Switchable materials have tremendous potential for application in sensor development that could be applied to many fields. We are focusing on emerging area of wireless sensor networks due to the potential impact of this concept in society. Spiropyran-based sensors are probably the most studied type of photoswitchable sensing devices. They suffer from many issues but photofatigue, insufficient selectivity and lack of sensitivity are probably the most important characteristics that hinder their wider application. Here, we are address these issues and demonstrate that covalent attachment of modified spiropyran into a polymeric film significantly reduces photodegradation. The observed signal loss after 12 th cycle of switching between the spiropyran and merocyanine forms is only about 27% compared to the loss of 57% of the initial signal in an equivalent experiment based on nonimmobilized spiropyran. This has enabled us to demonstrate at least 5 reversible cycles of detection of an ion of interest (in our case H + ) with minimal signal loss. Furthermore, we demonstrate that the sensitivity can be increased by incorporation of additional binding groups in the parent spiropyran molecule. Using molecular modeling to calculate the relevant bond lengths as a measure of interaction between MC and H + , the calculated increase of H-bond strength is approximately an order of magnitude for a derivative containing a methoxy group incorporated in the o-position of the parent spiropyran in comparison to the equivalent unsubstituted phenol. This theoretical result was found to correspond very well with experimental observation. As a result, we have increased the sensitivity to H + by approximately one order of magnitude.3

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A simple linear relationship between the functionalization reaction energies for the exohedral monovalent addition on the surface of an ideal, infinitely long, single-walled carbon nanotube (SWCNT) and the reciprocal SWCNT radius has been derived employing the hardsoft acid basis principle and the tight binding model. The slope of the derived linear relationship is a function of the effective number of valence electrons involved in the functionalization reaction. The intercept of the derived linear relationship, equal to the reaction energies on a planar graphite surface, is a function of the electrophilicity of the monovalent addend and of the condensed Fukui function of its reacting atom. The theoretical predictions of this simple formula are coherent with the computational density functional theory data reported in the literature.

In carbon materials the mobile π electrons are situated in topologically different circumstances at edge sites, and their π electronic states, essentially controlled by the network structure of sp2 carbon, may be significantly affected. In this work, we derived topological indications about the reactivity of carbon nanotubes and fullerenes with the hydroxyl radical (OH•), the most important oxidizing species in the troposphere. For each molecular structure, we computed the local softness, the Mulliken charges of the reacting carbons of (n,n) and (n,0) clusters, and their Huckel-type aromaticity rules, as an index to determine topologically independent sites and predicting a certain grade of reactivity of the nanotube and fullerenic carbon atoms. Using local softness, closely related to the energy gap, it was possible to separate the periodical nanotubes in three families according to their reactivity. A connection between the reactivity index ΔE and the topology was established by means of the Fukui integrated function. It resulted that for (n,0) clusters, odd n implies aromaticity, whereas even n, non-aromaticity; (n,n) clusters are in any case non-aromatic. For a better understanding of some experimental results, we also discussed how edge effects can influence topological reactivity due to the increment of the number of benzene rings in some cluster arrangements

Based on the free electron molecular orbital theory (FEMO) the derivation of a simple expression for evaluation of the condensed Fukui's function for the molecular models of linear conjugated transpolyacetyle of the general formula CH 2 (CH-CH n CH 2 was described. The predicted condensed Fukui's function are in good agreement with the DFT:B3LYP/6-31G (d) values. An extension of the present theory for radical reactions is presented. We investigated also the functionalization energy with OH radical for the molecular and periodical models of linear conjugated transpolyacetyle. Our FEMO-based functionalization reaction energy is in agreement with the DFT:B3LYP/6-31G(d) calculated values. The functionalization reaction energy in the infinite length limit of our transpolyacetyle model is in agreement with the functionalization reaction energy for our DFT-based periodical model.