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1.
J Phys Chem Lett ; 12(37): 9011-9019, 2021 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-34515494

RESUMO

The cubic-phase antimony trioxide (α-Sb2O3) is a room-temperature stable molecular crystal, composed of cage-like tetraantimony hexoxide (Sb4O6) molecules. Despite its versatile functionality, the van der Waals (vdW) bond-dominated nanomechanics is still unclear. Here, the bending plate-like linear behaviors of high-quality α-Sb2O3 nanoflakes were observed using the nanoindentation method. It is found that the cage-molecular crystal owns a very low in-plane Young's modulus of 14.9 ± 0.8 GPa and a remarkable maximum tensile strain of 6.0-8.8%, corresponding to a rupture strength of 0.89-1.31 GPa. Elucidated by the atomistic simulations, the compliant elastic modulus and the unexpectedly strong rupture strain are associated with the high-symmetry vdW bonding structure. The vdW nanomechanics is of fundamental and technological relevance to nanoelectronics.

2.
Nano Lett ; 21(1): 203-208, 2021 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-33372783

RESUMO

For the interlayer dielectric in microelectronics, light element compounds are preferably accepted due to less electronic polarization. Here, the nontrivial dielectric nature of the Sb4O6 cage-molecular crystal, known as α-antimony trioxide (α-Sb2O3), is reported. The gas-phase synthesized α-Sb2O3 nanoflakes are of high crystal quality, from which the abnormal local admittance responses were revealed by scanning microwave impedance microscopy (sMIM). The remarkably low dielectric constant (k), 2.0∼2.5, is corroborated by the analysis of the thickness-dependent sMIM-capacitance signal. In light of the theoretical calculations, the ultralow molecular density and the significantly suppressed ionic polarization are both crucial to the highly reduced k. Combining with the excellent optical band gap, thermal stability, and breakdown strength, α-Sb2O3 is a promising low k dielectric.

3.
ACS Nano ; 10(1): 124-32, 2016 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-26650117

RESUMO

Block copolymer patterned holey silicon (HS) was successfully integrated into a microdevice for simultaneous measurements of Seebeck coefficient, electrical conductivity, and thermal conductivity of the same HS microribbon. These fully integrated HS microdevices provided excellent platforms for the systematic investigation of thermoelectric transport properties tailored by the dimensions of the periodic hole array, that is, neck and pitch size, and the doping concentrations. Specifically, thermoelectric transport properties of HS with a neck size in the range of 16-34 nm and a fixed pitch size of 60 nm were characterized, and a clear neck size dependency was shown in the doping range of 3.1 × 10(18) to 6.5 × 10(19) cm(-3). At 300 K, thermal conductivity as low as 1.8 ± 0.2 W/mK was found in HS with a neck size of 16 nm, while optimized zT values were shown in HS with a neck size of 24 nm. The controllable effects of holey array dimensions and doping concentrations on HS thermoelectric performance could aid in improving the understanding of the phonon scattering process in a holey structure and also in facilitating the development of silicon-based thermoelectric devices.

4.
Nanoscale ; 7(28): 11915-21, 2015 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-26118367

RESUMO

Bismuth telluride (Bi2Te3) two-dimensional (2D) nanosheets prepared by van der Waals epitaxy were successfully detached, transferred, and suspended for nano-indentation measurements to be performed on freestanding circular nanosheets. The Young's modulus acquired by fitting linear elastic behaviors of 26 samples (thickness: 5-14 nm) is only 11.7-25.7 GPa, significantly smaller than the bulk in-plane Young's modulus (50-55 GPa). Compliant and robust Bi2Te3 2D nanosheets suggest the feasibility of the elastic strain engineering of topological surface states.

5.
Langmuir ; 31(12): 3644-52, 2015 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-25760309

RESUMO

Bismuth telluride (Bi2Te3) is a well-known thermoelectric material that has a layered crystal structure. Exfoliating Bi2Te3 to produce two-dimensional (2D) nanosheets is extremely important because the exfoliated nanosheets possess unique properties, which can potentially revolutionize several material technologies such as thermoelectrics, heterogeneous catalysts, and infrared detectors. In this work, ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) is used to exfoliate Bi2Te3 nanoplatelets. In both experiments and in molecular dynamics (MD) simulations, the Bi2Te3 nanoplatelets yield a stable dispersion of 2D nanosheets in the IL solvent, and our MD simulations provide molecular-level insight into the kinetics and thermodynamics of the exfoliation process. An analysis of the dynamics of Bi2Te3 during exfoliation indicates that the relative translation (sliding apart) of adjacent layers caused by IL-induced forces plays an important role in the process. Moreover, an evaluation of the MD trajectories and electrostatic interactions indicates that the [C4mim](+) cation is primarily responsible for initiating Bi2Te3 layer sliding and separation, while the Cl(-) anion is less active. Overall, our combined experimental and computational investigation highlights the effectiveness of IL-assisted exfoliation, and the underlying molecular-level insights should accelerate the development of future exfoliation techniques for producing 2D chalcogenide materials.

6.
Phys Chem Chem Phys ; 16(23): 11297-302, 2014 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-24789217

RESUMO

We demonstrate a facile technique to assemble solution phase-synthesized bismuth telluride (Bi2Te3) nanoplatelets into arrays of micropatterns. Aminosilane self-assembled monolayers (SAMs) are printed on silicon dioxide (SiO2) substrates using microcontact printing (µCP). The SAM printed surfaces are terminated with amine-groups allowing Bi2Te3 nanoplatelet selective adsorption by electrostatic attraction. Using Kelvin probe force microscopy, the electrical potential difference between aminosilane SAM and Bi2Te3 nanoplatelet surfaces is found to be ∼650 mV, which is larger than that (∼400 mV) between the SiO2 substrate and Bi2Te3 nanoplatelet surfaces. The selective adsorption provides an opportunity for integrating solution phase-grown topological insulators toward several device-level applications.

