Ionic liquids for synthesis of function-nanomaterials

Abstract: For the first time, ionic liquids were applied for the size-selective synthesis of thermoelectric antimony telluride (Sb2Te3) nanoplates by thermal decomposition of the single-source precursor bis(diethylstibino)telluride (Et2Sb)2Te. Herein, we report on the synthesis of Sb2Te3 nanoparticles with record-high thermoelectric figure of merit values of up to 1.5. For synthesis, Sb2Te3 nanoplates with a good thermoelectric figure of merit are prepared by using ionic liquids and the microwave technique. The three substantially important thermoelectric parameters, namely electrical conductivity, thermal conductivity and the Seebeck coefficient, were independently addressed to improve the overall performance of the material by making use of a tailor-made metal organic precursor and a specific ionic liquid as the reaction medium and particle stabilizer. The critical influence of porosity for the fabrication of highly efficient thermoelectric materials was demonstrated for the first time. Unequivocal trends could be observed for synthesis of optimal thermoelectric materials in ionic liquids is required. This knowledge simplifies the work in this area for other projects in the near future

Improving the zT value of thermoelectrics by nanostructuring: Tuning the nanoparticle morphology of Sb2Te3 by using ionic liquids

A systematic study on the microwave-assisted thermolysis of the single source precursor (Et2Sb)2Te (1) in different asymmetric 1-alkyl-3-methylimidazolium- and symmetric 1,3-dialkylimidazolium-based ionic liquids (ILs) reveals the distinctive role of both the anion and the cation in tuning the morphology and microstructure of the resulting Sb2Te3 nanoparticles as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). A comparison of the electrical and thermal conductivities as well as the Seebeck coefficient of the Sb2Te3 nanoparticles obtained from different ILs reveals the strong influence of the specific IL, from which C4mimI was identified as the best solvent, on the thermoelectric properties of as-prepared nanosized Sb2Te3. This work provides design guidelines for ILs, which allow the synthesis of nanostructured thermoelectrics with improved performances

Sacrificial-layer free transfer of mammalian cells using near infrared femtosecond laser pulses.

Laser-induced cell transfer has been developed in recent years for the flexible and gentle printing of cells. Because of the high transfer rates and the superior cell survival rates, this technique has great potential for tissue engineering applications. However, the fact that material from an inorganic sacrificial layer, which is required for laser energy absorption, is usually transferred to the printed target structure, constitutes a major drawback of laser based cell printing. Therefore alternative approaches using deep UV laser sources and protein based acceptor films for energy absorption, have been introduced. Nevertheless, deep UV radiation can introduce DNA double strand breaks, thereby imposing the risk of carcinogenesis. Here we present a method for the laser-induced transfer of hydrogels and mammalian cells, which neither requires any sacrificial material for energy absorption, nor the use of UV lasers. Instead, we focus a near infrared femtosecond (fs) laser pulse (λ = 1030 nm, 450 fs) directly underneath a thin cell layer, suspended on top of a hydrogel reservoir, to induce a rapidly expanding cavitation bubble in the gel, which generates a jet of material, transferring cells and hydrogel from the gel/cell reservoir to an acceptor stage. By controlling laser pulse energy, well-defined cell-laden droplets can be transferred with high spatial resolution. The transferred human (SCP1) and murine (B16F1) cells show high survival rates, and good cell viability. Time laps microscopy reveals unaffected cell behavior including normal cell proliferation

Measuring Single-Bond Rupture Forces Using High Electric Fields in Microfluidic Channels and DNA Oligomers as Force Tags

The disruption force of specific biotin-streptavidin bonds was determined using DNA oligomers as force tags. Forces were generated by an electric field acting on a biotinylated fluorescently labeled DNA oligomer. DNA oligomers were immobilized via biotin-streptavidin bonds on the walls of microfluidic channels. Channel layout and fluid-based deposition process were designed to enable well-defined localized deposition of the oligomers in a narrow gap of the microchannel. Electric fields of up to 400 V/cm were applied and electric field induced desorption of DNA oligomers was observed. At T ≈ 30°C, field-induced desorption of both a 12 mer as well as a 48 mer yielded a streptavidin-biotin disruption force of 75 fN. Streptavidin-functionalized surfaces remained intact and could be reloaded with biotinylated oligomers. At ≈20°C, however, no field-induced unbinding of the oligomers was observed at electric field strength of up to 400 V/cm, indicating a significant temperature dependence of the bond strength

Clusters [M_<i>a</i>(GaCp*)_<i>b</i>(CNR)_<i>c</i>] (M = Ni, Pd, Pt): Synthesis, Structure, and Ga/Zn Exchange Reactions

