Conducting Polymers Incorporated with Related Graphene Compound Films for Use for Humidity and NH3 Gas Sensing

Using spin-coating technique, PEDOT:PSS + GQD + CNT (GPC), PEDOT:PSS + GQD + AgNW (GPA) films used for humidity sensors and P3HT + rGO + CNT (P3GC) films used for NH3 gas sensors were prepared. At room temperature and atmospheric pressure, all the sensing devices have extremely simple structure and they respond well to the humidity change (for GPC and GPA) and NH3 gas (for P3GC). The sensitivity of both the GPC and GPA humidity sensing devices was found to be dependent on the additives of CNT or AgNW. For the GPA sensors, the best sensitivity attained a value as large as 15.2% with a response time of 30 s. For the NH3 gas sensors made from P3GC films with a content of 20 wt.% of rGO and 10% of CNTs, the best performance parameters were obtained, such as responding time of ca. 30 s, sensing response of 0.8% at ammonia gas concentration of 10 ppm and a relative sensitivity of 0.05%/ppm. The fact that the P3HT + rGO + CNT sensors do not respond to humidity suggests useful applications in gas thin-film sensors for selectively sensing ammonia gas in a humid environment

Light Absorption and Photoluminescence Quenching Properties of Bulk Heterojunction Materials Based on the Blend of Poly(n-vinylcarbazole)/poly(n-hexylthiophen)

The enhancement of light absorption and photoluminescence quenching properties of the bulk heterojunction systems which were fabricated using poly(N-vinylcarbazole) (PVK); poly(N-hexylthiophene)(P3HT) and fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6] C61 (PCBM) were investigated. The optimized material showed a broad absorption in the region from ultra violet to near infra-red and the luminescence quenching higher than 90%. The obtained results provide further insight into photophysics of the heterojunction system and device performance improvement by using this system as an active layer

Effect of Annealing Temperature on the Li+^{ + } Ionic Conductivity of La0.67−x_{0.67 - x}Li3x_{3x}TiO3_{3 }

Perovskite La0.67-xLi3xTiO3 with x = 0.10, 0.11, 0.12 and 0.13 were firstly annealed at 800 oC then treated by reactive milling, followed by post-annealing at temperatures from 1100 to 1200oC. The crystalline structure of grain and grain-boundary were characterized by XRD and SEM. The impedance measurements showed that nanocrystalline La0.67-xLi3xTiO3 after being annealed at 1150 oC possessed a grain conductivity as high as 1.3×10-3 S.cm-1. The grain-boundary conductivity was enhanced one order in magnitude after annealing at temperature higher 1100oC and consists of 5.8×10-5 S.cm-1. The results have also showed the limitation of the adiabatic thermal treatment for the improvement of the grain-boundary conductivity and suggested the way to overcome the limitation by rapidly cooling the samples from the high temperature to room temperature

Investigation of Energy Transfer in a Blend of electroluminescent Conducting Polymers

With the aim of improving the photonic efficiency of an organic light emitting diode a blend of electroluminescent polymers, poly[9-vinylcarbarzole] (PVK) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) was prepared. The energy transfer in the blend was investigated through the comparison of absorption, photoluminescence (PL) and current-voltage (I-V) characteristics of the blend and standard polymers. The obtained results showed that energy transfer from PVK to MEH-PPV enable to form localized excited-state complexes (e.g. exciplexes) in MEH-PPV. The PL intensity of the blended polymers was enhanced as the relative content of MEH-PPV was increased, and particularly, the highest improved PL was observed for an weight fraction of 15 wt{\%} of MEH-PPV in PVK. Organic light emitting diodes made from these blends would exhibit a large photonic efficiency

Optical Property and Photoelectrical Performance of a Low-bandgap Conducting Polymer Incorporated with Quantum Dots Used for Organic Solar Cells

By using spin-coating technique, a low bandgap conjugated polymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopen-ta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT)  and its composite thin films have been prepared. The optical absorption and photoconductive properties with over a wide spectral range, from 350 to 950  nm, were characterized. The obtained results showed that PCPDTBT:10 wt% CdSe  composite is the most suitable for efficient light-harvesting in polymer-based photovoltaic cells. The photoelectrical conversion efficiency (PCE) of the device with  a multilayer structure of ITO/PEDOT/ PCPDTBT:CdSe /LiF/Al  reached a value as large as 1.34% with an open-circuit voltage (Voc) = 0.57 V, a short-circuit current density (Jsc) = 4.29 mA/cm2, and a fill factor (FF) = 0.27. This suggests a useful application in further fabrication of quantum dots/polymers based solar cells

