Peer review information Nature Communications thanks the anonymous reviewer(s) for their contribu... more Peer review information Nature Communications thanks the anonymous reviewer(s) for their contribution to the peer review of this work.
Molecular electron spins are promising candidates as scalable and tunable qubits but often suffer... more Molecular electron spins are promising candidates as scalable and tunable qubits but often suffer from air sensitivity or other undesirable decomposition pathways. Furthermore, significant spin-lattice relaxation and nuclear spinmediated decoherence limit their applications. While significant advances in the synthesis of new molecular electron spin qubit candidates have led to improved coherence lifetimes, one key question is whether coherence can be maintained under conditions relevant for employment as quantum sensors, for instance in solution and at room temperature for sensing in biological systems. Here we report a tetrathiafulvalene-based molecular qubit candidate with spin centered on a nuclear spin-free bridging ligand. This unique air and water-stable scaffold exhibits a long spin decoherence time of hundreds of nanoseconds at ambient temperatures and in nuclear spin-rich protonated solvents. These results distinguish this system as a promising candidate for the development of novel room temperature, solution-phase quantum sensing technologies, and suggest that molecular electron spin qubits can be ideal candidates for these applications.
Employing electrons for direct control of nanoscale reaction is highly desirable since it provide... more Employing electrons for direct control of nanoscale reaction is highly desirable since it provides fabrication of nanostructures with different properties at atomic resolution and with flexibility of dimension and location. Here, applying in situ transmission electron microscopy, we show the reversible oxidation and reduction kinetics in Ag, well controlled by changing the dose rate of electron beam. Aberration-corrected high-resolution transmission electron microscopy observation reveals that O atoms are preferably inserted and extracted along the {111} close-packed planes of Ag, leading to the nucleation and decomposition of nanoscale Ag 2 O islands on the Ag substrate. By controlling electron beam size and dose rate, we demonstrated fabrication of an array of 3 nm Ag 2 O nanodots in an Ag matrix. Our results open up a new pathway to manipulate atomistic reaction with electron beam towards the precise fabrication of nanostructures for device applications.
Titanium dioxide is the most studied photocatalytic material and has been reported to be active f... more Titanium dioxide is the most studied photocatalytic material and has been reported to be active for a wide range of reactions including oxidation of hydrocarbons and reduction of nitrogen. However, the molecular-scale interactions between the titania photocatalyst and dinitrogen are still debated, particularly in the presence of hydrocarbons. Here, we used several spectroscopic and computational techniques to identify interactions between nitrogen, methanol, and titania under illumination. Electron paramagnetic resonance spectroscopy (EPR) allowed us to observe the formation of carbon radicals upon exposure to ultraviolet radiation. These carbon radicals are
We present an epitaxial Er3+:Y2O3/silicon material platform for scalable quantum photonic devices... more We present an epitaxial Er3+:Y2O3/silicon material platform for scalable quantum photonic devices. We discuss a system integrating suspended Er3+:Y2O3 membranes with a fiber Fabry-Perot cavity for coherent spectroscopy enabling quantum memory and transduction.
International Journal of High Speed Electronics and Systems, 2008
The interactions of charges in DNA with the vibrational modes in DNA depend on the spectra of the... more The interactions of charges in DNA with the vibrational modes in DNA depend on the spectra of these vibrational modes. Using (a) the Su-Schrieffer-Heeger (SSH) Hamiltonian approach, (b) integrated structures of DNA and manmade nanostructures, and (c) gel electrophoresis techniques,1 the interaction between charges in DNA and the vibrational modes of DNA are investigated. As is well-known, DNA has a rich spectrum of modes in the THz spectral regime. The use of manmade nanostructures integrated with DNA facilitates the engineering of nanoscale systems useful in studying the role of environmental effects on the vibrational modes of DNA as well as the interaction of these modes with charge carriers in DNA. Among the DNA-based structures considered in this account are: B-DNA and Z-DNA strands related by a conformational change; and DNA molecules bound on one terminal to indirect bandgap semiconductor quantum dots. Gel electrophoresis is used as a tool for the analysis of carrier interact...
