EMSL: Dehong Hu's Publications

Brown E, D Hu, N Abu-Lail, and X Zhang. 2013. "Potential of nanocrystalline cellulose-fibrin nanocomposites for artificial vascular graft applications." Biomacromolecules 14(4):1063-1071. Abstract Nanocrystalline cellulose, a new bio-nanomaterial is utilized as a reinforcing material for biocompatible fibrin matrix to form into a nanocomposite for small-diameter replacement vascular graft application (SDRVG). The periodate oxidation of NCC, which provided it with a reactive carbonyl group, allowed molecular interaction between NCC and fibrin. Such interaction resulted into an effective mechanical reinforcement indicated by the improvement of max. force, elongation at break and modulus when oxidized NCC (ONCC) was incorporated into fibrin. The nanocomposite’s mechanical properties can be manipulated to conform to the native blood vessel by varying the ONCC to fibrin ratio and/or by controlling the degree of oxidation of NCC. Using atomic force microscopy had provided fundamental information on the effects of molecular interactions to the nanolevel mechanical properties of NCC/fibrin nanocomposites. This fundamental information established the positive feasibility and commenced continuing investigation for the practical SDRVG application of NCC/fibrin nanocomposite.

El-Khoury PZ, D Hu, VA Apkarian, and WP Hess. 2013. "Raman Scattering at Plasmonic Junctions Shorted by Conductive Molecular Bridges." Nano Letters 13(4):1858-1861. doi:10.1021/nl400733r Abstract Intensity spikes in Raman scattering, accompanied by switching between line spectra and band spectra, can be assigned to shorting the junction plasmon through molecular conductive bridges. This is demonstrated through Raman trajectories recorded at a plasmonic junction formed by a gold AFM tip in contact with a silver surface coated either with biphenyl-4,4’-dithiol or biphenyl-4-thiol. The fluctuations are absent in the monothiol. In effect, the making and breaking of chemical bonds is tracked.

El-Khoury PZ, SJ Peppernick, D Hu, AG Joly, and WP Hess. 2013. "The Origin of Surface-Enhanced Raman Scattering of 4,4' -Biphenyldicarboxylate on Silver Substrates." Journal of Physical Chemistry C 117(14):7260-7268. doi:10.1021/jp401026x Abstract We combine scanning electron microscopy, atomic force microscopy, surface-enhanced Raman scattering (SERS), and tools of computational chemistry to investigate the origin of Raman scattering of 4,4’-biphenyldicarboxylic acid adsorbed as 4,4’-biphenyldicarboxylate on two different silver substrates. The first consists of a 100 nm deep cylindrical aperture embedded in an array of cylindrical nano-holes featuring an average diameter of 350 nm and a periodicity of 700 nm. The second is a nano-junction formed by a 100 nm silver nano-particle coated with the adsorbate and a flat silver surface. We find that the underlying background signal in the SERS spectra collected from the former strongly resemble the SERS spectra of the nano-sphere-featuring substrate, engineered to operate in the charge transfer plasmon limit. Our analysis of a series of SERS spectra consecutively collected from one nano-cylinder suggests that the optical response of a single molecule can be extracted, its brightest Raman active mode enhanced by a factor of 7.4 x 106.

Liu Y, C Zhang, D Hu, MS Kuhlenschmidt, TB Kuhlenschmidt, SE Mylon, R Kong, R Bhargava, and TH Nguyen. 2013. "Role of collector alternating charged patches on transport of Cryptosporidium parvum oocyst in a patchwise charged heterogeneous micromodel." Environmental Science & Technology 47(6):2670-2678. doi:10.1021/es304075j Abstract The role of collector surface charge heterogeneity on transport of Cryptosporidium parvum oocyst and carboxylate microsphere in 2-dimensional micromodels was studied. The cylindrical silica collectors within the micromodels were coated with 0, 10, 20, 50 and 100% Fe2O3 patches. The experimental values of average single collector removal efficiencies (η) of the Fe2O3 patches and on the entire collectors were determined. In the presence of significant (>3500 kT) Derjaguin–Landau–Verwey–Overbeek (DLVO) energy barrier between the microspheres and the silica collectors at pH 5.8 and 8.1, the values of η determined for Fe2O3 patches were significantly less (p < 0.05, t-test) than that obtained for collectors coated entirely with Fe2O3. However, η on Fe2O3 patches for microspheres at pH 4.4 and for oocysts at pH 5.8 and 8.1, where the DLVO energy barrier was relatively small (ca. 200-360 kT), were significantly greater (p < 0.05, t-test) than that on the collectors coated entirely with Fe2O3. The dependence of η determined for Fe2O3 patches on the DLVO energy barrier indicated the importance of periodic favorable and unfavorable electrostatic interactions between colloids and collectors with alternating Fe2O3 and silica patches. Differences between experimentally determined η and that predicted by a patchwise geochemical heterogeneous model was observed, but can be explained by the model’s lack of consideration for the spatial distribution of charge heterogeneity on the collector surface and colloid migration on patchwise heterogeneous collectors.

Nasybulin EN, W Xu, MH Engelhard, XS Li, M Gu, D Hu, and J Zhang. 2013. "Electrocatalytic properties of poly(3,4-ethylenedioxythiophene) (PEDOT) in Li-O2 battery." Electrochemistry Communications 29:63-66. doi:10.1016/j.elecom.2013.01.011 Abstract Poly(3,4-ethylenedioxythiophene) (PEDOT)/carbon composite was prepared by in situ chemical polymerization of EDOT monomer in carbon matrix. PEDOT has electrocatalytic activity toward oxygen reduction and evolution reactions in Li-O2 battery significantly lowering charging voltage. The electrocatalytic effect is probably due to the redox activity of PEDOT which apparently acts as a mediator in electron transfer during discharge and charge processes.

