翻译1环境化学实验教学的案例研究.doc

Creative Education2012. Vol.3, No.4, 600-602Published Online August 2012 in SciRes (http:/www.SciRP.org/journal/ce)DOI:10.4236/ce.2012.34088Teaching an Environmental Chemistry ExperimentACase StudySimple Test for Measuring the Emission Spectra of LampsLin Zhang, Long Chen, Mei Xiao, Feng Wu*, Nansheng DengDepartment of Environmental Science, School of Resources and Environmental Science,Wuhan University, Wuhan, ChinaEmail: *Received May 24th 2012; revised June 30th, 2012; accepted July 10th, 2012Here we present the significance, content, results, and teaching effect of a selective self-design experi-menta simple test for measuring the emission spectra of artificial light sources, and discuss its function and potential problems in an environmental chemistry class for undergraduate students. Also, we propose several ways to reform experimental teaching, and provide references to other experimental courses.Keywords: Self-Design Experiment; Spectrophotometer; Spectrum; High Pressure Mercury Lamp;Deuterium LampIntroductionLaboratory courses are a crucial component of a National Quality Course (NQC)Environmental Chemistry. In this re-search group, we believe that the construction and reform of this subject is important, and our core task is to develop teach-ing quality, improve students experimental abilities, promote motivation and enthusiasm, inspire a spirit of scientific explora-tion and creativity, thus enabling students to conduct scientific research and solve practical problems.The aim of the NQC is to settle various problems regarding the construction of course content, and we as NQC instructors manage and design the laboratory teaching ourselves, and in-creasingly self-design comprehensive experiments. We offer opportunities for students to gain knowledge, develop their re-search abilities, and enhance their independence. Meanwhile, we reform the laboratory teaching methods, and encourage dis-cussion and an active class atmosphere, to inspire students brainstorming abilities, and to enhance the teaching effect.In the following casea simple test for a lamp emission spectrum, we briefly illustrate how students research abilities are clearly improved through designing an experiment.Objective of This StudyUltraviolet and visible (UV-Vis) spectrophotometry is one of the most practical and functional tools in quantitative analysis, and a UV-Vis spectrophotometer (UVVS) is one of the most commonly used instruments in laboratory teaching for envi-ronmental major undergraduates. Therefore, most instructors will regard this as critical. While in laboratory class, the pur-pose of setting up this experiment is to: make students learn about the inner structure and working principle of a UVVS through disassembling it, e.g. the characteristics of emission spectra of a high pressure mercury lamp (HPML) and deute-*Corresponding author.rium lamp (DL) using remolded UVVS; increase their theoreti-cal knowledge about optics via determining emission spectra of several artificial light sources; promote their comprehensive scientific research ability and the ability to design experiments by composing an experimental plan, accomplishing it and sub-mitting the final result in the form of an essay.Experimental PrincipleThe UVVS consists of four major parts: a light source, a beam splitting system, an absorption cell, and a detection sys- tem (Figure 1). In order to determine the illumination intensity of our target lamps (HPML and DL), in different wavelengths, we need to utilize the beam splitting system to split the con-tinuous spectra, thus fully taking advantage of regular UVVS. Therefore, we only have to alter the light source for other sources to be examined, and after adjusting the wavelength we can obtain the transmissivity (T) for different wavelengths.In this