7.
Anal Chem ; 83(15): 6082-9, 2011 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-21728281

RESUMO

Mass spectrometry (MS) is the enabling technology for proteomics and metabolomics. However, dramatic improvements in both sensitivity and throughput are still required to achieve routine MS-based single cell proteomics and metabolomics. Here, we report the silicon-based monolithic multinozzle emitter array (MEA) and demonstrate its proof-of-principle applications in high-sensitivity and high-throughput nanoelectrospray mass spectrometry. Our MEA consists of 96 identical 10-nozzle emitters in a circular array on a 3 in. silicon chip. The geometry and configuration of the emitters, the dimension and number of the nozzles, and the micropillar arrays embedded in the main channel can be systematically and precisely controlled during the microfabrication process. Combining electrostatic simulation and experimental testing, we demonstrated that sharpened-end geometry at the stem of the individual multinozzle emitter significantly enhanced the electric fields at its protruding nozzle tips, enabling sequential nanoelectrospray for the high-density emitter array. We showed that electrospray current of the multinozzle emitter at a given total flow rate was approximately proportional to the square root of the number of its spraying-nozzles, suggesting the capability of high MS sensitivity for multinozzle emitters. Using a conventional Z-spray mass spectrometer, we demonstrated reproducible MS detection of peptides and proteins for serial MEA emitters, achieving sensitivity and stability comparable to the commercial capillary emitters. Our robust silicon-based MEA chip opens up the possibility of a fully integrated microfluidic system for ultrahigh-sensitivity and ultrahigh-throughput proteomics and metabolomics.


Assuntos
Espectrometria de Massas/métodos , Nanotecnologia/métodos , Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas/instrumentação , Metaboloma , Proteoma/análise , Software
8.
Nano Lett ; 10(10): 4279-83, 2010 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-20839780

RESUMO

This work investigated the thermoelectric properties of thin silicon membranes that have been decorated with high density of nanoscopic holes. These "holey silicon" (HS) structures were fabricated by either nanosphere or block-copolymer lithography, both of which are scalable for practical device application. By reducing the pitch of the hexagonal holey pattern down to 55 nm with 35% porosity, the thermal conductivity of HS is consistently reduced by 2 orders of magnitude and approaches the amorphous limit. With a ZT value of ∼0.4 at room temperature, the thermoelectric performance of HS is comparable with the best value recorded in silicon nanowire system.

9.
Sensors (Basel) ; 9(6): 4669-94, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-22408548

RESUMO

In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs). ZnO nanowires are particularly interesting because they have a large surface area to volume ratio, which will improve sensitivity, and because they operate at low current levels, will have low power requirements in a sensor module. GaN-based devices offer the advantage of the HEMT structure, high temperature operation, and simple integration with existing fabrication technology and sensing systems. Improvements in sensitivity, recoverability, and reliability are presented. Also reported are demonstrations of detection of other gases, including CO(2) and C(2)H(4) using functionalized GaN HEMTs. This is critical for the development of lab-on-a-chip type systems and can provide a significant advance towards a market-ready sensor application.

10.
Biomaterials ; 29(27): 3743-3749, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18550161

RESUMO

The ability to control the behavior of cells that interact with implanted biomaterials is desirable for the success of implanted devices such as biosensors or drug delivery devices. There is a need to develop materials that can limit the adhesion and viability of cells on implanted biomaterials. In this study, we investigated the use of zinc oxide (ZnO) nanorods for modulating the adhesion and viability of NIH 3T3 fibroblasts, umbilical vein endothelial cells, and capillary endothelial cells. Cells adhered far less to ZnO nanorods than the corresponding ZnO flat substrate. The few cells that adhered to ZnO nanorods were rounded and not viable compared to the flat ZnO substrate. Cells were unable to assemble focal adhesions and stress fibers on nanorods. Scanning electron microscopy indicated that cells were not able to assemble lamellipodia on nanorods. Time-lapse imaging revealed that cells that initially adhered to nanorods were not able to spread. This suggests that it is the lack of initial spreading, rather than long-term exposure to ZnO that causes cell death. We conclude that ZnO nanorods are potentially useful as an adhesion-resistant biomaterial capable of reducing viability in anchorage-dependent cells.


Assuntos
Adesão Celular , Sobrevivência Celular , Nanotubos , Óxido de Zinco , Animais , Bovinos , Células Cultivadas , Humanos , Camundongos , Microscopia Eletrônica de Varredura
11.
Nanotechnology ; 16(10): 2218-21, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20817998

RESUMO

Thin, uniform, single-walled carbon nanotube films, made by a simple filtration process, subsequently coated with palladium, are shown to be promising detectors of hydrogen. The films detected hydrogen with relative responses of 20% at 100 ppm and 40% at 500 ppm concentrations. Most of the initial film conductance was recovered within 30 s by exposing the samples to air. This quick and easy recoverability make the Pd-coated nanotubes suitable for practical applications in room temperature hydrogen sensing while consuming only approximately 0.25 mW power. The film fabrication process provides highly reproducible control over the film thickness; an important ingredient for commercial production. In the course of this research strong evidence was obtained indicating that sputter deposition of metal onto the nanotubes, even under very low power, short exposure time conditions, does damage to the nanotubes.

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