纳米铜粉的制备及其分散性研究

采用液相还原法制备纳米铜粉和纳米铜胶体,选用十六烷基三甲基溴化铵(CTAB)或聚乙烯吡咯烷酮(PVP)为分散剂,通过X射线衍射仪、扫描电镜对纳米铜粉进行表征,通过重力沉降法测试纳米铜胶体的稳定性。结果表明:液相还原法能够制备纯度较高的纳米铜粉;CTAB浓度为0.12 mol/L时,铜粉平均粒径最小,为20 nm,CTAB浓度为0.14 mol/L且超声粉碎20 min时,纳米铜胶体最稳定;PVP浓度为6×10^-4 mol/L时,铜粉平均粒径最小,为20 nm,PVP浓度为7×10^-4 mol/L且超声粉碎20 min时,纳米铜胶体最稳定。     

新型自组装卟啉纳米材料及其光学性质研究

在水/乙醇混合溶液体系中,利用自组装方法,使5-对磺酸基苹基-10,15,20-三苯基卟啉(TPPS1)分子聚集成功能化卟啉纳米材料.利用AFM、SEM、FE-SEM对卟啉纳米材料表面形貌性质及样品处理条件进行了研究:可获得50～70nm不同粒径的卟啉纳米材料;通过控制、调节样品的处理条件,可实现纳米材料尺寸的可控.利用紫外可见光谱和荧光光谱分析自组装卟啉与卟啉单体光学性质的差别:在紫外-可见光谱中,自组装卟啉Soret带吸收峰从原来的412nm分别蓝移和红移到361和451nm,呈现明显的劈裂状,且峰形变宽.以上特征性变化预示了卟啉纳米材料的形成;在荧光光谱中,纳米卟啉的荧光强度以及荧光量子产率分别约为未纳米化TPPS1单体的4和3倍,体现出良好的光敏性能,可作优良的光敏元件及光敏材料.     

TPPS在EVAL膜表面的吸附及超分子自组装

TPPS(四-(4-磺酸基苯基)卟啉)在一定条件下可以自组装形成超分子聚集体.将TPPS超分子聚集体与膜材料结合,可制备一种超分子负载膜.本实验以EVAL(乙烯-乙烯醇共聚物)为基膜,以DMAEMA(甲基丙烯酸N,N-二甲氨基乙酯)为单体,采用紫外接枝的方法制备了EVAL-g-PDMAEMA接枝膜,利用氢键、静电作用等非共价键作用将TPPS负载于EVAL原膜及EVAL-g-PDMAEMA接枝膜上.研究了pH值、离子强度、接枝率对吸附过程的影响及等温吸附机理.结果表明,当pH=3.6时接枝膜对TPPS的吸附容量最大,pH=7时,原膜对TPPS的吸附容量最大;离子强度的增大不利于膜对TPPS的吸附;EVAL-gPDMAEMA接枝率的增大,接枝膜对TPPS的吸附容量也随之增大;Langmuir吸附等温方程可以对吸附过程进行很好的描述.改变EVAL/TPPS负载膜的pH条件,利用紫外漫反射光谱表征膜表面TPPS的聚集状态,考察不同DMAEMA接枝率的负载膜实现超分子结构的条件.实验结果显示,当pH1时,TPPS在接枝膜和原膜表面均形成超分子J-聚集体,而pH1时,TPPS仅在接枝膜表面形成H-聚集;并且DMAEMA的接枝率越高,越有利于TPPS聚集体的形成,进而有利于超分子负载膜的构筑.     

