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À̹ø ¼öÁúÁ¤È ±â¼úÀº A*STARÀÇ IMRE(Institute of Materials Research and Engineering)¿¡ ±Ù¹«ÇÏ´Â He-Kuan Luo ¹× Andy Hor µîÀÇ °úÇÐÀڵ鿡 ÀÇÇØ °³¹ßµÇ¾ú´Ù. IMREÀÇ Hor(executive director)´Â º» ¿¬±¸°á°ú¿¡ ´ëÇØ, º¸ÅëÀÇ Á¶°Ç¿¡¼ ¹°·ÎºÎÅÍ À¯±â ¿À¿°¹°ÁúÀ» Á¦°ÅÇϰųª Æı«ÇÏ´Â À¯ÀÍÇÏ°í Çõ½ÅÀûÀÎ ±â¼ú·Î ¸Å¿ì ȯ¿µÇÒ ¸¸ÇÑ ¼º°ú¶ó°í Æò°¡ÇÏ¿´´Ù.
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Hor ¹× ¿¬±¸ÆÀÀº ±âÁ¸ÀÇ Ã˸Ÿ¦ °³·®Çϱ⠽ÃÀÛÇÏ¿´´Ù. SrTiO3 (strontium titanate)°ú °°Àº »ê¼Ò ±â¹ÝÀÇ ÈÇÕ¹°Àº °ß°íÇÏ°í ¾ÈÁ¤ÀûÀÌ¸ç ¹°¿¡¼ »ç¿ëÇϱ⿡ Àû´çÇϱ⠶§¹®¿¡ À¯¸ÁÇÑ Èĺ¸¹°ÁúÀÌ´Ù. ¿¬±¸ÆÀÀÇ Çõ½ÅÀûÀÎ °á°ú¹° Áß Çϳª´Â ¼Ò·®ÀÇ ±Ý¼Ó ¶õŸ´½(lanthanum)À» ÷°¡ÇÏ¿© Ã˸ÅÀÇ È°¼ºÀ» Çâ»ó½ÃÄ×´Ù´Â Á¡ÀÌ´Ù. ¶õŸ´½Àº ºÎ°¡ÀûÀ¸·Î »ç¿ëÇÒ ¼ö ÀÖ´Â ÀüÇÏ(electrical charge)¸¦ Á¦°øÇØ ÁØ´Ù.
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±×¸² 1> Au/La-SrTiO3 ¸¶ÀÌÅ©·Î½ºÇǾîÀÇ ÀüÇüÀûÀÎ Åõ°úÀüÀÚÇö¹Ì°æ »çÁø. (a) Au/La-SrTiO3 ¸¶ÀÌÅ©·Î½ºÇǾî(»ðÀԱ׸²: ´ÜÀÏ ¸¶ÀÌÅ©·Î½ºÇǾîÀÇ È®´ë¿µ»ó). (b) Au/La-SrTiO3 ¸¶ÀÌÅ©·Î½ºÇǾîÀÇ °íÇØ»óµµ Åõ°úÀüÀÚÇö¹Ì°æ ¿µ»ó ±×¸² 2> SrTiO3 »ùÇÃÀÇ ÀüÇüÀûÀÎ ÁÖ»çÀüÀÚÇö¹Ì°æ »çÁø. (a) SrTiO3 ¸¶ÀÌÅ©·Î½ºÇǾî, (b) SrTiO3 ³ª³ë°áÁ¤ ±×¸² 3> ±¤Ã˸ÅÀÛ¿ë¿¡ ´ëÇÑ Á¦¾ÈµÈ ¸ÞÄ¿´ÏÁò(RhB=rhodamine B, CB=conduction band, VB=valence band)
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A gold nanocatalyst for clear water
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This water purification technology was developed by He-Kuan Luo, Andy Hor and colleagues from the A*STAR Institute of Materials Research and Engineering (IMRE). ¡°Any innovative and benign technology that can remove or destroy organic pollutants from water under ambient conditions is highly welcome,¡± explains Hor, who is executive director of the IMRE and also affiliated with the National University of Singapore.
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Photocatalytic materials harness sunlight to create electrical charges, which provide the energy needed to drive chemical reactions in molecules attached to the catalyst¡¯s surface. In addition to decomposing harmful molecules in water, photocatalysts are used to split water into its components of oxygen and hydrogen; hydrogen can then be employed as a green energy source.
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Hor and his team set out to improve an existing catalyst. Oxygen-based compounds such as strontium titanate (SrTiO3) look promising, as they are robust and stable materials and are suitable for use in water. One of the team¡¯s innovations was to enhance its catalytic activity by adding small quantities of the metal lanthanum, which provides additional usable electrical charges.
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Catalysts also need to capture a sufficient amount of sunlight to catalyze chemical reactions. So to enable the photocatalyst to harvest more light, the scientists attached gold nanoparticles to the lanthanum-doped SrTiO3 microspheres (see image). These gold nanoparticles are enriched with electrons and hence act as antennas, concentrating light to accelerate the catalytic reaction.
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The porous structure of the microspheres results in a large surface area, as it provides more binding space for organic molecules to dock to. A single gram of the material has a surface area of about 100 square meters. ¡°The large surface area plays a critical role in achieving a good photocatalytic activity,¡± comments Luo.
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To demonstrate the efficiency of these catalysts, the researchers studied how they decomposed the dye rhodamine B in water. Within four hours of exposure to visible light 92 per cent of the dye was gone, which is much faster than conventional catalysts that lack gold nanoparticles.
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These microparticles can also be used for water splitting, says Luo. The team showed that the microparticles with gold nanoparticles performed better in water-splitting experiments than those without, further highlighting the versatility and effectiveness of these microspheres.