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Zhao Y, Anderson NC, Ratzloff MW, Mulder DW, Zhu K, Turner JA, Neale NR, King PW, Branz HM. Proton Reduction Using a Hydrogenase-Modified Nanoporous Black Silicon Photoelectrode. ACS Appl Mater Interfaces 2016; 8:14481-7. [PMID: 27219350 DOI: 10.1021/acsami.6b00189] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Metalloenzymes featuring earth-abundant metal-based cores exhibit rates for catalytic processes such as hydrogen evolution comparable to those of noble metals. Realizing these superb catalytic properties in artificial systems is challenging owing to the difficulty of effectively interfacing metalloenzymes with an electrode surface in a manner that supports efficient charge-transfer. Here, we demonstrate that a nanoporous "black" silicon (b-Si) photocathode provides a unique interface for binding an adsorbed [FeFe]-hydrogenase enzyme ([FeFe]-H2ase). The resulting [FeFe]-H2ase/b-Si photoelectrode displays a 280 mV more positive onset potential for hydrogen generation than bare b-Si without hydrogenase, similar to that observed for a b-Si/Pt photoelectrode at the same light intensity. Additionally, we show that this H2ase/b-Si electrode exhibits a turnover frequency of ≥1300 s(-1) and a turnover number above 10(7) and sustains current densities of at least 1 mA/cm(2) based on the actual surface area of the electrode (not the smaller projected geometric area), orders of magnitude greater than that observed for previous enzyme-catalyzed electrodes. While the long-term stability of hydrogenase on the b-Si surface remains too low for practical applications, this work extends the proof-of-concept that biologically derived metalloenzymes can be interfaced with inorganic substrates to support technologically relevant current densities.
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Affiliation(s)
- Yixin Zhao
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Nicholas C Anderson
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Michael W Ratzloff
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - David W Mulder
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Kai Zhu
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - John A Turner
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Nathan R Neale
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Paul W King
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Howard M Branz
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
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Zhao Y, Anderson NC, Zhu K, Aguiar JA, Seabold JA, van de Lagemaat J, Branz HM, Neale NR, Oh J. Oxidatively stable nanoporous silicon photocathodes with enhanced onset voltage for photoelectrochemical proton reduction. Nano Lett 2015; 15:2517-2525. [PMID: 25723908 DOI: 10.1021/acs.nanolett.5b00086] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Stable and high-performance nanoporous "black silicon" photoelectrodes with electrolessly deposited Pt nanoparticle (NP) catalysts are made with two metal-assisted etching steps. Doubly etched samples exhibit an ∼300 mV positive shift in photocurrent onset for photoelectrochemical proton reduction compared to oxide-free planar Si with identical catalysts. We find that the photocurrent onset voltage of black Si photocathodes prepared from single-crystal planar Si wafers by an Ag-assisted etching process increases in oxidative environments (e.g., aqueous electrolyte) owing to a positive flat-band potential shift caused by surface oxidation. However, within 24 h, the surface oxide layer becomes a kinetic barrier to interfacial charge transfer that inhibits proton reduction. To mitigate this issue, we developed a novel second Pt-assisted etch process that buries the Pt NPs deep into the nanoporous Si surface. This second etch shifts the onset voltage positively, from +0.25 V to +0.4 V versus reversible hydrogen electrode, and reduces the charge-transfer resistance with no performance decrease seen for at least two months. PEC performance was stable owing to Pt NP catalysts that were buried deeply in the photoelectrode by the second etch, below a thick surface layer comprised primarily of amorphous SiO2 along with some degree of remaining crystalline Si as observed by scanning and transmission electron micrographs. Electrochemical impedance studies reveal that the second etch leads to a considerably smaller interfacial charge-transfer resistance than samples without the additional etch, suggesting that burying the Pt NPs improves the interfacial contact to the crystalline silicon surface.
