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In search of heavy metal-free mid-IR active colloidal materials, self-doped silver selenide colloidal quantum dots (CQDs) can be an alternative offering tunable mid-IR wavelength with a narrow bandwidth. One of the challenges in the study of the intraband transition is developing a method to widen the intraband transition energy range as well as reducing the toxicity of the materials. Here, we present Ag

A zeolite immobilized hybrid catalyst [Cu(bpy)2]2+NaY [bpy = 2,2′-bipyridine](1) was prepared by immobilizing Cu(II)-bipyridine complex onto NaY zeolite and characterized by spectral methods. X-ray powder diffraction analysis of 1 revealed that the structural integrity of the mother zeolite in the hybrid material remained intact upon immobilization of the complex. Spectroscopic studies showed that the coordination geometry of 1 undergoes a significant distortion when it is entrapped in the zeolite cavity. The catalytic oxidation of a series of alkenes was carried out with the neat and the immobilized complexes in the presence of the ecofriendly oxidant tert-BuOOH (TBHP) at an ambient condition. The catalyst exhibited excellent catalytic potency and product selectivity, with respect to the neat complex in these reactions. The activity of the immobilized catalyst remained nearly the same after several cycles, indicating the true heterogeneous nature of the catalyst.

One dinuclear copper(II) complex {μ-[2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}- bis(phenolato)]}-{μ-[2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}bis(phenolato)]}- dicopper(II), [Cu2(salen)2] (1) [salen2− = [2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}- bis(phenolato)] has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. X-ray single crystal structure examination revealed that each Cu(II) center in the asymmetric unit of 1 adopts a distorted square planar geometry with a CuN2O2 chromophore, where two asymmetric units are attached through congregation of Salen involving Cu-O bond to form dinuclear molecular unit [Cu2(salen)2]. In crystalline state, these dinuclear entities in 1 are extended through C-H···π interactions and π···π interactions displaying a 3D network structure. The variable-temperature magnetic susceptibility measurement asserted a dominant antiferromagnetic interaction between the copper(II) centers through Cu-O-Cu linkage in 1 with J = -1.46 cm-1. The catalytic efficacy of complex 1 was studied in a series of solvents for the oxidation of styrene and cyclooctene using tert-butyl-hydroperoxide (TBHP) as an active oxidant under mild conditions. The catalytic reaction mixture has been analyzed by gas chromatography and it displayed that the yield of the epoxidation and its selectivity is optimum in acetonitrile medium.

Two-dimensional (2D) cadmium chalcogenide nanoplatelets (NPLs) have been grown as an emerging material for optoelectronic applications because of their unique properties. Here, we investigate the c...

In this paper, a conductor backed coplanar waveguide (CB-CPW) 3rd order bandpass filter is designed using coupled open-ended stub resonator placed vertically to the signal line. Vertically loaded open ended stubs are designed at quarter wavelength so as to behave like a short circuit at the input terminal thus giving a band-accepted response with lesser metallic area or minimum size. Four such coupled open ended resonators are placed in series and also in closely manner to provide greater field confinement of the proposed bandpass filter. The bandpass filter is designed for a center frequency of 2.5 GHz with FBW of 97.89%, insertion loss of

A dimeric copper(II) complex, bis{(2-[1-(aminoethylimino)ethyl]-phenoxo}-di-μ1,1-azido-dicopper(II), [Cu2(L)2(μ2-1,1-N3)2] (1) [L = 2-[1-(aminoethylimino)ethyl]-phenoxo ion], has been isolated using a self-assembly reaction using a 1:1:1 molar ratio of Cu(NO3)2·3H2O, HL and NaN3 in methanol at room temperature and characterized through X-ray diffraction analysis and spectroscopic studies. X-ray structural analysis reveals that 1 consists of two distinct dinuclear molecular units, where each copper(II) center in the individual dinuclear unit adopts a distorted square pyramidal geometry with a CuN4O chromophore ligated through a tridentate (NNO) Schiff base and two N atoms of two different bridging azides in µ1,1-mode. Two Cu(II) centers are linked through double µ2-1,1-N3 bridges to form the dinuclear unit [Cu2(L)2(μ2-1,1-N3)2]. In the crystalline state, the dinuclear units in 1 are associated through weak intermolecular N-H⋯O hydrogen bonds to afford a 2-D sheet structure viewed along the crystallographic a-axis. The small magnitude of the antiferromagnetic interaction (J = –0.45 cm−1) is a result of the long Cu···Cu separation (3.205(2) Å). The catalytic efficacy of 1 was studied in a series of solvents for the epoxidation of alkenes using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions.