International Journal of High Speed Electronics and Systems, 2007
This paper presents models and experimental measurements that shed light on THz-phonon mediated t... more This paper presents models and experimental measurements that shed light on THz-phonon mediated transport of polarons in biomolecules. Polaron transport in DNA has been considered recently in view of the expected derealization of charge carriers on a one-dimensional wire as well as the highly charged nature of DNA.1,2 An understanding of the electrical transport properties and THz-phonon interactions of biomolecules is important in view of DNA's potential applications both as electrically conductive wires and as structures that facilitate the chemically-directed assembly of massively integrated ensembles of nanoscale semiconducting elements into terascale integrated networks. Moreover, understanding these interactions provides information of the THz spectrum of vibrational modes in DNA. A primary focus of this paper is on charge transport in biomolecules using indirect-bandgap colloidal nanocrystals linked with biomolecules.3 Through a combination of theoretical and experimental...
The reaction mechanism of nitric oxide (NO) reduction by excess electrons on TiO2 nanoparticles (... more The reaction mechanism of nitric oxide (NO) reduction by excess electrons on TiO2 nanoparticles (eTiO2-) has been studied under anaerobic conditions. TiO2 was loaded with 10-130 electrons per particle using -irradiation of acidic TiO2 colloid solutions containing 2-propanol. The study is based on time resolved kinetics and reactants and products analysis. The reduction of NO by eTiO2- is interpreted in terms of competition between a reaction-path leading to formation of NH3 and a path leading to N2O and N2.The proposed mechanism involves consecutive one-electron transfers of NO and its reduction intermediates HNO, NH2O• and NH2OH. The results show that eTiO2- does not reduce N2O and N2. Second order rate constants of eTiO2- reactions with NO (740 ± 30 M-1s-1) and NH2OH (270 ± 30 M-1s-1) have been determined employing the rapid-mixing stopped-flow technique, and that with HNO (> 1.3 x106 M-1s-1) was derived from fitting the kinetic traces to the suggested reaction mechanism, whic...
Photocatalytic production of clean hydrogen fuels using water and sunlight has attracted remarkab... more Photocatalytic production of clean hydrogen fuels using water and sunlight has attracted remarkable attention due to the increasing global energy demand. Natural and synthetic dyes can be utilized to sensitize semiconductors for solar energy transformation using visible light. In this study, reduced graphene oxide (rGO) and a membrane protein bacteriorhodopsin (bR) were employed as building modules to harness visible light by a Pt/TiO2 nanocatalyst. Introduction of the rGO boosts the nano-bio catalyst performance that results in hydrogen production rates of approximately 11.24 mmol of H2 (μmol protein)(-1) h(-1). Photoelectrochemical measurements show a 9-fold increase in photocurrent density when TiO2 electrodes were modified with rGO and bR. Electron paramagnetic resonance and transient absorption spectroscopy demonstrate an interfacial charge transfer from the photoexcited rGO to the semiconductor under visible light.
Irradiation by visible light of an aqueous solution containing a photosensitizer, methyl viologen... more Irradiation by visible light of an aqueous solution containing a photosensitizer, methyl viologen (MV **) and ethylenediaminetetraacetic acid leads to the formation of the reduced form of methyl viologen (MV3. The quantum yield for the formation of MV' depends strongly on the time during which the formation is observed owing to the reaction of MV' with oxidative products and its reduction to MV '. Proflavin, acrldine yellow and ruthenium( II)tris( 2,2-bipyridyl) were used as photosensitizers and showed the same ability to promote hydrogen evolution. When CdS was used as a sensitizer a factor of 10 less hydrogen was obtained than when the dyes were used. The redox catalysts platinum, Pt-TiO,-Ru02 and Pt-CdS in colloidal systems showed approximately the same activity towards the reduction of water. The reduction of MV*' and the evolution of hydrogen were enhanced at higher temperatures (70 "C). The optimum conditions for water reduction on redox catalysts in colloidal systems under continuous illumination are analysed.
