土壤的中红外光声光谱研究

红外光声光谱是基于光声理论的新型数据采集方式,与传统红外光谱相比,其吸收系数大,适合高吸收和高散射的土壤分析。以中国三种典型土壤为试验材料,研究了这三种土壤(红壤,潮土和水稻土)的中红外光声光谱特征。结果表明,土壤的中红外光声光谱的测定快速方便,土壤样品不需前处理,光谱吸收值适中,具有更丰富的吸收,且土壤主要组成成分的中红外光声光谱也具有明显不同的吸收特征,因此中红外光声光谱能更好地适用于土壤分析;利用主成分分析处理土壤中红外光声光谱时,第1和第2主成分包含了光谱98.17%的信息;利用这两个主成分作二维散点分布图,结果表明该分布能对这三种土壤进行有效分类,这为土壤鉴定提供了快捷的新手段,并使中红外光声光谱在进一步的土壤定量分析中将具有潜在的应用前景。     

光声光谱在纤维样品分析中的应用

本文通过不同状态纤维样品的红外光声光谱的比较以及同一样品的红外光声光谱与红外光谱的比较表明：红外光声光谱用于纤维样品的分析，与红外光谱相比具有简单快速，分辨率好，信噪比高等优点，是研究纤维样品很好的分析手段。     

基于中红外光声光谱的聚合物包膜控释肥料养分释放曲线预测

以聚丙烯酸酯类系列水基聚合物包膜控释肥料为样品,测定了包膜肥料养分的释放曲线并原位测定了肥料包膜的中红外光声光谱,分析了不同肥料的养分释放曲线以及不同包膜材料的红外光声光谱特征;采用广义回归神经网络模型(GRNN),以肥料包膜红外光声光谱的主成分作为GRNN模型的输入层,并以包膜肥料养分释放曲线为输出层,构建了预测养分释放曲线的GRNN模型。结果表明,GRNN模型能快速有效地预测包膜肥料养分释放曲线,其预测相关系数(R2)达0.93以上;包膜的探测深度明显影响释放曲线的预测误差,最小预测误差为7.14%,平均为10.28%,且基于包膜表层红外光声光谱的预测误差最小。因此,结合GRNN模型,红外光声光谱可为包膜肥料养分释放曲线的快速预测提供新手段。     

两种卷柏科药用蕨类植物的红外光谱分析研究

本文首次利用傅里叶红外光谱对翠云草全草和兖州卷柏叶、茎及根的红外光谱图进行了对比研究。结果表明:由于它们所含的化学成分不同和相对含量的差异,其红外光谱的吸收峰的位置和强度均有不同,它们具有各自的特征谱,为药用蕨类植物鉴定提供了科学依据。     

石椒草和夏枯草的红外光谱

石椒草和夏枯草是两味典型的中草药材,它们都是清凉药,都是双子叶草本植物。采用傅里叶变换红外光谱法,直接、快速、准确地测定石椒草和夏枯草的红外光谱图,分析比较了2个样品在红外光谱图上的异同。石椒草和夏枯草的红外光谱的部分特征峰与其疗效有着直接关系：石椒草和夏枯草在1727cm-1附近均有吸收峰,说明石椒草和夏枯草均有杀菌抗病毒的功效;石椒草在1378、1251cm-1附近有吸收峰,说明石椒草有活血化瘀、抗炎抑菌的功效。通过分析红外光谱,为石椒草和夏枯草的识别、鉴定和药理分析提供了一定的科学依据。     

桑叶的红外光谱和紫外光谱研究

桑叶为药食两用的原料,具有降血糖、降血压、降血脂、延缓衰老等多种保健功效。本文首先采用了傅立叶变换红外光谱法直接、快速、准确地测定了桑叶的红外光谱图,根据桑叶的峰位,我们可以推断出桑叶可能含有醇、酚、烷烃、烯、蛋白质和多糖等化学成分;然后进行了紫外光谱分析及红外光谱和紫外光谱的对比分析,其结论为桑叶的识别、鉴定和药理分析提供了一定的科学依据。     