Here, we have synthesized rod and flake shaped morphology of porphyrin aggregates from 5, 10, 15, 20-tetra (4-n-octyloxyphenyl) porphyrin (4-opTPP) molecule which are evident from scanning electron microscopy (SEM). The formation of J-type aggregation is evident from steady state and time-resolved fluorescence spectroscopic studies. Ultrafast transient absorption spectroscopic studies reveal that the excited state lifetime is controlled by the morphology and the time constant for S1→S0 relaxation changes from 3.05 ps to 744 ps with changing the shape from rod to flake, respectively. In spite of similar exciton coupling energy in both the aggregates, the flake shaped aggregates undergo a faster exciton relaxation process and the non-radiative relaxation channels are found to depend on the shape of aggregates. The fundamental understanding of morphology controlled ultrafast relaxation processes of aggregated porphyrin is important for designing efficient light harvesting devices.

A one-dimensional Cu(II) coordination polymer of [Cu(L)(μ-ONO2)]n (1) (HL = 4-methoxy-2-[1-(methylaminoethylimino)methyl]-phenol) with bidentate bridging nitrate has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. Single crystal X-ray analysis revealed that each copper(II) center in the asymmetric unit of complex 1 adopts a distorted square pyramidal geometry with a CuN2O3 chromophore ligated through a tridentate Schiff base (L) with (NNO) donor sets and two O atoms of bridging nitrate ion. The adjacent copper atoms are connected by bridging nitrate (μ-ONO2) in bidentate fashion affording a 1D coordination polymeric chain structure along the crystallographic b-axis. In the polymeric framework, the Cu…Cu separation is 4.3749(4) A. The catalytic efficacy of complex 1 was studied in a series of solvents for the epoxidation of cyclooctene using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions. The catalytic reaction mixture was analyzed by gas chromatography and the data indicated that the yield of the epoxidation reaction and its selectivity is maximum in acetonitrile medium.

Two-dimensional (2D) semiconductor colloidal nanoplatelets (NPLs) have shown great potential as light-harvesting materials due to their advanced optical properties. Here, we have designed hybrid na...

Realizing bright colloidal infrared emitters in the midwavelength infrared (or mid-IR), which can be used for low-power IR light-emitting diodes (LEDs), sensors, and deep-tissue imaging, has been a challenge for the last few decades. Here, we present colloidal tellurium nanowires with strong emission intensity at room temperature and even lasing at 3.6 μm (ω) under cryotemperature. Furthermore, the second-harmonic field at 1.8 μm (2ω) and the third-harmonic field at 1.2 μm (3ω) are successfully generated thanks to the intrinsic property of the tellurium nanowire. These unique optical features have never been reported for colloidal tellurium nanocrystals. With the colloidal midwavelength infrared (MWIR) Te nanowire laser, we demonstrate its potential in biomedical applications. MWIR lasing has been clearly observed from nanowires embedded in a human neuroblastoma cell, which could further realize deep-tissue imaging and thermotherapy in the near future.

Two-dimensional (2D) nanostructures are an emerging class of materials for designing artificial light-harvesting system because of their unprecedented electronic properties. Here, we design 2D nano...

Considerable attention has been paid to designing graphene based 2D hybrid nanostructures for their potential applications in various areas from healthcare to energy harvesting. Herein, we have prepared 2D-2D hybrid structures of 2D CdSe nanoplatelets (NPLs) with thiol (-SH) functionalized reduced graphene oxide (G-Ph-SH). Microscopic and spectroscopic studies reveal that the G-Ph-SH surface is successfully decorated by CdSe NPLs through a thiophenol (-SH) linker. The significant photoluminescence quenching (65%) and the shortening of decay time from 1 ns to 0.4 ns of CdSe NPLs are observed after adding 100 μg of G-Ph-SH. Furthermore, the femto-second transient absorption spectroscopic (fs-TAS) study reveals that the growth time of CdSe NPLs in the composite is reduced to 0.4 ps from 0.8 ps due to faster hot electron cooling. A faster component of 1.4 ps in the kinetic parameters of the composite system further suggests that the ultrafast electron transfer occurs from the conduction band of CdSe NPLs to surface functionalized reduced graphene oxide. This type of 2D-2D hybrid structure may open up new possibilities in light harvesting applications.