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Affiliation(s)
- Y Zhao
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
| | - N C Anderson
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
| | - K Zhu
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
| | - J A Aguiar
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
| | - J A Seabold
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
| | - J van de Lagemaat
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
| | - H M Branz
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
| | - N R Neale
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
| | - J Oh
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Korea Advanced Institute of Science and Technology, Daejeon 305-338, South Korea
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Shircliff RA, Stradins P, Moutinho H, Fennell J, Ghirardi ML, Cowley SW, Branz HM, Martin IT. Angle-resolved XPS analysis and characterization of monolayer and multilayer silane films for DNA coupling to silica. Langmuir 2013; 29:4057-4067. [PMID: 23445373 DOI: 10.1021/la304719y] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We measure silane density and Sulfo-EMCS cross-linker coupling efficiency on aminosilane films by high-resolution X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements. We then characterize DNA immobilization and hybridization on these films by (32)P-radiometry. We find that the silane film structure controls the efficiency of the subsequent steps toward DNA hybridization. A self-limited silane monolayer produced from 3-aminopropyldimethylethoxysilane (APDMES) provides a silane surface density of ~3 nm(-2). Thin (1 h deposition) and thick (19 h deposition) multilayer films are generated from 3-aminopropyltriethoxysilane (APTES), resulting in surfaces with increased roughness compared to the APDMES monolayer. Increased silane surface density is estimated for the 19 h APTES film, due to a ∼32% increase in surface area compared to the APDMES monolayer. High cross-linker coupling efficiencies are measured for all three silane films. DNA immobilization densities are similar for the APDMES monolayer and 1 h APTES. However, the DNA immobilization density is double for the 19 h APTES, suggesting that increased surface area allows for a higher probe attachment. The APDMES monolayer has the lowest DNA target density and hybridization efficiency. This is attributed to the steric hindrance as the random packing limit is approached for DNA double helices (dsDNA, diameter ≥ 2 nm) on a plane. The heterogeneity and roughness of the APTES films reduce this steric hindrance and allow for tighter packing of DNA double helices, resulting in higher hybridization densities and efficiencies. The low steric hindrance of the thin, one to two layer APTES film provides the highest hybridization efficiency of nearly 88%, with 0.21 dsDNA/nm(2). The XPS data also reveal water on the cross-linker-treated surface that is implicated in device aging.
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Affiliation(s)
- Rebecca A Shircliff
- Chemistry and Geochemistry Department, Colorado School of Mines, Golden, Colorado 80401, United States
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Oh J, Yuan HC, Branz HM. An 18.2%-efficient black-silicon solar cell achieved through control of carrier recombination in nanostructures. Nat Nanotechnol 2012; 7:743-8. [PMID: 23023643 DOI: 10.1038/nnano.2012.166] [Citation(s) in RCA: 217] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 08/27/2012] [Indexed: 05/11/2023]
Abstract
Silicon nanowire and nanopore arrays promise to reduce manufacturing costs and increase the power conversion efficiency of photovoltaic devices. So far, however, photovoltaic cells based on nanostructured silicon exhibit lower power conversion efficiencies than conventional cells due to the enhanced photocarrier recombination associated with the nanostructures. Here, we identify and separately measure surface recombination and Auger recombination in wafer-based nanostructured silicon solar cells. By identifying the regimes of junction doping concentration in which each mechanism dominates, we were able to design and fabricate an independently confirmed 18.2%-efficient nanostructured 'black-silicon' cell that does not need the antireflection coating layer(s) normally required to reach a comparable performance level. Our results suggest design rules for efficient high-surface-area solar cells with nano- and microstructured semiconductor absorbers.
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Affiliation(s)
- Jihun Oh
- National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
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Weiss DN, Lee BG, Richmond DA, Nemeth W, Wang Q, Keszler DA, Branz HM. Diffractive light trapping in crystal-silicon films: experiment and electromagnetic modeling. Appl Opt 2011; 50:5728-5734. [PMID: 22015368 DOI: 10.1364/ao.50.005728] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Diffractive light trapping in 1.5 μm thick crystal silicon films is studied experimentally through hemispherical reflection measurements and theoretically through rigorous coupled-wave analysis modeling. The gratings were fabricated by nanoimprinting of dielectric precursor films. The model data, which match the experimental results well without the use of any fitting parameters, are used to extract the light trapping efficiency. Diffractive light trapping is studied as a function of incidence angle, and an enhancement of light absorption is found for incidence angles up to 50° for both TE and TM polarizations.
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Affiliation(s)
- Dirk N Weiss
- Washington Technology Center and University of Washington, Department of Electrical Engineering, Seattle, Washington 98195, USA.
