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Two-dimensional (2D) piezoelectric nanomaterials have widely been studied recently due to their promise for various applications in technology. Investigation of vertical piezoelectricity will contribute to a deeper understanding of the intrinsic mechanism of piezoelectric effects in the 2D structures. In this paper, we report a first-principle study for the structural, electronic, piezoelectric, and transport properties of new-designed Janus WSi Z 3 H (Z = N, P, and As) monolayers. The structural stability of WSi Z 3 H is theoretically confirmed based on the energetic, phonon dispersion, and also elastic analyses. At the ground state, while WSiN 3 H is an indirect semiconductor, both WSiP 3 H and WSiAs 3 H are predicted to be direct semiconductors with smaller bandgaps. When the spin-orbit coupling effects are taken into account, a large valley spin splitting is observed at the K point of WSi Z 3 H materials. Interestingly, a giant Rashba spin splitting is found in WSiP 3 H and WSiAs 3 H with Rashba constant α R up to 770.91 meV Å. Additionally, our first-principles study indicates that Janus WSi Z 3 H monolayers are piezoelectric semiconductors with high out-of-plane piezoelectric coefficient | d 31 | , up to 0.15 pm/V, due to the broken mirror symmetry. Besides, with high electron mobilities and also possessing direct band gaps, WSiP 3 H and WSiAs 3 H monolayers are favorable for applications in optoelectronics. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the optical response of the PbBiI single-layer by developing a strain-induced Kane–Mele model from Peierls substitution and by employing the Kubo formula at low temperatures. We address three different regimes of uniform and non-uniform classes created by tuning the strength of the strain. From a detailed analysis of the electronic band structure, we find that the Rashba spin splitting gap is destroyed with strain, while the bulk gap slightly changes. We also find that interband optical transitions exhibit a blueshift spectrum with strain. Interestingly, all these findings are independent of the regime and class of strain. However, our simulations show that only the non-uniform class of strain leads to anisotropic optical conductivity. These results enhance optoelectronic applications of low-dimensional materials. [ABSTRACT FROM AUTHOR]

Mesoporous calcium phosphate based-bioceramics with ionic substitution have attracted attention for treatment of bone diseases and bone regeneration. Carbonate apatite (CO3Ap) is a promising candidate for bone replacement through bone remodelling, similar to that of autologous bone, owing to the chemical composition of the bone mineral. In this work, we present a dual approach to synthesize mesoporous carbonate apatite (CO3Ap) and strontium-substituted CO3Ap (Sr-CO3Ap) artificial bone nanocrystals, aiming to assess the impact of strontium on CO3Ap characteristics and biological performance. Mesoporous CO3Ap was created by transforming hard templates composed of CaCO3, while Sr-substituted CaCO3 (Sr-CaCO3) microspheres were formed using an organic complexing agent to induce pore formation. The resulting CO3Ap and Sr-CO3Ap granules exhibited an irregular shape, with rod-like nanocrystals composing their particles. Adsorption/desorption isotherms confirmed the mesoporous nature of the structures, featuring pore sizes ranging from 10 to 50 nm. Specifically, mesoporous CO3Ap displayed slit-like pores, while Sr-CO3Ap showed cylinder-like ones. High-resolution transmission electron microscopy images of Sr-CO3Ap powder revealed mesopores within the particles, with Sr-CO3Ap exhibiting larger pore volume and specific surface area compared to CO3Ap. When osteoblast-like MC3T3-E1 cells were cultured on both CO3Ap and Sr-CO3Ap samples, they demonstrated good cell attachment, proliferation rates, and increased ALP activity, particularly evident at higher strontium concentrations. These findings suggest promising potential for further exploration of mesoporous apatite nanocrystals in bone replacement and drug delivery applications. [ABSTRACT FROM AUTHOR]

Recently, by forming a P‐rich P–S system, the P3S monolayer has been predicted to have good resistance to air oxidation, large band gap, high absorption, and superior mobility. Inheriting this prediction, a series of ternary Janus P6XY (X/Y = S, Se, and Te; X ≠ Y) monolayers based on P3X nanosheet are designed and studied. The structures of P6XY monolayers are confirmed to be stable based on the evaluation of calculated results for phonon spectra, ab initio molecular dynamic simulations. It is also found that P6XY compounds possess anisotropic mechanical characteristics. All Janus structures are indirect semiconductors with large energy gaps varying from 2.12 to 2.60 eV calculated by the hybrid functional. Besides, biaxial strain significantly affects the electronic properties of the P6XY monolayers. In particular, the biaxial strains can induce a transition from indirect to direct bandgap in all three P6XY structures. The carrier mobility in the three proposed structures exhibits directional anisotropy and high electron mobility value, up to 1.27 × 103 cm2 V−1 s−1, which are suitable for applications in high‐performance and direction‐dependent nanoelectronic devices. [ABSTRACT FROM AUTHOR]

In this work, we investigate the complexities (coupling range and magnetic ordering) of the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction on the (001) surface of SnTe which is a topological crystalline insulator. We aim to enable the transition between ferromagnetic and antiferromagnetic couplings, as well as between collinear and noncollinear magnetic spins by manipulating doping and the gap structure. The gap is achieved through electron–phonon coupling and gate voltage. The spin susceptibility is calculated by Green's functions in real space. The modulation of RKKY interactions via doping occurs specifically over short (large) impurity separations, with the influence of electron–phonon coupling (gate) only manifesting when the doped Fermi level lies outside the gap. Additionally, electron–phonon coupling leads to weaker adjustments in magnetic orderings, attributed to the renormalized Fermi velocities, while gate voltage induces stronger modifications. This inquiry is of considerable interest due to the potential applications in the realm of spintronics. • Coupling range and magnetic ordering of the RKKY interaction on the (001) surface of SnTe are investigated. • The modulation of RKKY interactions occurs specifically over short impurity separations. • Electron–phonon coupling leads to weaker adjustments in magnetic orderings, attributed to the renormalized Fermi velocities while gate voltage induces stronger modifications. • The results are of considerable interest due to the potential applications in the realm of spintronics. [ABSTRACT FROM AUTHOR]