Intraband transitions of colloidal semiconductor nanocrystals, or the electronic transitions occurring in either the conduction band or valence band, have recently received considerable attention because utilizing the intraband transitions provides new approaches for applications such as photodetectors, imaging, solar cells, lasers, and so on. In the past few years, it has been revealed that observing the intraband transition is not limited for temporal measurement such as ultrafast spectroscopy but available for steady-state measurement even under ambient conditions with the help of self-doped semiconductor nanocrystals. Considering the large absorption coefficient of the steady-state intraband transition comparable to that of the bandgap transition, the use of the intraband transition will be promising for both fundamental and application studies. Here, we summarize the recent progress in studies on intraband photoluminescence of self-doped semiconductor nanocrystals and discuss key questions to be addressed in future research.

This paper presents a realization of a 3rd order coplanar waveguide (CPW) wide-band bandpass filter (BPF) using the combination of series open stubs and folded shunt short stubs. Four such stubs are placed in close proximity to increase the coupling level and provide the bandpass response of FBW 82.15% at 2.97 GHz, covering the entire S-band frequency regime. Folded shunt stubs minimizes the overall circuit area. A new type of metallic bridge with vias is used to persist the ground planes at the same potential. This type of backside ground metallic bridge is found very simple and cheap compared with formal sophisticated air-bridges. The design mechanism is advantageous in terms of complete planar in nature, easy to integrate with other MMICs, low loss, high roll-off rate and cost effectiveness.

A highly sensitive and environment friendly multimodal nanosensor encompassing magnetic and fluorescent functionality is designed for the simultaneous detection and removal of mercury ion in water. A significant fluorescence quenching is observed with the increasing concentration of Hg 2 + with surprisingly low limit of detection. The detected analyte is successfully removed with the help of a bar magnet leaving no residual secondary pollution. The details mechanism of sensing is also investigated. The simple and elegant nanochemistry reported here provides a facile route towards field based mercury sensor development in future.

The understanding of ultrafast carrier relaxation process in doped semiconductor quantum dots (QDs) is very important for their potential applications in light-emitting diodes, optoelectronics. Here, we have studied the change in electronic properties of Cu-doped CdSe QDs upon light illumination. The light-induced effect leads to the enhancement of the band edge decay time and reduces the decay time of the dopant emission due to photocorrosion of Cu-doped CdSe QDs. The bleaching recovery kinetics and the hot electron cooling dynamics have been studied by using femtosecond transient absorption spectroscopy. It is observed that the electron cooling process of doped CdSe QDs is dependent on the dopant concentration and the cooling kinetics of doped CdSe QDs are found to be slower than undoped QDs. After light irradiation, the cooling processes of hot electron and recovery process in doped systems are modified.

The design of nano-heterostructures for light-harvesting systems for photocatalysis and photovoltaic applications is an emerging area of research. Here, we report the synthesis of a one-dimensional quasi-type-II CdS/CdSe heterostructure where holes are confined in CdSe nanoparticles and electrons can delocalize throughout the conduction bands of both CdS nanorods and CdSe nanoparticles because of the smaller conduction band offset. By controlling the oxidation and reduction sites of the CdS/CdSe heterostructure, we achieved a maximum H2 generation of 5125 μmol/g/h for 27.5 wt % CdSe-loaded CdS heterostructure, which is found to be 44 times higher than that of bare CdS nanorods and 22 times higher than that of CdSe nanoparticles. Furthermore, this heterostructure exhibits a photovoltaic effect (Voc = 0.8 V, Jsc = 0.56 mA/cm2, FF = 40%, and η = 0.18), which could be useful for solar cell application. The bleaching recovery kinetics and hot electron cooling dynamics have been studied by using femtosecond tra...

