Nanoparticles, laboratory experiments

Klupinski et al. (2004) report a laboratory experiment on the degradation of a fungicide, pentachloronitrobenzene (C Cl NO ), in the presence of goethite and iron oxide nanoparticles this study was intended to illustrate the fate of organic agrochemical contaminants in an iron-rich subsurface. To compare the effects of iron with and without a mineral presence, experiments were performed using... 

Equally as speculative as our attempts to foresee possible toxicity issues is the issue of nanomaterial exposure. Exposure will be determined in large part by the chain of production, use, and disposal of nanomaterials. Although the mobility of nanoscale particles in the environment is poorly understood, speculation based on laboratory experience in making nanomaterials and experience garnered from colloid science suggest that the mobility of anthropogenic nanoparticles, and thus the potential for exposure, may often be small. Nonetheless, as in the case of toxicity, the relevance of our current experience in this domain is unclear. 

The nanoparticle band gap energy (Eg" ) can be approximated from the cutoff wavelength in the absorbance spectrum. The cutoff wavelength is the x-intercept of a line drawn through the absorbance data points loeated near the onset of absorbance. Equation 2 is then rearranged to solve for the partiele radius. A spectrum typical of 5.4 nm diameter CdS particles prepared aeeording to this laboratory experiment procedme is shown in Figure 1. 

When titanium dioxide nanoparticles and nanocrystallines are irradiated with UV-visible light, this semiconductor can exhibit strong bactericidal activity. For instance, Chang et al. showed that the irradiation of suspensions of Escherichia coli and Ti02 (P-25) with of wavelengths longer than 380 nm led to bactericidal action within minutes [26]. Furthermore, the trends in these simulated laboratory experiments were mimicked in outdoor tests conducted under the summer, noonday sun [27]. Elsewhere, Maness et al. presented the first evidence that Hpid peroxida-... 

One of the points made in Schwenz and Moore was that the physical chemistry laboratory should better reflect the range of activities found in current physical chemistry research. This is reflected in part by the inclusion of modem instrumentation and computational methods, as noted extensively above, but also by the choice of topics. A number of experiments developed since Schwenz and Moore reflect these current topics. Some are devoted to modem materials, an extremely active research area, that I have broadly construed to include semiconductors, nanoparticles, self-assembled monolayers and other supramolecular systems, liquid crystals, and polymers. Others are devoted to physical chemistry of biological systems. I should point out here, that with rare exceptions, I have not included experiments for the biophysical chemistry laboratory in this latter category, primarily because the topics of many of these experiments fall out of the range of a typical physical chemistry laboratory or lecture syllabus. Systems of environmental interest were well represented as well. 

In vitro drug release kinetic was also performed in non-sink conditions using decane as solvent (to prevent drug loss from nanoparticles dissolution) and a laboratory designed release cell. About 10 mg of gliadins nanoparticles (containing 824 fig/g gliadins) were resuspended in 10 ml of decane. Aliquots were collected at successive time intervals and replaced by the same quantity of solvent in order to get a constant volume in the release cell. The samples were analysed by HPLC as described above for encapsulation experiments. 

In the first set of experiments, we will test the barrier effectiveness of fabrics to aerosols (singlets) of monodisperse silver nanoparticles or titanium dioxide nanoparticles - each <50 nm. Although this first set of e eriments may not simulate the research or occupational environment, being more extreme than the normal laboratory atmosphere, wherein nanoparticles tend to aggregate into larger clusters, it will provide important information on the effectiveness of these fabrics or filters to the "worst case scenario" - i.e., aerosols of singlet nanoparticles. 

This chapter provides an overview of nanotechnology-themed experiments for general chemistry laboratory instructors. Prepartions of CdS, Fc304, Ag and An nanoparticles and Ni nanowires are presented as examples. Each experiment s description includes theoretical backgroimd, procedmes and applications of the nanomaterial. Additional resources for teaching nanotechnology to freshmen and designing new experiments are provided. 

All of the experiments described in this chapter have been performed by freshmen students in Florida Tech s Nanoscience and Technology (NST) introductory laboratory course. Since the only prerequisite of the NST lab is completion of one semester of general chemistiy, implementing these experiments in a general chemistry laboratoiy should not be difficult. The experiments are designed to use common reagents and laboratoiy equipment. Procedures yield only a small amount of solution containing nanoparticles so that the volume of chemical waste is minimal. 

Synthesis of CdS nanoparticles can be performed easily and safely by freshmen students. Based originally on research by Agostiano (P), the procedure has been adapted to use reagents commonly available to a general chemistry laboratory (JO, 11). This experiment illustrates how intermolecular forces affect the formation of micelles and how surfactants behave in oil-water mixtures. The difference in color between the bulk and nanosized CdS is visibly obvious but students can also calculate the nanoparticle size with the aid of a UV/visible spectrophotometer. The explanation for the color difference is based on quantum confinement of electrons and holes in the particle s semiconductor lattice. 

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