Understanding the intricacies of magnetism mechanisms on the surface of topological materials, and focusing on the Ruderman-Kittel-Kasuya-Yosida interaction and its modulation, proves to be intriguing for spintronic applications. In this study, we explore switching possibilities between ferromagnetic (FM) and antiferromagnetic (AFM) couplings on the surface of topological crystalline insulator SnTe through electron-phonon coupling (EPC) and magnetic proximity effect (MPE). Our calculations, based on retarded Green's functions in real space, provide insights into the impact of EPC and MPE on FM/AFM couplings at intermediate impurity separations, where significant responses occur. Importantly, both factors induce the switch between FM and AFM in the XYZ-Heisenberg J x / y / z and in-plane symmetric J x y components. • Tuning the ferromagnetic and antiferromagnetic couplings in TCIs via electron-phonon coupling and magnetic proximity effects. • Reduction and enhancement of the RKKY intensity depending on the electron-phonon coupling and exchange field strengths. • Strong anisotropy in tuning the RKKY components with the (co)existence of effects. [ABSTRACT FROM AUTHOR]

The spin–spin exchange interaction is an important observable that helps in understanding the magnetism of materials. Topological materials are of particular interest due to their strong spin–orbit coupling, which makes them promising for applications in valleytronics and spintronics. In this study, we have theoretically demonstrated the ability to control the switching of ferromagnetic (FM) and antiferromagnetic (AFM) couplings between two magnetic impurities on the (001) surface of the topological crystalline insulator SnTe. By considering experimental parameters such as doping, strain, and gap opening at surface Dirac cones, we provide a generic way to build the FM-AFM and clockwise–counterclockwise phase diagrams of SnTe(001), which are still missing in the literature, especially for the spintronics community. • Controlling the RKKY coupling on the (001) surface of SnTe as a well-known topological crystalline insulator by doping, strain, and electric field. • Proposing the effective possibilities for switching ferromagnetic (FM) and antiferromagnetic (AFM) couplings between two magnetic impurities in different adjustable ways. • Seeking topological materials for future spintronic applications. [ABSTRACT FROM AUTHOR]

We theoretically investigate the electrical conductivity (EC) of topological crystalline insulators SnTe (001) and related alloys in the presence of external static local perturbations employing a continuum model and the Kubo-Greenwood formalism. Particularly, we have found the conditions for which the Dirac and saddle points can be altered in the presence of the perpendicular electric field, the on-site energy difference and the exchange field. Then, the EC of these alterations is addressed for potentials smaller and larger than the intervalley scattering parameter. Numerical results show that the band gap opens by the exchange field, while the electric field and on-site energy difference shift the Dirac/saddle points and the Fermi level, respectively. These phenomena result in the increasing and decreasing of the EC with electric field/on-site energy difference and exchange field, respectively. Finally, we find that the EC becomes non-zero at zero temperature when the Fermi level is shifted. These findings will bring applications to topological electronics. [ABSTRACT FROM AUTHOR]

We theoretically observe the cyclotron–phonon resonance (CPR) in monolayer silicene by considering the magneto-optical absorption power (AP) of the system. The AP is calculated utilising the projection operator technique when a static magnetic field is subjected perpendicularly to the plane of the material and the electron–optical phonon scattering is involved. The absorption spectra show the resonance behaviour where the photon energies at resonant peaks satisfy the cyclotron–phonon (CPR) conditions in which the CPR energy depends linearly on the square root of the magnetic field strength. This dependence is similar to that in graphene and different from that in monolayer MoS 2 and conventional low-dimensional semiconductors. The dependence of the full-width at half maximum (FWHM) on the magnetic field strength has the laws similar to those obtained for graphene and monolayer MoS 2. However, the FWHM value in silicene is two times smaller than it is in graphene and has the same order as it does in monolayer MoS 2. At relatively high temperature (T > 300 K), the FWHM for phonon emission differs very little from that for phonon absorption and becomes identical in two cases when T > 350 K. • The cyclotron–phonon resonance is observed in the absorption spectra. • The CPR energy is proportional to the square root of magnetic field strength. • The FWHM is proportional to the square root of magnetic field strength. • The FWHM increases slightly with increasing temperature. • At high temperatures the roles of phonon emission and phonon absorption are identical. [ABSTRACT FROM AUTHOR]

Abstract Transition-metal dichalcogenide monolayers recently have attracted much attention motivated by their exotic physical properties. In this paper, we theoretically investigate the optical absorption in the monolayer MoS 2 which is subjected to a uniform static magnetic field and an electromagnetic wave. The magneto-optical absorption power (MOAP) is calculated using the projection operator technique in the linear response scheme, taking account of the electron–optical phonon interaction at high temperature. Both phonon emission and phonon absorption processes are included. The cyclotron–phonon resonance (CPR) is observed in the photon energy dependence of the MOAP. Numerical analyses show that the photon energy satisfying CPR condition depends linearly on the strength of magnetic field, which is similar to that in conventional low-dimensional semiconductors but different from that in graphene. The increase of the full width at half maximum (FWHM) of CPR peaks with increasing magnetic field shows a similar behaviour to that in graphene. In addition, FWHM increases slightly with temperature, which is different from that in graphene where the FWHM is temperature independent. Our investigation provides basic information about the magneto-optical properties of the monolayer MoS 2 that are useful for further experiments and applications. Highlights • The cyclotron-phonon resonance is observed in the absorption power. • The CPR peaks exhibit a blue-shift as the magnetic field increases. • The FWHM is proportional to the magnetic field. • The FWHM increases slightly with increasing temperature. [ABSTRACT FROM AUTHOR]

This paper reviews the state of the art in the theory of multisets, i.e., mathematical models of sets with repetitions (duplicates or copies of their elements). The corresponding bibliography is categorized as follows: the general theory of multisets, reviews, and application of multisets, in particular, in computer science. [ABSTRACT FROM AUTHOR]

We use the Kubo formula and linear response theory to study the radiation of energy and angular momentum from biased monolayer PbBiI. Our results show that a critical bias field V b c ≃ 0.326 eV emerges for the radiations. For bias fields below V b c , there is a negligible shift of the threshold frequency at which the spin-dependent energy radiation is maximum, while above which, it significantly moves to the higher frequencies. At all the threshold frequencies, the sign of possible angular momentum radiations is switched. Further, we find that contrary to Planck's law which is valid for the unbiased energy radiation (proportionality to T 4), the biased one is proportional to T 5. Also, it is possible to confirm the behaviors of the system below and above V b c via the temperature-dependent angular momentum radiation. This work illuminates/engineers the application of angular momentum degree of freedom in processing data. • Spin-dependent biased low-energy dispersion and phase transition of monolayer PbBiI. • Tuning the spin-dependent energy radiation of biased monolayer PbBiI. • Tuning the spin-dependent angular momentum radiation of biased monolayer PbBiI. • Deviation of energy radiation of biased monolayer PbBiI from the Planck's law. [ABSTRACT FROM AUTHOR]

