Small dopant effects

Of course the reduction process also results in exclusion of small dopant anions from the polymer backbone. The dopants can be chosen so that the release process has the desired effect on the chemical composition of the immediate environment. For example. Miller described the triggered release of glutamate [59] and salicylate [60] amongst other compounds. In our own laboratories we have demonstrated the ability to release quinones [61] and metal complexing agents, dithiocarbamates (VII shown below) [62]. 

Valentini et al. [49] demonstrated that the three-dimensional hairlike CNFs can be used as resistive gas sensors for NO2 detection as well. A vertically aligned film with individual CNFs heavily entangled with each other is deposited between two Pt interdigital electrodes by PECVD. Because of the large diameter and abundant defects of these CNFs, the dopant effect due to the charge transfer between CNF and the NO2 adsorbates should be small. The adsorbed NO2 molecules may intercalate between the contact points of neighboring CNFs to contribute to the resistance change. 

The effect of doping is first and foremost to produce a swelling of the CP, which generally leads to a large increase in the microscopically observable volume of the CP. The swelling effect however may be less pronounced if small dopants, such as BF4 or methane sulfonate are used in a nonaqueous medium. 

For a given semiconductor at temperature T, Equation (9.51) shows that as the number of free electrons increases, the number of holes proportionately decreases, so that their product remains the same. Thus the amount of the phosphorus dopant that is introduced controls the amount of both the electrons and the holes in the semiconductor. We call the carriers of higher concentration the majority carriers, while those of lower concentration are the minority carriers. Since electrons are the majority carrier when we dope silicon with phosphorous, we call this material an n-type semiconductor. When the number densities of minority and majority carriers are controlled by the amount of dopant, we say we have an extrinsic semiconductor. In the limit of small dopant concentrations, [P i] << p, there is no effect of the substitutional impurity of the electronic defects in the semiconductor, and it behaves similarly to an intrinsic semiconductor. 

Using a stable dopant as the emissive dye has been shown to greatly enhance the lifetime of small molecule LEDs. Rubrene doped into the Alq, electron transport layer ] 184] or into the TPD hole transport layer 1185] can extend the lifetime by an order of magnitude. Similarly, dimclhylquinacridone in Alq has a beneficial effect ]45 ]. The likely mechanism responsible for this phenomenon is that the dopant acts as a trap for the excilon and/or the charge. Thus, molecules of the host maLrix are in their excited (cationic, anionic or cxcitonic) states for a smaller fraction of the time, and therefore have lower probability to undergo chemistry. 

Bare CuOx-supported nanostructures showed some activity in H 2 production from methanol-water mixture under UV-visible irradiation [180]. Ni is also used as a dopant, and small amounts (1 wt.%) of this element in mesoporous titania guarantee good activity in water-methanol mixtures under UV-visible light [181]. Indium-tantalum oxide Ni-doped materials also provided photocatalysts with promising efficiencies for direct water splitting [182]. TiOz nanotubes doped with Ir and Co nanopartides were effective for visible light water splitting even in the absence of... 

Acceptor dopants are impurity ions of a lower valence than that of the parent ions, as when small amounts of A1203 are incorporated into Ti02, so that the Al3+ ion substitutes for Ti4+. The acceptor species has an effective negative charge, Al i in this example, and the introduction of acceptor species tends to introduce counterbalancing... 

Other examples of dopants that can oxidise polyacetylene are I2, AsFs and HClOy. The effect of these dopants can be to raise the conductivity from 10 S m to as much as 10 S m using only small quantities of dopant. 

Stabilization of BP consisting of bent-core N with chiral dopant was also investigated [29-31]. One of the most dramatic results is that BPIII is easily induced by adding a very small amount of chiral dopant such as 1% [29]. The BPIII temperature range was more than 20°. If BSMs show the N phase at room temperature, the BPIII phase over 20° including room temperature is easily realized [30]. Since BSMs have low compared with Kn [25, 32], the effect of elastic constant on the BP stabilization is confirmed [28]. 

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