Hetero Systems Research Articles

Architectural design of core-shell nanotube systems based on aluminosilicate clay.

A nanoarchitectural approach to the design of functional nanomaterials based on natural aluminosilicate nanotubes and their catalysis, and practical applications are described in this paper. We focused on the buildup of hybrid core–shell systems with metallic or organic molecules encased in aluminosilicate walls, and nanotube templates for structured silica and zeolite preparation. The basis for such an architectural design is a unique Al2O3/SiO2 dual chemistry of 50 nm diameter halloysite tubes. Their structure and site dependent properties are well combined with biocompatibility, environmental safety, and abundant availability, which makes the described functional systems scalable for industrial applications. In these organic/ceramic hetero systems, we outline drug, dye and chemical inhibitor loading inside the clay nanotubes, accomplished with their silane or amphiphile molecule surface modifications. For metal–ceramic tubule composites, we detailed the encapsulation of 2–5 nm Au, Ru, Pt, and Ag particles, Ni and Co oxides, NiMo, and quantum dots of CdZn sulfides into the lumens or their attachment at the outside surface. These metal–clay core–shell nanosystems show high catalytic efficiency with increased mechanical and temperature stabilities. The combination of halloysite nanotubes with mesoporous MCM-41 silica allowed for a synergetic enhancement of catalysis properties. Finally, we outlined the clay nanotubes’ self-assembly into organized arrays with orientation and ordering similar to nematic liquid crystals, and these systems are applicable for life-related applications, such as petroleum spill bioremediation, antimicrobial protection, wound healing, and human hair coloring.

GO/Ag2O Composite Nanostructure as an Effective Antibacterial Agent

AbstractSilver oxide nano‐particles (Ag2O NPs) are prepared by wet chemical method and impregnated with graphene oxide (GO) nano‐sheets in different wt. % ratios. The Ag2O NPs showed peaks in with the face centered cubic crystalline structure as indicated by X‐ray diffraction (XRD). The characteristic peaks of GO are also appeared in XRD patterns of GO/Ag2O composites. SEM image of pure GO nano‐sheets represented thin flexible layered structure. In GO/Ag2O hybrid structure, the Ag2O nanoparticles are randomly anchored on the surface of GO nano‐sheets. FT‐IR spectra of GO/Ag2O composite illustrate the reduction in intensity of peaks as compared to pure Ag2O. Some oxygen functional groups are also reduced in the composites samples. The antibacterial activity of hetero systems was observed in case of E.coli and Staph aureus by disc diffusion method. In antibacterial activity, pure Ag2O and GO exhibited small zones of inhibition in comparison to 2.0 and 4.0% GO/Ag2O nano composite materials towards E. coli and S. aureus. The results indicated that GO/Ag2O nanocomposites can markedly inhibit E. coli reproduction as compared to S. aureus. In antibacterial mechanism, positively charged Ag ions and reactive oxygen species (ROS) are produced more in GO/Ag2O nanocomposites than singly Ag2O and GO nanomaterials which cause the disrupting interaction with bacterial cell wall through membrane proteins. The effectiveness of Ag2O NPs is enhanced by incorporating GO nano‐sheets.

ZnO/TiO2 nanocomposite photoanode as an effective UV-vis responsive dye sensitized solar cell