experiment, we need a baseline to quantify the relative emission intensity. Therefore, the value of T for a specific wavelength has to be fixed to 0%, in which there might be lu-minance. The relative intensity in other wavelengths can be quantified by subsequent comparison. Similarly, we can also fix the value of T of a specific wavelength to 100%, and then perform the same process described above. Given the fact that there is a glass cover on the mercury lamp and there is no transmission in wavelengths less than 280 nm, 280 nm was chosen as the baseline and fixed to 0%, and we determined the spectra up to 800 nm. However, for the DL, the cover is made of quartz, thus having lower absorption limit (160 nm). There-fore we should set 160 nm as the baseline, but because the shortest wavelength we can use in the UVVS is 180 nm, we set 180 nm as the baseline, and also continued up to 800 nm.Owing to the limits of the laboratory, we could not evacuate the absorption cell. However, in fact, the impact of air is negli-gible.600Copyright 2012 SciRes.L. ZHANG ET AL.Figure 1.Inner structure of a UVVS.InstrumentsInstruments included the UV-9100 UVVS, an HPML, an iron support, a screwdriver, nipper pliers and a wrench. The DL used was in the UVVS itself.Experimental MethodStudy of the DL Emission SpectrumBefore determination, the UVVS was switched on and the DL was preheated for 15 min. Then we put the lid on, adjusted the wavelength to 180 nm, and made T = 0%. The wavelength interval was preliminarily set at 10 nm, but when it approached the peak, 2 nm was more appropriate. Because the UV-9100 UVVS cannot achieve more accurate performance, and larger intervals cannot precisely portray the spectrum. The wavelength was altered and T was recorded until 800 nm was reached. Af-ter the experiment was completed, both the DL and UVVS were switched off, and the power cable was unplugged.Study of the HPML Emission SpectrumFor the sake of safety, the power cable was unplugged. To eliminate the effect of DL and the tungsten lamp, they had to be removed before the experiment. The outer cover was lifted, and the top lid on the lamp house was removed. Then the three wires connected to the DL were screwed off, clamped by the nipper pliers, then the tightened screws were unscrewed using a screwdriver. Then the DL could be extracted from UVVS. The tungsten lamp was removed using the same method. Then the outer cover was replaced, and the dam-board in front of the light sources was removed. With the iron support, the HPML was fixed opposite the optical channel. Then the position of HPML was adjusted to focus its radiation on the optical col-lector. After 15 min preheating the HPML, the UVVS was switched on. For this experiment, 250 nm was selected as the baseline, and 2 nm was chosen as the wavelength interval until 800 nm was reached. After the experiment the UVVS was re-stored, and the HPML was removed.ResultsThe data are presented respectively for the emission spectra of the HPML and DL. To analyze their accuracy, they were compared with standard emission spectra (Emission Spectra ofCopyright 2012 SciRes.mercury light, deuterium light and tungsten lamp. Available online) in detail. All the spectra are presented in Figures 2 and 3.DiscussionCoincidence Analysis between Standard and Experimental SpectraBy comparison with standard spectra, we found the experi-mental spectra of both HPML and DL coincided with them significantly. In particular, the emission peaks of HPML at 404 nm, 436 nm, 546 nm and 577 - 579 nm were all delineated. Moreover, the main peak at 365 nm was accurately depicted. However, the standard spectrum of the DL is far more complex than that of the HPML, since the spectral bandwidth of its slit is comparatively tiny, and can scan adjacent wavelengths. There-fore, to clearly demonstrate