Characterization of NH3_3 Sensing Properties of P3HT+rGO+CNT Composite Films Made by Spin-coating

Thin films of poly(3-hexylthiophene) (P3HT) incorporated with reduced graphene oxide (rGO) and multi-walled carbon nanotubes (CNTs) were prepared by spin-coating technique. Atomic force microscope (AFM) surface morphology, UV-Vis spectra and NH3 gas sensing of the films were studied. Results showed that the P3HT embedded with a content of 20 wt.% of rGO and 10 % of CNTs (abbreviated to P3GC) resulted in the formation of nanostructured composites, exhibiting 1.50 nm-roughness surface and a semiconducting material with a bandgap of 1.92eV. These structure and composition of the P3GC film are appropriate for making film sensors whose resistance changes as a function of gas concentration. Monitoring ammonia gas by the sensors showed that the responding time of the sensing reached a value as fast as 30 s, the response at ammonia gas content of 10 ppm attained a value as large as 0.8% and the relative sensitivity was of 0.05 %/ppm

NGHIÊN CỨU CHẾ TẠO VẬT LIỆU CACBORUN TỪ NANO SiO2

SiO2 từ tro trấu với kích thước hạt khoảng 50 nm (nano-SiO2) được chế tạo bằng công nghệ nghiền năng lượng cao. Khi thiêu kết hỗn hợp nano-SiO2 và graphite (C) phản ứng hoàn toàn tạo ra cacborun (SiC) dạng bột mịn xảy ra tại nhiệt độ 1550oC, thời gian 1 giờ. Sản phẩm SiC nhận được có độ sạch cao có thể ứng dụng làm tấm kê, gối đỡ trong công nghệ gốm sứ hay các thanh đốt trong lò nhiệt độ cao.Việc phát hiện SiC kết tinh hình que khi sử dụng hỗn hợp nano-SiO2 chứa tạp chất để thiêu kết gợi mở những nghiên cứu mới nhằm chế tạo vật liệu que nano SiC ứng dụng làm chip LED tử ngoại hay vật liệu tổ hợp nano polymer dẫn điện với những tính chất điện và quang điện tử nổi trội

Spectroscopic and Photoluminescent Properties of Nanostructured Polyfluorenes/TiO2 Composite Films used for OLEDs

In this work we present spectroscopic and photoluminescent properties of nanostructured polymeric composite films of nanocrystalline TiO2 and polyfuorenes (PF+nc-TiO2). The films were deposited onto glass and KBr substrates by spin-coating PF-in-toluene solution with embedding of 5-nm thick nc-TiO2 particles. The nc-TiO2 wt concentration embedded in PF was chosen as 1%, 2% and 4%. The FTIR, FTR, UV-VIS-NIR and photoluminescence characterization were carried-out to study the influence of oxide nanoparticles on the absorption spectra, molecular structures and emissive luminescence of the composites. It was shown that the presence of TiO2 nanoparticles results in improvement of charge separation of carriers generated by light excitation. Under a short wavelength excitation, in some samples a PL enhancement was observed. Under normal or long wavelength excitation, PF fluorescence quenching occurred for all the composites. Aging process of the composites was also investigated

Preparation and Inverstigation of MEH-PPV Films Used for White Light Emitting Diodes

With the aim to prepare white Light Emitting Diode (WLED), the conjugate polymer films like (Poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) were investigated. Spectroscopic (absorption and emission) spectra of the MEH-PPV films showed that this polymer is suitable for casting onto the chips of the blue InGaN LED to make WLED. The luminous flux measured on the WLEDs in the integrating sphere proved that the white light emission can be obtained from the combination of inorganic LED and conjugate (MEH-PPV) polymers with an optimal thickness and a high quality. The aging process of MEH-PPV films was found to be strongly dependent post-treatment conditions. Reasonable heat treatment condition for the MEH-PPV polymers was suggested as in vacuum of 5×10-2 Pa at a temperature of 120°C in, for 2 hous