New organic FET-like photoactive device, experiments and DFT modeling

We present the possible construction of an organic FET-like photoactive device in which source-drain current through a phthalocyanine ( H2Pc film is affected by a photo-induced dipolar field in a photoactive “gate” electrode. The influence of the dipolar electric field on charge transfer between H2Pc molecules is modeled by DFT quantum-chemical calculations on H2Pc dimers and tetramers

Fluorescent Nanodiamonds: Effect of Surface Termination

ABSTRACT It has been reported that physico-chemical properties of diamond surfaces are closely related to the surface chemisorbed species on the surface. Hydrogen chemisorption on a chemical vapor deposition grown diamond surface is well-known to be important for stabilizing diamond surface structures with sp 3 hybridization. It has been suggested that an H-chemisorbed structure is necessary to provide a negative electron affinity condition on the diamond surfaces. Negative electron affinity condition could change to a positive electron affinity by oxidation of the Hchemisorbed diamond surfaces. Oxidized diamond surfaces usually show characteristics completely different from those of the H-chemisorbed diamond surfaces. The unique electron affinity condition, or the surface potential, is strongly related to the chemisorbed species on diamond surfaces. The relationship between the surface chemisorption structure and the surface electrical properties, such as the surface potential of the diamond, has been modelled using DFT based calculations

Heyrovský Institute of Physical Chemistry

ABSTRACT It has been reported that physico-chemical properties of diamond surfaces are closely related to the surface chemisorbed species on the surface. Hydrogen chemisorption on a chemical vapor deposition grown diamond surface is well-known to be important for stabilizing diamond surface structures with sp 3 hybridization. It has been suggested that an H-chemisorbed structure is necessary to provide a negative electron affinity condition on the diamond surfaces. Negative electron affinity condition could change to a positive electron affinity by oxidation of the Hchemisorbed diamond surfaces. Oxidized diamond surfaces usually show characteristics completely different from those of the H-chemisorbed diamond surfaces. The unique electron affinity condition, or the surface potential, is strongly related to the chemisorbed species on diamond surfaces. The relationship between the surface chemisorption structure and the surface electrical properties, such as the surface potential of the diamond, has been modelled using DFT based calculations

Magnetical and optical properties of nanodiamonds can be tuned by particles surface chemistry: Theoretical and experimental study

© 2014 American Chemical Society. In this paper, new steps toward a better understanding and utilization of high-pressure high-temperature nanodiamonds (NDs) containing nitrogen-vacancy (NV) centers have been taken. NV--related long-term luminescence of oxygenated particles increased in comparison to plasma hydrogenated NDs' NV- luminescence. The optically detected NV- electron spin resonance process can be also significantly affected by ND termination. For H-terminated ND particles the NV- to NV0 conversion energy is lower than the NV- excitation energy, so that the delocalized triplet electrons can be more easily released from the original positions and drawn to the electron-attracting localities in the material. The final result of this study was application of luminescent NDs in cells, showing the detectability of luminescent NDs in a standard confocal microscope and ND subcellular distribution in the cells by TEM

Magnetical and optical properties of nanodiamonds can be tuned by particles surface chemistry: Theoretical and experimental study

© 2014 American Chemical Society. In this paper, new steps toward a better understanding and utilization of high-pressure high-temperature nanodiamonds (NDs) containing nitrogen-vacancy (NV) centers have been taken. NV--related long-term luminescence of oxygenated particles increased in comparison to plasma hydrogenated NDs' NV- luminescence. The optically detected NV- electron spin resonance process can be also significantly affected by ND termination. For H-terminated ND particles the NV- to NV0 conversion energy is lower than the NV- excitation energy, so that the delocalized triplet electrons can be more easily released from the original positions and drawn to the electron-attracting localities in the material. The final result of this study was application of luminescent NDs in cells, showing the detectability of luminescent NDs in a standard confocal microscope and ND subcellular distribution in the cells by TEM

La Patrie : journal quotidien, politique, commercial et littéraire

30 mars 18781878/03/30 (A38)

Charge carrier mobility in sulphonated and non-sulphonated Ni phthalocyanines: experiment and quantum chemical calculations

The objective of this interdisciplinary paper was to study theoretically and experimentally the electronic part of charge carrier transport in the class of sodium salts of sulphonated Ni phthalocyanine as candidates for p-type channels in organic field-effect transistors. These materials were selected because of their enhanced solubility as compared to their non-sulphonated counterparts. The values of the field-effect charge carrier mobility determined on the OFET structures using NiPc(SO3Na)x films were much higher than the charge carrier mobility obtained on the respective device prepared from non-substituted phthalocyanine. In order to explain differences between charge carrier mobility of sulphonated and non-sulphonated Ni phthalocyanines, quantum chemistry studies of molecular aggregates were performed. Quantum chemistry modeling of the semiconductive molecular systems is new and progressive – we highlighted factors at the molecular level which led to the enhancement of the charge carrier mobility in systems containing SO3Na groups

Conductivity of boron-doped polycrystalline diamond films: influence of specific boron defects

The resistivity of boron doped polycrystalline diamond films changes with boron content in a very complex way with many unclear factors. From the large number of parameters affecting boron doped polycrystalline diamond film’s conductivity we focused on the role of boron atoms inside diamond grains in terms of boron contribution to the continuum of diamond electronic states. Using a combination of theoretical and experimental techniques (plane-wave Density Functional Theory, Neutron Depth Profiling, resistivity and Hall effect measurements, Atomic Force Microscopy and Raman spectroscopy) we studied a wide range of B defect parameters – the boron concentration, location, structure, free hole concentration and mobility. The main goal and novelty of our work was to find the influence of B defects (structure, interactions, charge localisation and spins) in highly B-doped diamonds – close or above the metal-insulator transition – on the complex material charge transport mechanisms