the distinction, this standard spec-trum was fitted to a modified and smooth curve, in which the peaks were in good agreement with the experimental spectrum, as shown.Difference Analysis between HPML and DL Emission SpectraObvious differences in emission spectra can be observedExperimental Spectrum16Standard Spectrum1412108T6420 200 300 400 500 600 700 800 wavelength (nm)Figure 2.Emission spectra of DL.Experimental SpectrumStandard Spectrum1510T50 300 400 500 600 700 800 wavelength (nm)Figure 3.Emission spectra of HPML.601L. ZHANG ET AL.between the HPML and DLthe spectrum of the former is scattered, while the spectrum of the latter is more continuous. This is because the irradiation of the mercury lamp depends on atoms. After they absorb energy from the high voltage, the electrons can move to higher energy levels, and this process is called transition. Because higher energy levels result in unsta-ble states, some electrons will return to lower energy levels, releasing electromagnetic radiation. Moreover, with increasing mercury vapor pressure, the atomic collision becomes more frequent and intense, so the emission spectra will be more and more continuous. In fact, the emission spectrum of an ultra high pressure mercury lamp is almost band spectrum. However, a DL can radiate a continuous spectrum in the ultraviolet band. That is why the DL can be the ultraviolet light source for a UVVS.Effect Analysis of This Experimental MethodWith the widespread use of various lamps and developments in lamp technology, nowadays the life span, energy saving performance, light color etc. are greatly improved. Sometimes, the absolute calibration of the spectral irradiance, especially in modern research, is necessary. Tang et al. (Tang & Li, 1996) has studied the absolute calibration in short wave areas of the DL. Huang et al. (Huang, Wang, Zhang, Lin, & Li, 2007) once used a DL to standardize the irradiance in wavelengths between 200 and 300 nm, while Wang et al. (Wang & Zhu, 1992) dis-cussed methods to automatically collect mercury lamp spectra. Although very precise, these methods are very costly, and un-necessary for undergraduate students. However, in this experi-ment, we determined the spectra by comparison with the base-line, and obtained relatively accurate and practical emission spectra for the HPML and DL. Therefore, using this original and cheap method, undergraduate students obtained a good command of the characteristics of emission spectra of several artificial light sources, and how to explore scientifically and practically.ConclusionThis self-design experiment system fully takes advantage of a UVVS in the laboratory setting, utilizing its basic principle to determine the emission spectra of a HPML and DL. The results fit very well with standard spectra. The reason for lack of de-tailed spectral characteristics of DL is because the spectral bandwidth is too large to achieve a more detailed determination. Compared with absolution calibration, which is prevalent now-adays, this method is quite simple and inexpensive. In addition, it can enhance students understanding of UVVS, as well as the emission spectra of lamps discussed above.Implications of the StudyThis entire process is a self-design experiment. Initially, stu-dents were requested to consult the literatures through the li-brary or Internet resources, and put forward a plan after group discussions which included 10 - 12 members. Then the instruc-tor organized all the students to participate in the discussion, and each group was required to state their plan, and to reply to various questions raised by the other students. Before the ex-periment, the plan was recomposed accordingly. In addition, an essay was required for submission after the experiment.This is the 5th year of this self-design experiment series. We aimed