A facile and simple sol-gel process has been used for the synthesis of TiO2 and ZnO nanomaterials. The varied amount of ZnO is incorporated onto surface of TiO2 by wet chemical impregnation method to fabricate ZnO/TiO2 hetero structures. These hetero systems are employed as photoanodes for dye sensitized solar cell in paste form. The loading of ZnO onto TiO2 surface suppressed the diffraction peaks of anatase phase of TiO2. The particle size is decreased in the composite structure. SEM images showed the spherical agglomerated structure in all samples. The band gap energy values have been reduced in case of ZnO/TiO2 heterojunctions up to concentration of 15.0% ZnO/TiO2. Zn–O–Ti bridging was responsible for low band gap and reduced in the recombination of electron hole. Fourier transforms infra-red spectroscopy confirms the Zn–O–Ti linkage. The depth profile of thin films was determined by Rutherford backscattering spectroscopy. The photoanodes of DSSC fabricated with ZnO/TiO2 nanocomposites were characterized by photocurrent-voltage measurements and exhibited the enhancement in photovoltaic properties as compared to bare TiO2. 15.0% ZnO/TiO2 heterojunction is optimum quantity which delivered 2.8% greater photovoltaic efficiency than bare TiO2 based DSSC. The enhancement is attributed to superior dye loading and reduction in recombination of charge carriers leading to long life time of free electrons that are beneficial for the overall efficiency of device.

Fused Pyrrolo[2,3-d]pyrimidines (7-Deazapurines) by Palladium-Catalyzed Direct N–H and C–H Arylation Reactions

Palladium-catalyzed intramolecular direct C–H arylations for the synthesis of hitherto unknown fused hetero systems containing an incorporated pyrrolo[2,3-d]pyrimidine scaffold are described. Pyrimido[5′,4′:4,5]pyrrolo[2,1-a]isoindoles were synthesized from 2,4-di­arylpyrrolo[2,3-d]pyrimidines and o-bromobenzyl bromides by using a cascade N-benzylation/C–H arylation reaction sequence. A series of pyrimido[5′,4′:4,5]pyrrolo[1,2-f]phenanthridines were successfully assembled via a domino process involving the palladium-catalyzed direct double C–H arylation reactions of 2,4,7-triarylpyrrolo[2,3-d]pyrimidines with o-bromoiodobenzenes.

Mesomorphic dependence on molecular rigidity by central bridge and homo–hetero ring systems

ABSTRACTA novel homologous series of thermotropic derivatives containing a heterocyclic ring was synthesized and studied with a view to understanding and establishing a relation between liquid crystal (LC) properties and the molecular structure of chalconyl derivative in general. The series comprises 12 homologues, of which smectogenic LC property commences from the decyloxy (C10) homologue and continues for C12, C14, and C16 homologues. Homologues C1 to C8 are non-liquid crystals. Exhibition of nematogenic mesophase is totally absent. Transition and melting temperatures were determined by an optical polarizing microscope equipped with a heating stage. Spectral and analytical data confirmed the molecular structures of homologues. The textures of smectic mesophase are A or C, and are determined by a miscibility method. The average thermal stability of the smectic phase is 113.57°C. The mesogenic phase length ranges between 4.1°C and 11.1°C. Thus, it is a middle-ordered melting-type series of shorter range of liquid crystallinity with absence of nematogenic character. Some LC properties of the present series are compared with a structurally similar known homologous series.

Tuned electronic, optical and mechanical properties of pristine and hetero nanotubes of group IV elements (C, Si and Ge)

Density functional theory has been used to investigate the structural, electronic, optical and mechanical properties of pristine nanotubes of carbon, silicon, germanium and their hetero nanotubes having armchair conformation with chirality (6,6). In the pristine nanotubes it is found that the cohesive energy per atom is more for CNT as compared to other nanotubes under investigation. However, in hetero systems under study its value is highest for SiCNT system and least for GeCNT. GeNT and SiGeNT have been observed to be more puckered in comparison to other systems. All the pristine and heteronanotubes in our study are found to be semiconducting in nature, except GeNT, which is found to be metallic in nature with a conductance of 2G0, indicating GeNT to be an ideal material for ballistic transport. Three different types of hetero nanotubes have wide band gap spectrum which opens up an arena for band gap selective engineered devices. The band gap for SiCNT and GeCNT lie in the visible region, while the band gap for other systems lie in the infrared region. The tuning of electronic band structure by means of compression, tensile strain and external electric field indicates that the band gap can be altered considerably. There is a band gap closure under both compression and expansion at a certain value in all the cases except SiCNT, revealing that its band gap can be varied considerably. The decreasing order of tensile strength is CNT>SiCNT>GeCNT>SiNT>GeNT>SiGeNT. The effective mass of holes decreases for pristine systems on the application of compression. Under no strain the effective mass of electrons is generally found to be larger than holes in hetero systems, while it is reverse in pristine systems. In case of unstrained systems, we generally observed that the more the effective mass of electron, the more is the band gap in the corresponding system.

