Abstract
In this work, we have obtained colloidal solutions of Si nanocrystals (Si-ncs), starting from free-standing porous silicon (PSi) layers. PSi layers were synthesized using a two-electrode Teflon electrochemical cell; the etching solution contained hydrogen peroxide 30%, hydrofluoric acid 40% (HF), and methanol. The anodizing current density was varied to 250 mA cm-2, 1 A cm-2, and 1.2 A cm-2. Thus obtained, PSi was mechanically pulverized in a mortar agate; then, the PSi powders were poured into different solutions to get the final Si-ncs colloidal solutions. The different optical, morphological, and structural characteristics of the colloidal solutions with Si-ncs were measured and studied. These Si-ncs colloidal solutions, measured by photoluminescence (PL), revealed efficient blue-green or violet emission intensities. The results of X-ray diffraction (XRD) indicate that the colloidal solutions are mainly composed of silicon nanocrystallites. The result of UV–vis transmittance indicates that the optical bandgap energies of the colloidal solutions varied from 2.3 to 3.5 eV for colloids prepared in methanol, ethanol, and acetone. The transmission electron microscopy (TEM) images showed the size of the nanocrystals in the colloidal solutions. Fourier transform infrared spectroscopy (FTIR) spectra showed different types of chemical bonds such as Si-O-Si, Si-CH2, and SiH x , as well as some kind of defects.PACS61.46Df.-a; 61.43.Gt; 61.05.cp; 78.55.-m; 81.15.Gh
Highlights
The research of nanoparticles with unique dimensionality dependent on the chemical-physical properties of nanoscale matter has propelled efforts towards controllable fabrication and in-depth characterization of inorganic nanostructures with desirable compositional and geometric features
At the forefront of the current scientific revolution of colloidal nanocrystals (C-nc), crystalline particles grown in liquid media stand out over other classes of inorganic nanomaterials due to the high degree of control with which their crystal structure, size, shape, and surface functionalities can be engineered in the synthesis stage and to the versatility with which they can be processed and implemented into a large number of materials and devices [1,2,3]
transmission electron microscopy (TEM) images With X-ray diffraction (XRD), we find that the silicon nanocrystals with an average size of approximately 6 nm have similar sizes with those obtained with TEM images (4.34 nm)
Summary
The research of nanoparticles with unique dimensionality dependent on the chemical-physical properties of nanoscale matter has propelled efforts towards controllable fabrication and in-depth characterization of inorganic nanostructures with desirable compositional and geometric features. Particles with uniform structural properties are offering best properties for applications in different fields such as catalysis [11,12], gas sensors [13], biosensors [14], magnetic materials [15], and photonics [16] among others [17,18] Significant efforts in this direction are being made to develop simple and reproducible methods capable of generating colloidal samples monodispersed and polydispersed in small and large quantities [8,9,10,19] based on colloidal chemistry [17,20]. Special attention is paid to a surprising observation of intense green and blue PL in C-Si-nc suspensions, which opens the possibility to propose novel applications in a future work
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