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Shircliff RA, Martin IT, Pankow JW, Fennell J, Stradins P, Ghirardi ML, Cowley SW, Branz HM. High-resolution X-ray photoelectron spectroscopy of mixed silane monolayers for DNA attachment. ACS Appl Mater Interfaces 2011; 3:3285-3292. [PMID: 21797205 DOI: 10.1021/am200604q] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The amine density of 3-aminopropyldimethylethoxysilane (APDMES) films on silica is controlled to determine its effect on DNA probe density and subsequent DNA hybridization. The amine density is tailored by controlling the surface reaction time of (1) APDMES, or (2) n-propyldimethylchlorosilane (PDMCS, which is not amine terminated) and then reacting it with APDMES to form a mixed monolayer. High-resolution X-ray photoelectron spectroscopy (XPS) is used to quantify silane surface coverage of both pure and mixed monolayers on silica; the XPS data demonstrate control of amine density in both pure APDMES and PDMCS/APDMES mixed monolayers. A linear correlation between the atomic concentration of N atoms from the amine and Si atoms from the APDMES in pure APDMES films allows us to calculate the PDMCS/APDMES ratio in the mixed monolayers. Fluorescence from attached DNA probes and from hybridized DNA decreases as the percentage of APDMES in the mixed monolayer is decreased by dilution with PDMCS.
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Affiliation(s)
- Rebecca A Shircliff
- Chemistry and Geochemistry Department, Colorado School of Mines, Golden, Colorado 80401, United States
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Abstract
ABSTRACTWe review evidence for the vital role of H in metastability and defect equilibration in hydrogenated amorphous silicon. H pairs act both as an H reservoir that equilibrates with DB's and dopants and as the metastable H state of light-induced metastability. With ab initio pseudopotential theory, we calculate energies and configurations for two novel H pairing sites associated with small hydrogenated vacancies. We describe microscopic models of equilibration and metastability based on our calculations.
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Abstract
ABSTRACTWe examine the treatment of the hydrogenated Amorphous silicon (a-Si:H) dangling-bond defect used in the Analysis of microelectronic and Photonic Structures (AMPS) computer model and in other models of a-Si:H semiconductor devices. The dangling bond defect (D) is trivalent, with two correlated electronic levels in the gap. However, Modelers typically employ two uncorrelated bivalent levels to represent D; this introduces fictitious neutral dangling bond (D°) levels whenever D is charged. We find that the bivalent (AMPS) representation captures the important aspects of D physics and introduces only small errors into simulations. To reach this conclusion, we examine charge density and recombination and compare the trivalent D defect and its bivalent representation in both thermal equilibrium and non-equilibrium (illuminated) cases. The charge density is identical, implying that band bending computed by the simulation is accurate. We find errors in the recombination rate for the bivalent representation are normally less than or equal to σ0/σch, where σ° is the capture cross section of D0 and σch is the capture cross section of a charged state of D. Typically Modelers use σ0/σch of 1:10 to 1:100 yielding insignificant errors in the recombination rate with the uncorrelated bivalent representation.
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Abstract
AbstractX-ray irradiation-induced structural changes in undoped a-Si:H have been investigated in detail by X-ray photoemission spectroscopy (XPS). The Si2s and the Si2p peaks were found to shift simultaneously to lower bonding energies, by the same amount, with X-ray irradiation. The shifts are near saturation, at about 0.1 eV, after one hour of irradiation at the intensity used; they can be reversed almost completely, seemingly with an activation energy lower than that for the metastable changes in electronic properties (Staebler-Wronski effect). The present results suggest that essentially the whole Si network structure is affected by the X-ray irradiation.
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Bullock JN, Bechinger C, Xu Y, Benson DK, Branz HM. Improved Monolithic Photovoltaic-Electrochromic Devices Incorporating an a-SiC:H Solar Cell. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-420-183] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractIn the tandem photovoltaic-electrochromic (PV-EC) device, a wide-gap, semitransparent, amorphous silicon-carbon alloy (a-SiC:H) photovoltaic device and an electrochromic optical transmittance modulator (EC device) are deposited sequentially to form a monolithic device on a single substrate. This device can be used as a “smart” window for active control of daylighting and building cooling load without an external electrical connection.Last year we reported preliminary results on our development of a semi-transparent PV cell incorporating an a-SiC:H i-layer. Here we report our recent progress on the semitransparent PV component of a PV-EC device and development of a Li-based EC device that colors at voltages below 0.9 V. Finally, we discuss both recent progress and difficulties in integrating the two devices on one substrate.
