Interfacial electron transfer (ET) between semiconductor nanomaterials and molecular adsorbates is an important fundamental process that relevant to applications of these materials. Using femtosecond midinfrared spectroscopy, we have simultaneously measured the dynamics injected electrons by directly monitoring mid-IR absorption in change adsorbate vibrational spectrum, respectively. We report on a series studies designed understand how interfacial ET depends properties adsorbates,...

The photophysics and electron injection dynamics of Ru(dcbpy)2(NCS)2 [dcbpy = (4,4'-dicarboxy-2,2'-bipyridine)] (or Ru N3) in solution adsorbed on nanocrystalline Al2O3 TiO2 thin films were studied by femtosecond mid-IR spectroscopy. For N3 ethanol after 400 nm excitation, the long-lived metal-to-ligand charge transfer (3MLCT) excited state with CN stretching bands at 2040 cm-1 was formed less than 100 fs. No further decay excited-state absorption observed within 1 ns consistent previously...

We have used femtosecond pump−probe spectroscopy to time resolve the injection of electrons into nanocrystalline TiO2 film electrodes under ambient conditions following photoexcitation adsorbed dye, [Ru(4,4'-dicarboxy-2,2'-bipyridine)2(NCS)2] (N3). Pumping at one metal-to-ligand charge-transfer absorption peaks and probing by injected in 1.52 μm range 4.1−7.0 μm, we directly observed arrival film. Our measurements indicate an instrument-limited ∼50 fs upper limit on electron time. compared...

We report two ruthenium(II) polypyridyl complexes with pendant phenol/catechol functionality that act as colorimetric sensors for fluoride ions. Experiments have revealed hydrogen bond formation occurs a slight excess of ion. However, in higher [F-], deprotonation the O-H resulted. Time-dependent (TD-DFT) calculations at B3LYP/LANL2DZ level shown new bands appear longer wavelengths upon complexation These are mixed character, MLCT (dpi(Ru)-->pi*(L1/bpy)), and intra- interligand...

A porphyrin aggregate is reported that exhibits novel exciton state properties for light-harvesting applications. This enables control of energy dissipation coherent excited states by changing the self-assembly pattern. New spectral features create a new route transfer in this aggregate. The kinetic model decay addressed Perspective reporting steady-state and transient emission absorption studies J- H-aggregates. J-aggregate emerges with better coverage dynamics, which are suitable antenna...

Carbon dots (C-Dots) are promising new materials for the development of biocompatible photosensitizers solar-driven catalysis and hydrogen production in aqueous solution. Compared to common semiconducting quantum dots, C-Dots have good physicochemical, as well photochemical stability, optical brightness, stability nontoxicity, while their carbon based source results tunable surface chemistry, chemical versatility, low cost, biocompatibility. Herein we show that doping with phosphate or boron...

Albeit enormous achievement has already been made in photovoltaic and optoelectronic fields with perovskites, further advancement is needed to address key challenges encountered these systems. Here, we synthesized polyhedral dodecahedron cesium lead bromide (dodecahedron-CsPbBr3) perovskite, which offers new polar facets exposed on the surface, longer carrier lifetime, high photoluminescence (PL) quantum yield. PL investigation conducted at cryogenic temperature for dodecahedron-CsPbBr3...

Transient infrared (IR) absorption of injected electrons in colloidal TiO2 nanoparticles the 1900−2000 cm-1 region are measured by femtosecond IR spectroscopy. The direct detection with subpicosecond time resolution provides a new approach to study ultrafast interfacial electron transfer between semiconductor and molecular adsorbates. dynamics injection from sensitizers subsequent back-transfer relaxation correspond rise decay transient signal electrons. Using this technique, for coumarin...

Photoinduced electron-transfer (ET) dynamics in Fe(II)(CN)64- sensitized TiO2 nanoparticles D2O solution are studied by subpicosecond tunable laser spectroscopy the mid-infrared and visible region. The of injected electrons monitored mid-IR absorption semiconductor, corresponding adsorbate vibrational spectra CN stretching mode region electronic visible. After 400 nm excitation, forward electron injection time from to occurs <50 fs, indicating a direct photoinduced charge-transfer process....

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharge recombination reactions in photoexcited fullerene C60-amine complexes studied by picosecond pump probe spectroscopyHirendra N. Ghosh, Haridas Pal, Avinash V. Sapre, and Jai P. MittalCite this: J. Am. Chem. Soc. 1993, 115, 25, 11722–11727Publication Date (Print):December 1, 1993Publication History Published online1 May 2002Published inissue 1 December...

Electron injection and back electron transfer dynamics of xanthene dyes adsorbed on TiO2 nanoparticles have been studied by picosecond transient absorption time-resolved fluorescence spectroscopy. When the are surface, a good fraction dye molecules forms charge (CT) complex with nanoparticle. On excitation above system, from molecule to nanoparticle takes place. has observed direct detection in conduction band bleach as detected The corresponding determined monitoring recovery kinetics...

We are reporting ultrafast charge carrier and transfer dynamics of the CdTe quantum dot (QD) type II CdTe/CdS core−shell QD materials with different shell (CdS) thicknesses. Herein, we have synthesized dots by using 3-mercaptopropionic acid as a capping agent. Steady state absorption emission studies confirmed successful synthesis materials. Time-resolved indicate longer lifetime compared to materials, where in both cases only gets excited. carried out femtosecond transient these exciting...

