Dimitar Panayotov

Dimitar Panayotov
Bulgarian Academy of Sciences | BAS · Institute of General and Inorganic Chemistry

About

37
Publications
2,633
Reads
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2,813
Citations
Citations since 2016
6 Research Items
1364 Citations
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
Additional affiliations
December 2015 - present
Bulgarian Academy of Sciences
Position
  • Professor (Associate)
November 2006 - November 2011
Virginia Tech (Virginia Polytechnic Institute and State University)
Position
  • Researcher
July 2002 - October 2006
University of Pittsburgh
Position
  • Researcher

Publications

Publications (37)
Article
Full-text available
The variety of functionalities and porous structures inherent to metal-organic frameworks (MOFs) together with the facile tunability of their properties makes these materials suitable for a wide range of existing and emerging applications. Many of these applications are based on processes involving interaction of MOFs with guest molecules. To optim...
Article
Full-text available
The purpose of this paper is to provide a clear and simple introduction to the application of isotopically labelled molecules in the characterization of various surfaces by vibrational spectroscopies. Although the possible applications are multifarious, we have tried to systematize the most important of them in several groups. Initially we provide...
Article
Nanoscale gold-titania (Au/TiO2) catalysts may provide the right combination of electronic structure, structural dynamics, and stability to affect the activity and selectivity towards wide ranging chemical transformations, including reactions for utilization of renewable energy sources such as biomass and fuel cells. The Au/TiO2–based systems have...
Article
Surface adsorption and activation of propene, to catalytically produce propene oxide, is the first step in the industrially important gas-phase epoxidation reaction. Motivated by the significant practical importance of this reaction, site-specific adsorption of propene on nanoparticulate titania-supported Au (Au/TiO2) has been systematically charac...
Article
Direct gas-phase epoxidation of propene to propene oxide over a heterogeneous catalyst holds the potential to revolutionize production of one of the world's major commodity chemicals. New research into fundamental aspects of propene chemistry on nanoparticulate catalysts will help guide strategies for materials development. In the current study, Fo...
Article
The fascinating particle size dependence to the physical, photophysical, and chemical properties of gold has motivated thousands of studies focused on exploring the ability of supported gold nanoparticles to catalyze chemical transformations. In particular, titanium dioxide-supported gold (Au/TiO2) nanoparticles may provide the right combination of...
Article
Comparison of methanol photochemistry at three-dimensionally (3D) networked aerogels of TiO2 or Au–TiO2 reveals that incorporated Au nanoparticles strongly sensitize the oxide nanoarchitecture to visible light. Methanol dissociatively adsorbs at the surfaces of TiO2 and Au–TiO2 aerogels under dark, high-vacuum conditions. Upon irradiation of either...
Article
The use of nanoparticulate TiO2 as a photocatalyst for the conversion of organic molecules has grown tremendously in recent years; however, the roles of excited electrons, holes, and surface adsorbates in titania photochemistry remain poorly understood. In this work, detailed infrared measurements, which are sensitive to both vibrational and electr...
Article
Transmission FTIR spectroscopy is used to explore the electronic structure of excited TiO2 nanoparticles. Broad infrared spectral features in UV-photoexcited, n-doped, and thermally reduced titania are found to be well-described by two theoretical models, which independently account for the creation of free conduction band electrons and trapped loc...
Article
Transmission Fourier transform infrared spectroscopy, coupled with CO adsorption, was used to study how the oxidation state of Au surface sites change during H2 dissociation, migration, and electronic excitation of TiO2 in a nanoparticulate Au/TiO2 catalyst. Data reveals that atomic H, produced by H2 dissociation on Au particles, readily hydroxylat...