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Wang Q, Perkins J, Moutinho H, To B, Branz HM. Amorphous to Microcrystalline Transition in Thickness-graded Hot-Wire CVD Silicon Films. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-715-a17.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractWe study the amorphous to microcrystalline silicon phase transition in hot-wire chemical vapor deposition thin-film silicon by depositing a series of unique, thickness-graded, samples on a glass substrate at 200°C. By inserting or withdrawing a motor-driven shutter during growth, we make samples that vary from 200 to about 2000 Å thick across each 5-cm along stripe. Each stripe is grown at a different dilution ratio of hydrogen to silane in the source gas. The phase composition at various locations was determined by Raman and ultraviolet-reflectivity measurements. Atomic force microscopy (AFM) images of topology reveal that the surface changes from a rather smooth a-Si phase to more granular microcrystalline-Si (rms roughness increases from 10 to 47 Å).
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Abstract
AbstractRecent doping experiments in n-type perylene diimide (PPEEB) semiconducting thin films showed an unexpected quadratic dependence of electrical conductivity upon dopant molecule concentration. We propose that singly-ionized dopant pairs outnumber ionized unpaired dopants and dominate conductivity. Random association into dopant pairs during spin coating then explains the quadratic dependence. Classical calculations confirm that dopant pairing reduces the binding energy of the easiest-to-ionize electron. Our model agrees with the measured conductivity activation energy and magnitude, assuming typical electron mobility in the crystal. The random distribution of dopants implies their distribution cannot equilibrate during the spincoating process.
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Xiang HJ, Da Silva JLF, Branz HM, Wei SH. Understanding the clean interface between covalent Si and ionic Al2O3. Phys Rev Lett 2009; 103:116101. [PMID: 19792386 DOI: 10.1103/physrevlett.103.116101] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Indexed: 05/28/2023]
Abstract
The atomic and electronic structures of the (001)-Si/(001)-gamma-Al(2)O(3) heterointerface are investigated by first principles total energy calculations combined with a newly developed "modified basin-hopping" method. It is found that all interface Si atoms are fourfold coordinated due to the formation of Si-O and unexpected covalent Si-Al bonds in the new abrupt interface model. And the interface has perfect electronic properties in that the unpassivated interface has a large LDA band gap and no gap levels. These results show that it is possible to have clean semiconductor-oxide interfaces.
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Affiliation(s)
- H J Xiang
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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Du MH, Branz HM, Crandall RS, Zhang SB. Bistability-mediated carrier recombination at light-induced boron-oxygen complexes in silicon. Phys Rev Lett 2006; 97:256602. [PMID: 17280375 DOI: 10.1103/physrevlett.97.256602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2005] [Indexed: 05/13/2023]
Abstract
A first-principles study of the BO2 complex in B-doped Czochralski Si reveals a defect-bistability-mediated carrier recombination mechanism, which contrasts with the standard fixed-level Shockley-Read-Hall model of recombination. An O2 dimer distant from B causes only weak carrier recombination, which nevertheless drives O2 diffusion under light to form the BO2 complex. Although BO2 and O2 produce nearly identical defect levels in the band gap, the recombination at BO2 is substantially faster than at O2 because the charge state of the latter inhibits the hole capture step of recombination.
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Affiliation(s)
- Mao-Hua Du
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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Fixe F, Branz HM, Louro N, Chu V, Prazeres DMF, Conde JP. Electric-field assisted immobilization and hybridization of DNA oligomers on thin-film microchips. Nanotechnology 2005; 16:2061-71. [PMID: 20817972 DOI: 10.1088/0957-4484/16/10/014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Single, square voltage pulses in the microsecond timescale result in selective 5'-end covalent bonding (immobilization) of thiolated single-stranded (ss) DNA probes to a modified silicon dioxide flat surface and in specific hybridization of ssDNA targets to the immobilized probe. Immobilization and hybridization rates using microsecond voltage pulses at or below 1 V are at least 10(8) times faster than in the passive control reactions performed without electric field (E), and can be achieved with at least three differently functionalized thin-film surfaces on plastic or glass substrates. The systematic study of the effect of DNA probe and target concentrations, of DNA probe and target length, and the application of asymmetric pulses on E-assisted DNA immobilization and hybridization showed that: (1) the rapidly rising edge of the pulse is most critical to the E-assisted processes, but the duration of the pulse is also important; (2) E-assisted immobilization and hybridization can be performed with micrometre-sized pixels, proving the potential for use on microelectronic length scales, and the applied voltage can be scaled down together with the electrode spacing to as low as 25 mV; and (3) longer DNA chains reduce the yield in the E-assisted immobilization and hybridization because the density of physisorbed single-stranded DNA is reduced. The results show that the E-induced reactions can be used as a general method in DNA microarrays to produce high-density DNA chips (E-immobilization) and speed the microarray-based analysis (E-hybridization).