Landslides are natural hazards that pose a significant threat to human lives and infrastructure. Landslide susceptibility mapping aims to classify areas at risk of landslides. Multi-Criteria Decision Making (MCDM) algorithms have the advantage of incorporating expert opinions, while Statistics and Machine Learning models demonstrate greater objectivity. This study compares three representative models, namely Analytic Hierarchy Process (AHP), Frequency Ratio (FR), and Random Forest (RF), for developing a landslide susceptibility model in Van Yen District, Yen Bai Province. The classification points for landslides were divided into a 70% training set and a 30% testing set. Thirteen conditioning factors were used to evaluate the landslide's influences. The results show that the AHP and FR models perform well with AUC = 0.842 and AUC = 0.852, respectively, while the RF model outperforms them with AUC = 0.949. The study demonstrates the applicability of these models for analyzing landslide susceptibility in the research area, highlighting the strong potential of machine learning models. [ABSTRACT FROM AUTHOR]

Background and objective The impact of ambient wood smoke and traffic-related air pollution on adult asthma has not been well studied. This paper aims to investigate associations between exposure to ambient wood smoke, traffic-related air pollution and current asthma/asthma severity in middle age, and whether any associations are modified by atopic status. Methods Using data from the Tasmanian Longitudinal Health Study, associations between ambient wood smoke and two indices of traffic-related air pollution (frequency of heavy vehicles near the home and frequency of intense traffic noise) and current asthma/asthma severity were investigated. Unconditional logistic regression to examine current asthma and ordinal logistic regression to examine asthma severity was used. Results For asthmatics, both exposure to ambient wood smoke (odds ratio 1.11; 95% confidence interval 1.02-1.20) and being frequently exposed to heavy vehicles (odds ratio 1.80; 95% confidence interval 1.09-2.96) were associated with increased asthma severity. Neither association varied by atopic status. Conclusions In middle-aged adults, ambient wood smoke and traffic pollution were associated with increased asthma severity. These findings suggest that avoiding or limiting exposure to traffic pollution and wood smoke may help to reduce asthma. Future studies to replicate this finding are recommended and should examine specific biological mechanisms for this effect. [ABSTRACT FROM AUTHOR]

Techniques based on non-linear acoustics have been proven sensitive to micro-defects in heterogeneous materials, such as concrete, but their implementation on-site is very restrictive. Ultrasonic travel time shift, a technique where a high frequency ultrasonic wave probes the medium while a low frequency elastic wave disturbs it to create a 'time delay', is a new promising technique that may be used efficiently on-site. This technique is based on nonlinear behaviour of concrete. Moreover, this technique offers the possibility of evaluating linear parameter, such as ultrasonic pulse velocity of direct waves. The scope of this paper is to study the applicability of the technique at different level of concrete damage and define its advantages, limitations in order to optimize its use. Because of the large dimensions, the geometry and limited access to various faces of existing structures, the transducers often have to be set on the same side. Two types of configurations, the indirect transmission (with incident waves at 90) and the semi-direct transmission (with incident waves at 45), were studied with cement base samples at different levels of damage (generated by freeze-thaw cycles). Up to now, test results have shown that time-shift is more sensitive when used in an indirect configuration of transmission rather than in a semi-direct configuration. Overall, the non-linear time-shift technique is much more sensitive to the initiation of cracking than linear indicators and its versatility (different indicators for different levels of damage) is of interest for rapid testing of structures. [ABSTRACT FROM AUTHOR]

An analysis of the strain-induced group velocity(GV) and effective mass(EM) of massless topological Dirac fermions on the SnTe(001) surface, protected by crystalline symmetry, is presented. Using the traditional semi-classical k → ⋅ p → approach by associating fermions with wave-packets, we find that the expression for the energy dispersion surface as well as both GV and EM are anisotropic in the absence and presence of strain. The band structure calculations indicate that the massive Dirac fermions emerge for strained SnTe(001) surface. However, under strong strains, GVs and EMs of all branches of conduction and valence bands are the same quantitatively, but still anisotropic along different directions. On the other hand, depending on the special critical compressive and/or tensile strains, the direction of the fermionic waves is reversed. Further, the behavior of heavy and light masses are characterized qualitatively with strain modulus and direction. Our results are favorable for the thermoelectric properties of SnTe semiconductor since electronic features are coupled to the heat transports. • The anisotropic dispersion energy of the strain-induced topological crystalline insulator (TCI) SnTe (001) is examined theoretically. • There appears a band gap opening. • The group velocity of surface Dirac fermions in TCI SnTe (001) with strain illustrates anisotropic behaviors. • Depending on the special critical compressive and/or tensile strain, the direction of the fermionic waves in TCI SnTe (001) is reversed. • The behavior of heavy and light masses in TCI SnTe (001) with strain modulus and direction shows a strong anisotropy. [ABSTRACT FROM AUTHOR]

A compact low-loss microstrip diplexer that forms by two band-stop filters using interdigital capacitor and a stepped-impedance resonator structure when joined by a miniature T-junction is introduced. The diplexer operates at global system for mobile communication frequency 1800 MHz and 2.45 GHz WLAN frequency which are the most available frequency bands for RF energy harvesting applications. Simulated and measured results are in very good agreement with low insertion loss of 0.4 dB and high selectivity characteristics. [ABSTRACT FROM AUTHOR]

We consider a polling system with adaptive dynamic polling order for modeling a broadband wireless network with a centralized control mechanism. A new algorithm has been developed for calculating the steady-state probability distribution of the number of packets in subscriber stations. The algorithm makes it possible to calculate the average waiting time and other network performance characteristics. We investigate a queuing system with several queues in which the server serves queues in a dynamic polling order. This order of queuing involves skipping queues that had been empty in the previous polling cycle. The queues that have been skipped in the current cycle can be polled by the server only in the next cycle. The specified queue servicing algorithm allows one to reduce the queue polling time and thus increase the system performance. A comparative numerical analysis of various options for constructing and evaluating the performance characteristics of broadband wireless IEEE 802.11 networks with a centralized control mechanism is presented. Numerical studies have been carried out using a software package for evaluating stochastic polling systems. [ABSTRACT FROM AUTHOR]

