Nanomaterials and Nanotechnology

Singh, L. P.; Agarwal, S. K.; Bhattacharyya, S. K.; Sharma, U.; Ahalawat, S.

doi: 10.5772/50950pmid: N/A

Abstract Spherical silica nanoparticles (n-SiO2) with controllable size have been synthesized using tetraethoxysilane as starting material and ethanol as solvent by sol-gel method. Morphology and size of the particles was controlled through surfactants. Sorbitan monolaurate, sorbitain monopalmitate and sorbitain monostearate produced silica nanoparticles of varying sizes (80-150 nm), indicating the effect of chain length of the surfactant. Increase in chain length of non-ionic surfactant resulted in decreasing particle size of silica nanoparticles. Further, the size of silica particles was also controlled using NH3 as base catalyst. These silica nanoparticles were incorporated into cement paste and their role in accelerating the cementitious reactions was investigated. Addition of silica nanoparticles into cement paste improved the microstructure of the paste and calcium leaching is significantly reduced as n-SiO2 reacts with calcium hydroxide and form additional calcium-silicate-hydrate (C-S-H) gel. It was found that calcium hydroxide content in silica nanoparticles incorporated cement paste reduced ∼89% at 1 day and up to ∼60% at 28 days of hydration process. Synthesized silica particles and cement paste samples were characterized using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), infrared spectroscopy (IR) and thermogravimetric analysis (TGA).

Levy, Shai; Shlimak, Issai; Dressler, David H.; Grinblat, Judith; Gofer, Yossi; Lu, Tiecheng; Ionov, Alexander N.

doi: 10.5772/50951pmid: N/A

Abstract The influence of fast neutron irradiation on the structure and spatial distribution of Ge nanocrystals (NC) embedded in an amorphous SiO2 matrix has been studied. The investigation was conducted by means of laser Raman Scattering (RS), High Resolution Transmission Electron Microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The irradiation of Ge-NC samples by a high dose of fast neutrons lead to a partial destruction of the nanocrystals. Full reconstruction of crystallinity was achieved after annealing the radiation damage at 8000C, which resulted in full restoration of the RS spectrum. HR-TEM images show, however, that the spatial distributions of Ge-NC changed as a result of irradiation and annealing. A sharp decrease in NC distribution towards the SiO2 surface has been observed. This was accompanied by XPS detection of Ge oxides and elemental Ge within both the surface and subsurface region.

Filpponen, Ilari; Sadeghifar, Hasan; Argyropoulos, Dimitris S

doi: 10.5772/50949pmid: N/A

Abstract In this communication a method for the creation of fluorescent cellulose nanoparticles using click chemistry and subsequent photodimerization of the installed side-chains is demonstrated. In the first step, the primary hydroxyl groups on the surface of the CNCs were converted to carboxylic acids by using TEMPO-mediated hypohalite oxidation. The alkyne groups, essential for the click reaction, were introduced into the surface of TEMPO-oxidized CNCs via carbodiimide-mediated formation of an amide linkage between monomers carrying an amine functionality and carboxylic acid groups on the surface of the TEMPO-oxidized CNCs. Finally, the reaction of surface-modified TEMPO-oxidized cellulose nanocrystals and azido-bearing coumarin and anthracene monomers were carried out by means of a click chemistry, i.e., Copper(I)-catalyzed Azide-Alkyne Cycloaddition (CuAAC) to produce highly photo-responsive and fluorescent cellulose nanoparticles. Most significantly, the installed coumarin and/or anthracene side-chains were shown to undergo UV-induced [2+2] and [4+4] cycloaddition reactions, bringing and locking the cellulose nanocrystals together. This effort paves the way towards creating, cellulosic photo responsive nano-arrays with the potential of photo reversibility since these reactions are known to be reversible at varying wavelengths.

Sharma, Aditya; Varshney, Mayora; Kumar, Shalendra; Verma, K.D.; Kumar, Ravi

doi: 10.5772/50948pmid: N/A

Abstract In this work, we report the room temperature ferromagnetism in Sn1-xFexO2 and Sn1-xNixO2 (x = 0.00, 0.03 and 0.05) nano-crystalline powders. All the samples were prepared using co-precipitation method. X-Ray Diffraction (XRD), transmission electron microscopy (TEM), energy dispersive x-ray analysis (EDAX), UV-visible absorption spectroscopy and room temperature magnetization measurements were performed to study the crystal structure, morphology, elemental analysis, optical band gap and magnetic properties of Fe and Ni doped SnO2. TEM results depict the formation of spherically shaped and small sized nanoparticles of the diameter of ∼ 3 nm. The band gap energy of the Fe and Ni doped samples found to decrease with increasing their concentrations. The higher saturation magnetization was observed in low concentration Fe and Ni doped tin oxide.

Dini, Luciana; Panzarini, Elisa; Serra, Antonio; Buccolieri, Alessandro; Manno, Daniela

doi: 10.5772/50952pmid: N/A

Abstract Silver nanostructures were successfully synthesized through a simple and “green” method using saccharides as reducing and capping agent. Transmission electron microscopy (TEM) and UV–Vis absorption were used to certify the quality of the silver nanoparticles obtained: firstly, size and dispersion. In this work Silver NanoParticles (AgNPs) cytotoxicity related to saccharides capping (Glucose and Glucose-Sucrose) was explored in human epitheloid cervix carcinoma cells (HeLa). The cells were incubated with increasing AgNPs number/cell and HeLa cells viability was monitored for a period of 48 h compared with the positive and negative controls. We observed that the toxicity increases with incubation time and with AgNPs number/cell. In particular, the different cytotoxic degree of the AgNPs, i.e. AgNP-G are more toxic than AgNP-GS, suggests that the cytotoxic effects are largely depended on the capping agent. The highest concentration of AgNP-G number/cell is able to induce extensive cell death of HeLa cells soon after 1 hr of incubation; conversely the lowest concentration of Ag NP-GS number/cell, surprisingly, is able to induce cell proliferation.