Article
Infrared spectroscopy of adsorbed CO has been used to characterize the effect of adsorbed methanol on the Lewis acidity of 4 nm rutile TiO(2) nanoparticles. Measurements of CO absorbance and vibrational frequency have revealed that CO adsorbs primarily at one class of Lewis acid sites on clean TiO(2) particles, where evidence for lateral interactio...
Article
The thermal decomposition of dimethyl methylphosphonate (DMMP), a chemical warfare agent simulant, on high surface area TiO2 nanoparticles (Degussa P25) has been studied by transmission infrared spectroscopy. The dominant reaction channel in the low-temperature regime from 295 to 400 K is the nucleophilic attack of adsorbed DMMP by neighboring oxyg...
Article
Using Fourier transform infrared spectroscopy (FTIR) we studied the overall reaction pathways and ultimate fate of dimethyl methylphosphonate (DMMP), a chemical warfare agent simulant, on a commercial nanoparticulate (approximately 20 nm) titania material. Our data show that the initial uptake occurs through both molecular and reactive adsorption....
Article
High-vacuum transmission infrared spectroscopy is used to investigate the reaction pathways of the chemical warfare agent simulant dimethyl methylphosphonate (DMMP) on nanoparticulate Au/TiO2 and pure TiO2. The infrared spectral signature of adsorbed CO, a major reaction product, is used to track the oxidation state of Au and Ti during the reaction...
Article
Irradiation of powdered TiO2 by atomic hydrogen has been shown to produce electron-hole pairs in the TiO2. The electronic excitation from shallow traps is measured in the IR region by absorption spectroscopy, where IR photons excite H-atom derived electrons into the conduction band continuum. The activation energy for atomic H diffusion into the Ti...
Article
The spillover of atomic hydrogen from supported An particles on TiO2 has been studied. IR spectroscopy detects trapped electrons in the TiO2 lattice produced by the atomic H delivered from the An. The spillover process is one-half order in P-H2 and the activation energy for H-2 dissociation on An is 0.52 +/- 0.02 eV. It is shown that surface Ti-OH...
Article
The UV photoproduction of a hydrophilic TiO(2)(110)(1x1) surface has been investigated in a pressurized ultrahigh vacuum apparatus under controlled conditions of hydrocarbon concentration in oxygen gas at 1 atm pressure. Water droplet contact angles have been measured continuously as the droplet is exposed to UV irradiation, yielding the first obse...
Article
The chemisorption of water at 300 K onto reduced TiO2 produces both adsorbed Ti-OH groups and chemisorbed water. During the adsorption of H2O, the concentration of conduction band electrons is found to decrease as measured by transmission infrared spectroscopy. The TiO2 electron depletion process occurs predominantly during the first stages of wate...
Article
Ultraviolet light-induced electron-hole pair excitations in anatase TiO(2) powders were studied by a combination of electron paramagnetic resonance and infrared spectroscopy measurements. During continuous UV irradiation in the mW.cm(-2) range, photogenerated electrons are either trapped at localized sites, giving paramagnetic Ti(3+) centers, or re...
Article
A chemisorbed polyfunctional molecule containing both a S atom and a Cl atom, (2-chloroethylethyl sulfide, 2-CEES) is able to abstract electrons which reside near the bottom of the conduction band in TiO 2. By using analogous model compounds containing either the S moiety or the Cl moiety, it is found that electron transfer from TiO 2 occurs only i...
Article
The photodecomposition of chemisorbed 2-chloroethyl ethyl sulfide (2-CEES) on the TiO2 surface was investigated using several experimental methods involving both a rutile TiO2(110) surface and powdered P-25 Degussa TiO2. It is found that photooxidation of 2-CEES occurs in the absence of gas-phase oxygen. The oxygen for this process is supplied by t...
Article
The adsorption, desorption, and oxidative decomposition of the 2-chloroethyl ethyl sulfide molecule (2-CEES) has been investigated on the TiO2(110) surface as well as on high area anatase and rutile powdered samples. A combination of measurement tools has been employed. It has been found that a monolayer of 2-CEES desorbs in the temperature range f...