The results also indicated that monoterpenes and sesquiterpenes were the predominant compounds in the essential oils of a majority of these I Amomum i plants. This is the first report on the antimicrobial activity of essential oil of space I A. cinnamomeum. i The results in this study are comparable with data obtained on the antimicrobial action of other I Amomum i essential oil reported in the literature such as I A. rubidium i [[1]], I A. subulatum i [[5]], I A. cannicarpum i [[14]], I A. uliginosum i [[15]], I A. tsao-ko i [[7]], and I A. kravanh i [[16]]. Terpene compounds predominate in the essential oils, as was reported for other I Amomum i oil samples grown in Vietnam, such as I A. rubidium i [[1]] I A. gagnepainii i [[12]], I A. repoense i [[12]], I A. longiligulare i [[3]], I A. villosum i [[4]], I A. aculeatum i [[4]], I A. maximum i [[13]], and I A. microcarpum i [[9]]. The major classes of compounds were monoterpene hydrocarbons (46.9 and 31.9%), oxygenated monoterpenes (14.5 and 32.6%), sesquiterpene hydrocarbons (15.3 and 6.6%), and oxygenated sesquiterpene (16.4 and 25.7%); see Table 1. [Extracted from the article]

Abstract The magneto-optical transport properties in monolayer silicene subjected simultaneously to a perpendicular magnetic field and an electromagnetic wave (optical field) are theoretically studied. The nonlinear absorption coefficient is calculated using perturbation theory taking account of the electron–impurity scattering. The cyclotron–impurity resonance (CIR) is observed through the absorption spectrum. The photon energy at resonances is found to be proportional to the square root of magnetic field. This behaviour is similar to that in graphene but different from that in conventional low-dimensional semiconductors. The full width at half maximum (FWHM) of CIR peaks increases with increasing magnetic field by the laws FWHM [meV] ≈ 0.432 B [ T ] and FWHM [meV] ≈ 0.215 B [ T ] for one- and two-photon absorption, respectively. The obtained FWHM is about one order of magnitude smaller than it is in graphene monolayers. Moreover, the temperature dependence of the FWHM is similar to that in graphene but different from that in conventional low-dimensional semiconductors. Highlights • The cyclotron-impurity resonance (CIR) is observed in the absorption spectra. • The photon resonant energy is linearly proportional to the square root of magnetic field. • The FWHM increases with increasing the magnetic field similarly to graphene. • The FWHM is about one order of value smaller than it is in graphene. • The FWHM is independent on temperature. [ABSTRACT FROM AUTHOR]

In the present work, electronic properties and Schottky contact of graphene adsorbed on the MoS 2 monolayer under applied out-plane strain are studied using density functional theory calculations. Our calculations show that weak van derpp Waals interactions between graphene and monolayer MoS 2 are dominated at the interlayer distance of 3.34 Å and the binding energy per C atom of − 25.1 meV. A narrow band gap of 3.6 meV has opened in G/MoS 2 heterointerface, and it can be modulated by the out-plane strain. Furthermore, the Schottky barrier and Schottky contact types in the G/MoS 2 heterointerface can be controlled by the out-plane strain. At the equilibrium state ( d = 3.34 Å), the intrinsic electronic structure of G/MoS 2 heterointerface is well preserved and forms an n -type Schottky barrier of 0.49 eV. When the interlayer distance decreases, the transition from n -type to p -type Schottky contact occurs at d = 2.74 Å. Our studies promote the application of ultrathin G/MoS 2 heterointerface in the next-generation nanoelectronic and photonic devices such as van-der-Waals-based field effect transistors. [ABSTRACT FROM AUTHOR]

In this paper, the electronic properties of graphene/monolayer antimonene (G/m-Sb) heterostructure have been studied using the density functional theory (DFT). The effects of out-of-plane strain (interlayer coupling) and electric field on the electronic properties and Schottky contact of the G/m-Sb heterostructure are also investigated. The results show that graphene is bound to m-Sb layer by a weak van-der-Waals interaction with the interlayer distance of 3.50 Å and the binding energy per carbon atom of −39.62 meV. We find that the n -type Schottky contact is formed at the G/m-Sb heterostructure with the Schottky barrier height (SBH) of 0.60 eV. By varying the interlayer distance between graphene and the m-Sb layer we can change the n -type and p -type SBH at the G/m-Sb heterostructure. Especially, we find the transformation from n -type to p -type Schottky contact with decreasing the interlayer distance. Furthermore, the SBH and the Schottky contact could be controlled by applying the perpendicular electric field. With the positive electric field, electrons can easily transfer from m-Sb to graphene layer, leading to the transition from n -type to p -type Schottky contact. [ABSTRACT FROM AUTHOR]

The performance of narrow-band optical filters on the basis of frustrated total internal reflection was analyzed taking into account the Gaussian distribution of the angle of radiation incidence. The spectral characteristics of these optical filters are modelled with and without divergence of the incident beam. It is shown that, when measuring the spectral characteristics of optical filters, the divergence of the incident radiation beam should not be greater than a certain limit value that does not exceed several angular minutes. [ABSTRACT FROM AUTHOR]

In this work, using the compact density matrix approach, we study the linear and nonlinear magneto-optical properties of monolayer molybdenum disulfide (MoS2) via an investigation of the absorption coefficients (MOACs) and refractive index changes (RICs). The results are presented as functions of photon energy and external magnetic field. Our results show that the MOACs and the RICs appear as a series of peaks in the inter-band transitions between Landau levels, while the intra-band transitions result in only one peak. Because of the strong spin-orbit coupling, the peaks caused by the spin-up and -down states are different. With the increase in the magnetic field, both MOACs and RICs give a blue-shift and reduce in their amplitudes. These results suggest a potential application of monolayer MoS2 in the optoelectronic technology, magneto-optical, valleytronic, and spintronic devices. [ABSTRACT FROM AUTHOR]