Optical effects due to size quantization in three dimensions have been observed for CdS and PbS c... more Optical effects due to size quantization in three dimensions have been observed for CdS and PbS colloids with particle diameters less than 50 A and 20 to 200 A, respectively. The optical absorption edge is blue shifted approx.0.9 eV for the CdS colloid; for PbS colloids the shift is approx.2 eV for particle diameters 20 to 30 A, and approx.1
Three families of ZnTe magic sized nanoclusters (MSNCs) were obtained exclusively using poly-tell... more Three families of ZnTe magic sized nanoclusters (MSNCs) were obtained exclusively using poly-tellurides as a tellurium precursor in one-pot reaction by simply varying the reaction temperature and time only. Different ZnTe MSNCs exhibit different self-assembling or aggregation behavior, owing to their different structure, cluster size, and dipole-dipole interactions. The smallest family of ZnTe MSNCs (F323) does not reveal a crystalline structure and as a result assembles into lamellar triangle plates. Continuous heating of as synthesized ZnTe F323 assemblies resulted in the formation of ZnTe F398 MSNCs with wurzite structure and concomitant transformation into lamellar rectangle assemblies with organization of nanoclusters along <002> direction. Further annealing of ZnTe F398 assembled lamellar rectangles lead to full organization of MSNCs in all directions and formation of larger ZnTe F444 NCs that spontaneously form ultrathin nanowires following oriented attachment mechanism. The key step in control over the size distribution of ZnTe ultra-thin nanowires is, in fact, the growth mechanism of ZnTe F398 MSNCs; namely, step growth mechanism enables formation of more uniform nanowires compared to those obtained by continuous growth mechanism. High yield of ZnTe nanowires is achieved as a result of wurzite structure of F398 precursor. Transient absorption (TA) measurements show that all the three families possess ultra-fast dynamics of photo generated electrons, despite their different crystalline structures.
We report on various strategies for the synthesis of titania-based photocatalysts, including mixe... more We report on various strategies for the synthesis of titania-based photocatalysts, including mixed phase titania, and anatase nanotubes. These photocatalysts have shown improved efficiency for the transformation of CO2 to methane as tested in the absence of sacrificial hole scavengers. The EPR studies have revealed a high concentration of undercoordinated Ti atoms on the surface of photocatalysts that improve adsorption/binding of CO2, and thus, the photoefficiency of the reaction.
Raman scattering enhancement was observed in systems where different metal oxide semiconductors (... more Raman scattering enhancement was observed in systems where different metal oxide semiconductors (TiO 2 , Fe 2 O 3 , ZrO 2 , and CeO 2 ) were modified with enediol ligands. The intensity of Raman scattering was dependent on laser frequency and correlated with the extinction coefficient of the CT complex of the enediol ligands and nanoparticles. The mechanism of Raman enhancement was studied by varying both the chemical composition of the enediol ligand and the chemical composition (and crystal structure) of the nanoparticles. We found that the intensity of the Raman signal depends on the number of surface binding sites, electron density of the ligands, and their dipole moment. Changes in chemical composition caused variations in the intensity, frequency, and number of Raman bands observed. We also showed that Raman scattering is observed for the bioconjugated system, where a peptide is linked to the surface of the particle through a catechol linker, and further investigated the potential for such a system in the development of Raman-based in vivo and in vitro biodetection, cell labeling and imaging, and nanotherapeutic strategies.
ZnTe nanorods with controllable aspect ratios were synthesized using polytellurides a tellurium p... more ZnTe nanorods with controllable aspect ratios were synthesized using polytellurides a tellurium precursor. The use of polytellurides which allow nucleation and growth at relatively low temperature is the key to formation of wurtzite phase and controlled anisotropic growth along c-axis. The aspect ratio of the resulting ZnTe nanorods was controlled by tuning the temperature that in turn controls the kinetics of the nanocrystal growth. A diameter dependent quantum confinement effect in ZnTe nanorods was observed by UV-vis absorption spectroscopy. Transient absorption measurements show ultrafast charge injection dynamics from ZnTe nanorods, suggesting their strong potential for applications in photocatalysis.