基于共振型高灵敏度光声光谱技术探测痕量乙炔气体浓度

乙炔气体作为判断变压器运行状态的一种故障气体,其浓度的高低反映了变压器的运行状况,因此对其浓度的探测在变压器的维护中具有重要意义。为了准确探测变压器运行过程中产生的乙炔气体浓度,为变压器的维护提供技术参数,针对基于DFB激光器的共振型光声光谱技术痕量乙炔气体检测技术开展研究,对传统的光声光谱探测系统进行改进。根据光声光谱技术的理论可知,光声信号的强度与入射激光的功率成正比,所以在光声池的出射窗口采用一个平面反射镜将红外光再次反射到光声池中以增加入射光功率,增强光声信号强度,进一步提高了光声系统的探测灵敏度。通过一定浓度的乙炔气体在不同调制频率和不同调制深度下光声信号强度的变化,确定光声探测系统的最佳调制频率和最佳调制深度为767 Hz和0.3 mV。利用不同浓度乙炔气体对系统进行标定,然后采用最小二乘法对光声信号与气体浓度进行拟合,二者具有很好的线性度。通过Allan方差计算可知,系统在平均时间达到200 s时,能够达到最低探测极限浓度。实验表明,在一个大气压下,积分时间为10 ms时,改进后的共振型光声光谱探测系统对乙炔气体的最低探测极限浓度达到了0.3 μL·L-1。还将小波去噪技术引入到低浓度下乙炔气体的光声信号处理中,有效消除了低浓度气体光声信号中的噪声,提高了信噪比。设计的共振型光声光谱探测系统操作简单,最低探测浓度符合国标中对变压器维护过程中对乙炔气体的探测需求,在变压器维护领域具有广阔的应用前景。     

土壤碳酸钙中红外光声光谱特征及其应用

测定并分析了碳酸钙(CaCO3)的中红外光声光谱及光谱特征,利用中红外光声光谱并结合主成分回归(PCR)、偏最小二乘回归(PLSR)和人工神经网络(GRNN)三种分析方法建立回归模型,分析了土壤CaCO3的含量。结果表明CaCO3具有丰富的中红外吸收,最强吸收峰波数在1 450cm-1,且干扰少,可以作为土壤CaCO3的特征吸收峰;三种回归建模方法所建模型线性都很好,PLSR和GRNN最好,相关系数(R2)均大于0.9,PCR次之,为0.847;验证样本预测能力PLSR和PCR最佳,R2大于0.9;GRNN次之,为0.882。偏最小二乘回归在校正和预测过程中的结果都非常好,RPD值均大于3.0,具有较强的适用性。     

卓酚酮偶氮染料的合成及其光谱性质

选择卓酚酮为偶合组分,与对苯二胺为重氮组分合成偶氮染料,利用核磁共振氢谱、红外光谱、紫外光谱、荧光光谱对合成的偶氮染料进行了结构鉴定及分析,并对紫外光谱数据进行了回归分析。     

傅里叶变换红外光谱曲线的数据转换研究

为将打印纸质的傅里叶变换红外光谱图转化为数字光谱,测试了玉米黄质样品的傅里叶变换红外光谱,在光谱保存为数字光谱的同时也通过打印机打印出光谱曲线。使用扫描仪把打印出纸质的光谱转化为计算机储存的图像,对图像进行旋转调整,图像识别软件把图中的光谱曲线转换为数字光谱。对比从打印光谱中提取的数字光谱和直接保存的数字光谱,发现它们在吸收峰的位置上十分接近,最大偏差为0.85cm^-1,光谱的相关系数达到99.78%。研究表明该方法可以快速准确的把打印光谱图转换为数字光谱,为从老式傅里叶变换红外光谱仪的测试结果中获得数字光谱提供了一种便捷的方法。     

Broadly tunable quantum cascade laser in cantilever-enhanced photoacoustic infrared spectroscopy of solids

An external cavity quantum cascade laser (EC-QCL) is applied in the photoacoustic detection of solid samples. The EC-QCL used has a broad tuning range of 676 cm^?1 (970–1,646 cm^?1) in the mid-infrared region, which enables accurate broadband spectroscopy of large molecules. The high spectral power density of the EC-QCL is combined with an extremely sensitive optical cantilever microphone of the photoacoustic detector to achieve an ultimate sensitivity. The carbon black, polyethylene, and hair fiber samples were measured with the EC-QCL photoacoustic detection using electrical amplitude modulation to demonstrate the possibilities of the setup. The same measurements were repeated with a Fourier transform infrared (FTIR) spectrometer combined with a photoacoustic detector for a comparison. The EC-QCL photoacoustic setup yielded roughly a decade better signal-to-noise ratios than the FTIR setup with the same measurement time.     

Structure Elucidation of Textile Fabrics by Fourier Transform Infrared Photoacoustic Spectroscopy

A photoacoustic detection system mainly based on a Fourier transform infrared spectrometer has been constructed and some tentative evaluations of its performances have been made. Infrared photoacoustic spectra of cotton and nylon cloths have been obtained without troublesome sample preparations which are necessary in conventional infrared spectrometry. It can be said that the Fourier transform infrared photoacoustic spectroscopy is useful for the structure elucidation of organic polymers.     

Recent applications of FT-IR/PAS studies in catalysis

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) is one of the main IR techniques which successfully can be applied in catalysis research. There will be presented recent examples of this spectroscopic technique application.     

