{"id":189,"date":"2020-10-15T01:13:44","date_gmt":"2020-10-15T06:13:44","guid":{"rendered":"https:\/\/www.cd-bioparticles.com\/blog\/?p=189"},"modified":"2020-10-15T01:13:44","modified_gmt":"2020-10-15T06:13:44","slug":"how-quantum-dots-contribute-to-mitigate-urban-overheating","status":"publish","type":"post","link":"https:\/\/www.cd-bioparticles.com\/blog\/quantum-dots\/how-quantum-dots-contribute-to-mitigate-urban-overheating\/","title":{"rendered":"How Quantum Dots Contribute to Mitigate Urban Overheating?"},"content":{"rendered":"\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"\/blog\/wp-content\/uploads\/2020\/10\/How-Quantum-Dots-Contribute-to-Mitigate-Urban-Overheating-1-1024x683.jpg\" alt=\"\" class=\"wp-image-190\" srcset=\"\/blog\/wp-content\/uploads\/2020\/10\/How-Quantum-Dots-Contribute-to-Mitigate-Urban-Overheating-1-1024x683.jpg 1024w, \/blog\/wp-content\/uploads\/2020\/10\/How-Quantum-Dots-Contribute-to-Mitigate-Urban-Overheating-1-300x200.jpg 300w, \/blog\/wp-content\/uploads\/2020\/10\/How-Quantum-Dots-Contribute-to-Mitigate-Urban-Overheating-1-768x512.jpg 768w, \/blog\/wp-content\/uploads\/2020\/10\/How-Quantum-Dots-Contribute-to-Mitigate-Urban-Overheating-1-120x80.jpg 120w, \/blog\/wp-content\/uploads\/2020\/10\/How-Quantum-Dots-Contribute-to-Mitigate-Urban-Overheating-1.jpg 1920w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure><\/div>\n\n\n\n<p>The urban heat\nisland effect refers to the phenomenon that the temperature in the city is\nobviously higher than that in the outer suburbs. On the near-ground temperature\nmap, the temperature change in the suburbs is very small, while the urban area\nis a high-temperature area, like an island protruding from the sea. Because\nthis island represents a high-temperature urban area, it is vividly called an\nurban heat island. The urban heat island effect makes the annual average\ntemperature in the city 1\u00b0C or higher than that in the suburbs. In summer, the\ntemperature in some parts of the city is sometimes more than 6\u00b0C higher than\nthat in the suburbs. In addition, the dense and tall buildings in the city\nhinder the passage of airflow and reduce the wind speed in the city. Due to the\nurban heat island effect, a day-night opposite thermal circulation is formed\nbetween the city and the suburbs, which aggravates the extent of urban\noverheating.<\/p>\n\n\n\n<p>In\nrecent years, with the rapid development of urban construction, urban\noverheating is becoming more and more obvious. The main reasons for urban\noverheating are as follows. First, it is affected by the characteristics of the\nurban underlying surface. There are a large number of artificial structures in\nthe city, such as concrete, asphalt pavement, and various building walls, which\nchange the thermal properties of the underlying surface. These artificial\nstructures absorb heat quickly and have small heat capacity. Under the same\nsolar radiation conditions, their temperature rises faster than the natural\nunderlying surface (green space, water surface, etc.), so their surface\ntemperature is obviously higher than that of the natural underlying surface.\nAnother main reason is the influence of artificial heat sources. Factory\nproduction, transportation, and residential life all need to burn all kinds of\nfuel, emitting a lot of heat every day. In addition, the reduction of green\nspace, trees, and water bodies in cities is also a major reason. With the\ndevelopment of urbanization and the increase of urban population, the areas of\nbuildings, squares, and roads in the city increase greatly, but the green space\nand water body decrease accordingly, and thus the ability to alleviate the heat\nisland effect is weakened. Air pollution in cities is also an important reason.\nMotor vehicles, industrial production, and residents&#8217; life in the city produce\na lot of emissions such as nitrogen oxides, carbon dioxide, and dust. These\nsubstances absorb thermal radiation from the underlying surface and produce the\nGreenhouse Effect, which causes the atmosphere to warm up further. Hot weather\ncaused by urban overheating also has adverse effects on human health. Relevant\nstudies have shown that when the ambient temperature is higher than 28\u00b0C, people will feel uncomfortable; if the\ntemperature is consistently higher than 34\u00b0C,\nit can also lead to a series of diseases including the increase of the\nmorbidity and mortality of heart, cerebrovascular, and respiratory diseases.\nMoreover, the increase in temperature will accelerate the speed of\nphotochemical reaction, increasing the concentration of ozone in the\nnear-surface atmosphere, and affecting human health.