Peer review information Nature Communications thanks the anonymous reviewer(s) for their contribu... more Peer review information Nature Communications thanks the anonymous reviewer(s) for their contribution to the peer review of this work.
Molecular electron spins are promising candidates as scalable and tunable qubits but often suffer... more Molecular electron spins are promising candidates as scalable and tunable qubits but often suffer from air sensitivity or other undesirable decomposition pathways. Furthermore, significant spin-lattice relaxation and nuclear spinmediated decoherence limit their applications. While significant advances in the synthesis of new molecular electron spin qubit candidates have led to improved coherence lifetimes, one key question is whether coherence can be maintained under conditions relevant for employment as quantum sensors, for instance in solution and at room temperature for sensing in biological systems. Here we report a tetrathiafulvalene-based molecular qubit candidate with spin centered on a nuclear spin-free bridging ligand. This unique air and water-stable scaffold exhibits a long spin decoherence time of hundreds of nanoseconds at ambient temperatures and in nuclear spin-rich protonated solvents. These results distinguish this system as a promising candidate for the development of novel room temperature, solution-phase quantum sensing technologies, and suggest that molecular electron spin qubits can be ideal candidates for these applications.
Employing electrons for direct control of nanoscale reaction is highly desirable since it provide... more Employing electrons for direct control of nanoscale reaction is highly desirable since it provides fabrication of nanostructures with different properties at atomic resolution and with flexibility of dimension and location. Here, applying in situ transmission electron microscopy, we show the reversible oxidation and reduction kinetics in Ag, well controlled by changing the dose rate of electron beam. Aberration-corrected high-resolution transmission electron microscopy observation reveals that O atoms are preferably inserted and extracted along the {111} close-packed planes of Ag, leading to the nucleation and decomposition of nanoscale Ag 2 O islands on the Ag substrate. By controlling electron beam size and dose rate, we demonstrated fabrication of an array of 3 nm Ag 2 O nanodots in an Ag matrix. Our results open up a new pathway to manipulate atomistic reaction with electron beam towards the precise fabrication of nanostructures for device applications.
Titanium dioxide is the most studied photocatalytic material and has been reported to be active f... more Titanium dioxide is the most studied photocatalytic material and has been reported to be active for a wide range of reactions including oxidation of hydrocarbons and reduction of nitrogen. However, the molecular-scale interactions between the titania photocatalyst and dinitrogen are still debated, particularly in the presence of hydrocarbons. Here, we used several spectroscopic and computational techniques to identify interactions between nitrogen, methanol, and titania under illumination. Electron paramagnetic resonance spectroscopy (EPR) allowed us to observe the formation of carbon radicals upon exposure to ultraviolet radiation. These carbon radicals are
We present an epitaxial Er3+:Y2O3/silicon material platform for scalable quantum photonic devices... more We present an epitaxial Er3+:Y2O3/silicon material platform for scalable quantum photonic devices. We discuss a system integrating suspended Er3+:Y2O3 membranes with a fiber Fabry-Perot cavity for coherent spectroscopy enabling quantum memory and transduction.
International Journal of High Speed Electronics and Systems, 2008
The interactions of charges in DNA with the vibrational modes in DNA depend on the spectra of the... more The interactions of charges in DNA with the vibrational modes in DNA depend on the spectra of these vibrational modes. Using (a) the Su-Schrieffer-Heeger (SSH) Hamiltonian approach, (b) integrated structures of DNA and manmade nanostructures, and (c) gel electrophoresis techniques,1 the interaction between charges in DNA and the vibrational modes of DNA are investigated. As is well-known, DNA has a rich spectrum of modes in the THz spectral regime. The use of manmade nanostructures integrated with DNA facilitates the engineering of nanoscale systems useful in studying the role of environmental effects on the vibrational modes of DNA as well as the interaction of these modes with charge carriers in DNA. Among the DNA-based structures considered in this account are: B-DNA and Z-DNA strands related by a conformational change; and DNA molecules bound on one terminal to indirect bandgap semiconductor quantum dots. Gel electrophoresis is used as a tool for the analysis of carrier interact...