Synthesis, antibacterial and antioxidant evaluation of 4-substituted 1-(4-methoxyphenyl)pyrrolidin-2-ones

4-Substituted 1-(4-methoxyphenyl)pyrrolidin-2-ones containing azole, diazole, oxadiazole, thiadiazole, and triazole fragments have been synthesized, and the characterization of the obtained products is presented. The study compounds have been analyzed for antioxidant and antibacterial activities. Two types of hetero systems – 5-thioxo-4,5-dihydro-1,3,4-oxadiazole and [1,2,4]triazolo[3,4- b ][1,3,4]thiadiazine – showed a moderate activity against Rhizobium radiobacter , Xanthomonas campestris , and Escherichia coli microorganisms. Some compounds were tested for their antioxidant activity. DOI: http://dx.doi.org/10.5755/j01.ct.65.1.8881

Copper-Bronze Catalyst: An Efficient Green Approach for the Synthesis of Dibenzo[b,e][1,4]diazepine Derivatives

Dibenzo(b,e)(1,4)diazepine derivatives medicinally important hetero systems have been synthesized by green, efficient and convenient synthesis involving Cu-bronze as a novel catalyst by condensation of o-phenylenediamine with aromatic aldehydes. This method is advantageous because of high yield of product easy workup procedure. The synthesized compounds were characterized by 1 H NMR, Mass and IR spectral analysis.

Single Dirac cone on the Cs-covered topological insulator surface Sb2Te3(0001)

Using angle-resolved photoelectron spectroscopy we investigate the surface electronic structure of the three-dimensional topological insulator (TI) Sb2Te3(0001). Our data show the presence of a topological surface state in the bulk energy gap with the Dirac-point located above the Fermi level. The adsorption of Cs-atoms on Sb2Te3(0001) gives rise to a downward energy shift of the electronic valence band states which saturates at a value of ~200 meV. For the saturation coverage the Dirac-point of the linearly dispersive surface state resides in close proximity to the Fermi level. The electronic structure of the Cs/Sb2Te3 interface therefore considerably deviates from previously studied metal-TI interfaces based on the isostructural compound Bi2Se3 which points to the importance of atomic composition in these hetero systems.

TV대역에서 IEEE 802.11과 Extended Hata 채널모델을 이용한 인접채널간 시스템 공존을 위한 성능 분석

In this paper, we analyze the maximum allowable transmitting output level of transmitter, which meets the required interference probability, in order to get the method that different communication systems can be existed and used simultaneously in adjacent channels. We analyze the performance result according to various density of interfering transmitter and transmitter output in hetero systems. In order to get the relationship with between density of interfering transmitter and transmitter output, we consider WiBro as an interfering transmitter, WLAN as a victim receiver and Extended Hata and IEEE 802.11 model as a channel environment respectively. Analyzed coexistence results may be widely applied into the technique developed to get the coexisting condition for wireless devices using many communication protocols in same frequency.