Reactions of homoleptic isonitrile ligated complexes or clusters of d¹⁰-metals with the potent carbenoid donor ligand GaCp* are presented (Cp* = pentamethylcyclopentadienyl). Treatment of [Ni₄(CN<i>t</i>-Bu)₇], [{M­(CNR)₂}₃] (M = Pd, Pt) and [Pd­(CNR)₂Me₂] (R = <i>t</i>-Bu, Ph) with suitable amounts of GaCp* lead to the formation of the heteroleptic, tri- and tetranuclear clusters [Ni₄(CN<i>t</i>-Bu)₇(GaCp*)₃] (<b>1</b>), [{M­(CN<i>t</i>-Bu)}₃(GaCp*)₄] (M = Pd: <b>2a</b>, Pt: <b>2b</b>), and [{Pd­(CNR)}₄(GaCp*)₄] (R = <i>t</i>-Bu: <b>3a</b>, Ph: <b>3b</b>). The reactions involve isonitrile substitution reactions, GaCp* addition reactions, and cluster formation reactions. The new compounds were investigated for their ability to undergo Ga/Zn exchange reactions when treated with ZnMe₂. The novel tetranuclear Zn-rich clusters [Ni₄GaZn₇(Cp*)₂Me₇(CN<i>t</i>-Bu)₆] (<b>4</b>) and [{Pd­(CNR)}₄(ZnCp*)₄(ZnMe)₄] (R = <i>t</i>-Bu: <b>5a</b>, Ph: <b>5b</b>) were obtained and isolated. The electronic situation and geometrical arrangement of atoms of all compounds will be presented and discussed. All new compounds are characterized by solution ¹H, ¹³C NMR and IR spectroscopy, elemental analysis (EA), liquid injection field desorption ionization mass spectrometry (LIFDI-MS) as well as single crystal X-ray crystallography

Clusters [M_<i>a</i>(GaCp*)_<i>b</i>(CNR)_<i>c</i>] (M = Ni, Pd, Pt): Synthesis, Structure, and Ga/Zn Exchange Reactions

Reactions of homoleptic isonitrile ligated complexes or clusters of d¹⁰-metals with the potent carbenoid donor ligand GaCp* are presented (Cp* = pentamethylcyclopentadienyl). Treatment of [Ni₄(CN<i>t</i>-Bu)₇], [{M­(CNR)₂}₃] (M = Pd, Pt) and [Pd­(CNR)₂Me₂] (R = <i>t</i>-Bu, Ph) with suitable amounts of GaCp* lead to the formation of the heteroleptic, tri- and tetranuclear clusters [Ni₄(CN<i>t</i>-Bu)₇(GaCp*)₃] (<b>1</b>), [{M­(CN<i>t</i>-Bu)}₃(GaCp*)₄] (M = Pd: <b>2a</b>, Pt: <b>2b</b>), and [{Pd­(CNR)}₄(GaCp*)₄] (R = <i>t</i>-Bu: <b>3a</b>, Ph: <b>3b</b>). The reactions involve isonitrile substitution reactions, GaCp* addition reactions, and cluster formation reactions. The new compounds were investigated for their ability to undergo Ga/Zn exchange reactions when treated with ZnMe₂. The novel tetranuclear Zn-rich clusters [Ni₄GaZn₇(Cp*)₂Me₇(CN<i>t</i>-Bu)₆] (<b>4</b>) and [{Pd­(CNR)}₄(ZnCp*)₄(ZnMe)₄] (R = <i>t</i>-Bu: <b>5a</b>, Ph: <b>5b</b>) were obtained and isolated. The electronic situation and geometrical arrangement of atoms of all compounds will be presented and discussed. All new compounds are characterized by solution ¹H, ¹³C NMR and IR spectroscopy, elemental analysis (EA), liquid injection field desorption ionization mass spectrometry (LIFDI-MS) as well as single crystal X-ray crystallography

Pulse energy optimization.

<p>(a) Phase contrast microscopy images of droplet arrays printed by femtosecond laser-induced transfer on an acceptor slide with varying laser pulse energies. Scale bar = 200 μm. (b) Plot of transferred droplet diameter versus the laser pulse energy. Pulse energies were determined behind the focusing objective, which has a transmittance of 65% at 1030 nm.</p

Schematic representation of the cell transfer setup.

<p>The fs-laser beam is focused through the transparent acceptor petri dish into the reservoir containing the cell-laden hydrogel. The cells accumulate at the hydrogel surface due to the density of histopaque-1083 used for gel preparation. The focus depth is chosen to be between 50 and 65 μm and is therefore located directly beneath the cells. The highly confined optical breakdown generates a rapidly expanding cavitation bubble, which ejects a cell-laden hydrogel jet towards the acceptor slide.</p

Representative microscope images of cell-laden hydrogel droplets.

<p>(a) In the bright field image, the large droplets show a diameter of about 200 μm, while the small droplets size up to a diameter of only 80 μm. (b) The fluorescence image reveals a cell survival of up to 91 ± 2% in the larger droplets (red PI staining indicates dead cells, live cells are displayed in green), in small droplets only 62 ± 14% of cells survive the laser-induced transfer.</p