The development of drug delivery systems with microencapsulated therapeutic agents is a promising approach to the sustained and controlled delivery of various drug molecules. The incorporation of dual release kinetics to such delivery devices further adds to their applicability. Herein, novel core-shell scaffolds composed of sodium deoxycholate and trishydroxymethylaminomethane (NaDC-Tris) have been developed with the aim of delivering two different drugs with variable release rates using the same delivery vehicle. Data obtained from XRD studies, sol-gel transition temperature measurement, rheology and fluorescence studies of the core-shell systems indicate a significant alteration in the core and the shell microstructural properties in a given system as compared to the pure hydrogels of identical compositions. The release of the model drugs Fluorescein (FL) and Rhodamine B (RhB) from the shell and the core, respectively, of the two core-shell designs studied exhibited distinctly different release kinetics. In the 25@250 core-shell system, 100% release of FL from the shell and 19% release of RhB from the core was observed within the first 5 hours, while 24.5 hours was required for the complete release of RhB from the core. For the 100@250 system, similar behaviour was observed with varied release rates and a sigmoidal increase in the core release rate upon disappearance from the shell. Cell viability studies suggested the minimal toxicity of the developed delivery vehicles towards NMuMG and WI-38 cells in the concentration range investigated. The reported core-shell systems composed of a single low molecular weight gelator with dual release kinetics may be designed as per the desired application for the consecutive release of therapeutic agents as required, as well as combination therapy commonly used to treat diseases such as diabetes and cancer.

Luminescent copper nanoclusters (Cu NCs) have emerged as fascinating nanomaterials for potential applications in optoelectronics, catalysis, and sensing. Here, we demonstrate the synthesis of l-cysteine-capped Cu NCs in aqueous medium having a bright cyan emission (489 nm) with a quantum yield of 6.2%. The structure of the Cu NCs (Cu7L3) is investigated by using density functional theory (DFT) calculation and mass spectrometric study. Further, time-dependent density functional theory (TD-DFT) calculations provide the insights of electronic transitions, and it is correlated with experimental data. With near-HOMO–LUMO gap excitation, Cu NCs are excited to the S4 state and subsequently relaxed to the S1 state through an internal conversion process with a time scale in the ultrafast region (326.8 ± 6.5 fs). Furthermore, the structural relaxation in S1 takes place at a picosecond time scale, and the radiative relaxation occurs from S1 to S0. Finally, Cu NCs are attached with imidazole-functionalized partially ...

Side lobe level (SLL) reduction is the key challenge in antenna array synthesis. In order to achieve low SLL in array pattern, many conventional optimization methods are proposed to handle complex, nonlinear and non-differentiable array factor of antenna array. In this article, we present an improved optimization scheme; Wavelet Mutation based Novel Particle Swarm Optimization (NPSOWM) for the synthesis of various single-ring planar arrays of isotropic antenna elements. The primary objective is to achieve the radiation pattern with minimum SLL and maximum directivity for the non-uniform, planar circular array (CA), hexagonal array (HA) and elliptical array (EA) antenna. The array pattern synthesis is done based on two parameters of the array; namely, excitation amplitude and element spacing. Two design examples are presented which illustrate the effectiveness of the NPSOWM algorithm. As compared with conventional optimization techniques like genetic algorithm (GA), simulated annealing (SA), particle swarm optimization (PSO) and its variant NPSO, NPSOWM outperforms with the goal of maximum SLL suppression.

We report an enhanced power conversion efficiency (PCE) of 11.7% ± 0.2 and a fill factor (FF) of 71% for dye-sensitized solar cells (DSSC) with an active area of 0.16 cm2 after modifying the TiO2photoanode with size-selective (ca. 2 nm) N,F,S-codoped graphene quantum dots (NFS-GQDs) that exhibit a photoluminescence quantum yield (PLQY) of 70%. An upward shift in the Fermi level has been observed, perhaps responsible for the improved performance along with the possibility of preventing the back electron transfer from TiO2. Mott Schottky analysis indicates a shift (52 mV)in the flat band potential, which is directly related to the Voc of the system. Detailed characterization (IPCE, TCSPC etc) indicates the important role of hetero atoms in facilitating the enhanced performance. Thus, our results suggest that the incorporation of size controlled, hetero atom doped GQDs can enhance the efficiency of DSSCs enabling more opto-electronic applications.

In this paper, optimal design of single-ring and multi-ring circular array, hexagonal array, and elliptical array of isotropic antenna has been carried out using Simplex Particle Swarm Opti...