Article
The photooxidation of 2-chloroethyl ethyl sulfide (2-CEES), a simulant for mustard gas, was studied using transmission IR spectroscopy on a mixed-oxide TiO2-SiO2 photocatalyst. Ultraviolet irradiation in the photon energy range from 2.1 to 5 eV was employed at a catalyst temperature of 200 K. Rapid photooxidation was observed by the loss of infrare...
Article
The photooxidation of an organic compound, 2-chloroethyl ethyl sulfide (2-CEES), over a TiO2-SiO2 mixed oxide photocatalyst has been studied using transmission infrared spectroscopy. The purpose of this work was to determine the influence of an inert perfluoroalkane buffer layer on the photooxidation properties of the photocatalyst. Both oxygen gas...
Article
The mixed oxide photocatalyst, TiO2–SiO2 has been observed to contain trapped conduction band electrons after annealing in vacuum. These electrons are consumed by adsorption of particular electrophilic molecules. It is found that O2 and an adsorbed organic molecule containing a Cl moiety can remove trapped electrons, whereas a similar organic molec...
Article
The photocatalytic oxidation of 2-chloroethyl ethyl sulfide (2-CEES, a simulant for mustard gas) on high area TiO2-SiO2 powder has been studied by transmission infrared spectroscopy. It has been found that the photocatalytic oxidation of 2-CEES occurs on the surface of TiO2-SiO2 at 200 K with an appreciable rate, causing 40-50% depletion of the ini...
Article
The adsorption of 2-chloroethyl ethyl sulfide on a high area TiO2-SiO2 mixed oxide powder has been studied by transmission infrared spectroscopy. It has been found that hydrogen bonding of this molecule to Si-OH groups occurs through both the Cl and the S moieties and that characteristic Si-OH red-shifts are found for each of the hydrogen bonds pro...
Article
The activity of the mixed copper–manganese oxides CuO–MnOx (1.5<x<2), obtained by coprecipitation and activated at 300°C, has been studied for CO–NO and CO–NO–O2 reactions. As shown by magnetic susceptibility data, X-ray diffraction, FTIR spectra, and catalytic tests, an interaction between CuO and MnOx with formation of a disordered mixed oxide wi...
Article
The activity of γ−Al2O3-supported CuxMn3-xO4 catalysts towards the reduction of NO with CO has been investigated at temperatures of 150–500°C. It was established that the most active sample is Cu1.01Mn1.99O4/γ−Al2O3,i.e. the sample where the CuMn2O4 spinel is formed. In the presence of oxygen and the reducing agents CO and HC (a propane-butane mixt...
Article
NO was adsorbed on Cu-ZSM-5 at temperatures between 173 K < T < 773 K. The IR spectra indicated that three types of adsorbed NO species are formed: NO(delta+) (1900 cm-1), NO(delta-) (1810 cm-1) and dimeric or dinitrosyl (NO)2 (1824 cm-1 and 1730 cm-1). Disproportionation of NO at low temperature produced N2O and NO2. Bands stemming from adsorption...
Article
For the first time, direct IR spectroscopic evidence is obtained indicating that specific OH groups on Al2O3 and SiO2 are consumed as CO interacts with supported Rh crystallites to produce atomically dispersed Rh(I)(CO)2.
Article
The interaction of NO with CO on a CuCo2O4 catalyst has been investigated in the temperature range 60–240°C. The surface state during the catalytic process was studied by the transient response method upon successive treatments of the catalyst with mixtures of NO+CO+Ar (stoichiometric), NO+Ar and CO+Ar. After treatment with NO+CO+Ar, the catalyst s...
Article
Specific OH(a) groups on Al2O3 or SiO2 are consumed as CO interacts with supported Rh crystallites to produce Rh/sup I/(CO)2(a). The reaction Rh + -OH(a) + 2CO(g) Rh/sup I/(CO)2(a) + 1/2 H2(g) has been shown to involve isolated OH(a) groups rather than H-bonded associated OH(a) species. This reaction can be reversed by using H2(g) to destroy Rh/sup...
Article
The interaction between NO and CO on the surface of CuCo2O4 spinel was investigated at 293–700 K. IR studies were carried out on a γ-Al2O3-supported spinel using a flow-cell reactor and a gradientless cell reactor. TPD experiments were performed on supported and unsupported spinels. Exposure of the support to NO+CO at 293 K produced bands at 1330–1...

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