Newsletter No. 444

444 • 4.10.2014 5 Professor Yu has been working on materials with environmental applications since 1995. But it was only recently that he and one of his doctoral students, Feng Wang , turned their attention to red phosphorous. They were examining a large group of elements that can act as semiconductors, a prerequisite for acting as a photocatalyst. The key finding was that red phosphorous can act as a semiconductor, a property that other researchers had not recognized. The conventional wisdom was that red phosphorus was really only useful as an insulator. The discovery came as a shock to Professor Yu, a chemistry professor who is also the head of United College at CUHK. He and his student double and triple checked the results. ‘It was a very exciting development—we were surprised by its photocatalytic properties,’ Professor Yu says. ‘That had never been reported for a single element. That’s as simple as you can get.’ Then Professor Yu worked with a colleague who specializes in theoretical calculations to explain why and how the element acts as a photocatalyst. Now Professor Yu and his team are experimenting with various crystal forms of red phosphorous, since different crystals vary in their effectiveness in generating hydrogen. A Japanese scientist, Akira Fujishima , performed the earliest work on splitting hydrogen out of water. He discovered that titanium dioxide could produce the gas, findings reported in Nature in 1972. But the compound is more difficult to produce than red phosphorous, and also requires ultraviolet light to break apart water molecules. Only around four per cent of regular sunlight is UV, so titanium dioxide requires artificial light to be effective. By contrast, red phosphorous works across the spectrum of natural sunlight, making it ideal for use in the generation of clean power. The light acts as an irradiation source that stimulates the catalyst and induces chemical reactions. Professor Yu’s water-splitting process functions at room temperature, with the phosphorous separating the individual elements in H 2 O. Hydrogen has a very high fuel capacity, meaning it creates more energy than any other chemical fuel. Unlike petrol-based fuels, there’s no greenhouse-gas byproduct when it burns, with only water left at the end of the reaction. Professor Yu’s research has been some of the most ground- breaking in the world, in terms of recognition by his peers. Hemade the ranks of the ‘World’sMost Influential Scientific Minds’ in 2014, as compiled by Reuters, who rated him as one of the most-cited researchers in the field of materials science over the last 11 years. His research put him in the top one per cent of academics in his field in terms of citations over that time frame. Still, it will be some time before red phosphorus can be used to produce energy for commercial or industrial applications. The material is less efficient than traditional photocatalysts, and the amount of hydrogen it can produce is currently very small. The prevalence of fossil fuels has negated the need for investing in the technology necessary to bring photocatalysts to a commercial scale. Even conventional solar power is considerably more efficient. But with a greater emphasis on the environmental degradation that traditional fuels cause, the thinking may change. Inspired by Professor Yu, another member of his group has uncovered a way to use other elements to generate hydrogen from water. The research associate, Dr. Gang Liu , is now honing the process at the Institute of Metal Research in Shenyang. ‘The final goal is to develop an environmentally friendly way to generate clean fuel,’ Professor Yu says. ‘We hope to offer some possible solutions.’ 向「123456」宣戰 （下） 現今科技公司競相推出新方法，試圖取代密碼 保護的方式，可能不久，我們就有更安全和方便 的方法。但淘汰密碼後，我們會用甚麼？ 許多公司在研究以生物特徵取代密碼。在眾多 用於識別的生物特徵中，最為人熟悉的是指 紋。你每次離開或返回香港，以 e- 道辦理出入 境手續，就使用了這種科技。 有些人認為流動裝置大行其道，令生物特徵認 證變得更方便，有助提高資訊安全。蘋果公司 已在新型號智能電話加入指紋感應器，其他可 用於辨識的生物特徵還有掌紋、耳紋、瞳孔、聲 音和臉孔等。本刊前兩期曾報道，本校信息工 程學系和電子工程學系研究隊伍開發的人面識 別系統，不管光暗變化和拍攝角度，都能達到 99.15%的識別率，堪稱世上最準確。中大在這 方面擁有領先技術。 放眼更遠的未來，心跳、血管分布和步態都是有 可能利用的生物特徵。加州大學的研究人員則 提出更前衞的想法，他們正在研究以腦電波來 識別不同的人，據說準確度達到99%。 識別這些生物特徵，無需科幻電影中那些尖端設備。你 的口袋中已有必需的裝置，因為現今的智能電話擁有多 種功能強大的感應器，如加速計、陀螺儀、觸控屏幕、麥 克風、攝影機。 生物特徵看來有望取代現在的用戶名稱和密碼認證，但 這項科技也不是萬無一失。例如，製作精良的假指紋可以 騙過指紋掃瞄器。廣泛使用生物特徵技術也令人擔心私 隱問題，有些公司的職員已不願向公司呈交指紋。另外， 要是智能電話被偷呢？要是外國情報組織想蒐集這些資 料呢？畢竟，改密碼容易，要改臉孔和手指頭，可不是按 幾個鍵那麼簡單。 字裏科技 Tech Talks War on ‘123456’ (Part II) As technology companies are rushing to provide alternatives to the method of password protection, we may have more secure and convenient solutions to passwords before long. What will we use when we kill passwords? Many companies are exploring the possibilities of using biometrics to replace passwords. Fingerprints are the most well-known biometric identifier. You use this technology every time you leave or return to Hong Kong by using an e-Channel for immigration clearance. Some analysts suggest that the proliferation of mobile devices can improve security by making it easier to use biometric authentication. Apple has made an early stab at this technology by embedding a fingerprint reader in its new smartphone. Other biometric data include palm prints, ear prints, irises, voices, faces. As reported by the Newsletter earlier, CUHK is one of those at the leading edge of this area. The facial recognition system developed by the research team from our Department of Information Engineering and the Department of Electronic Engineering is said to have achieved the highest accuracy rate (99.15%) in the world, regardless of changes in lighting and camera angles. Looking further into the future, heartbeat, vein patterns, and gait are other possible biometric features that can be used. Researchers at the University of California, Berkeley, may offer a more futuristic solution. They are studying the use of brain waves as authentication and were reportedly able to distinguish between different people with 99% accuracy. You don’t need some fancy equipment in sci-fi movies to detect these biometric data. With smartphones featuring powerful sensors like accelerometers, gyros, touchscreens, microphones, cameras, the necessary device is already in your pocket. While biometrics seem to be a promising alternative to current username and password authentication, the technology is not perfect. For example, fingerprint scanners can be fooled by sophisticated fake fingerprints. There are privacy concerns about the widespread use of biometrics. Some companies have found employees resistant to handing over their fingerprints. And what if your smartphone is stolen? What if some foreign intelligence agencies decide to collect them? After all, it is easy to change your password, but changing your faces and thumbs requires more than just a few keystrokes.