Extended Hata 채널 환경에서 인접채널간 시스템 공존을 위한 파라미터 분석

본 논문에서는 인접채널에서 다른 통신 시스템이 공존할 수 있는 방안으로 공유 파라미터를 분석하였다. 이기종시스템에서 간섭 송신기의 다양한 밀도와 전송출력에 따른 성능 결과를 분석하였다. 두 시스템간의 간섭밀도와 허용 최대 송신출력의 관계를 분석하기 위해 간섭 송신기가 WiBro이고 WLAN이 희생 수신기인 경우를 고려하였다. 간섭원 밀도가 50개/<TEX>$km^2$</TEX>이고, WLAN, WiBro의 중심주파수가 각각 185, 201MHz 인 경우 요구되는 보호대역은 4MHz 이었다. 분석된 상호 공존 결과는 향후 동일 주파수 환경에서 다양한 통신 프로토콜을 이용하는 무선기기에 대한 상호 공존 조건을 마련하는 기술개발에 활용할 수 있을 것이다. In this paper, we analyze the sharing parameters in order to co-use of different communication systems in adjacent channels. We analyze the performance result according to various density of interfering transmitter and transmitter output in hetero systems. In order to get the relationship with between density of interfering transmitter and transmitter output, we consider the case that WiBro is an interfering transmitter an WLAN is a victim receiver. When the interferer density is 50/<TEX>$km^2$</TEX> and the center frequency of WLAN and WiBro are 185 and 201MHz respectively, required guard band is 4MHz. Analyzed coexistence results may be widely applied into the technique developed to get the coexisting condition for wireless devices using many communication protocols in same frequency.

간섭 송신기 신호 duty cycle에 따른 시스템 공유 성능 분석

In this paper, we analyze the total performance according to duty cycle of interfering transmitter in hetero systems. We analyze this criteria as a parameter for co-use when hetero systems share the same frequency channels. In order to make an analysis of relationship between duty cycle and performances of two systems. We take into consideration on the case that WiBro is an victim receiver and WLAN is a interfering transmitter. Analyzed coexistence results may be widely applied into the technique developed to get the coexisting condition for wireless devices using many communication protocols in same frequency.

이기종시스템에서 동일채널공유시 단말간 이격거리에 따른 최대 송신전력 분석

In this paper, we consider to obtain the criteria for maximal power of interfering transmitter according to distance between WiBro and WLAN in TVWS. We analyze this criteria as a parameter for co-use when hetero systems share the same frequency channels. In order to make an analysis of relationship between distance and power of two systems, we take into consideration on two cases. First, WiBro is an interfering transmitter and WLAN is a victim receiver. Second, WLAN is an interfering transmitter and WiBro is a victim receiver. Analyzed coexistence results under various co-use scenarios may be widely applied into the technique developed to get the coexisting condition for wireless devices using many communication protocols in same frequency.

Synthesis and reactions of 1-R-3-benzoyl-5-ethoxycarbonyl-6-oxo-1,2,3,6-tetrahydropyridine-2-thiones

Cycloacylation of N-R-3-oxo-3-phenylpropanethioamides by diethyl ethoxymethylenemalonate occurs selectively to form 1-R-3-benzoyl-5-ethoxycarbonyl-6-oxo-1,2,3,6-tetrahydropyridine-2-thiones which are convenient starting materials for the synthesis of bi-and tricyclic hetero systems including the previously unknown 9-R-7-ethoxycarbonyl-5-phenyl-8,9-dihydropyrido[2,3-d][1,2,4]triazolo[1,5-a]-pyrimidin-8-ones.

Theoretical investigation on the structures of silicon and carbon hetero clusters

Structures and energies of Si m C n clusters ( m = 2 − 6, n = 1 − m) have been investigated systematically at MP2/6-311G(d) level of theory. Several stable structures of Si 6C n are predicted for the first time. All the structures show that carbon atoms prefer forming kernels at the center of framework, surrounded by silicon atoms with small coordination number. The strong C C bond favored over Si C bond determines the structure of Si m C n clusters. The binding energies show that the systems with the ratio of Si:C=1:1 have the larger stability compared to the Si-rich hetero systems.