International Journal of High Speed Electronics and Systems, 2007
This paper presents models and experimental measurements that shed light on THz-phonon mediated t... more This paper presents models and experimental measurements that shed light on THz-phonon mediated transport of polarons in biomolecules. Polaron transport in DNA has been considered recently in view of the expected derealization of charge carriers on a one-dimensional wire as well as the highly charged nature of DNA.1,2 An understanding of the electrical transport properties and THz-phonon interactions of biomolecules is important in view of DNA's potential applications both as electrically conductive wires and as structures that facilitate the chemically-directed assembly of massively integrated ensembles of nanoscale semiconducting elements into terascale integrated networks. Moreover, understanding these interactions provides information of the THz spectrum of vibrational modes in DNA. A primary focus of this paper is on charge transport in biomolecules using indirect-bandgap colloidal nanocrystals linked with biomolecules.3 Through a combination of theoretical and experimental...
The reaction mechanism of nitric oxide (NO) reduction by excess electrons on TiO2 nanoparticles (... more The reaction mechanism of nitric oxide (NO) reduction by excess electrons on TiO2 nanoparticles (eTiO2-) has been studied under anaerobic conditions. TiO2 was loaded with 10-130 electrons per particle using -irradiation of acidic TiO2 colloid solutions containing 2-propanol. The study is based on time resolved kinetics and reactants and products analysis. The reduction of NO by eTiO2- is interpreted in terms of competition between a reaction-path leading to formation of NH3 and a path leading to N2O and N2.The proposed mechanism involves consecutive one-electron transfers of NO and its reduction intermediates HNO, NH2O• and NH2OH. The results show that eTiO2- does not reduce N2O and N2. Second order rate constants of eTiO2- reactions with NO (740 ± 30 M-1s-1) and NH2OH (270 ± 30 M-1s-1) have been determined employing the rapid-mixing stopped-flow technique, and that with HNO (> 1.3 x106 M-1s-1) was derived from fitting the kinetic traces to the suggested reaction mechanism, whic...
Photocatalytic production of clean hydrogen fuels using water and sunlight has attracted remarkab... more Photocatalytic production of clean hydrogen fuels using water and sunlight has attracted remarkable attention due to the increasing global energy demand. Natural and synthetic dyes can be utilized to sensitize semiconductors for solar energy transformation using visible light. In this study, reduced graphene oxide (rGO) and a membrane protein bacteriorhodopsin (bR) were employed as building modules to harness visible light by a Pt/TiO2 nanocatalyst. Introduction of the rGO boosts the nano-bio catalyst performance that results in hydrogen production rates of approximately 11.24 mmol of H2 (μmol protein)(-1) h(-1). Photoelectrochemical measurements show a 9-fold increase in photocurrent density when TiO2 electrodes were modified with rGO and bR. Electron paramagnetic resonance and transient absorption spectroscopy demonstrate an interfacial charge transfer from the photoexcited rGO to the semiconductor under visible light.
Irradiation by visible light of an aqueous solution containing a photosensitizer, methyl viologen... more Irradiation by visible light of an aqueous solution containing a photosensitizer, methyl viologen (MV **) and ethylenediaminetetraacetic acid leads to the formation of the reduced form of methyl viologen (MV3. The quantum yield for the formation of MV' depends strongly on the time during which the formation is observed owing to the reaction of MV' with oxidative products and its reduction to MV '. Proflavin, acrldine yellow and ruthenium( II)tris( 2,2-bipyridyl) were used as photosensitizers and showed the same ability to promote hydrogen evolution. When CdS was used as a sensitizer a factor of 10 less hydrogen was obtained than when the dyes were used. The redox catalysts platinum, Pt-TiO,-Ru02 and Pt-CdS in colloidal systems showed approximately the same activity towards the reduction of water. The reduction of MV*' and the evolution of hydrogen were enhanced at higher temperatures (70 "C). The optimum conditions for water reduction on redox catalysts in colloidal systems under continuous illumination are analysed.