Infrared photoacoustic spectroscopy in catalysis and surface science

The analysis of solid samples can often be a difficult problem for the researchers dealing with infrared (IR) spectroscopy. In conventional absorption spectroscopy the measurement of absorption is transferred to that of the radiation transmitted through the sample. Three methods stand out as being more suitable for studying solid materials. These methods are: diffuse reflectance (DR), photoacoustic spectroscopy (PAS), and Fourier transform (FT) Raman. All three methods require little or no sample preparation, and therefore are ideal for the samples that may change during the preparation as mineral oil mulls or KBr disks. In the case of PAS, the adsorbed radiation is determined directly via its heat and hence the sound produced in the sample. Fourier transform infrared PAS (FT-IR/PAS) is one of the main IR techniques which can be successfully applied in catalysis and surface science research. Recent examples of this spectroscopic technique application will be presented.     

Absolute line intensities in the ν1 + 3ν3 band of 12C2H2 by laser photoacoustic spectroscopy and Fourier transform spectroscopy

Line intensities and self-broadening coefficients in the ν₁ + 3ν₃ band of ¹²C₂H₂ near 0.8 μm at room temperature were measured by means of both laser photoacoustic and Fourier transform spectroscopy. An experimental protocol has been developed to obtain absolute intensities from the photoacoustic measurements. Namely, the spectrometer was calibrated using water vapour line intensities available in Hitran 1996 [L. S. Rothman et al. (1998) J. quant. Spectrosc. Radiat. Transfer, 60, 665–710]. These photoacoustic line intensities were found to be on average 5% higher than corresponding measurements performed using Fourier transform spectroscopy, the accuracy of the latter being estimated to better than 4%. The accuracy of the photoacoustic intensities is discussed. Previous results from the literature [F. Herregodts, D. Hurtmans, J. Vander Auwera, and M. Herman (1999) J. chem. Phys., 111, 7954—7960] are revised.     

Infrared spectroscopy of intraband transitions in Ge/Si quantum dot superlattices

We report the study of infrared spectroscopy of intraband transitions in Ge/Si quantum dot superlattices. The superlattices, which were grown on (001) oriented Si substrates by a solid source molecular beam epitaxy system, are composed mainly of 20 or 30 periods of Ge dot layers and Si spacer films. The structural properties of them and of the uncapped Ge dots grown on the surfaces of some of them were tested by cross-sectional transmission electron and atomic force microscopes, respectively. It is found that the Ge quantum dots have flat lens-like shapes. Infrared absorption signals peaking in the mid-infrared range were observed using Fourier transform infrared and Raman scattering spectroscopy techniques. Experimental and theoretical analysis suggests that the mid-infrared response be attributed to intraband transitions within the valence band of the Ge quantum dots in the superlattices. The fact that the intraband absorption is strongly polarized along the growth axis of the superlattices signifies that the Ge quantum dots with flat lens-like shapes perform as Ge/Si-based quantum wells. This study demonstrates the application potential of these kinds of Ge/Si quantum dot superlattices for developing mid-infrared photodetectors.     

健康人体乳腺傅里叶变换红外光谱特征参数分析

通过应用傅里叶变换红外光谱仪(FTIR)的中红外光导纤维并联合衰减全反射探头(ATR)对招募的200名女性健康志愿者的右侧乳腺外上限部位皮肤进行扫描采集相应的傅里叶变换红外光谱,由此共获取200条正常人体乳腺的傅里叶变换红外光谱图。进一步对所得的200条正常人体乳腺傅里叶变换红外光谱图中与脱氧核糖核酸、核糖核酸、蛋白质、脂类、糖类等生物化学成分相关的12条特征谱带进行分析研究,并对这些特征谱带的峰位(P)、峰强(I)、半高宽(F)等36个特征性红外光谱参数进行统计学分析,同时计算相应特征红外光谱参数的90%正常参考值范围、均值、标准差等数值。研究结果首次对正常人体乳腺傅里叶变换红外光谱图相关特征光谱参数的数据建立了正常参考范围,同时为傅里叶变换红外光谱技术进一步实现其在乳腺良恶性疾病诊断方面无创、快速、高效的特有临床应用价值提供相应的理论依据。     

Application of quantum cascade lasers to trace gas analysis

Quantum cascade (QC) lasers are virtually ideal mid-infrared sources for trace gas monitoring. They can be fabricated to operate at any of a very wide range of wavelengths from ∼ 3 μm to ∼ 24 μm. Seizing the opportunity presented by mid-infrared QC lasers, several groups world-wide are actively applying them to trace gas sensing. Real world applications include environmental monitoring, industrial process control and biomedical diagnostics. In our laboratory we have explored the use of several methods for carrying out absorption spectroscopy with these sources, which include multipass absorption spectroscopy, cavity ring down spectroscopy (CRDS), integrated cavity output spectroscopy (ICOS), and quartz-enhanced photoacoustic spectroscopy (QEPAS). PACS 42.62.Fi; 42.62.Be; 07.88.+y; 33.20.Ea