In the early 1970s, works by Fujishima and Honda (1) et al. (2) reported on results of a now famous experiment. They showed that band gap excitation anatase TiO2 in photoelectrochemical cell with Pt counter electrode an applied bias resulted water splitting into hydrogen oxygen. The timing result was impeccable. 1973, Organization Petroleum Exporting Countries (OPEC) declared embargo oil imports to West, resulting gasoline shortages long lines at gas pumps. Suddenly, there pressing need for...

The dye-sensitized photoelectrosynthesis cell (DSPEC) integrates high bandgap, nanoparticle oxide semiconductors with the light-absorbing and catalytic properties of designed chromophore–catalyst assemblies. goals are photoelectrochemical water splitting into hydrogen oxygen reduction CO2 by to give carbon-based fuels. Solar-driven oxidation occurs at a photoanode or cathode photocathode initiated molecular-level light absorption. Light absorption is followed electron hole injection,...

Isomorphous metal-organic frameworks (MOFs) based on {M[4,4'-(HO(2)C)(2)-bpy](2)bpy}(2+) building blocks (where M = Ru or Os) were designed and synthesized to study the classic Os energy transfer process that has potential applications in light-harvesting with supramolecular assemblies. The crystalline nature of MOFs allows precise determination distances between metal centers by X-ray diffraction, thereby facilitating Ru→Os process. mixed-metal 0.3, 0.6, 1.4, 2.6 mol % doping also order...

Microscale metal-organic frameworks (MOFs) were synthesized from photoactive Ru(II)-bpy building blocks with strong visible light absorption and long-lived triplet metal-to-ligand charge transfer ((3)MLCT) excited states. These MOFs underwent efficient luminescence quenching in the presence of either oxidative or reductive quenchers. Up to 98% emission was achieved an quencher (1,4-benzoquinone) a (N,N,N',N'-tetramethylbenzidine), as result rapid energy migration over several hundred...

We report temperature-dependent excited-state lifetime measurements on [Ru(bpy)2dppz]2+ in both protic and aprotic solvents. These experiments yield a unifying picture of the photophysics that accounts for observations types solvent. Our support notion bpy-like phz-like states associated with dppz ligand show orbital bright state is similar size to corresponding 3MLCT [Ru(bpy)3]2+. In contrast current thinking, presented here indicate light-switch effect not driven by reversal. Rather, they...

We have developed a pump-probe microscope capable of exciting single semiconductor nanostructure in one location and probing it another with both high spatial temporal resolution. Experiments performed on Si nanowires enable direct visualization the charge cloud produced by photoexcitation at localized spot as spreads along nanowire axis. The time-resolved images show clear evidence rapid diffusional spreading recombination free carriers, which is consistent ambipolar diffusion surface...

Temperature-dependent excited-state lifetime measurements have been performed on four different Ru(II)-based dppz compounds in protic and aprotic solvents. This work supports the existence of a dynamic equilibrium between two MLCT states associated with ligand: one is bright state ligand orbital similar size to that 3MLCT [Ru(bpy)3]2+, other dark phz-like state. Our results are consistent light-switch mechanism involving competition energetic factors favor (phz) entropic (bpy) paper explores...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotodissociation and Geminate Recombination Dynamics of I2- In Mass-Selected I2-(CO2)n Cluster IonsJohn M. PapanikolasJohn PapanikolasMore by John Papanikolas, James R. GordJames GordMore Gord, Nancy E. LevingerNancy LevingerMore Levinger, Douglas RayDouglas RayMore Ray, Vasil VorsaVasil VorsaMore Vorsa, W. C. LinebergerW. LinebergerMore LinebergerCite this: J. Phys. Chem. 1991, 95, 21, 8028–8040Publication Date (Print):October 1, 1991Publication...

The emitting metal-to-ligand charge transfer (MLCT) excited state of [Ru(bpy)2(bpz)]2+ (bpy is 2,2'-bipyridine; bpz 2,2'-bipyrazine) reductively quenched by hydroquinone (H2Q) proton-coupled electron (PCET), most likely concerted electron−proton (EPT). identity the transient products ([Ru(bpy)2(bpzH•)]2+ and HQ•) kinetics their formation disappearance have been established steady-state emission time-resolved emission, absorption, EPR measurements. protonated, reduced complex...

The simultaneous, concerted transfer of electrons and protons—electron-proton (EPT)—is an important mechanism utilized in chemistry biology to avoid high energy intermediates. There are many examples thermally activated EPT ground-state reactions excited states following photoexcitation thermal relaxation. Here we report application ultrafast excitation with absorption Raman monitoring detect a photochemically driven process (photo-EPT). In this process, both protons transferred during the...

Si nanowires (NWs) have been widely explored as a platform for photonic and electronic technologies. Here, we report bottom-up method to break the conventional "wire" symmetry synthetically encode high-resolution array of arbitrary shapes, including nanorods, sinusoids, bowties, tapers, nanogaps, gratings, along NW growth axis. Rapid modulation phosphorus doping combined with selective wet-chemical etching enabled morphological features small 10 nm be patterned over wires more than 50 μm in...