In line with ongoing efforts on discovering new materials for the utilization in advanced nanotechnologies, in the present work, based on the original Fe 3 GeTe 2 material, two-dimensional Janus Fe 3 Ge X Te (X = S and Se) monolayers are constructed and analyzed by using first-principles calculations. All three monolayers of Fe 3 GeTe 2 , Fe 3 GeSTe, and Fe 3 GeSeTe exhibit hexagonal structures with good dynamical stability. No negative frequency is observed in the phonon dispersion spectra. During the ab initio molecular dynamics simulation at room temperature, the Fe 3 Ge X Te structures are predicted to be thermally stable without any reconstruction/fracture, suggesting the high thermal stability of these systems. In addition, the Fe 3 Ge X Te monolayers show high negative cohesive energy of about − 5 eV/atom and the obtained elastic constants satisfy the Born and Huang condition. Their Young's modulus and Poisson's ratio exhibit isotropic elastic behaviors due to the isotropic structures. These results confirm that the Fe 3 Ge X Te monolayers are energetically and mechanically stable for experimental synthesis. Especially, the electronic properties of our studied structures are explored for applications in electronic devices. The Fe 3 Ge X Te monolayers show a metallic nature for both the spin-up and spin-down cases. The projected density of states reveals that the Fe 3 GeTe 2 , Fe 3 GeSTe, and Fe 3 GeSeTe are magnetic materials due to their different spin-up and-down configurations. The results of our study can provide more information for the Janus Fe 3 Ge X Te materials and stimulate future experimental studies for practical applications in magnetic and electronic devices. [ABSTRACT FROM AUTHOR]

Background: Delay in tuberculosis diagnosis and treatment initiation may increase disease severity and mortality. In evaluations of tuberculosis control programmes high fatality rates during tuberculosis treatment, are used as an indicator of long delays in low HIV-prevalence settings. However, data for this presumed association between delay and fatality are lacking. We assessed the association between diagnostic delay and mortality of new smear-positive pulmonary tuberculosis patients in Vietnam. Methods: Follow-up of a patient cohort included in a survey of diagnostic delay in 70 randomly selected districts. Data on diagnosis and treatment were extracted from routine registers. Patients who had died during the course of treatment were compared to those with reported cure, completed treatment or failure (survivors). Results: Complete data were available for 1881/2093 (89.9%) patients, of whom 82 (4.4%) had died. Fatality was 4.5% for patients with ≤ 4 weeks delay, 5.0% for 5- ≤ 8 weeks delay (aOR 1.11, 95%CI 0.67-1.84) and 3.2% for > 9 weeks delay (aOR 0.69, 95%CI 0.37-1.30). Fatality tended to decline with increasing delay but this was not significant. Fatality was not associated with median diagnostic delay at district level (Spearman's rho = -0.08, P = 0.5). Conclusion: Diagnostic delay is not associated with treatment mortality in Vietnam at individual nor district level, suggesting that high case fatality should not be used as an indicator of long diagnostic delay in national tuberculosis programmes. [ABSTRACT FROM AUTHOR]

Background: Tuberculosis treatment failure and death rates are low in the Western Pacific Region, including Vietnam. However, failure or death may also occur among patients who did not complete treatment, i.e. reported as default or transfer-out. We aimed to assess the proportion failures and deaths among new smear-positive pulmonary tuberculosis patients with reported default or transfer-out. Treatment outcomes rates were 1.4% default, 3.0% transfer-out, 0.4% failure and 2.6% death in northern Vietnam in 2003. Methods: Tuberculosis patients in 32 randomly selected district tuberculosis units in northern Vietnam were followed up 1 to 3 years after treatment initiation for survival, recent treatment history and bacteriologically confirmed tuberculosis. Results: Included were 85 transferred patients and 42 who defaulted. No information was available of 41 (32%), 28 (22%) had died. Fifty-eight were available for follow-up (46%); all had sputum smear results. Tuberculosis was recorded in 11 (13%), including 6 (7%) with positive sputum smears, 3 (3%) with negative smears but positive culture and 2 (2%) who had started re-treatment for bacteriologically confirmed tuberculosis. Fifteen (17%, 95%CI 10-27%) had died within 8 months after treatment initiation. Of 86 patients with known study outcomes, 39 (45%, 95%CI 35-56%) had died or had bacteriologically confirmed tuberculosis. This was recorded for 29/53 (55%, 95%CI 40-68%) transferred patients and 10/33 (30%, 95%CI 16-49%) patients who defaulted. Conclusion: The total failure and death rates are 0.6% and 0.8% higher than based on routine reporting in northern Vietnam. Although this was a large proportion of treatment failures and deaths, failure and death rates were low. Defaulting and transfer carry a high risk of failure and in particular death. [ABSTRACT FROM AUTHOR]

Background: Treatment delay is an important indicator of access to tuberculosis diagnosis and treatment. Analyses of patient delay (i.e. time interval between onset of symptoms and first consultation of a health care provider) and health care delay (i.e. time interval between first consultation and start of treatment) can inform policies to improve access. This study assesses the patient, health care provider and total delay in diagnosis and treatment of new smear-positive pulmonary tuberculosis patients, and the risk factors for long delay, in Vietnam. Methods: A cross-sectional survey of new patients treated by the National Tuberculosis Control Programme was conducted in 70 randomly selected districts in Vietnam. All consecutively registered patients in one quarter of 2002 were interviewed using a pre-coded structured questionnaire. Results: Median (range) delay was 4 weeks (1-48) for total, 3 (1-48) weeks for patient and 1 (0-25) week for health care delay. Patients with long total delay (≥ 12 weeks, 15%) accounted for 49% of the cumulative number of delay-weeks. Independent risk factors (p < 0.05) for long total delay were female sex, middle age, remote setting, residence in the northern or central area, and initial visit to the private sector. For long patient delay (≥ 6 weeks) this was female sex, belonging to an ethnic minority, and living at > 5 km distance from a health facility or in the northern area. For long health care delay (≥ 6 weeks) this was urban setting, residence in the central area and initial visit to a communal health post, TB hospital or the private sector. Conclusion: Analyses of patient and treatment delays can indicate target groups and areas for health education and strengthening of the referral system, in particular between the private sector and the NTP. [ABSTRACT FROM AUTHOR]

