Electric field-assisted laser ablation fabrication and assembly of zinc oxide/carbon nanocomposites into hierarchical structures for supercapacitor electrodes.

One of the major challenges in the field of electrochemical energy storage device performance improvement is the development of suitable synthetic materials for electrodes that can provide high power and high energy density features combined with their long-term stability. Here, we have developed a novel two-step approach based on DC glow discharge plasma pre-treatment of a carbon cloth substrate followed by electric field-assisted laser ablation for the synthesis of ZnO/C nanocomposites in a liquid and their simultaneous assembly into hierarchically organized nanostructures onto the pre-processed carbon cloth to produce a supercapacitor electrode. To form such nanostructures, a processed carbon cloth was included in the electrical circuit as a cathode during laser ablation of zinc in water, while a zinc target served as an anode. A series of studies have been performed to explore the structure, morphology, composition and electrochemical characteristics of the synthesized ZnO/C nanocomposites. Application of the external field provided additional possibilities for tuning the particle morphology. The parameters of the obtained nanostructures were shown to depend on the direction of the applied electric field and liquid composition. SEM studies revealed a nanoflower-like morphology of the prepared nanomaterial having potential in supercapacitor applications due to a large surface area. The ZnO/C nanoflowers, deposited onto a carbon cloth substrate, were tested for energy storage by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analysis. The results showed a pseudocapacitor behavior with a maximum specific capacitance of about 3045 F g-1 (at a scan rate of 1 mV s-1). These results demonstrate a promising storage efficiency of the synthesized ZnO/C nanocomposite as a material for supercapacitors.

Photoluminescent neodymium-doped ZnO nanocrystals prepared by laser ablation in solution for NIR-II fluorescence bioimaging.

The work reports on the use of laser ablation and post-ablation irradiation techniques for the preparation Nd3+ doped ZnO nanoparticles (NPs). The focus has been made on photoluminescence of Nd-doped ZnO NPs in the second near infrared (NIR-II) spectral window (1000-1700 nm) of the biological transparency. Morphology, phase composition and optical properties of the synthesized NPs were studied by absorption and photoluminescence spectroscopy, X-Ray diffraction (XRD) and transmission (TEM) electron microscopy. Near-infrared luminescence of Nd3+ doped ZnO nanocrystals in the region of 1000-1400 nm was detected both upon excitation from the ground state (800 nm) and upon UV excitation. The latter proves the incorporation of the Nd3+ into ZnO lattice as photoluminescence occurs through the transfer of excitation energy from the ZnO matrix to the Nd3+ ion. The possibility of control over the luminescence properties by a variation of solvent composition and by additional laser irradiation was demonstrated.

Laser Irradiation of Gd-Si and Gd-Si-Ge Colloid Mixtures for the Fabrication of Compound Nanoparticles.

Binary (Gd5 Si4 , GdSi) and ternary (Gd5 Si2 Ge2 ) compound nanoparticles (NPs) were prepared by laser irradiation of a mixture of colloidal solutions containing NPs of the relevant elements. It is assumed that the compound NPs are formed by heating, co-melting, and chemical interactions in the alloyed droplets. The blackbody-like radiation of the heated NPs was used for temperature control of the NP-preparation process. The obtained results demonstrate that laser irradiation of colloidal NPs provides unique possibilities not only for the synthesis of compound NPs but also for control of their phase composition and size. The synthesized Gd-based compound NPs exhibited magnetic transition at an ordering temperature, TC , in the range of 310-320 K. Thus, the magnetic properties of the synthesized particles confirm their potential for biomedical applications, in particular, for magnetic hyperthermia treatment.

Structure and Optical Properties of Carbon Nanoparticles Generated by Laser Treatment of Graphite in Liquids.

In this paper, we report the one-step synthesis of luminescent carbon nanoparticles (NPs) via laser irradiation of a graphite target in a solvent [H2 O, ethanol, or a 0.008 m aqueous diethylenetriaminepentaacetic acid (DTPA) solution]. This is a simple approach for the fabrication of carbon dots with tunable photoluminescence (PL) that differs from other preparation methods, as no post-passivation step is required. The unfocused beam of the second harmonic (wavelength 532 nm) of the Nd:YAG laser was used in our experiments. The sizes of the prepared NPs were mainly distributed in the range of 1-8 nm with an average value of 3 nm. Carbon NPs of different inner structure were prepared: hexagonal diamond phase in aqueous DTPA solution, orthorhombic carbon phase in ethanol, and amorphous carbon in water. The synthesized carbon NPs have strong luminescence in the visible region, which makes them attractive for numerous biological applications. The photoluminescence of the synthesized NPs was investigated at different excitation wavelengths, from 260 to 450 nm. The highest intensities of the emission bands were detected for an excitation wavelength of 400 nm.