纳米银溶胶中超痕量分子的拉曼光谱研究

根据Lee等的方法制备约80～90nm大小的银纳米颗粒溶胶,采用1mW激光功率和5sffZ分时间,通过表面增强拉曼散射技术检测到浓度低至10-13mol／L的水中超痕量若丹明6G分子（R6G）;通过制备银纳米膜的方法检测到浓度低至10川mo扎的超痕量R6G分子,实验表明,银纳米颗粒的密度降低,则其表面增强拉曼散射能力大大减弱。     

四苯基卟啉铟纳米材料的制备及其光学传感性能研究

在水/二甲基亚砜(DMSO)的混合溶液体系中,利用自组装方法,使5,10,15,20-四苯基卟啉铟(InTPP)分子聚集成纳米材料,并研究了其最优制备温度为50℃。通过场发射扫描电子显微镜(FE-SEM)对铟卟啉纳米材料的表面形貌进行了研究,可获得粒径为100～200nm的棒状铟卟啉纳米材料。利用紫外-可见光谱分析了铟卟啉单体与纳米材料光学性质的差别:在紫外-可见光谱中,铟卟啉纳米分散体系的Soret带吸收峰从原来的423nm分别红移到433和453nm,吸光值明显减小,峰形呈劈裂状且明显变宽。利用紫外-可见光谱对铟卟啉的光学检测性能进行了研究,将铟卟啉单体和纳米溶液体系对低浓度甲基膦酸二甲酯(DMMP)的检测效果进行了对比,结果显示铟卟啉纳米溶液体系的检测效果明显优于单体。     

CdTe纳米棒的水相合成与铜离子识别研究

水相以巯基乙酸和半胱氨酸为混合稳定剂合成了光谱可调的CdTe纳米棒, 具有双波长发射纳米棒被用作铜离子荧光探针.铜离子加入后, 纳米棒645nm处的缺陷发射显著减弱,535nm处的激子发射未见变化.在弱碱性条件下,纳米棒缺陷发射强度与铜离子的浓度成良好线性相关,响应区间为 0～2.8×10-6 mol/L,检测下限为4.0×10-9mol/L.本文初步探讨了铜离子与CdTe纳米棒之间的作用机理.     

四(4-磺酸苯基)-卟啉在聚4-乙烯基吡啶接枝的乙烯-乙烯醇膜表面的吸附和自组装行为

四(4-磺酸苯基)-卟啉(TPPS)是一种水溶性卟啉,在一定条件下可以自组装形成超分子聚集体,将这种超分子聚集体与膜材料相结合,可以形成超分子负载膜。文中以乙烯-乙烯醇共聚物(EVAL)为膜材料,4-乙烯基吡啶(4VP)为单体,采用紫外辐照表面接枝法制备了表面带有P4VP接枝链的EVAL-P4VP接枝膜,利用非共价键作用将TPPS负载于EVAL原膜及EVAL-P4VP接枝膜上,研究了p H值、离子强度、接枝率等因素对TPPS吸附过程以及TPPS在膜表面存在形态和自组装行为的影响。结果表明,TPPS溶液中自身聚集及离子强度的增加对其在膜上的吸附产生不利影响;吸附过程可用Langmuir等温吸附模型进行描述;接枝率的增加、p H值的减小和吸附量的增加有利于TPPS在接枝膜表面形成J-聚集体。     

用单壁纳米碳管制备葡萄糖生物传感器的研究

以单壁纳米碳管为代表材料,对利用纳米碳管制备葡萄糖生物传感器中纳米碳管的作用和纳米碳管修饰电极的方法、酶的固定化方法及电极种类等因素对传感器性能的影响进行了研究.研究结果表明,纳米碳管的加入能有效地改善传感器的电化学性能,利用二茂铁和单壁纳米碳管共同修饰电极所制得的传感器的性能要好于仅用单壁纳米碳管修饰电极制得的传感器.在酶的固定化方法中,戊二醛交联法要略好于明胶包埋法;而利用铂电极制备出的生物传感器对葡萄糖的响应电流要明显高于利用金电极和玻碳电极制备出的生物传感器.这些结论对于开发纳米碳管在生物传感领域及生命科学相关领域的应用有参考价值.     

纳米多孔氧化铝膜的制备

以草酸为电解液,采用二次阳极氧化法于室温下制备了多孔阳极氧化铝膜,研究了电解液浓度和试样退火处理对膜表面形貌的影响.利用扫描电镜(SEM)对其表面形貌进行表征,并对其微观形貌进行分析.结果表明,草酸浓度在0.2～0.4 mol/,L范围内所制备的样品结构符合Keller结构模型,孔洞均匀分布于氧化铝膜表面,纳米孔阵列呈高度有序、紧密堆积的排列,孔径大小一致,约为86 nm,退火处理对膜的形貌没有明显影响.     