Conventional method for modeling reservoir flow performance in vertical and horizontal wells assumes constant reservoir permeability throughout the life of the reservoir. However, as a reservoir is being depleted, the formation rock expands leading to the change in reservoir permeability. The main objective of this paper is to develop a semi-mechanistic model to investigate the effect of Permeability Compliance (PC), defined as pressure dependent permeability, on the inflow reservoir performance, where mass and momentum balances and PC were used to derive pressure distribution profiles in the reservoir. For model simplification, the concept of average pressure was applied to transform the pressure profiles to average reservoir pressure. The developed model was then incorporated into the existing horizontal inflow reservoir equations to study the flow performance of pressure-dependent reservoirs. The impact of downhole pumps on pressure-dependent permeability is also presented as case studies. The results show that at optimal values of PC, further increase of pressure drawdown does not lead to higher production rate. This study also optimizes drawdown values for reservoirs with reversible inflow performance. The paper also introduces correlations to estimate how reservoir pressure-dependent impacts PC and to find optimal drawdown values for the reservoir during production operations. Finally, Computational Modeling Group Software was used to validate the analytical results. This study has laid a fundamental, which is a very promising approach, to model the performance of pressure-dependent reservoirs using PC. • The concept of permeability compliance is very promising to quantify the effects of pressure on reservoir permeability and reservoir performance. • The developed equation can be used to estimate the pressure distribution, which is a function of PC, in pressure-dependent reservoirs. • The modified inflow performance may vary significantly from the conventional IPR, depending on PC value. If the PC is high, reversal in the IPR can be observed. • Analyzing the performance of pressure dependent permeability in the reservoirs has enabled us to clearly perceive the uncommon well behavior. [ABSTRACT FROM AUTHOR]

In this work, the electronic and optical properties of monolayer GaTe under biaxial strain and external electric field were investigated by density functional theory. Our calculated results indicate that the monolayer GaTe is an indirect-semiconductor with an energy gap of 1.41eV at equilibrium. Electronic properties of monolayer GaTe, especially the energy gap, depend greatly on the biaxial strain and external electric field. While the compressive strain slightly increases the energy gap, the tensile strain reduces quite rapidly the energy gap of the monolayer GaTe. In particular, semiconductor–metal phase transition can be observed when the external electric field was introduced. The GaTe monolayer strongly absorbs light in the ultraviolet region and the biaxial strain greatly changes its optical characteristics, especially the compression strain significantly increasing the absorption coefficient of the monolayer. Our results can provide more useful information for the prospect of application of the GaTe monolayer in next-generation optoelectronic devices. • Monolayer GaTe is an indirect-semiconductor with a moderate gap of 1.41eV at equilibrium. • Band gap of monolayer GaTe depends strongly on the biaxial strain. • Semiconductor–metal phase transition can be occurred in monolayer GaTe due to electric field. • Monolayer GaTe strongly absorbs light in the ultraviolet region. • Biaxial strain causes a significant shift in the first optical peaks of the GaTe monolayer. [ABSTRACT FROM AUTHOR]

In this work, we study systematically low-energy bands, optical absorbance and spin/valley-Hall conductivity of silicene and germanene in the presence of a perpendicular electric field. Our analytical calculations indicate that both silicene and germanene are semiconductors with a tiny energy gap and we can control their energy gap by the perpendicular electric field. Our calculations also demonstrate that the low-frequency optical absorbance of silicene is much greater than that of germanene and the external electric field plays an important role in determining the optical absorption peaks. When the Fermi level is in the forbidden band, the Hall conductivity is quantized, while spin/valley-Hall conductivities of both silicene and germanene depend strongly on the Fermi energy when the Fermi level is in the conduction band. Analytical results for spin/valley-Hall conductivities of silicene and germanene are presented in detail in this work. [ABSTRACT FROM AUTHOR]

Monolayer β 12 -borophene hosts two different Dirac and triplet fermions. Due to the large number of atoms in its unit cell, a description of their perturbed models leads to interesting phenomena. In this paper, we focus on an analytical tight-binding framework to describe the effect of adsorbed gas molecules on the magnetic properties of β 12 -borophene. We employ the Green's function approach to calculate the Pauli spin paramagnetic susceptibility of the system. With this, we explain the peculiar characteristics of magnetic responses of the system depending on the position of gas molecules on the host boron atoms. From a wider perspective, these results can be useful for practical applications based on low-dimensional gas sensors. • Tuning the magnetic properties of monolayer b12-borophene via gas molecules. • Shift of the Neel temperature of the antiferromagnetic phase with adsorbed gas molecule. • Increase and decrease of the PSPS depending on the position of the gas molecule. [ABSTRACT FROM AUTHOR]

• Monolayer GaS at equilibrium is an indirect semiconductor with a large band gap of 2.568 eV. • Band gap of monolayer GaS depends strongly on tensile biaxial strain. • Semiconductor–metal phase transitions can be found in monolayer GaS in the presence of an external electric field. • Our calculated results give a more insight into the applicability of monolayer GaS in nanoelectronics. In the present study, the effects of the strain engineering and electric field on electronic properties of the GaS monolayer are investigated by ab initio investigations. Our calculated results demonstrate that the GaS monolayer is a semi-conductor with a large indirect bandgap of 2.568 eV at the equilibrium. In the presence of a biaxial strain, the band structure of the GaS monolayer, especially the conduction band, changes significantly. However, while the effect of compressive strain on the energy gap of the GaS monolayer is quite weak, its energy gap depends strongly on the tensile strain. On the other hand, external electric fields can cause the semiconductor–metal transition in the monolayer. Being able to control electronic properties, especially the occurrence of the semiconductor–metal phase transition, makes the GaS monolayer a prospective material for nanoelectromechanical and nanospintronic applications. [ABSTRACT FROM AUTHOR]

Abstract In this study, we investigate systematically the effect of strain engineering and electric field on electronic properties of single-layer SnSe 2 using density functional theory. Our calculated results indicate that the single-layer SnSe2 is a semiconductor with a small band gap of 0.715 eV at the equilibrium state. The electronic states near the Fermi level are mainly contributed by Sn- d and Se- p orbitals, especially the contribution of the Se- p orbital to the valence band is dominant. Under biaxial strain, the band gap of the single-layer SnSe 2 changes abnormally. While compressive biaxial strain reduces band gap rapidly, the band gap of the single-layer SnSe 2 only increases slightly when increasing the tensile biaxial strain. In contrast to the strain-dependence case, the influence of the external electric field on the electronic properties of the single-layer SnSe 2 is quite small and the energy gap of the single-layer SnSe 2 does not depend on the direction of the perpendicular electric field. Our calculated results can provide more information for application possibility of the single-layer SnSe 2 in nanoelectronic devices. Highlights • Single-layer SnSe 2 is an indirect semiconductor with band gap of 0.715 eV at equilibrium. • Band gap of single-layer SnSe 2 depends strongly on the biaxial strain. • Effect of electric field on band gap of single-layer SnSe 2 is quite small. • Control of single-layer SnSe 2 band gap by strain is useful in nanoelectronic applications. [ABSTRACT FROM AUTHOR]