Varga T, T Droubay, ME Bowden, RJ Colby, S Manandhar, V Shutthanandan, D Hu, BC Kabius, E Apra, WA Shelton, and SA Chambers. 2013. "Coexistence of Weak Ferromagnetism and Polar Lattice Distortion in Epitaxial NiTiO3 thin films of the LiNbO3-Type Structure." Journal of Vacuum Science and Technology B--Microelectronics and Nanometer Structures 31(3):Article No. 030603. doi:10.1116/1.4801664 Abstract We report the magnetic and structural characteristics of epitaxial NiTiO3 films grown by pulsed laser deposition that are isostructural with acentric LiNbO3 (space group R3c). Optical second harmonic generation and magnetometry demonstrate lattice polarization at room temperature and weak ferromagnetism below 250 K, respectively. These results appear to be consistent with earlier predictions from first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LiNbO3 structure. This acentric form of NiTiO3 is believed to be one of the rare examples of ferroelectrics exhibiting weak ferromagnetism generated by a Dzyaloshinskii-Moriya interaction.

Chen X, W Xu, J Xiao, MH Engelhard, F Ding, D Mei, D Hu, J Zhang, and J Zhang. 2012. "Effects of cell positive cans and separators on the performance of high-voltage Li-ion batteries." Journal of Power Sources 213:160-168. doi:10.1016/j.jpowsour.2012.04.009 Abstract The effects of different cell cans and separators on the first-cycle Coulombic efficiency and long-term cycling stability of high voltage spinel cathode were investigated systematically. Compared to stainless steel (SS) positive-cans, aluminum (Al)-clad SS-316 positive-cans have a much better resistance to oxidation at high voltages thus improving the initial Coulombic efficiency of the batteries by more than 13%. Among the five separators studied in this work, polyethylene (PE) separator shows the best electrochemical stability. The cells using LiCr0.05Ni0.45Mn1.5O4 as cathode, Al-clad positive-can, and PE separator exhibit the first-cycle Columbic efficiency of about 90% and a capacity fading of only 0.01% per cycle.

Clayton DA, T McPherson, S Pan, M Chen, DA Dixon, and D Hu. 2012. "Spatial and temporal variation of surface-enhanced Raman scattering at Ag nanowires in aqueous solution." Physical Chemistry Chemical Physics. PCCP 15(3):850-859. Abstract We present surface enhanced Raman spectroscopy (SERS) and Raman imaging of small organic molecules at well-defined nanostructures formed by single silver nanowires (NWs). We show that SERS can be obtained at single, crossed, and bundled Ag NWs for mercaptopyridine, adenine, cytosine, guanine, and thymine. Crossed wires and parallel Ag NWs have SERS enhancement factors much higher than single Ag NWs. New additional junctions formed by a silver nanoparticle and a single Ag NW, and bundled NWs provide SERS intensity higher than a single Ag NW. The SERS signal of single Ag NWs can be further enhanced by decorating the Ag NW surface with gold nanoparticles using electroless deposition. Single Ag NW Raman imaging with a 10 ms time resolution when compared with photoluminescence (PL) imaging results reveal a different dynamic response of SERS and PL under steady state laser excitation. Dynamic photoluminescence blinking activities are suppressed in the presence of the surface coating of Raman active molecules (e.g., mercaptopyridine) and the SERS signal is quite stable in a wide field excitation configuration. The Discrete Dipole Approximation (DDA) method was used to calculate the local field intensity that can be applied to help understand the enhanced PL and SERS at the junction of Ag NWs

Jin H, Y Yu, WB Chrisler, Y Xiong, D Hu, and C Lei. 2012. "Delivery of MicroR A-10b with Polylysine Nanoparticles for Inhibition of Breast Cancer Cell Wound Healing." Breast Cancer: Basic and Clinical Research 6:9-19. doi:10.4137/BCBCR.S8513 Abstract Recent studies revealed that micro RNA-10b (mir-10b) is highly expressed in metastatic breast cancer cells, and positively regulates breast cancer cell migration and invasion through inhibition of HOXD10 targets synthesis. In this study we designed anti-mir-10b molecules and combined with poly L-lysine (PLL) nanoparticles to test the delivery effectiveness. RNA molecule sequence exactly matching the mature mir-10b minor antisense showed strong inhibition when mixed with PLL in our wound healing assay. In addition the nanoparticles deliver the anti-microRNA molecules into cytoplasm of breast cancer cells in a concentration dependent manor which are sustainable for long term and slow-release effectiveness.

Xu W, AL Read, PK Koech, D Hu, CM Wang, J Xiao, AB Padmaperuma, GL Graff, J Liu, and J Zhang. 2012. "Factors Affecting the Battery Performance of Anthraquinone-based Organic Cathode Materials." Journal of Materials Chemistry 22(9):4032-4039. doi:10.1039/c2jm15764k Abstract Two organic cathode materials based on poly(anthraquinonyl sulfide) structure with different substitution positions were synthesized and their electrochemical behavior and battery performances were investigated. The substitution positions on the anthraquinone structure, binders for electrode preparation and electrolyte formulations have been found to have significant effects on the battery performances of such organic cathode materials. The substitution position with less steric stress has higher capacity, longer cycle life and better high-rate capability. Polyvinylidene fluoride binder and ether-based electrolytes are favorable for the high capacity and long cycle life of the quinonyl organic cathodes.