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Dynamic Modulation of Photonic Bandgaps in Crystalline Colloidal Arrays Under Electric Field
Shim, Tae Soup,Kim, Shin‐,Hyun,Sim, Jae Young,Lim, Jong‐,Min,Yang, Seung‐,Man WILEY‐VCH Verlag 2010 Advanced Materials Vol.22 No.40
<P><B>Dynamic modulation of photonic bandgaps</B> in crystalline colloidal arrays is achieved by application of electric field. Highly charged polystyrene particles spontaneously create the crystal lattice, which is compressed or relaxed under external electric field by electrokinetic force. As a result, structural color of colloidal crystals as a photonic bandgap can be tuned or fixed with unprecedentedly fast and precise manner. </P>
Babu, Bathula,Akkinepally, Bhargav,Shim, Jaesool,Yoo, Kisoo Elsevier 2019 CERAMICS INTERNATIONAL Vol.45 No.12
<P><B>Abstract</B></P> <P>Graphitic carbon nitride (g-C<SUB>3</SUB>N<SUB>4</SUB>) has attracted increasing interest as a visible-light-active photocatalyst. In this study, saddle-curl-edge-like g-C<SUB>3</SUB>N<SUB>4</SUB> nanosheets were prepared using a pellet presser (referred to as g-CN P nanosheets). Urea was used as the precursor for the preparation of g-C<SUB>3</SUB>N<SUB>4</SUB>. Thermal polymerization of urea in a pellet form significantly affected the properties of g-C<SUB>3</SUB>N<SUB>4</SUB>. Systematic investigations were performed, and the results for the modified g-C<SUB>3</SUB>N<SUB>4</SUB> nanosheets are presented herein. These results were compared with those for pristine g-C<SUB>3</SUB>N<SUB>4</SUB> to identify the factors that affected the fundamental properties. X-ray diffraction analysis and high-resolution transmission electron microscopy revealed a crystallinity improvement in the g-CN P nanosheets. Fourier-transform infrared spectroscopy provided clear information regarding the fundamental modes of g-C<SUB>3</SUB>N<SUB>4</SUB>, and X-ray photoelectron spectroscopy (XPS) peak-fitting investigations revealed the variations of C and N in detail. The light-harvesting property and separation efficiency of the photogenerated charge carriers were examined via optical absorption and photoluminescence studies. The valence band edge and conduction band edge potentials were calculated using XPS, and the results indicated a significant reduction in the bandgap for the g-CN P nanosheets. The Brunauer–Emmett–Teller surface area increased for the g-CN P nanosheets. The photocatalytic degradation performance of the g-CN P nanosheets was tested by applying a potential and using the classical dye Rhodamine B (RhB). The RhB dye solution was almost completely degraded within 28 min. The rate constant of the g-CN P nanosheets was increased by a factor of 3.8 compared with the pristine g-C<SUB>3</SUB>N<SUB>4</SUB> nanosheets. The high crystallinity, enhanced light absorption, reduced bandgap, and increased surface area of the saddle-curl-edge-like morphology boosted the photocatalytic performance of the g-CN P nanosheets.</P>
한용운,이의진,박종남,문두경 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Organic-Inorganic hybrid solar cells are currently attracting a great attention due to ease of fabrication and potential of flexible device based on properties of polymers and some inorganic semiconductors. Among them, quantum dots (QDs) is attractive inorganic semiconductors for modified photoactive layer because of their broad light absorption property, size-dependent optical, electrical properties. Among QDs, size-distributed QDs have recently received attention for their ability to control bandgap energy be favored to energy transfer from QDs to polymers. In this study, hybrid solar cells with polymer and two size-distributed QDs were fabricated via solution process. When two size-distributed QDs introduced in photoactive layer, they absorbed near-ultraviolet and visible wavelength, and transferred photon energy to polymers with high quantum yield. As a result, photovoltaic performance was improved by increased Jsc, FF.