We investigate the combined effects of hydrostatic pressure, Al-concentration, temperature, and well-width parameter on the magneto-optical absorption properties (MOAPs) of a hyperbolic-type quantum well (HTQW). The results covered all possible processes: both phonon absorption and emission as well as both one- and two-photon. Our results show that the MOAPs of the HTQW significantly depend on the pressure, the Al-concentration, the temperature, and the well-width. We also suggest two new expressions for the dependence of the full-width at half-maximum on the pressure and concentration which need an experimental study to evaluate their validity. Our study provides a systematic results of the combined effects of pressure, Al-concentration, temperature, electron-phonon scattering, and the two-photon absorption on the nonlinear optical properties of such two-dimensional semiconductors, which would be useful for the applications in photonic devices. [ABSTRACT FROM AUTHOR]

Highlights • WX 2 (X = S, Se) monolayers are semiconductors with direct band gaps at equilibrium. • Biaxial strain ε b can lead to the indirect-direct gap transition in WX 2 monolayers. • Semiconductor-metal transition was observed in the WS 2 monolayer at ε b = −10%. • Bandgap control by strain in WX 2 monolayers is useful for nanoelectronic devices. Abstract In the present work, we consider electronic properties of WX 2 (X = S, Se) monolayers under a biaxial strain ε b using the first principles study. Our calculations indicate that, at equilibrium, the WS 2 and WSe 2 monolayers are semiconductors with a direct band gap of respectively 1.800 eV and 1.566 eV while their bulk structures are indirect semiconductors. The electronic properties of the WX 2 monolayers are very sensitive with the biaxial strain, especially compression strain. The biaxial strain ε b is the cause of the band gap of the WX 2 monolayers and especially the semiconductor-metal phase transition has occurred in the WS 2 monolayer at ε b = - 10 %. In addition, the direct-indirect band gap transition was observed in both WS 2 and WSe 2 monolayers at a certain elongation of biaxial strain ε b . The phase transitions in these monolayers can be very useful for their applications in nanoelectromechanical devices. [ABSTRACT FROM AUTHOR]

Abstract Using the synergy between the tight-binding model and the Green's function approach, this paper deals with the linear magneto-electron-light interaction in ultranarrow armchair graphene and boronitrene nanoribbons theoretically. In particular, we study the effect of ribbon width and the magnetic field on the refractive index, the absorption coefficient, and the extinction coefficient of abovementioned structures. Here, we reveal that there exists an increasing behavior for static refractive index of both structures when the ribbon width and the magnetic field are increased, whereas the dynamical refractive index increases (oscillates) in average with the ribbon width (magnetic field) at different light frequencies. We further show that the effect of ribbon width (magnetic field) on the absorption coefficient is generally increasing (oscillating) when the photon energy is altered. No refraction and absorption is reported at high enough photon frequencies independent of the ribbon width and the magnetic field strength. In addition, we find that the scattering process in the presence of the magnetic field manifests itself in the extinction coefficient. This information provides insights into the engineers in determining which ribbon width and magnetic field strength to use in the solar cell designs. Highlights • Investigation and comparison the optical responses of ultranarrow armchair graphene and boronitrene nanoribbons in the presence of Zeeman magnetic field by using the tight-binding model and Greens function technique. • Observation of increasing increasing behavior for static refractive index of both structures when the ribbon width and the magnetic field are increased, whereas the dynamical refractive index increases (oscillates) averagely with the ribbon width (magnetic field) at different light frequencies. • The absorption coefficient is generally increasing (oscillating) with the ribbon width (magnetic field). • The extinction coefficient introduces the scattering process in the presence of magnetic field. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Electronic properties of C 2 N/InSe heterostructure have investigated. • C 2 N/InSe heterostructure forms a type-II band alignment. • Transition from type-II to type-I band alignment and indirect to direct band gap can be achieved. • C 2 N/InSe heterostructure can be considered to be a good candidate for optoelectronic nanodevices. Abstract In this work, we construct the C 2 N/InSe heterostructure and investigate its electronic properties as well as the effect of strain and electric field. Our results demonstrate that the weak van der Waals interactions are dominated in such heterostructure. It forms the type-II band alignment and implies the spatial separation of photogenerated electron-hole pairs. The type-II band alignment can be switched to type-I one and an indirect to direct band gap transition can be achieved by applying the electric field or vertical strain. Our findings demonstrate that the C 2 N/InSe heterostructure can be considered to be a good candidate for optoelectronic and nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Highlights • Monolayer InSe is a semiconductor with an indirect bandgap of 1.38 eV at equilibrium. • Compression uniaxial strain can lead to the indirect-direct gap transition in monolayer InSe. • Bandgap of the monolayer InSe is strongly dependent on the negative electric field. • Control of bandgap by electric field is useful for applications of InSe in nanoelectronic devices. Abstract In this work, we consider systematically the influence of uniaxial strain and external electric field E on electronic properties of a monolayer InSe using ab initio approach based on density functional theory. Our calculations indicate that the monolayer InSe has a medium indirect energy bandgap of 1.38 eV at equilibrium. The calculated results also demonstrate that we can adjust the bandgap of the monolayer InSe by strain engineering or electric field. The bandgap of the monolayer InSe changes dramatically when the uniaxial strain is applied. Especially, under the compressed uniaxial strain, an indirect–direct bandgap transition has been observed at certain elongations. Within the electric field magnitude E range from 0 to 5 V/nm, the calculated results show that the negative electric field changes the bandgap of the monolayer InSe up to 23% while the positive electric field effect on its bandgap is negligible. [ABSTRACT FROM AUTHOR]

The magneto-optical absorption coefficients (MOAC) and the full-width at half-maximum (FWHM) in a quasi-zero-dimensional quantum dot (QD) via two-photon process are theoretically studied in which the electron–phonon (e–p) interaction is involved. It is found that the best range of the magnetic field to observe the MOAC is from B  = 3.49 T to B  = 15.77 T. As the magnetic field enhances, the peaks intensities firstly enhance, reach the maximum value at B  = 5.38 T, and then start reducing if the magnetic field continues increases further, while the peaks positions give a blue-shift. Besides, the magneto-optical absorption properties are found to be significantly affected not only by the quantum dot parameter but also by the temperature. The FWHM rises nonlinearly with the enhance of the magnetic field, the confinement frequency, and the temperature. The two-photon process makes an appreciable amount of the total absorption process. [ABSTRACT FROM AUTHOR]