Interfacial electron transfer at titanium dioxide (TiO2) is investigated for a series of surface bound ruthenium-polypyridyl dyes whose metal-to-ligand charge-transfer state (MLCT) energetics are tuned through chemical modification. The 12 complexes the form Ru(II)(bpy-A)(L)2(2+), where bpy-A bipyridine ligand functionalized with phosphonate groups attachment to TiO2. Functionalization ancillary ligands (L) enables potential excited Ru(III/)* couple, E(+/)*, in 0.1 M perchloric acid...

A detailed study of the excited state energy migration dynamics that take place within an assembly Ru(II) and Os(II) polypyridyl complexes linked together through a polymer backbone is presented. The process initiated by photoexcitation metal-to-ligand charge transfer (MLCT) transition in one terminated to lower trap. Energy sensitization can occur single step if formed adjacent trap, or after series hops between isoenergetic rutheniums prior reaching are followed monitoring growth Os(II)*...

Pump–probe techniques are used in conjunction with a tandem time-of-flight mass spectrometer to investigate the I...I− cage recombination dynamics following I−2 photodissociation size-selected I−2(CO2)n cluster ions. The absorption recovery, which reflects and vibrational relaxation of photodissociated I−2, exhibits strong size dependence range n=13–15. Over this limited range, recovery time decreases from ∼40 ps (n≤12) ∼10 (n≥15). In addition, recurrence is observed at ≊2 larger clusters...

Protocols for modifying gold nanoparticles with peptide-bovine serum albumin (BSA) conjugates are described within. The resulting constructs were characterized using a number of techniques including static fluorescence spectroscopy and time-correlated single photon counting (TCSPC) in order to quantify peptide-BSA binding isotherms, exchange rates, critical flocculation concentrations, the composition mixed monolayers on nanoparticles. TCSPC has proven be powerful technique observing...

Metal–organic frameworks (MOFs) are appealing candidates for use in energy harvesting and concentrating because of their high chromophore density structural tunability. The ability to engineer electronic excitation transport pathways is particular interest designing materials. In this study, theoretical analysis was performed on transfer MOFs that contain light absorbing ruthenium complexes serve as hopping intermediates kinetics trapping osmium complexes. We find the well described by a...

In the design of light-harvesting chromophores for use in dye-sensitized photoelectrosynthesis cells (DSPECs), surface binding to metal oxides aqueous solutions is often inhibited by synthetic difficulties. We report here a systematic synthesis approach preparing family Ru(II) polypyridyl complexes type [Ru(4,4'-R2-bpy)2(4,4'-(PO3H2)2-bpy)](2+) (4,4'(PO3H2)2-bpy = [2,2'-bipyridine]-4,4'-diylbis(phosphonic acid); 4,4'-R2-bpy 4,4'-R2-2,2'-bipyridine; and R OCH3, CH3, H, or Br). this series,...

Ultrafast charge carrier dynamics in silicon nanowires (NWs) grown by a vapor–liquid–solid mechanism were interrogated with optical pump–probe microscopy. The high time and spatial resolutions achieved the experiments provide insight into of single nanostructures. Individual NWs excited femtosecond pump pulse focused to diffraction-limited spot, producing photogenerated carriers (electrons holes) localized region structure. Photoexcited undergo both electron–hole recombination diffusional...

Silicon nanowires incorporating p-type/n-type (p-n) junctions have been introduced as basic building blocks for future nanoscale electronic components. Controlling charge flow through these doped nanostructures is central to their function, yet our understanding of this process inferred from measurements that average over entire structures or integrate long times. Here, we used femtosecond pump-probe microscopy directly image the dynamics photogenerated carriers in silicon encoded with p-n...

Interfacial electron transfer to and from conductive Sn-doped In2O3 (ITO) nanoparticles (NPs) in mesoporous thin films has been investigated by transient absorption measurements using surface-bound [Ru(II)(bpy)2(dcb)](2+) (bpy is 2,2'-bipyridyl dcb 4,4'-(COOH)2-2,2'-bipyridyl). Metal-to-ligand charge excitation 0.1 M LiClO4 MeCN results efficient injection into the ITO NPs on picosecond time scale followed back nanosecond scale. Rates of are dependent thermal annealing conditions with rate...

Transition metal dichalcogenides (TMDCs) have garnered considerable interest over the past decade as a class of semiconducting layered materials. Most studies on carrier dynamics in these materials focused monolayer due to its direct bandgap, strong photoluminescence, and strongly bound excitons. However, comparative understanding multilayer (e.g., >10 layers) flakes is still absent. Recent computational suggested that excitons bulk TMDCs are confined individual layers, leading...

We have employed picosecond pump–probe techniques in conjunction with a tandem time-of-flight mass spectrometer to investigate the caging dynamics of photodissociated I2− solvated specific number CO2 molecules. In this paper, we report observation recurrence at ≊2 ps absorption recovery, feature which is attributed coherent I...I− nuclear motion following photoexcitation.