Co-reporter:Sang Ho Lee, Andrew C. Jamison, David M. Hoffman, Allan J. Jacobson, T. Randall Lee
Thin Solid Films 2014 Volume 558() pp:200-207
Publication Date(Web):2 May 2014
DOI:10.1016/j.tsf.2014.02.021
•Prepared gold nanoshells with broad light absorption from visible to near IR.•Added the gold nanoshells to polyethyleneimine films via layer-by-layer assembly.•The resulting layered thin films exhibited minimal gold nanoshell aggregation.As an initial step in the development of surfaces for collecting thermal energy, gold shell/silica core particles (~ 200 nm in diameter with shells ~ 25 nm thick) were synthesized and incorporated into organic polymeric thin films. The morphologies of these nanoshells were characterized with scanning and transmission electron microscopy. Powder X-ray diffraction demonstrated that the gold layers were highly crystalline. Thin films containing the gold nanoshells and polyethyleneimine were generated using dip-coating techniques based on electrostatic layer-by-layer self-assembly methods. Scanning electron microscopy was used to image the resultant composite films, which contained uniformly distributed gold nanoshells with limited aggregation. The optical properties were analyzed by absorption spectroscopy, revealing broad extinctions ranging from the visible to the near-IR spectral regions. X-ray photoelectron spectroscopy spectra were also obtained to determine the elements present and the oxidation states of these elements.
Co-reporter:Sang Ho Lee, David M. Hoffman, Allan J. Jacobson, and T. Randall Lee
Chemistry of Materials 2013 Volume 25(Issue 23) pp:4697
Publication Date(Web):October 28, 2013
DOI:10.1021/cm402098n
A sol–gel-based approach to the fabrication of tin oxide (SnO2) thin films containing SnO2-coated gold nanoparticles is described. In this approach, gold nanoparticles with a mean diameter of ∼15 nm were coated with thin layers of SnO2. The composite particles were ∼55 nm in diameter with SnO2 shells that were ∼20 nm thick. These nanoparticles were doped homogeneously into a SnO2 sol–gel precursor, and the mixture was deposited as a thin film via spin-coating methods. The SnO2-coated nanoparticles and the SnO2 films doped with the nanoparticles were characterized by transmission and scanning electron microscopy (TEM and SEM) and X-ray diffraction (XRD). The optical properties of the nanoparticles and the composite films were evaluated by UV–vis spectroscopy.Keywords: nanoparticle thin films; SnO2-coated nanoparticles; sol−gel; tin oxide;
Co-reporter:Rosanna A. D. Soriaga ; Jennifer M. Nguyen ; Thomas A. Albright
Journal of the American Chemical Society 2010 Volume 132(Issue 51) pp:18014-18016
Publication Date(Web):December 2, 2010
DOI:10.1021/ja108265y
The addition of 4 equiv of LiN═C-t-Bu2 to CrCl3, MoCl5, and WCl6 in diethyl ether produced the complexes M(N═C-t-Bu2)4 (M = Cr, Mo, W). Single-crystal X-ray diffraction studies revealed that the molecules have flattened tetrahedral geometries with virtual D2d symmetry in the solid state. 1H and 13C NMR spectra indicated that the complexes are diamagnetic, and a qualitative MO analysis showed that the orthogonal π-donor and -acceptor orbitals of the ketimide ligand cooperatively split the dxy and dz2 orbitals sufficiently to allow spin pairing in the dxy orbital. A more sophisticated quantum-mechanical analysis of Cr(N═C-t-Bu2)4 using density functional/molecular mechanics methods confirmed the qualitative analysis by showing that the singlet state is 27 kcal/mol more stable than the triplet state.
