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Here, one-step synthesis of Zn/ZnO hollow nanoparticles along with solid nanoparticles is reported using the laser ablation in liquid (LAL) technique. Laser radiation of the 1064 nm wavelength is emitted from a Q-switched Nd:YAG laser and is incident on a solid zinc target kept in a water medium. The as-obtained hollow and solid particles are characterized by transmission electron microscopy (TEM) and UV-visible absorption spectroscopy. Hollow nanoparticles are produced by the laser generated bubbles produced in water. The surface of a hollow nanoparticle is assembled from smaller solid nanoparticles. A strong laser-particle interaction is also observed when laser ablation is carried out for a longer time duration. Photoluminescence (PL) emission measurements at room temperature show that all samples exhibit PL emission in the UV-visible region. A reduction in size and an increase in concentration of the synthesized nanoparticles is observed with increasing laser ablation time.

The synthesis of silver nanoparticles of varying size has been achieved using different molar concentrations of NaOH while the effect of changing the temperature has been studied. AgNO3, gelatine, glucose and NaOH are used as a silver precursor, stabilizer, reducing agent and accelerator respectively. The synthesized nanoparticles have been characterized by a FESEM study, X-ray diffractometry, Raman spectroscopy and UV-vis spectroscopy. The colloidal sols of the silver nanoparticles in a biopolymer gelatine show strong surface plasmon resonance absorption peaks. The visible photoluminescence emission from the synthesized silver nanocrystals has been recorded within the wavelength range of 400-600 nm under UV excitation. The synthesized nanoparticles may be extremely useful in making biosensor devices as well as for other applications.

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Copper (Cu) nanoparticles of average sizes (radius in nm) varying between 1.7 and 6 nm have been prepared by 1,064 nm Nd:YAG laser ablation of solid copper target in water medium. The nanostructures of the samples have been characterized using high-resolution transmission electron microscopes (HRTEM). The UVvisible absorption spectra obtained with a UV-visible spectrophotometer show sharp absorptions in the ultraviolet region and visible region due to the interband transition and surface plasmon resonance (SPR) oscillations in Cu nanoparticles, respectively. The increase in the linewidth of the SPR absorption peaks with the reduction in particle sizes are observed due to the intrinsic size effects. The behaviour of the UV-visible spectra associated with the Cu nanoparticles is studied as a function of laser fluence and laser ablation time.

Enhanced three-photon absorption (3PA) and self-focusing nonlinear refraction are reported for the first time in ZnS and (1%–2.5%) Mn2+ doped ZnS quantum dots (QDs) of average size of 1.5 nm by using z-scan technique at 532 nm laser radiations. At this wavelength, the obtained maximum value of the 3PA coefficient both in the ZnS and in the doped ZnS QDs is ∼107 times that of bulk ZnS. Also intensity dependent saturation of 3PA has been observed and the characteristic saturation intensity is estimated to be 0.85±0.09 GW/cm2 for ZnS QDs.

Body-centered-tetragonal (BCT) ZnS nanocrystals have been synthesized, for the first time to the best of our knowledge, by using the chemical coprecipitation method at higher synthesis temperatures of 65 and 95 8C. It is confirmed from X-ray diffraction (XRD) studies that in the high-temperaturesynthesized samples, cubic and BCT phases coexist, in contrast to the room-temperature-synthesized sample, which consists of only cubic phase with sizes of the particles lying between 2 and 3 nm. The sizes of BCT phase nanocrystals are bigger than those of cubic phase of ZnS. The presence of BCT phase of ZnS in the samples is increased from 40 to 90% when the temperature of synthesis is increased from 65 to 95 8C. The nanocrystalline nature and UV-Vis absorption characteristics of the prepared samples have been studied with a transmission electron microscope (TEM) and a UV-Visible spectrophotometer, respectively. The room-temperature-synthesized ZnS sample shows photoluminescence (PL) emission in the blue region with multiple peaks, whereas the high-temperature-synthesized samples show PL emissions in the visible region. The Gaussian fittings of the measured PL spectra shows that three PL peaks at 429, 477, and 525 nm are appeared in the 65 8C sample and two peaks at 491 and 540 nm appear in the 95 8C sample with the enhanced PL intensity of the green peak at 540 nm.