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量子点让二极管发出白光的疑问  发帖心情 Post By:2005-10-27 14:26:24 [只看该作者]

量子点让二极管发出白光的疑问,这个技术可行马

拿一个发着强烈蓝光的二极管(LED),用一层薄薄的名为量子点的特殊精微细珠包裹起来。你就做成了一盏能取代传统白炽灯泡的新式灯。
这种合二为一的发光二极管发出带有轻微黄色的柔柔的白光,效果和白炽灯一样。
到目前为止,通过改变单个纳米晶体的尺寸,量子点只能简单地发射出十二种不同区段的色光。这只适合专门用于生物医学领域中的荧光标记。
但是美国Vanderbilt大学的一位研究生迈克尔·鲍尔斯在一次实验中偶然发现了一种混合“涂料”,涂在发光二极管灯上后,原本发蓝光的灯会像普通白炽灯泡那样发出白光。从最新一期出版的《美国化学学会杂志》网络版的“白光从硒化镉纳米晶体中发射出来”的报道可以看出,他们的研究发现也是偶然间得到的。

过去的几年中,发光二极管在生态位研究领域已经开始替代白炽灯和荧光灯。虽然这些固态光源在电子学中用了几十年,但最近的研究进展才使他们的应用领域扩展到建筑照明、交通照明、闪光灯和阅读灯。
虽然发光二极管比普通灯光昂贵许多,但发光二极管每瓦产生的光是白炽灯的两倍,寿命是50,000小时,相当于60瓦灯泡的50倍。而且,它们非常结实,不易破损。由于发光二极管能以类似计算机芯片设计的方式生产出来,它们的成本慢慢降下来。
到1993年,发光二极管只能发红光、绿光、和黄光。不久,日本化学家研制出发蓝光的发光二极管。生产厂家把发蓝光的二极管与红光和绿光二极管组合起来,或给发蓝光的二极管加上黄色的无机发光材料,二极管就发射出白光,从而开辟了许多新的应用领域。然而,这些发光二极管只产生冷的带有蓝色光晕的白光。
迈克尔·鲍尔斯说,相比之下,发射白光的量子点在可见光波段产生平和的光波分布,发射出柔和的、略带黄色光晕的白光。











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  发帖心情 Post By:2005-10-27 14:28:21 [只看该作者]

Take an LED that produces intense, blue light. Coat it with a thin layer of special microscopic beads called quantum dots. And you have what could become the successor to the venerable light bulb.

The resulting hybrid LED gives off a warm white light with a slightly yellow cast, similar to that of the incandescent lamp.

Until now quantum dots have been known primarily for their ability to produce a dozen different distinct colors of light simply by varying the size of the individual nanocrystals: a capability particularly suited to fluorescent labeling in biomedical applications.

But chemists at Vanderbilt University discovered a way to make quantum dots spontaneously produce broad-spectrum white light. The report of their discovery, which happened by accident, appears in the communication “White-light Emission from Magic-Sized Cadmium Selenide Nanocrystals” published online October 18 by the Journal of the American Chemical Society.

In the last few years, LEDs (short for light emitting diodes) have begun replacing incandescent and fluorescent lights in a number of niche applications. Although these solid-state lights have been used for decades in consumer electronics, recent technological advances have allowed them to spread into areas like architectural lighting, traffic lights, flashlights and reading lights.

Although they are considerably more expensive than ordinary lights, they are capable of producing about twice as much light per watt as incandescent bulbs; they last up to 50,000 hours or 50 times as long as a 60-watt bulb; and, they are very tough and hard to break. Because they are made in a fashion similar to computer chips, the cost of LEDs has been dropping steadily.

Until 1993 LEDs could only produce red, green and yellow light. But then Nichia Chemical of Japan figured out how to produce blue LEDs. By combining blue LEDs with red and green LEDs – or adding a yellow phosphor to blue LEDs – manufacturers were able create white light, which opened up a number of new applications. However, these LEDs tend to produce white light with a cool, bluish tinge.

The white-light quantum dots, by contrast, produce a smoother distribution of wavelengths in the visible spectrum with a slightly warmer, slightly more yellow tint, reports Michael Bowers, the graduate student who made the quantum dots and discovered their unusual property.



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  发帖心情 Post By:2005-10-27 14:28:35 [只看该作者]

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  发帖心情 Post By:2005-11-1 12:42:10 [只看该作者]

能否提供JACS的原文?从这条新闻的内容来看,他的方案与现在流行的蓝色芯片加黄色荧光粉的方案没有什么本质区别,也就是把部分蓝光转换成黄光再与剩余的部分蓝光合成白光。如果这样,那么跟"量子点"关系就不太大。所谓蓝色光晕和黄色光晕只是色温调节的问题,这可以通过添加别的荧光粉来解决。

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