Spectrophotometric determination of the transition system for interactions involving model hydrogen bonds in acetonitrile

AbstractThe bonds formed by interactions of picric acid (HA) with each of 12 (un)substituted pyridines (B) in acetonitrile (AN) were studied by UV–vis spectrophotometry to determine the $\Delta \hbox{p}K_{\rm a}^{\rm AN}=$ $\hbox{p}K_{{\rm BH}^{+}}^{\rm AN} - \hbox{p}K_{\rm HA}^{\rm AN}$ corresponding to the transition system. The choice of both model system and experimental technique enabled the effect of heteroconjugation to be observed and the effects of formation of two theoretically possible homoconjugates (AHA− and BHB+) to be eliminated. The relationship between the wavelength at the absorbance maximum (λmax) for 10−4 M solutions of complexes of picric acid with (un)substituted pyridines in acetonitrile and $\Delta \hbox{p}K_{\rm a}^{\rm AN}$ was found to have a sigmoidal shape with an inflection point at $\Delta \hbox{p}K_{\rm a}^{\rm AN}$ of ca −0.3. On the basis of this relationship and UV–vis spectra, the picric acid–3‐acetylpyridine system was recognized as that being the nearest to the transition system. The fact that the transition $\Delta \hbox{p}K_{\rm a}^{\rm AN}$ was lower than zero has been explained by the remarkable effect of species having the average structures A−···+HB on the established λmax values. The general results of this work and our previous results based on IR and 1H NMR studies, and also the lack of any experimental counterexamples, indicate that the zero value of $\Delta \hbox{p}K_{\rm a}^{\rm AN}$ constitutes a fundamental basis for predicting which one, among the given family of protonic hetero systems, is the most likely to show transitional properties in acetonitrile. Finally, it is postulated that the protonic hetero systems which are the most likely to show transitional properties in a given solvent S are those for which $\Delta \hbox{p}K_{\rm a}^{\rm S}$ is close to zero, the eventual shift arising from peculiarity of the technique applied. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Synthesis of fused pyrimidines with N‐, S‐heterocyclic moieties by double‐annelation reaction

AbstractA variety of tri‐ and tetracyclic hetero systems were obtained by reaction of heteroaromatic ortho‐aminoesters or ortho‐aminonitriles with iminothioether, yielding double‐annelation of a thiazolo[3,2‐a]‐pyrimidine, pyrimido[2,l‐b]thiazine, imidazo[1,2‐a]pyrimidine, and pyrimido[1,2‐a]pyrimidine moieties in a one‐pot process.

Reagents for new heteroannelation reactions III. 2-(Methylthio)-2-thiazoline

A variety of partly novel tri- and tetracyclic hetero systems were obtained by reaction of heteroaromatic 2-aminoesters with 2-(methylthio)-2-thiazoline, yielding double-annelation of a thiazolo[2,3-b]pyrimido moiety in a one-pot process.

Conjugation and proton exchange equilibria I. Significant role of proton exchange and homoconjugation equilibria in protonic hetero systems

The significant role of the proton exchange and homoconjugation (formation of AHA− and A1HA 1 − complexes) equilibria in protonic hetero systems (HA+A 1 − ) has been shown from analysis of published data and from my own simple experiments. It is concluded that there is a need to reconsider some basic hydrogen bond problems. One of these problems-the existence of heteroconjugates in polar solvents — has been verified and illustrated with suitable experimental evidence (IR and UV-VIS spectra). The most accepted experimental evidence for the double minimum potential in the hydrogen bridge has been questioned as being in disagreement with the equilibrium law. A simple relation between the heteroconjugation constant, the parent homoconjugation constants and the proton exchange constant is also postulated. This relation fulfills important theoretical requirements, however, it is not applicable in extreme cases.

ChemInform Abstract: Observation of “Intramolecular” Ion‐Molecule Reactions Within Ionized Clusters: Hetero Systems Involving Methyl Halides and Oxygen‐Containing Compounds.

AbstractWithin ionized heteroclusters (oxy compound: acetone, MeOH, H2O, and dimethyl ether; methyl halide: X: ‐Cl, ‐I) the rates of protonation increase with increasing cluster size in contrast to the protonation within the homoclusters.