Polymer-graphene nanocomposites are promising candidates for light harvesting applications such as photocatalysis and photovoltaics, where significant charge separation occurs due to photoinduced electron transfer. Much attention has been paid to using reduced graphene oxide (r-GO) as template for anchoring various nanomaterials due to its efficient electron accepting and transport properties. Here, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) nanoparticles are prepared from MEH-PPV polymer and the change in photophysical properties upon formation of polymer nanoparticles (PNPs) from the molecular state are investigated by using steady-state and time-resolved spectroscopy. Nanocomposites are constructed by adding hexadecylamine-functionalized positively charged MEH-PPV PNPs to a solution of negatively charged r-GO. Steady-state and time-resolved spectroscopy are also used to study the electronic interactions between PNPs and r-GO. Ultrafast femtosecond up-conversion and transient absorption spectroscopy unequivocally confirms the electron transfer process from the excited state of MEH-PPV PNPs to r-GO at the interface of the nanocomposite. Analysis reveals that the charge separation time is found to be pulse-width-limited (

Considerable attention has been paid to designing graphene based hybrid materials for developing new light-harvesting systems. Here, we have synthesized CdTeSe alloy nanorods and modified the surface of CdTeSe nanorods by porphyrin molecules to attach to graphene surface through π–π stacking. In this CdTeSe nanorod–porphyrin–graphene hybrid system, porphyrin acts as an antenna material which harvests light and consequently transfers electrons to the adjacent conduction band of nanorods and finally to reduced graphene oxide (RGO). An ultrafast spectroscopic study suggests that the rate of electron transfer from porphyrin to RGO via conduction band of CdTeSe nanorods is 17.4 × 10–2 ps–1. It is to be noted that this ternary hybrid system exhibits 240-fold enhancement of photocurrent under visible light irradiation which reveals that this new type of graphene based inorganic and organic hybrid system is very promising for solar light harvesting.

The development of light harvesting systems based on heterostructures for efficient conversion of solar energy to renewable energy is an emerging area of research. Here, we have designed heterostructures by using carbon dots (C-dots) and zinc oxide nanoparticles (ZnO NP) to develop an efficient light harvesting system. Interestingly, the conduction band and the valence band positions of ZnO NP are lower than the LUMO and HOMO positions of C-dots in this type II heterostructure of C dot-ZnO NP, which causes efficient charge separation and photocurrent generation. Steady state and time resolved spectroscopic studies reveal that an efficient photoinduced electron transfer occurs from C dots to ZnO NP and a simultaneous hole transfer occurs from the valence band of ZnO NP to the HOMO of C dots. The calculated rate of electron transfer is found to be 3.7 × 10

Inorganic–organic semiconductor hybrid nanostructures remain a frontier area of research to design optoelectronic, photovoltaic and light harvesting devices because of efficient energy or charge transfer process. Here, we have designed a system where inorganic semiconducting nanocrystals (Cd0.52Zn0.48S) are encapsulated into semiconducting organic poly (9-vinylcarbazole) [PVK] nanoparticles with 5-(4-aminophenyl)-10,15,20-triphenyl-21,23H-porphyrin (APTPP) molecule. Steady state and time resolved spectroscopic study reveal the efficient energy transfer from host PVK nanoparticle to QD and prophyrin molecule which is found to be cascade energy transfer. The energy transfer enhances from 68% to 86% by incorporating porphyrin molecule into QD doped PVK nanoparticles. This high efficiency of cascade energy transfer opens further prospects to design new porphyrin and quantum dot based functional polymer nanoparticles for the application in efficient light harvesting system and other photodriven devices.

Well-defined organic nanostructures of porphyrin are promising candidates toward photocatalysis, photovoltaics, and electronics applications where a photoinduced electron transfer process occurs. On the other hand, reduced graphene oxides (RGO) have attracted much attention in light energy conversion owing to their efficient charge separation property. In this respect, we have demonstrated a composite of a one-dimensional (1D) nanostructure of 5, 10, 15, and 20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) and RGO for enhancing photoinduced charge separation. The composite was characterized by scanning electron microscopy (SEM), UV–visible spectroscopy, fluorescence spectroscopy, time-correlated single photon counting (TCSPC), and femtosecond fluorescence upconversion spectroscopy. It is noted that a very fast decay of TCPP NR was observed in the TCPP NR–RGO composite due to the electron transfer process, and the electron transfer rate is found to be 10.0 × 10–4 ps–1 for the TCPP NR–RGO system. An increment...

Significant research attention has been given to graphene–porphyrin hybrid materials for light harvesting. In this report, we demonstrate the influence of graphene surface and aging time on the formation of porphyrin [5-(4-hydroxyphenyl)-10,15,20-triphenyl porphyrin (4-HPTP)] aggregates. The large sp2 conjugated network of reduced graphene oxide (RGO) may facilitate strong π–π stacking interactions that influence the aggregation of 4-HPTP. The morphologies of these assembled structures are characterized by field emission scanning electron microscopy (FE-SEM). Steady state and time resolved spectroscopic studies reveal that the formation of J-type aggregation of 4-HPTP on an RGO surface is higher than on a graphene oxide (GO) surface. In situ growth of porphyrin nanoassemblies on an RGO surface improves the electronic interaction by shortening the interfacial distance between graphene and porphyrin. It is evident that the electron transfer process is enhanced in the presence of RGO upon the photoexcitation of porphyrin nanoassemblies which eventually generate a photocurrent. These graphene decorated porphyrin nanoassemblies are promising materials for the development of new generation optoelectronic devices.