to perfect these self-design experiments so that students can display their creativity, actively participate and boost mo-rale, enjoy the sense of success, and share their skills with oth-ers. However, some problems were inevitable. First, laboratory instruments, reagents and funds are limited, and sometimes cannot fulfill the students ideas. Second, due to the lack of laboratory class hours, we could not conduct some time-con-suming and complicated experiments, which may have facili-tated their subsequent studies. According to this experience, we will re-schedule class time distribution for basic, comprehend-sive and self-design experiments, leaving more time for the self-design series. Beyond that, more channels for funds, in-struments and reagents will be definitely explored.In conclusion, time has shown the benefits of self-design ex-periments. Not only can the students attain increased creativity and comprehensive knowledge, but also attain a solid founda-tion for their future success.REFERENCESEmission spectra of mercury light, deuterium light and tungsten lamp. /result/shtml/17427.shtmlHuang, Y., Wang, S. R., Zhang, Z. D., Lin, G. Y., & Li, F. T. (2007). Calibration of 200 - 300 nm spectral irradiance using 150 W deute-rium lamp. Optics and Precision Engineering, 15, 1215-1219.Tang, Y. G., & Li, F. T. (1996). Absolute calibration of the spectral irradiance of quartz window deuterium lamp in 200 - 350 nm. Spec-troscopy and Spectral Analysis, 16, 7-10.Wang, Q., & Zhu, Z. Q. (1992). Automatic collecting method of mer-cury lamp spectrum. Opto-Electronic Engineering, 19, 52-56.602Copyright 2012 SciRes.环境化学实验教学的案例研究测量灯的发射光谱的简单测试本文的研究课题是一个选择性的自我设计实验的简单测试测量，以及高压水银灯的发射光谱的教学效果，并探讨其功能和潜在问题的环境化学。同时，我们提出了实验教学改革的几个方面，并为其他实验课程提供参考。关键词：自行设计的实验研究；分光光度法；光谱；高压水银灯；引言环境化学实验教学是一个国家级精品课程的一个重要组成部分，在本项研究中，我们相信这一学科的建设和改革是重要的，我们的核心任务是改善高级教学质量，提高学生的动机、积极性及实验能力，激发其科学探索和创新精神，从而使学生进行科学研究能够解决实际问题。国家级精品课程的目的是解决各种问题，对于构建课程内容，我们作为国家级精品课程管理教师，。我们自己设计实验教学，为学生提供获取知识的机会，培养他们的研究能力，并提高他们的独立性。在下面的一个灯的发射光谱的简单测试的案例中，我们通过设计一个实验使学生的研究能力得到了明显的提高。研究目的紫外-可见（UV-Vis）分光光度法定量分析是最实用方法之一，与紫外可见分光光度计（uvvs）是在环境专业本科生实验教学的最常用的工具之一。因此，大多数教师会认为此方法和仪器最为关键。而在实验班，开设这个实验的姿势是：通过拆解它，使学生了解一个紫外可见分光光度计内部结构和工作原理，例如：一个高压汞灯发射谱的特性（SDBS）和氘灯（DL）使用重塑紫外可见分光光度计；通过测定几种人工光源的发射光谱，增加他们的光学理论知识；培养学生的综合科研能力和实验方案设计的能力，完成它和子铣削加工的最终呈现在此篇论文中。 实验原理该紫外可见分光光度计由三个主要部分：一个光源，一个分束系统吸收细胞，并检测sys -透射电镜（图1）。为了确定我们的目标灯的发光强度（高压汞灯和DL），在不同的波长，我们需要利用分光系统分裂的连续光谱，从而充分利用正则紫外可见分光光度计。因此，我们只需要改变其他来源进行检查和调整后的光源，波长可以得到不同波长的透射率（T）。在这个实验中，我们需要一个基线量化的相对发光强度。因此，t值为一个特定的波长是固定的0%，其中可能有路亮度。可以通过后续的量化比较的其他波长的相对强度。同样，我们也可以确定T 100%特定波长值，然后执行上述相同的过程。考虑到在水银灯玻璃罩在波长小于280纳米的无传输，280 nm作为基线和固定为0%，我们确定的光谱为800 nm。然而，为DL，盖是由石英，具有较低的吸收限（160 nm）。因此，我们应该设置160 nm作为基线，而是因为我们可以用在uvvs最短波长为180 nm，我们设置180 nm作为基线，并持续到800 nm。由于实验室的限制，我们不能将吸收细胞疏散。然而，事实上，空气的影响是可以忽略的图1。一个紫外可见分光光度计内部结构仪器工具包括一个uv-9100紫外可见分光光度计，高压汞灯，铁支架，螺丝刀，尖嘴钳子和扳手。DL用在紫外可见分光光度计本身。试验方法DL（数据传输线路）发射光谱的研究：在测定前，该紫外可见分光光度计接通和DL预热15分钟。然后我们把盖子盖上，调整至180纳米的波长，和T = 0%。初步确定的波长间隔10 nm，但当它接近峰值，2 nm更合适。因为uv-9100紫外可见分光光度计不能实现更精确的性能，和更大的间隔不能精确地描述光谱。波长的改变和T被记录到800 nm。实验完成后，双方的DL和紫外可见分光光度计被关掉，与电力电缆被拔出。高压汞灯发射光谱的研究为安全起见，电力电缆被拔出。消除DL和钨灯的作用，他们必须在实验之前取下。外盖被，在灯箱的上盖被取下。然后，三线连接到DL拧下来，用尖嘴钳夹住，然后拧紧螺钉旋开使用螺丝刀。然后，从中可以取得紫外可见分光光度计DL。钨灯是用同样的方法获取。然后外壳所取代，并在光源前挡板被取下。与铁的支持，高压汞灯是固定的相对光通道。然后高压汞灯的位置进行了调整，将其辐射在光学集电极。15分钟预热后的高压汞灯，紫外可见分光光度计打开。结果数据分别对高压汞灯和DL发射光谱：分析他们的准确性，他们（水银灯，发射光谱的氘灯、钨灯。）与标准的发射光谱进行比较详细。所有的光谱，在图2和图3。论述标准和实验光谱之间的对应分析：通过与标准谱图的比较，我们发现两个高压汞灯和DL实验光谱正好与他们显著。特别是，发射峰在404 nm处的高压汞灯，436 nm，546 nm和577 - 579 nm的划定。此外，在365 nm处的主要峰进行精确的描述。然而，该DL标准谱比的影响因素复杂得多，因为它的狭缝光谱带宽比较小，可以扫描相邻的波长。因此，清楚地表明的区别，这个标准谱拟合修正的光滑曲线，其中峰与实验谱的好协议，如图所示。高压汞灯和DL发射光谱之间的差异分析,在发射光谱中可以观察到明显的差异Experimental Spectrum16Standard Spectrum14200 300 400 500 600 700 800 wavelength (nm)图2 DL发射光谱。Experimental SpectrumStandard Spectrum300 400 500 600 700 800 wavelength (nm)图3 高压汞灯的发射光谱。在高压汞灯和DL前者的频谱分散之间，后者光谱是连续的。这是由于水银灯照射取决于原子。他们吸收从高电