL DISPLAYS
(2010-11-01)
Lin, Hong-Cheu
;
Jiang, Meng-Dan
;
Wang, Ling-Yung
;
Chen, Wei-Hong
;
Chen, Szu-Fen
Photoreactive ZnO nanoparticles containing surface-modified acrylate groups were synthesized and applied to improve the threshold voltage in optical compensated bend (OCB) mode liquid crystal display (LCD) cells. The dopant effects of ZnO nanoparticles with or without commercial reactive monomer additives (1 wt% doping ratio) on the values of threshold voltage (V-th) and response time in OCB cells were explored by applying different voltages to photo-reactive ZnO nanoparticles during UV curing processes in OCB cells to compare the influences of doped ZnO nanoparticles. As a result, we successfully eliminated or reduced the splay state of OCB mode and thus reduced threshold voltage. However, lower transmissions and higher values of the response time were observed in OCB cells doped with photoreactive ZnO nanoparticles, and the decreasing of V-th, is independent of various doping materials. Moreover, lower transmission and high response time could be improved through sequential voltage-applied procedures, i.e., bend black mode (10 V) -> bend white mode (2.5 V), under the immobile minimum threshold voltage at the bent state during UV curing processes to achieve lower pre-transition and fast response time properties by only doping photoreactive ZnO nanoparticles.

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