多巴胺改性聚四氟乙烯膜及表面固载溶菌酶

用多巴胺对聚四氟乙烯膜表面改性,然后固定化溶菌酶,制备防水透气的抗菌材料。考察了改性条件对膜性能的影响,结果表明,随反应时间延长,膜表面氨基密度增加,接触角和气通量下降;12 h后,氨基密度和接触角均达到饱和。多巴胺浓度低于0.5 mg/m L时,膜表面氨基密度随着多巴胺浓度的增大而增加,接触角下降;多巴胺浓度超过1 mg/m L后,氨基密度和接触角基本不变。以溶壁微球菌为水解对象,探讨了固定化工艺条件对溶菌酶活力的影响。最优固定化条件为:戊二醛质量分数0.1%,酶浓度2 mg/m L,固定化时间8 h,p H值7.0。固载后的酶活最高可达3.5 U/cm2。X射线光电子能谱、衰减全反射傅里叶变换红外光谱和扫描电镜表征证实了聚多巴胺涂层的存在。用平板计数法测定了材料的抗菌性能,对金黄色葡萄球菌的抗菌率达到89%。     

Dimethyl methylphosphonate detection with a single-walled carbon nanotube capacitive sensor fabricated by airbrush technique

Single-walled carbon nanotube (SWNT) films were prepared on interdigitated electrodes by airbrush technique, and their sensing properties to dimethyl methylphosphonate (DMMP) were studied. The SWNT films were characterized by field-emission scanning electron microscope. The response to different concentrations of DMMP vapors were investigated at room temperature. The results showed that the capacitance of airbrush SWNT sensor decreased rapidly in varying concentrations ranging from 12 to 60 mg/m³ (2.4–12 ppm). The capacitance sensitivity was about 12.5 % when exposed to 12 mg/m³ DMMP vapor. The capacitance sensitivity was higher when the initial capacitance and loss tangent were higher and the SWNT film was denser. It was found that the capacitance sensitivity was nearly 10 times to the resistance sensitivity. The airbrush SWNT sensor exhibited highly and fast capacitance response, good repeatability and selectivity for DMMP vapor.     

The fabrication of a MWNTs–polymer composite chemoresistive sensor array to discriminate between chemical toxic agents

In this study, a chemoresistive sensor was fabricated by the chemical polymerization and coating of either polyaniline (PANI), poly[2-methoxy-5-(2-ethyloxy)-p-phenylenevinylene], or commercial poly(methyl methacrylate) on MWNTs. We investigated the resistance responsiveness of the multilayer samples to simulated chemical warfare agents, including dimethyl methyl phosphonate (DMMP) and dichloromethane (DCM), as well as to organic agents, such as chloroform, tetrahydrofuran, methyl-ethyl ketone, and xylene. The MWNTs–PANI film was characterized by SEM and FT-IR, and the resistivity values for the six solvents were measured at different temperatures. We observed that the MWNTs-PANI sensing film exhibited a high sensitivity, excellent selectivity, and good reproducibility to the detection of all of the aforementioned agent vapors. In addition, we used atomic force microscopy to demonstrate the MWNTs–PANI absorption of DMMP vapor, wherein the sensing film exhibited a swelling phenomenon, such that the film thickness increased from 0.8 to 1.3 μm. In addition, we used principal component analysis to evaluate the performance of the sensor in detecting DMMP, DCM, and the aforementioned organic agent vapors.     

Screen-printed single-walled carbon nanotube networks and their use for dimethyl methylphosphonate detection

Single-walled carbon nanotube (SWNT) films were prepared on silicon/silica substrates by screen-printed technique at a wafer scale, and their sensing properties to dimethyl methylphosphonate (DMMP) were studied. The SWNT networks were characterized by field-emission scanning electron microscope. The resistance responses to different concentrations of DMMP vapors were investigated at room temperature. The results showed that the resistance changes of the screen-printed SWNT films increased rapidly in varying concentrations ranging from 20 to 200?ppm. The sensor exhibited high resistance responses, good reproducibility and excellent long-term stability for DMMP vapor detection. The screen-printed SWNT networks would be potentially extended to large-scale, low cost and simple manufacturing sensor applications.     