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Affiliation(s)
- F Fixe
- INESC Microsistemas e Nanotecnologias (INESC-MN), Rua Alves Redol, 9, 1000-029 Lisboa, Portugal. Centro de Engenharia Biológica e Química, Instituto Superior Técnico, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal
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Chen SG, Branz HM, Eaton SS, Taylor PC, Cormier RA, Gregg BA. Substitutional n-Type Doping of an Organic Semiconductor Investigated by Electron Paramagnetic Resonance Spectroscopy. J Phys Chem B 2004. [DOI: 10.1021/jp049628c] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Si-Guang Chen
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401-3393, Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, Department of Physics, University of Utah, Salt Lake City, Utah 84112-0830, and Department of Chemistry, Metropolitan State College of Denver, Denver, Colorado 80204
| | - Howard M. Branz
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401-3393, Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, Department of Physics, University of Utah, Salt Lake City, Utah 84112-0830, and Department of Chemistry, Metropolitan State College of Denver, Denver, Colorado 80204
| | - Sandra S. Eaton
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401-3393, Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, Department of Physics, University of Utah, Salt Lake City, Utah 84112-0830, and Department of Chemistry, Metropolitan State College of Denver, Denver, Colorado 80204
| | - P. Craig Taylor
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401-3393, Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, Department of Physics, University of Utah, Salt Lake City, Utah 84112-0830, and Department of Chemistry, Metropolitan State College of Denver, Denver, Colorado 80204
| | - Russell A. Cormier
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401-3393, Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, Department of Physics, University of Utah, Salt Lake City, Utah 84112-0830, and Department of Chemistry, Metropolitan State College of Denver, Denver, Colorado 80204
| | - Brian A. Gregg
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401-3393, Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, Department of Physics, University of Utah, Salt Lake City, Utah 84112-0830, and Department of Chemistry, Metropolitan State College of Denver, Denver, Colorado 80204
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Fixe F, Branz HM, Louro N, Chu V, Prazeres DMF, Conde JP. Immobilization and hybridization by single sub-millisecond electric field pulses, for pixel-addressed DNA microarrays. Biosens Bioelectron 2004; 19:1591-7. [PMID: 15142592 DOI: 10.1016/j.bios.2003.12.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2003] [Revised: 12/11/2003] [Accepted: 12/12/2003] [Indexed: 11/22/2022]
Abstract
Single square voltage pulses applied to buried electrodes result in dramatic rate increases for (1) selective covalent bonding (immobilization) of single-stranded DNA (ssDNA) probes to a functionalized thin film SiO(2) surface on a plastic substrate and (2) hybridization of ssDNA to the immobilized probe. DNA immobilization and hybridization times are 100 ns and 10 micros, respectively, about 10(9) times faster than the corresponding passive reactions without electric field. Surface coverage is comparable. Duration, magnitude and slew rate of the voltage pulse are all key factors controlling the rates of ssDNA immobilization and hybridization. With rise times of 4.5 ns, pulses shorter than 1 ms and voltages below 1V are effective. The ssDNA adsorbed on the surface is reoriented by the rapidly changing electric field. This reduces steric barriers and speeds the immobilization and hybridization reactions. These results open the way for pixel-addressed microarrays driven by silicon microelectronics circuits.
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Affiliation(s)
- F Fixe
- INESC Microsistemas e Nanotecnologias (INESC-MN), Rua Alves Redol, 9, 1000-029 Lisbon, Portugal.