<\/p>\n\n\n\n<p>To balance\nthis, several mitigation techniques are available. A common technique is to use\nreflective materials on buildings and urban structures that can reflect some of\nthe incident solar radiation back into space. Cities can also use dense green\nplants, such as building-integrated vegetation, as well as evaporation\ntechnology, solar control systems, and heat dissipation technology to direct\nexcess heat to the ground or low-temperature radiators in the sky. The\nlarge-scale application of these ideas in cities shows that it is possible to\nreduce the peak temperature by up to 2.5\u00b0C. Next-generation mitigation\ntechnologies may bring even greater reductions, up to 4\u00b0C.<\/p>\n\n\n\n<p>Samira\nGarshasbi <em>et al.<\/em> first studied the\nfluorescent cooling capacity of quantum dots as a new type of nano-fluorescent\nmaterial with tunable fluorescent cooling potential. In addition, a new\nalgorithm for accurately calculating fluorescent cooling indices is proposed,\nincluding re-emission energy (Q<sub>PL<\/sub>) and fluorescent cooling surface\ntemperature reduction potential. The results were published on <em><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0038092X20306162\">Solar\nEnergy<\/a><\/em> in August this year.<\/p>\n\n\n\n<p>They\nfound that quantum dots can be used as additives for advanced cooling coatings\n(near-infrared high reflective materials) to improve their heat dissipation\nefficiency and alleviate urban overheating. They also proposed a theoretical\nmethod to calculate the reemission energy and temperature decrease by\nphotoluminescence (PL) effect and used <a href=\"https:\/\/www.cd-bioparticles.com\/product\/cis-se-cigs-se-czts-se-quantum-dots-list-210.html\">CIS\/ZnS\nquantum dots<\/a> (a kind of nano-sized material with tunable\nfluorescence properties, purchased from CD Bioparticles) to verify the\neffectiveness of the model. The results show that the solar absorptivity of\nCIS\/ZnS quantum dots film is equal to 0.52 nm, quantum yield PL peak is 42-56%,\nindicating that the maximum heat loss of PL is 54.2 W\/m<sup>2<\/sup>, which is\nequivalent to 8.5% of the absorbed shortwave solar irradiation (285 to 3000 nm).\nIn Sydney, Australia, under two different boundary conditions, the surface\ntemperature of quantum dots with a temperature decrease due to PL effect is 2\u00b0C\nlower than that of their corresponding non-fluorescent reference samples.<\/p>\n\n\n\n<p>Professor Mat Santamouris said, &#8220;the algorithm we developed algorithm could be utilized as a reliable model to optimize fluorescent properties of QDs in the future. The proposed algorithm is a very useful tool for precise calculation of PL effect contribution in urban overheating mitigation for all other fluorescent materials.&#8221; CD Bioparticles provides non-toxic I\u2013III\u2013VI2 type CIS(Se), CIGS(Se), CZTS(Se) semiconductor quantum dots with excellent optical property, large absorption coefficient and stable performance. Our quantum dots are ideal for highly sensitive cellular imaging, photovoltaic devices, thin film solar cells, light emitting devices, and biomedical devices. <\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>Reference:<br>Garshasbi, S., Huang, S., Valenta, J., &amp; Santamouris, M. (2020). Can quantum dots help to mitigate urban overheating? An experimental and modelling study. <em>Solar Energy<\/em>, 206, 308-316. <\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>The urban heat island effect refers to the phenomenon that the temperature in the city is obviously higher than that<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[31],"tags":[49,10,50],"class_list":["post-189","post","type-post","status-publish","format-standard","hentry","category-quantum-dots","tag-cis-zns-quantum-dots","tag-quantum-dots","tag-urban-overheating"],"_links":{"self":[{"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/posts\/189","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/comments?post=189"}],"version-history":[{"count":1,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/posts\/189\/revisions"}],"predecessor-version":[{"id":191,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/posts\/189\/revisions\/191"}],"wp:attachment":[{"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/media?parent=189"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/categories?post=189"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/tags?post=189"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}