We have employed ultrafast optical pump–probe spectroscopy to study excited dynamics of graphene oxide (GO) and reduced (RGO) dispersed in water by exciting the samples at 400 nm laser light. observed multiexponential relaxation nonequilibrium photogenerated carriers for both GO RGO with time constants varying from 0.8 >400 ps. Our analysis on charge revealed involvement phonon trap states dynamics. Transient absorption visible region longer scale is attributed mainly due electron which been...

A distributed model for a junction transistor has been analyzed to include both dc and ac biasing effects in the active base region, with particular emphasis on small-geometry diffused planar transistor. For such devices extremely narrow width, cannot be neglected. At high frequencies, response of these is greatly modified by which are accentuated significant at large emitter current levels. Two-dimensional flow under conditions was studied region. From model, expressions emitter-base diode...

Femtosecond time-resolved absorption and picosecond emission studies have been carried out to study the indirect type exciton of CdS/ZnSe core/shell quantum dots (QDs). The QD samples are synthesized with increasing thickness ZnSe shell on CdS core QDs. In these samples, a new energy band lower than gap both has observed attributed bandgap transitions from valence conduction core. transient PL revealed that exciton, e(CdS)/h(ZnSe) due photoexcitation this low-energy band, endures less...

Rapid hot carrier cooling is the key loss channel overriding all possible energy pathways that limit achievable solar conversion efficiency. Thus, delayed in cell absorber layer can make extraction a less cumbersome task, assisting realization of cells. There have been plentitude reports concerning slow perovskite materials, which eventually triggered interest radical understanding native photophysics driving device design. Here this finding, further dramatic dip rate has discerned upon...

We have employed femtosecond transient absorption spectrocopy to monitor charge carrier delocalization in CdSe/CdS quasi-type II and CdS/CdSe inverted type I core–shell nanocrystals (NCs). Interestingly, CdSe CdS QD pairs can make both structures, depending on their band alignment localization. Steady-state optical luminescence studies show a gradual red-shift emission spectra with increasing shell thickness. The quantum yield drastically increases Notably, shows huge which closely matches...

Multicomponent hybrid nanocrystals (HNC) consisting of a semiconductor and metallic domains are an important class nanostructured materials demonstrating useful applications interesting basic knowledge. In this scenario, Au nanoparticle (NP) islands ∼2 nm have been grown on unique two dimensional (2D) CdSe/CdS core@shell hexagonal nanoheteroplatelets 20 diameter to form unprecedented 2D CdSe/CdS-Au HNCs detailed optical characterization has carried out determine the dimensionality based...

Elemental doping has already been established to be one of the most effective approaches for band-gap engineering and controlled material response improved photocatalytic activity. Herein atomically thin ZnIn2S4 (ZIS) nanosheets were doped with O N separately, effects spectroscopically investigated H2 evolution. Steady-state photoluminescence studies revealed an enhanced charge-carrier population in systems along a defect-state-induced broad peak red region spectra. Transient absorption (TA)...

The photophysics and reactivity of quantum size ZnO nanoparticles have been studied using static time-resolved emission absorption spectroscopy. Size quantization is confirmed by steady-state optical On band gap excitation, give both exciton trap-state emission. from readily quenched hole scavengers such as catechol (cat.) naphthyl (Ncat.). Quenching has attributed to the with adsorbed catechols. Studies on particle variation revealed that decreases their increases. maximum excited catechols...

TiO2 nanoparticles capped with sodium dodecylbenzenesulfonate (DBS) have been synthesized so that they can be dispersed in many organic and nonaqueous solvents. It has found DBS-capped a significant red shift of the optical absorption band edge clear photoluminescence at room temperature contrast to bare nanoparticles. The results obtained indicate surface structure, is, capping group defect states, plays an important role electronic states recombination dynamics photoexcited charge carriers...

Dynamics of interfacial electron transfer (ET) in the ruthenium−polypyridyl complex [{bis(2,2'-bpy)-(4-[2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl]benzene-1,2-diol)} ruthenium(II) hexafluorophosphate] (Ru-cat)-sensitized TiO2 nanoparticles has been investigated using femtosecond transient absorption spectroscopy detecting visible and near-infrared region. It observed that Ru-cat is coupled strongly with through its pendant catechol moiety. Electron injection confirmed by direct detection...

Steady-state fluorescence and time-resolved absorption measurements in pico- femtosecond time domain have been used to investigate the dynamics of hydrogen bond excited singlet (S1) state fluorenone alcoholic solvents. A comparison features steady-state spectra various kinds media demonstrates that two spectroscopically distinct forms S1 state, namely non-hydrogen-bonded (or free) molecule as well hydrogen-bonded complex, are responsible for dual-fluorescence behavior solutions normal...

Electron injection and back-electron-transfer dynamics of 7-diethyl amino coumarin 3-carboxylic acid (D-1421) 343 (C-343) dyes adsorbed on TiO2 nanoparticles have been studied by picosecond transient absorption time-resolved fluorescence spectroscopy. has observed direct detection electron in the conduction band nanoparticle cation radical as detected efficiency found to be much higher for D-1421-sensitized compared C-343-sensitized system. Steady state measurements show that high polar...