23 research outputs found
Metal Ion Dependence, Thermodynamics, and Kinetics for Intramolecular Docking of a GAAA Tetraloop and Receptor Connected by a Flexible Linker
Low temperature solution-phase growth of ZnSe and ZnSe/CdSe core/shell nanowires
High quality ZnSe nanowires (NWs) and complementary ZnSe/CdSe core/shell species have been synthesized using a recently developed solution-liquid-solid (SLS) growth technique. In particular, bismuth salts as opposed to pre-synthesized Bi or Au/Bi nanoparticles have been used to grow NWs at low temperatures in solution. Resulting wires are characterized using transmission electron microscopy and possess mean ensemble diameters between 15 and 28 nm with accompanying lengths ranging from 4-10 μm. Subsequent solution-based overcoating chemistry results in ZnSe wires covered with CdSe nanocrystals. By varying the shell's growth time, different thicknesses can be obtained and range from 8 to 21 nm. More interestingly, the mean constituent CdSe nanocrystal diameter can be varied and results in size-dependent shell emission spectra.Fil: Petchsang, Nattasamon. University of Notre Dame; Estados Unidos. Thailand Ministry of Education; Tailandia. Mahidol University; TailandiaFil: Shapoval, Liubov. Herzen State Pedagogical University Of Russia; RusiaFil: Vietmeyer, Felix. University of Notre Dame; Estados UnidosFil: Yu, Yanghai. University Of Wisconsin Madison;Fil: Hodak, Jose Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Tang, I-Ming. Mahidol University; Tailandia. Thailand Ministry Of Education; TailandiaFil: Kosel, Thomas H.. University of Notre Dame; Estados UnidosFil: Kuno, Masaru. University of Notre Dame; Estados Unido
Direct Observation of Single Layer Graphene Oxide Reduction through Spatially Resolved, Single Sheet Absorption/Emission Microscopy
Laser reduction of graphene oxide
(GO) offers unique opportunities
for the rapid, nonchemical production of graphene. By tuning relevant
reduction parameters, the band gap and conductivity of reduced GO
can be precisely controlled. In situ monitoring of single layer GO
reduction is therefore essential. In this report, we show the direct
observation of laser-induced, single layer GO reduction through correlated
changes to its absorption and emission. Absorption/emission movies
illustrate the initial stages of single layer GO reduction, its transition
to reduced-GO (rGO) as well as its subsequent decomposition upon prolonged
laser illumination. These studies reveal GO’s photoreduction
life cycle and through it native GO/rGO absorption coefficients, their
intrasheet distributions as well as their spatial heterogeneities.
Extracted absorption coefficients for unreduced GO are α<sub>405 nm</sub> ≈ 6.5 ± 1.1 × 10<sup>4</sup> cm<sup>–1</sup>, α<sub>520 nm</sub> ≈ 2.1 ±
0.4 × 10<sup>4</sup> cm<sup>–1</sup>, and α<sub>640 nm</sub> ≈ 1.1 ± 0.3 × 10<sup>4</sup> cm<sup>–1</sup> while corresponding rGO α-values are α<sub>405 nm</sub> ≈ 21.6 ± 0.6 × 10<sup>4</sup> cm<sup>–1</sup>, α<sub>520 nm</sub> ≈ 16.9 ±
0.4 × 10<sup>4</sup> cm<sup>–1</sup>, and α<sub>640 nm</sub> ≈ 14.5 ± 0.4 × 10<sup>4</sup> cm<sup>–1</sup>. More importantly, the correlated absorption/emission
imaging provides us with unprecedented insight into GO’s underlying
photoreduction mechanism, given our ability to spatially resolve its
kinetics and to connect local rate constants to activation energies.
On a broader level, the developed absorption imaging is general and
can be applied toward investigating the optical properties of other
two-dimensional materials, especially those that are nonemissive and
are invisible to current single molecule optical techniques
Controlling the preferential orientation in sol-gel prepared CaCu3Ti4O12 thin films by LaAlO3 and NdGaO3 substrates
Direct Observation of Spatially Heterogeneous Single-Layer Graphene Oxide Reduction Kinetics
Graphene
oxide (GO) is an important precursor in the production
of chemically derived graphene. During reduction, GO’s electrical
conductivity and band gap change gradually. Doping and chemical functionalization
are also possible, illustrating GO’s immense potential in creating
functional devices through control of its local hybridization. Here
we show that laser-induced photolysis controllably reduces individual
single-layer GO sheets. The reaction can be followed in real time
through sizable decreases in GO’s photoluminescence efficiency
along with spectral blueshifts. As-produced reduced graphene oxide
(rGO) sheets undergo additional photolysis, characterized by dramatic
emission enhancements and spectral redshifts. Both GO’s reduction
and subsequent conversion to photobrightened rGO are captured through
movies of their photoluminescence kinetics. Rate maps illustrate sizable
spatial and temporal heterogeneities in sp<sup>2</sup> domain growth
and reveal how reduction “flows” across GO and rGO sheets.