Co-reporter:Saba Javed and David M. Hoffman
Dalton Transactions 2010 vol. 39(Issue 47) pp:11439-11444
Publication Date(Web):26 Oct 2010
DOI:10.1039/C0DT00847H
The zinc hydrazide complexes [EtZn(N(SiMe3)NMe2)]2, [EtZn(N(Me)NMe2)]4, and Zn3Et4(N(Et)NMe2)2 were synthesized by allowing excess hydrazine, HN(R)NMe2, to react with diethyl zinc. The product of the reaction between ZnEt2 and HN(i-Pr)NMe2ortho-metalated 4-(dimethylamino)pyridine (DMAP) at room temperature, producing the complex Zn[(NC5H3-p-NMe2)ZnEt(N(i-Pr)NMe2)]2. At elevated temperatures, Zn3Et4(N(Et)NMe2)2 also ortho-metalated DMAP, but [EtZn(N(Me)NMe2)]4 did not. Single-crystal X-ray diffraction studies revealed that the hydrazide ligands in [EtZn(N(SiMe3)NMe2)]2 act as bridging mono-hapto amide ligands, and in Zn3Et4(N(Et)NMe2)2 and Zn[(NC5H3-p-NMe2)ZnEt(N(i-Pr)NMe2)]2 the hydrazide ligands are di-hapto.
Co-reporter:Edixa de L. Jiménez, Saba Javed, David M. Hoffman
Inorganica Chimica Acta 2009 Volume 362(Issue 2) pp:385-388
Publication Date(Web):20 January 2009
DOI:10.1016/j.ica.2008.04.020
The complex Hf[N(SiMe2H)2]4 was synthesized, structurally characterized, and used as a precursor with oxygen to prepare hafnium silicate thin films at substrate temperatures ⩾500 °C in a low-pressure CVD process. The as-deposited films were amorphous, and they remained amorphous upon annealing up to 1100 °C.Tetrakis(bis(dimethylsilyl)amido)hafnium and oxygen produce amorphous hafnium silicate films in a low-pressure CVD process.
Co-reporter:Saba Javed and David M. Hoffman
Inorganic Chemistry 2008 Volume 47(Issue 24) pp:11984-11992
Publication Date(Web):November 13, 2008
DOI:10.1021/ic801451v
The zinc hydrazonide complexes [ClZn(CH2C(Me)═NNMe2)(py)]2, [ClZn(CH2C(t-Bu)═NNMe2)]2, [Zn(CH2C(Me)═NNMe2)2]2, Zn(CH2C(i-Pr)═NNMe2)2, and Zn(CH2C(t-Bu)═NNMe2)2 were synthesized by salt metathesis reactions, and the coordination polymer [EtZn(CH2C(Me)═NNMe2)]n was obtained from the reaction between excess ZnEt2 and [Zn(CH2C(Me)═NNMe2)2]2. Single crystal X-ray crystallography studies revealed that the hydrazonide ligands were bound to zinc as chelating alkyl ligands. The ligand precursor [Li(CH2C(i-Pr)═NNMe2)(THF)]n was also structurally characterized. In the anion of [Li(CH2C(i-Pr)═NNMe2)(THF)]n, the hydrazonide ligand in [EtZn(CH2C(Me)═NNMe2)]n, and the bridging hydrazonide ligands in [Zn(CH2C(Me)═NNMe2)2]2 and [ClZn(CH2C(Me)═NNMe2)(py)]2, there is evidence for three-center charge delocalization. In solution, the dimer [Zn(CH2C(Me)═NNMe2)2]2 is in equilibrium with the monomer Zn(CH2C(Me)═NNMe2)2. The thermodynamic parameters ΔH° = 55.8(2.9) kJ/mol, ΔS° = 144(2) J/mol K, and ΔG°298K = 13(2) kJ/mol for the equilibrium were obtained from a variable temperature 1H NMR study.