Chemical agent identification by field-based attenuated total reflectance infrared detection and solid-phase microextraction

Attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy is used to identify liquid and solid-phase chemicals. This research examines the feasibility of identifying vapor-phase chemicals using a field-portable ATR-FT-IR spectrometer (TravelIR) combined with solid-phase microextraction (SPME). Two nerve agent simulants, diisopropyl methylphosphonate (DIMP) and di-methyl methylphosphonate (DMMP), and three sorbent polymers were evaluated. Each polymer was deposited as a thin film on the instrument's sampling interface to partition and concentrate the simulants from air samples prepared in Tedlar bags. The lowest vapor concentrations identified were 50 ppb (v/v) (DIMP) and 250 ppb (v/v) (DMMP). The ATR-FT-IR instrument demonstrated a linear response at concentrations of 1 ppm (v/v) and below. Increasing the sample exposure time, the sample air velocity, and the film thickness was demonstrated to increase the amount of analyte extracted from the air sample. This research demonstrates that it is feasible to use a portable ATR-FT-IR spectrometer with SPME sampling to detect and identify vapor-phase chemicals.     

Semiconducting tin oxide nanowires and thin films for Chemical Warfare Agents detection

In this work we report the preparation and structural characterization of tin oxide nanowires as functional materials for the development of chemical sensors. Aspects of material preparation relevant for gas sensing applications, such as the control of the wire diameter, are emphasized. The functional characterization is focused on the detection of Chemical Warfare Agents (CWAs) simulants, with particular regard to poisoning effects induced by dimethyl methyl phosphonate (DMMP), a simulant for Sarin nerve agent. Tin oxide thin films, prepared by means of rheotaxial growth and thermal oxidation (RGTO) technique, are used as reference to better compare the performance of nanowires with thin films traditionally used in gas sensing field.     

Detection of a nerve agent simulant using single-walled carbon nanotube networks: dimethyl-methyl-phosphonate

Single-walled carbon nanotube (SWNT) networks were used to detect hazardous dimethyl-methyl-phosphonate (DMMP) gas in real time, employing two different metals as electrodes. Random networks of SWNTs were simply obtained by drop-casting a SWNT-containing solution onto a surface-oxidized Si substrate. Although the electrical responses to DMMP at room temperature were reversible for both metals, the Pd-contacting SWNT network sensors exhibited a higher response and a shorter response time than those of the Au-contacting SWNT network sensors at the same DMMP concentration, due to the stronger interactions between the SWNTs and Pd surface atoms. In Pd-contacting SWNT network sensors, the response increased linearly with increasing DMMP concentration and reproducible response curves were obtained for DMMP levels as low as 1 ppm. These results indicate that SWNT networks in contact with Pd electrodes can function as good DMMP sensors at room temperature with scalable and fast response and excellent recovery.     

Rational design of a Nile Red/polymer composite film for fluorescence sensing of organophosphonate vapors using hydrogen bond acidic polymers

The solvatochromic dye Nile Red dispersed in selected hydrogen bond acidic polymer matrixes demonstrated strong fluorescence enhancement at the presence of dimethyl methylphosphonate (DMMP) vapors. Two hydrogen bond acidic polymers were examined as dye matrixes, one with fluorinated alcohol groups on a polystyrene backbone (PSFA) and the other with fluorinated bisphenol groups alternating with oligo(dimethylsiloxane) segments (BSP3). The combination of hydrogen bond acidic polymer (a strong sorbent for DMMP) with the solvatochromic dye led to initial depression of the dye fluorescence and a significant red shift in the absorbance and fluorescence spectra. DMMP sorption changed the dye environment and dramatically altered the fluorescence spectrum and intensity, resulting in a strong fluorescence enhancement. It is proposed that this fluorescence enhancement is due to the competition set up between the dye and the sorbed vapor for polymeric hydrogen-bonding sites. The highest responses were obtained with BSP3. DMMP detection has been demonstrated at sub-ppm DMMP concentrations, indicating very low detection limits compared to previous Nile Red/polymer matrix fluorescence vapor sensors. Nile Red/poly(methyl methacrylate) films prepared for comparisons exhibited substantially lower response to DMMP. Rational selection of polymers providing high sorption for DMMP and competition for hydrogen-bonding interactions with Nile Red yielded flourescent films with high sensitivity.     