In this paper, we design novel ultra-thin graphene/MoSeS and graphene/MoSSe heterostructures and investigate systematically their structural and electronic properties as well as the effect due to perpendicularly applied electric field on the heterostructure. Our results show that the electronic properties of both the graphene (Gr) and Janus MoSeS monolayer are well kept in the Gr/MoSeS and Gr/MoSSe heterostructures due to weak interaction between them. The interlayer distance between the Gr and Janus MoSeS monolayer is derived to be 3.34 Å, whereas the binding energy in the heterostructure is found to be - 3  meV per carbon atom, indicating the weak interactions between the Gr and Janus MoSeS layers. We find that in both Gr/MoSeS and Gr/MoSSe heterostructures, the Gr becomes a semiconductor with a tiny band gap of about 3 meV, forming between the π and π ∗ bands at the high symmetry K point. The appearance of the fundamental band gap in the Gr makes it suitable for application in electronics and optoelectronics like as field effect transistors. Furthermore, the Gr/MoSeS heterostructure forms an n -type Schottky contact with the Schottky barrier height of 0.53 eV at the equilibrium state. Our results also indicate that the electric field applied perpendicularly to the heterostructure could control not only the Schottky barrier height, but also the Schottky contact type from the n -type to p -type. Based on these extraordinary electronic properties of ultra-thin Gr/MoSeS heterostructures, which are expected to be with applications in nanoelectronic and optoelectronic devices in the future experiments. [ABSTRACT FROM AUTHOR]

Abstract Graphene-based van der Waals heterostructures by stacking graphene on other two-dimensional materials have recently attracted much attention due to their extraordinary properties and greatly extend the applications of the parent materials. By means of the density functional theory from first-principles calculations, in this work, the electronic properties and Schottky contact of the Graphene/InSe heterostructure, together with the effect of strain, are investigated systematically. Our results show that in the graphene/InSe heterostructure, graphene is very weakly bound to the InSe monolayer. Furthermore, we find that due to the sublattice symmetry breaking, a tiny band gap of 5 meV is opened in the graphene/InSe heterostructure, making it suitable for applications in electronic and optoelectronic devices. Moreover, we also find that the n -type Schottky contact is formed in the graphene/InSe heterostructure with a very small Schottky barrier height of 0.05 eV. The Schottky barrier height as well as Schottky contact types in the graphene/InSe heterostructure could be controlled by vertical strain applied perpendicularly to the heterostructure. When the interlayer distance between graphene and the topmost InSe monolayer is smaller than 2.40 Å, one can observe a transformation of the Schottky contact of the graphene/InSe heterostructure. Our results may provide helpful information for designing novel high-performance graphene-based van der Waals heterostructures and explore their potential applications in future nanoelectronic and optoelectronic devices. Highlights • Electronic properties and Schottky contact of the G/InSe heterostructure under strain were investigated. • Band gap opening in the G/InSe heterostructure due to the sublattice symmetry breaking. • G/InSe heterostructure forms an n -type Schottky contact with the SBH 0.05 eV. • Schottky contacts and SBH of the G/InSe heterostructure could be controlled by vertical strain. • Transformation of the Schottky contact from the n -type to p -type was observed at the d = 2.40 Å. [ABSTRACT FROM AUTHOR]

Abstract In this work, we consider the effect of biaxial ɛ b and uniaxial ɛ ac ∕ zz strains on electronic properties and optical parameters of monolayer SnS using first-principles calculations. Our calculations show that the monolayer SnS is a semiconductor with an indirect energy gap of 1.63 eV at the equilibrium state. While an effect of tensile strains on bandgap is quite small, the bandgap of monolayer SnS depends strongly on the compressive strains, especially a semiconductor-metal phase transition is occurred due to the uniform compressive biaxial strain at −14 % elongation. The optical spectra of the monolayer are high anisotropic, and the absorption coefficient of monolayer SnS tends to increase in the presence of compression strains, while the tensile strains reduce the absorption coefficient of the monolayer SnS. We believe that the phase transition and extraordinary optical properties of the strained monolayer SnS will make it become a useful material in nanoelectromechanical devices and optoelectronic applications. Highlights • Monolayer SnS is a semiconductor with an indirect bandgap of 1.63 eV at the equilibrium state. • Compression biaxial strain can lead to the semiconductor-metal phase transition in monolayer SnS. • The optical spectra of SnS monolayer are highly anisotropy. • Absorption coefficient of monolayer SnS tends to increase in the presence of compression strains. [ABSTRACT FROM AUTHOR]

In the present work, using density functional theory (DFT), we investigate the influence of biaxial strain ε b on electronic and optical properties of single-layer GeS. Our DFT calculations show that single-layer GeS is a semiconducting material at equilibrium and semiconductor-metal phase transition may occur at large compression biaxial strain. The optical absorption of single-layer GeS is high in the range of the middle ultraviolet lights. Besides, the biaxial has a great impact on the optical spectra of single-layer GeS in the high energy domains. The semiconductor-metal phase transition and the computational results of the absorption of GeS can provide more useful information for applications in nanoelectromechanical and optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this work, we theoretically investigate electronic properties of GaSe MoS2 and GaS MoSe2 heterojunctions using density functional theory based on first-principles calculations. The results show that both GaSe MoS2 and GaS MoSe2 heterojunctions are characterized by the weak vdW interactions with a corresponding interlayer distance of 3.45 Å and 3.54 Å, and the binding energy of −0.16 eV per GaSe GaS cell. Furthermore, one can observe that both the GaSe MoS2, and GaS MoSe2 heterojunctions are found to be indirect band gap semiconductors with a corresponding band gap of 1.91 eV and 1.23 eV, respectively. We also find that the band gaps of these semiconductors belong to type II band alignment. A type–II band alignment in both GaSe MoS2 and GaS MoSe2 heterojunctions open their potential applications as novel materials such as in designing and fabricating new generation of photovoltaic and optoelectronic devices. [ABSTRACT FROM AUTHOR]