Co-reporter:Saba Javed
European Journal of Inorganic Chemistry 2008 Volume 2008( Issue 33) pp:5251-5256
Publication Date(Web):
DOI:10.1002/ejic.200800793
Abstract
Complexes [XAl{CH2CR=NNMe2}2] {X = Cl and R = Me or iPr, X = Me and R = Me, and X = N(NMe2)[CR=CH2] and R = Me or iPr} were synthesized by salt metathesis reactions involving lithium salts of hydrazones, Li[CH2CR=NNMe2]. X-ray crystallographic studies showed that all the complexes contain two chelating hydrazonido ligands bonding to aluminum through the methylene carbon and amine nitrogen(–NMe2). For the complexes in which X = N(NMe2)[CR=CH2] (R = Me or iPr), the N(NMe2)[CR=CH2] ligand represents a linkage isomer in which the hydrazonido ligand bonds through nitrogen rather than through carbon, thereby becoming a hydrazido ligand. In the single crystal containing [Al{CH2CiPr=NNMe2}2{N(NMe2)(CiPr=CH2)}], its isomer [Al{CH2CiPr=NNMe2}3], having two chelating hydrazonido and one monodentate hydrazonido ligands, is present 45 % of the time. In solution, the [Al{CH2CR=NNMe2}2{N(NMe2)(CR=CH2)}] (R = Me or iPr) complexes are in equilibrium with [Al{CH2CR=NNMe2}3]. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Co-reporter:J.-S. M. Lehn;S. Javed;D. M. Hoffman
Chemical Vapor Deposition 2006 Volume 12(Issue 5) pp:
Publication Date(Web):19 MAY 2006
DOI:10.1002/cvde.200506434
Alternatives to tetrakis(dialkylamido)zirconium and hafnium for use as precursors to zirconium and hafnium oxide films are examined. Tetrakis(trimethylhydrazido)zirconium and hafnium, Zr(NMeNMe2)4 and Hf(NMeNMe2)4, and Hf[tBuNCH2CH2N-tBu]2 are used with oxygen as precursors to zirconium and hafnium oxide films in a low-pressure CVD process at substrate temperatures <400 °C. The as-deposited films are amorphous, featureless, and transparent on glass. X-ray photoelectron spectroscopy (XPS) data shows that the films deposited using the hydrazido complexes and oxygen as precursors are carbon- and nitrogen-free, while the films obtained from Hf[tBuNCH2CH2N-tBu]2 and oxygen have a composition HfO1.6C0.06N0.2. A thin (<1500 Å) zirconium oxide film remains amorphous after annealing for 2 h at 950 °C. The X-ray crystal structure of Hf[tBuNCH2CH2N-tBu]2, which was synthesized along with its Zr congener from MCl4 and Li2[tBuNCH2CH2N-tBu], reveals that it has an elongated tetrahedral geometry in the solid state.
Co-reporter:S. Suh;D. M. Hoffman;L. M. Atagi;D. C. Smith
Chemical Vapor Deposition 2001 Volume 7(Issue 2) pp:
Publication Date(Web):7 MAR 2001
DOI:10.1002/1521-3862(200103)7:2<81::AID-CVDE81>3.0.CO;2-X
Thin films containing zinc silicate were prepared by metal–organic (MO) CVD, at substrate temperatures at or below 550 °C, by using the precursors Zn[N{Si(CH3)3}2]2 or Zn[NC(CH3)3{Si(CH3)3}]2, and O2. In both cases, infrared (IR) data for the as-deposited films suggested they were composed of a mixture of SiO2 and material having Zn–O–Si linkages, and after annealing, X-ray and IR data were consistent with the presence of crystalline Zn2SiO4 in the films.
