Electron efficiency

Based on extensive screening of hundreds of ruthenium complexes, it was discovered that the sensitizer s excited state oxidation potential should be negative of at least —0.9 V vs. SCE, in order to inject electrons efficiently into the Ti02 conduction band. The ground state oxidation potential should be about 0.5 V vs. SCE, in order to be regenerated rapidly via electron donation from the electrolyte (iodide/triiodide redox system) or a hole conductor. A significant decrease in electron injection efficiencies will occur if the excited and ground state redox potentials are lower than these values. 

Dissociative electron attachment is a radiation chemical reaction suitable for cutting a polymer just in half. If two equivalent polymer skeletons R are connected with a functional group XY that has a large cross section of dissociative electron attachment, the polymer captures an ejected electron at the center of the polymer skeleton and is broken into two fragments with similar molecular weight, as R-XY-R + e —>R-X + Y-R. The key to construct such a polymer is to find a functional group that is possible to connect two polymer chains, to capture an electron efficiently, and to dissociate into two fragments after the capture. 

By analogy with cation complexing crown ethers like 47-50, attachment of a defined number and type of Lewis acids to a rigidified molecular scaffold in such a way that their electron-efficient sites are... 

Fig. 2 Scheme depicting the radiological behavior of the waters of hydration in DNA. For the first nine waters, ESR evidence suggests that both holes and electrons efficiently transfer to the DNA. For samples with additional waters from F=9 to F=21 (F is defined as the number of water molecules per nucleotide), holes form hydroxyl radicals with ESR parameters characteristic of a glassy environment and electrons efficiently transfer to the DNA. For samples with F>21, a crystalline ice phase forms holes in the ice phase form hydroxyl radicals with parameters characteristic of a crystalline ice environment. There is no ESR evidence that electrons from this phase transfer to the DNA. For samples with F>21, the glassy phase is reduced to about 14 waters per nucleotide with the remainder ice phase [3c]... 

There are two important experimental factors that must be accounted for if we are to be successful in running 15N experiments. The 15N nucleus tends to relax very slowly Tj s of greater than 80 seconds have been measured. Thus, either long pulse delays must be incorporated into our pulse sequence or, alternatively, we could provide another route for spin relaxation. A common procedure is to add a catalytic amount of chromium (III) acetylacetonate, a paramagnetic substance, whose unpaired electrons efficiently stimulate transfer of spin. In cases where Tt s are not known (and not intended to be measured), pulse delays and pulse angles must be considered carefully because the signal from one (or more) 15N resonance can accrue too slowly or be missed altogether. 

The difficulties in achieving direct electron transfer between GOD and electrodes have led to the use of small electroactive molecules, called mediators, which shuttle electrons efficiently between the enzyme and the electrode. A new design of glucose electrodes depends (79) on ferricinium (Fc) ions as the mediator ... 

Gd is also known to generate Auger and internal conversion electrons efficiently by irradiation with a neutron beam. Based on this, an increase of the local concentration of Gd should enhance the properties for tumor cell detection, and Gd neutron capture therapy could be more efficient. For this purpose, a novel water-soluble PAMAM-based dendrimers terminated with DPTA extremities covered with 254 Gd atoms were prepared with excellent results [69]. 

Vogel et al. [88] used PbS and CdS Q-particles of different sizes for the sensitization of various oxide substrate materials which differ in the absolute position of the flatband potentials. They showed that Q-particles of a characteristic minimal size were required to inject electrons efficiently in... 

The fluorescence induction curve in the absence of DCMU has two phases of increase. Starting from a non-variable yield (F ) fluorescence increases to an initial plateau (Fpx), followed by a second increase to a peak (Fp) (5). The increase from F to F is interpreted to arise from PSII reaction centers which are photochemically competent but unable to transfer electrons efficiently from to Qg (5). This fluorescence rise accounts for about 15% of total variable fluorescence and has been shown to emanate from the PSIIg-Qg-nonreducing (5). 

A significant extension of the utilization of amperometric probes could be obtained by electron transfer mediators. The idea is to replace oxygen by an alternative redox couple, allowing a rapid reaction of the reduced enzyme with the mediator, which shuttles electrons efficiently between electrode and... 

---