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Zhang SB, Branz HM. Hydrogen above saturation at silicon vacancies: H-pair reservoirs and metastability sites. Phys Rev Lett 2001; 87:105503. [PMID: 11531485 DOI: 10.1103/physrevlett.87.105503] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2001] [Indexed: 05/23/2023]
Abstract
We propose that hydrogen-passivated multivacancies which appear to be fully saturated with H can actually capture additional H in electrically inactive sites. In silicon, first-principles total energy calculations show that splitting an (m>or=2) multivacancy into a mono- and an (m-1) vacancy provides a low-strain pairing site for H, 0.4 eV per H lower than any known bulk pairing site. This monovacancy ejection mechanism is an excellent candidate for the H reservoir found both in crystalline and amorphous Si. A distinct H pairing on the fully saturated m vacancies, by forming an internal surface Si-Si dimer, provides the final state of light-induced metastable degradation of hydrogenated amorphous silicon.
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Affiliation(s)
- S B Zhang
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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Zhang SB, Branz HM. Nonradiative electron-hole recombination by a low-barrier pathway in hydrogenated silicon semiconductors. Phys Rev Lett 2000; 84:967-970. [PMID: 11017417 DOI: 10.1103/physrevlett.84.967] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/1999] [Indexed: 05/23/2023]
Abstract
A microscopic pathway for nonradiative electron-hole recombination by large structural reconfiguration in hydrogenated Si is found with first-principles calculations. Trapped-biexciton formation leads to a low-barrier reconfiguration of the H atom, accompanied by crossing of doubly occupied electron and hole levels in the band gap. This crossing represents the nonradiative recombination of the carriers, without multiphonon emission. The proposal provides a mechanism for carrier-induced H emission during metastable degradation of hydrogenated amorphous silicon.
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Affiliation(s)
- SB Zhang
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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Kemp M, Branz HM. Hydrogen diffusion in a-Si:H: Solution of the tracer equations including capture by exchange. Phys Rev B Condens Matter 1995; 52:13946-13954. [PMID: 9980610 DOI: 10.1103/physrevb.52.13946] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Branz HM, Iwaniczko E. Evidence for the hydrogen-glass model of metastability annealing in phosphorus-doped amorphous silicon. Phys Rev B Condens Matter 1993; 48:17114-17120. [PMID: 10008315 DOI: 10.1103/physrevb.48.17114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Branz HM, Schiff EA. Dangling-bond relaxation and deep-level measurements in hydrogenated amorphous silicon. Phys Rev B Condens Matter 1993; 48:8667-8671. [PMID: 10007080 DOI: 10.1103/physrevb.48.8667] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kemp M, Branz HM. Analytic solution of trap-controlled tracer diffusion in amorphous solids. Phys Rev B Condens Matter 1993; 47:7067-7070. [PMID: 10004702 DOI: 10.1103/physrevb.47.7067] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Branz HM, Asher SE, Nelson BP. Light-enhanced deep deuterium emission and the diffusion mechanism in amorphous silicon. Phys Rev B Condens Matter 1993; 47:7061-7066. [PMID: 10004701 DOI: 10.1103/physrevb.47.7061] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Yelon A, Movaghar B, Branz HM. Origin and consequences of the compensation (Meyer-Neldel) law. Phys Rev B Condens Matter 1992; 46:12244-12250. [PMID: 10003136 DOI: 10.1103/physrevb.46.12244] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Branz HM, Silver M. Potential fluctuations due to inhomogeneity in hydrogenated amorphous silicon and the resulting charged dangling-bond defects. Phys Rev B Condens Matter 1990; 42:7420-7428. [PMID: 9994885 DOI: 10.1103/physrevb.42.7420] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Branz HM. Dangling bonds in doped amorphous silicon: Equilibrium, relaxation, and transition energies. Phys Rev B Condens Matter 1989; 39:5107-5115. [PMID: 9948899 DOI: 10.1103/physrevb.39.5107] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Branz HM. Charge-trapping model of metastability in doped hydrogenated amorphous silicon. Phys Rev B Condens Matter 1988; 38:7474-7479. [PMID: 9945474 DOI: 10.1103/physrevb.38.7474] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Branz HM, Capuder K, Lyons EH, Haggerty JS, Adler D. Conductivity and quenched-in defects in hydrogenated amorphous silicon. Phys Rev B Condens Matter 1987; 36:7934-7940. [PMID: 9942590 DOI: 10.1103/physrevb.36.7934] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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