Co-reporter:Liliana A. Mîinea and David M. Hoffman
Journal of Materials Chemistry A 2000 vol. 10(Issue 10) pp:2392-2395
Publication Date(Web):14 Aug 2000
DOI:10.1039/B003886P
Fluorine-doped indium oxide films are of interest as a transparent conducting material. Polycrystalline indium oxide films were deposited at 400–550°C in a low-pressure chemical vapor deposition process from In[OCMe(CF3)2]3(H2N-t-Bu) and O2 precursors. The films deposited at ≤500°C contained 2–3 atom% fluorine while the film deposited at 550°C had no detectable fluorine incorporation (by X-ray photoelectron spectroscopy with sputtering). Films deposited on quartz (≈1800 Å thickness) showed >85% transmittance in the 400–800 nm region and had band gaps of 3.65–3.75 eV. Resistivities of 1.25 × 10−2–9.96 × 10−3 Ω cm were measured for the as-deposited films. The resistivities of films grown on silicon decreased markedly after annealing to values as low as 1.43 × 10−3 Ω cm.
Co-reporter:Siddhartha Panda, Jungsook Kim, Bruce H. Weiller, Demetre J. Economou, David M. Hoffman
Thin Solid Films 1999 Volume 357(Issue 2) pp:125-131
Publication Date(Web):15 December 1999
DOI:10.1016/S0040-6090(99)00659-8
Titanium nitride films were deposited from tetrakis(ethylmethylamido)titanium and ammonia at 250–350°C and 0.7–2 Torr by thermal chemical vapor deposition. The effect of process parameters such as deposition temperature, precursor temperature, carrier gas flow, and ammonia flow on the film properties was studied, the apparent activation energy of film growth was calculated and the film composition was determined. The film step coverage was better than for films grown from tetrakis(dimethylamido)titanium and ammonia.
Co-reporter:Seigi Suh, Zuhua Zhang, Wei-Kan Chu, David M. Hoffman
Thin Solid Films 1999 Volume 345(Issue 2) pp:240-243
Publication Date(Web):21 May 1999
DOI:10.1016/S0040-6090(98)01421-7
Fluorine-doped tin oxide films were deposited on silicon, glass and quartz substrates at 370–490°C by atmospheric-pressure chemical vapor deposition from (CH3(CH2)3)2Sn(O2CCF3)2 and oxygen. Backscattering spectra indicate the films are stoichiometric with O/Sn ratios of 1.9–2.0. Nuclear reaction analysis (NRA) for fluorine gives F/Sn ratios of 0.005–0.015 with the amount of fluorine in the films increasing with increasing deposition temperature. The films are transparent in the visible region (>75%) and have resistivities as low as 8.2×10−4 Ω cm. X-ray diffraction studies indicate the films deposited on glass are polycrystalline.
Co-reporter:Saba Javed and David M. Hoffman
Dalton Transactions 2010 - vol. 39(Issue 47) pp:NaN11444-11444
Publication Date(Web):2010/10/26
DOI:10.1039/C0DT00847H
The zinc hydrazide complexes [EtZn(N(SiMe3)NMe2)]2, [EtZn(N(Me)NMe2)]4, and Zn3Et4(N(Et)NMe2)2 were synthesized by allowing excess hydrazine, HN(R)NMe2, to react with diethyl zinc. The product of the reaction between ZnEt2 and HN(i-Pr)NMe2ortho-metalated 4-(dimethylamino)pyridine (DMAP) at room temperature, producing the complex Zn[(NC5H3-p-NMe2)ZnEt(N(i-Pr)NMe2)]2. At elevated temperatures, Zn3Et4(N(Et)NMe2)2 also ortho-metalated DMAP, but [EtZn(N(Me)NMe2)]4 did not. Single-crystal X-ray diffraction studies revealed that the hydrazide ligands in [EtZn(N(SiMe3)NMe2)]2 act as bridging mono-hapto amide ligands, and in Zn3Et4(N(Et)NMe2)2 and Zn[(NC5H3-p-NMe2)ZnEt(N(i-Pr)NMe2)]2 the hydrazide ligands are di-hapto.
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![N-[dimethyl(methylamino)silyl]methanamine](http://img.cochemist.com/ccimg/10600/10519-99-0_b.png)