Optical effects due to size quantization in three dimensions have been observed for CdS and PbS c... more Optical effects due to size quantization in three dimensions have been observed for CdS and PbS colloids with particle diameters less than 50 A and 20 to 200 A, respectively. The optical absorption edge is blue shifted approx.0.9 eV for the CdS colloid; for PbS colloids the shift is approx.2 eV for particle diameters 20 to 30 A, and approx.1
Three families of ZnTe magic sized nanoclusters (MSNCs) were obtained exclusively using poly-tell... more Three families of ZnTe magic sized nanoclusters (MSNCs) were obtained exclusively using poly-tellurides as a tellurium precursor in one-pot reaction by simply varying the reaction temperature and time only. Different ZnTe MSNCs exhibit different self-assembling or aggregation behavior, owing to their different structure, cluster size, and dipole-dipole interactions. The smallest family of ZnTe MSNCs (F323) does not reveal a crystalline structure and as a result assembles into lamellar triangle plates. Continuous heating of as synthesized ZnTe F323 assemblies resulted in the formation of ZnTe F398 MSNCs with wurzite structure and concomitant transformation into lamellar rectangle assemblies with organization of nanoclusters along <002> direction. Further annealing of ZnTe F398 assembled lamellar rectangles lead to full organization of MSNCs in all directions and formation of larger ZnTe F444 NCs that spontaneously form ultrathin nanowires following oriented attachment mechanism. The key step in control over the size distribution of ZnTe ultra-thin nanowires is, in fact, the growth mechanism of ZnTe F398 MSNCs; namely, step growth mechanism enables formation of more uniform nanowires compared to those obtained by continuous growth mechanism. High yield of ZnTe nanowires is achieved as a result of wurzite structure of F398 precursor. Transient absorption (TA) measurements show that all the three families possess ultra-fast dynamics of photo generated electrons, despite their different crystalline structures.
We report on various strategies for the synthesis of titania-based photocatalysts, including mixe... more We report on various strategies for the synthesis of titania-based photocatalysts, including mixed phase titania, and anatase nanotubes. These photocatalysts have shown improved efficiency for the transformation of CO2 to methane as tested in the absence of sacrificial hole scavengers. The EPR studies have revealed a high concentration of undercoordinated Ti atoms on the surface of photocatalysts that improve adsorption/binding of CO2, and thus, the photoefficiency of the reaction.
Raman scattering enhancement was observed in systems where different metal oxide semiconductors (... more Raman scattering enhancement was observed in systems where different metal oxide semiconductors (TiO 2 , Fe 2 O 3 , ZrO 2 , and CeO 2 ) were modified with enediol ligands. The intensity of Raman scattering was dependent on laser frequency and correlated with the extinction coefficient of the CT complex of the enediol ligands and nanoparticles. The mechanism of Raman enhancement was studied by varying both the chemical composition of the enediol ligand and the chemical composition (and crystal structure) of the nanoparticles. We found that the intensity of the Raman signal depends on the number of surface binding sites, electron density of the ligands, and their dipole moment. Changes in chemical composition caused variations in the intensity, frequency, and number of Raman bands observed. We also showed that Raman scattering is observed for the bioconjugated system, where a peptide is linked to the surface of the particle through a catechol linker, and further investigated the potential for such a system in the development of Raman-based in vivo and in vitro biodetection, cell labeling and imaging, and nanotherapeutic strategies.
ZnTe nanorods with controllable aspect ratios were synthesized using polytellurides a tellurium p... more ZnTe nanorods with controllable aspect ratios were synthesized using polytellurides a tellurium precursor. The use of polytellurides which allow nucleation and growth at relatively low temperature is the key to formation of wurtzite phase and controlled anisotropic growth along c-axis. The aspect ratio of the resulting ZnTe nanorods was controlled by tuning the temperature that in turn controls the kinetics of the nanocrystal growth. A diameter dependent quantum confinement effect in ZnTe nanorods was observed by UV-vis absorption spectroscopy. Transient absorption measurements show ultrafast charge injection dynamics from ZnTe nanorods, suggesting their strong potential for applications in photocatalysis.
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