Chemical vapor detection using a capacitive micromachined ultrasonic transducer

Distributed sensing of gas-phase chemicals using highly sensitive and inexpensive sensors is of great interest for many defense and consumer applications. In this paper we present ppb-level detection of dimethyl methylphosphonate (DMMP), a common simulant for sarin gas, with a ppt-level resolution using an improved capacitive micromachined ultrasonic transducer (CMUT) as a resonant chemical sensor. The improved CMUT operates at a higher resonant frequency of 47.7 MHz and offers an improved mass sensitivity of 48.8 zg/Hz/μm(2) by a factor of 2.7 compared to the previous CMUT sensors developed. A low-noise oscillator using the CMUT resonant sensor as the frequency-selective device was developed for real-time sensing, which exhibits an Allan deviation of 1.65 Hz (3σ) in the presence of a gas flow; this translates into a mass resolution of 80.5 zg/μm(2). The CMUT resonant sensor is functionalized with a 50-nm thick DKAP polymer developed at Sandia National Laboratory for dimethyl methylphosphonate (DMMP) detection. To demonstrate ppb-level detection of the improved chemical sensor system, the sensor performance was tested at a certified lab (MIT Lincoln Laboratory), which is equipped with an experimental chemical setup that reliably and accurately delivers a wide range of low concentrations down to 10 ppb. We report a high volume sensitivity of 34.5 ± 0.79 pptv/Hz to DMMP and a good selectivity of the polymer to DMMP with respect to dodecane and 1-octanol.     

氧化石墨烯薄膜厚度对元件湿敏性能的影响

以改进Hummers法获得的氧化石墨为原料制备氧化石墨烯,采用旋涂法通过使用不同浓度的氧化石墨烯水相分散液制备不同厚度的氧化石墨烯薄膜湿敏元件。采用X射线衍射仪(XRD)、红外光谱仪(FT-IR)、扫描电子显微镜(SEM)、扫描探针显微镜(SPM)和湿度测试仪对氧化石墨烯薄膜的结构、形貌和湿敏性能进行分析。结果表明,在室温下随氧化石墨烯薄膜厚度减小(139nm、102nm、65nm、35nm和18nm),湿敏元件响应时间由10s缩短至2s,恢复时间由37s缩短至8s;在11.3%~93.6%RH范围内,湿敏元件电阻随湿度增加而显著减小,从兆欧级减小至千欧级,变化达到3个数量级;湿敏元件的最佳响应时间为2s,恢复时间为8s,最高灵敏度可达96.06%,具有较好的湿敏性能。     

Viscoelastic properties of polymer films on surface acoustic wave organophosphorous vapor sensors

This work investigates the viscoelastic properties of the fluoropolyol (FPOL) polymer on the surface acoustic wave (SAW) organophosphorous vapor sensors. A complex shear modulus is used to express different polymer types (glassy, glassy-rubbery, and rubbery). The different polymer types leads to different propagating properties of SAW, such as attenuation change and velocity shift. Calculation results indicate that the glassy-rubbery film exhibits the highest sensitivity for detecting organophosphorous vapor. The thicker the glassy and glassy-rubbery film implies a higher sensitivity. Moreover, the SAW vapor sensor based on the rubbery film represents the response of acoustically thick layers which has a peak in attenuation with an increasing vapor adsorption. The selectivity factor between DMMP (10 ppm) and H₂O (40%RH) is so low that the selectivity of FPOL film towards water is ineffecient. However, the selectivity factor between ethanol (10 ppm) and DMMP (10 ppm) is as high as 2512, thus confirming that the selectivity of FPOL film towards ethanol is good. Therefore, a precise and dry humidity control in the sensors system with FPOL coating is required.