Silicon Nanoparticles Research Papers - Academia.edu (original) (raw)

There are primary, secondary and improved recovery methods that are developed according to the Field's needs, however, the primary recovery does not influence the increase of reservoir´s energy as the secondary and improved recovery does. Mature fields require such an increase in energy due to their production time, so water, gas or chemical injection methods also known as enhanced recovery methods (EOR) are required to satisfy the hydrocarbon demand of the moment.
This project search to quantitatively evaluate the implementation of a new enhanced recovery technology, such as the injection of silica nanoparticles, comparing it with conventional chemical recovery methods (Surfactant and Polymer) and thus determine its effectiveness and viability in the model sector of Yariguí-Cantagallo Field.

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- Reservoir Engineering, Enhanced Oil Recovery, Numerical Simulation, Silicon Nanoparticles

Organic trihydridosilanes can be grafted to hydrogen terminated porous Si nanostructures with no catalyst. The reaction proceeds efficiently at 80 8C, and it shows little sensitivity to air or water impurities. The modified surfaces are stable to corrosive aqueous solutions and common organic solvents. Octadecylsilane H 3 Si(CH 2) 17 CH 3 , and functional silanes H 3 Si(CH 2) 11 Br, H 3 Si(CH 2) 9 CH = CH 2 , and H 3 Si(CH 2) 2-(CF 2) 5 CF 3 are readily grafted. When performed on a mesopo-rous Si wafer, the perfluoro reagent yields a superhydrophobic surface (contact angle 1518). The bromo-derivative is converted to azide, amine, or alkyne functional surfaces via standard transformations, and the utility of the method is demonstrated by loading of the antibiotic ciprofloxaxin (35 % by mass). When intrinsically photoluminescent porous Si films or nanoparticles are used, photoluminescence is retained in the grafted products, indicating that the chemistry does not introduce substantial nonradiative surface traps.

There is a growing demand for nanoparticles coated with graphene due their promise in various applications such as batteries and supercapacitors, sorbents, and biomedical applications. A good example is Si where its combination with carbon is considered important for electronics and energy applications, such as lithium ion batteries, polymer based composites and even bio-medical applications. In this study, we aim to develop a very simple chemical vapor deposition approach to form graphitized Si nanoparticles in which ethanol serves as the C feedstock. This differs from other CVD approaches which tend to use a gaseous hydrocarbon (e.g. CH4) as the carbon feedstock. The use of ethanol in which Ar is simply bubbled through liquid ethanol leads to a simpler and cheaper approach. Moreover, in conventional CVD, often an oxidant (e.g. CO2) is added to aid graphitization and minimize the formation of SiC at the Si surface. Ethanol provides a source of O which serves as an inbuilt oxidizer to aid graphitization and limit the formation of SiC. The simple synthesis approach allows one to tailor the number of graphene layers coating the Si nanoparticles through the three main synthesis parameters of ethanol supply, temperature and reaction time. Moreover, using ethanol as the precursor, lower graphitization temperatures than for methane can be used.

- by Jinbo Pang
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- Graphene, Graphene by CVD, Silicon Nanoparticles

Heterocyclic silanes containing Si−N or Si−S bonds in the ring undergo a ring opening reaction with −OH groups at the surface of porous Si nanostructures to generate −SH or −NH functional surfaces, grafted via O−Si bonds. The reaction is substantially faster (0.5−2 h at 25 °C) and more efficient than hydrolytic condensation of trialkoxysilanes on similar hydroxy-terminated surfaces, and the reaction retains the open pore structure and photoluminescence of the quantum-confined silicon nanostructures. The chemistry is sufficiently mild to allow trapping of the test protein lysozyme, which retains its enzymatic activity upon release from the modified porous nanostructure.

- by Barry Arkles
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- Heterocyclic chemistry, Nanophotonics, Silicon, Nanoparticles

Surface enhanced Raman spectroscopy (SERS) was used to probe the surface chemistry of chlorine-terminated silicon nanocrystal (Si-NC) surfaces in an air-free environment. SERS effect was observed from the thin films of AgxO using 514 nm laser wavelength. When a monolayer of Si-NCs were spin-coated on AgxO SERS substrates, a very clear signal of surface states, including Si-Clx, and Si-Hx were observed. Upon air-exposure, we observed the temporal reduction of Si-Clx peak intensity, and a development of oxidation-related peak intensities, like Si-Ox and Si-O-Hx. In addition, first, second and third order transverse optical (TO) modes of Si-NCs were also observed at 519, 1000 and 1600 cm−1, respectively. As a comparison, Raman analysis of a thick film (> 200 nm) of Si-NCs deposited on ordinary glass substrates were performed. This analysis only demonstrated the first TO mode of Si-NCs, and the all the other features originated from SERS enhancement did not appear in the spectrum. These results conclude that, SERS is not only capable of single-molecule detection, but also a powerful technique for monitoring the surface chemistry of nanoparticles.

- by İlker Doğan
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- Materials Science, Plasma Physics, Nanofabrication, Nanoparticle

We present results of a scanning tunneling spectroscopy (STS) study of the impact of dehydrogena- tion on the electronic structures of hydrogen-passivated silicon nanocrystals (SiNCs) supported on the Au(111) surface. Gradual dehydrogenation is achieved by injecting high-energy electrons into individual SiNCs, which results, initially, in reduction of the electronic bandgap, and eventually produces midgap electronic states. We use theoretical calculations to show that the STS spectra of midgap states are consistent with the presence of silicon dangling bonds, which are found in different charge states. Our calculations also suggest that the observed initial reduction of the electronic bandgap is attributable to the SiNC surface reconstruction induced by conversion of surface dihydrides to monohydrides due to hydrogen desorption. Our results thus provide the first visualization of the SiNC electronic structure evolution induced by dehydrogenation and provide direct evidence for the existence of diverse dangling bond states on the SiNC surfaces.