The observed heterogeneous reduction kinetics provides mechanistic
insight into GO’s conversion to chemically derived graphene
and highlights opportunities for overcoming its dynamic, chemical
disorder
Direct Observation of Spatially Heterogeneous Single-Layer Graphene Oxide Reduction Kinetics
Graphene
oxide (GO) is an important precursor in the production
of chemically derived graphene. During reduction, GO’s electrical
conductivity and band gap change gradually. Doping and chemical functionalization
are also possible, illustrating GO’s immense potential in creating
functional devices through control of its local hybridization. Here
we show that laser-induced photolysis controllably reduces individual
single-layer GO sheets. The reaction can be followed in real time
through sizable decreases in GO’s photoluminescence efficiency
along with spectral blueshifts. As-produced reduced graphene oxide
(rGO) sheets undergo additional photolysis, characterized by dramatic
emission enhancements and spectral redshifts. Both GO’s reduction
and subsequent conversion to photobrightened rGO are captured through
movies of their photoluminescence kinetics. Rate maps illustrate sizable
spatial and temporal heterogeneities in sp<sup>2</sup> domain growth
and reveal how reduction “flows” across GO and rGO sheets.
The observed heterogeneous reduction kinetics provides mechanistic
insight into GO’s conversion to chemically derived graphene
and highlights opportunities for overcoming its dynamic, chemical
disorder
Direct Observation of Spatially Heterogeneous Single-Layer Graphene Oxide Reduction Kinetics
Graphene
oxide (GO) is an important precursor in the production
of chemically derived graphene. During reduction, GO’s electrical
conductivity and band gap change gradually. Doping and chemical functionalization
are also possible, illustrating GO’s immense potential in creating
functional devices through control of its local hybridization. Here
we show that laser-induced photolysis controllably reduces individual
single-layer GO sheets. The reaction can be followed in real time
through sizable decreases in GO’s photoluminescence efficiency
along with spectral blueshifts. As-produced reduced graphene oxide
(rGO) sheets undergo additional photolysis, characterized by dramatic
emission enhancements and spectral redshifts. Both GO’s reduction
and subsequent conversion to photobrightened rGO are captured through
movies of their photoluminescence kinetics. Rate maps illustrate sizable
spatial and temporal heterogeneities in sp<sup>2</sup> domain growth
and reveal how reduction “flows” across GO and rGO sheets.
The observed heterogeneous reduction kinetics provides mechanistic
insight into GO’s conversion to chemically derived graphene
and highlights opportunities for overcoming its dynamic, chemical
disorder
Direct Observation of Spatially Heterogeneous Single-Layer Graphene Oxide Reduction Kinetics
Graphene
oxide (GO) is an important precursor in the production
of chemically derived graphene. During reduction, GO’s electrical
conductivity and band gap change gradually. Doping and chemical functionalization
are also possible, illustrating GO’s immense potential in creating
functional devices through control of its local hybridization. Here
we show that laser-induced photolysis controllably reduces individual
single-layer GO sheets. The reaction can be followed in real time
through sizable decreases in GO’s photoluminescence efficiency
along with spectral blueshifts. As-produced reduced graphene oxide
(rGO) sheets undergo additional photolysis, characterized by dramatic
emission enhancements and spectral redshifts. Both GO’s reduction
and subsequent conversion to photobrightened rGO are captured through
movies of their photoluminescence kinetics. Rate maps illustrate sizable
spatial and temporal heterogeneities in sp<sup>2</sup> domain growth
and reveal how reduction “flows” across GO and rGO sheets.
The observed heterogeneous reduction kinetics provides mechanistic
insight into GO’s conversion to chemically derived graphene
and highlights opportunities for overcoming its dynamic, chemical
disorder
Direct Observation of Spatially Heterogeneous Single-Layer Graphene Oxide Reduction Kinetics
Graphene
oxide (GO) is an important precursor in the production
of chemically derived graphene. During reduction, GO’s electrical
conductivity and band gap change gradually. Doping and chemical functionalization
are also possible, illustrating GO’s immense potential in creating
functional devices through control of its local hybridization. Here
we show that laser-induced photolysis controllably reduces individual
single-layer GO sheets. The reaction can be followed in real time
through sizable decreases in GO’s photoluminescence efficiency
along with spectral blueshifts. As-produced reduced graphene oxide
(rGO) sheets undergo additional photolysis, characterized by dramatic
emission enhancements and spectral redshifts. Both GO’s reduction
and subsequent conversion to photobrightened rGO are captured through
movies of their photoluminescence kinetics. Rate maps illustrate sizable
spatial and temporal heterogeneities in sp<sup>2</sup> domain growth
and reveal how reduction “flows” across GO and rGO sheets.
The observed heterogeneous reduction kinetics provides mechanistic
insight into GO’s conversion to chemically derived graphene
and highlights opportunities for overcoming its dynamic, chemical
disorder