In the following paper the Craziness based Particle Swarm Optimization (CRPSO) scheme has been used that entitles a recent technique in electromagnetic for optimizing the problems that are caused for the array pattern synthesis of 90-element Concentric Circular Array (CCA) and Concentric Elliptical Array (CEA) of isotropic antennas that produces directive beams with utmost reduction of the Side-Lobe-Level (SLL). The paper demonstrates a newly used algorithm which is CRPSO which is used for pattern synthesis of the arranged planar array, CEA, by optimizing the amplitude with required SLL value. Simultaneously, compare with conventional PSO method and its improved version (IPSO), CRPSO is used with the intention of producing utmost SLL reduction.

The ultraviolet light component in the solar spectrum is known to cause several harmful effects, such as allergy, skin ageing, and skin cancer. Thus, current research attention has been paid to the design and fundamental understanding of sunscreen-based materials. One of the most abundantly used sunscreen molecules is Avobenzone (AB), which exhibits two tautomers. Here, we highlight the preparation of spherically shaped nanoparticles from the sunscreen molecule AB as well as from sunscreen-molecule-encapsulated polymer nanoparticles in aqueous media and study their fundamental photophysical properties by steady-state and time-resolved spectroscopy. Steady-state studies confirm that the AB molecule is in the keto and enol forms in tetrahydrofuran, whereas the enol form is stable in the case of both AB nanoparticles and AB-encapsulated poly(methyl methacrylate) (PMMA) nanoparticles. Thus, the keto-enol transformation of AB molecules is restricted to a nanoenvironment. An enhancement of photostability in both the nanoparticle and PMMA-encapsulated forms under UV light irradiation is observed. The efficient excited energy transfer (60 %) from AB to porphyrin molecules opens up further prospects in potential applications as light-harvesting systems.

Graphene-based hybrid nanostructures have recently emerged as a new class of functional materials for light-energy conversion and storage. Here, we have synthesized reduced graphene oxide (RGO)-semiconductor composites to improve the efficiency of photocatalysis. Zero-dimensional CdS nanoparticles (0D), one-dimensional CdS nanorods (1D), and two-dimensional CdS nanosheets (2D) are grafted on the RGO sheet (2D) by a surface modification method using 4-aminothiophenol (4-ATP). Structural analysis confirms the attachment of CdS nanocrystals with RGO, and the strong electronic interaction is found in the case of a CdS nanosheet and RGO, which has an influence on photocatalytic properties. The degradation of dye under visible light varies with changing the dimension of nanocrystals, and the catalytic activity of the CdS NS/RGO composite is ∼4 times higher than that of CdS nanoparticle/RGO and 3.4 times higher than that of CdS nanorod/RGO composite samples. The catalytic activity of the CdS nanosheet/RGO composite is also found to be ∼2.5 times than that of pure CdS nanosheet samples. The unique 2D-2D nanoarchitecture would be effective to harvest photons from solar light and transport electrons to reaction sites with respect to other 0D-2D and 1D-2D hybrid systems. This observation can be extended to other graphene-based inorganic semiconductor composites, which can provide a valuable opportunity to explore novel hybrid materials with superior visible-light-induced catalytic activity.

The development of light harvesting systems based on heterostructures for efficient conversion of solar energy to renewable energy is an emerging area of research. Here, we have designed heterostructures by using carbon dots (C-dots) and zinc oxide nanoparticles (ZnO NP) to develop an efficient light harvesting system. Interestingly, the conduction band and the valence band positions of ZnO NP are lower than the LUMO and HOMO positions of C-dots in this type II heterostructure of C dot-ZnO NP, which causes efficient charge separation and photocurrent generation. Steady state and time resolved spectroscopic studies reveal that an efficient photoinduced electron transfer occurs from C dots to ZnO NP and a simultaneous hole transfer occurs from the valence band of ZnO NP to the HOMO of C dots. The calculated rate of electron transfer is found to be 3.7 × 109 s-1 and the rate of hole transfer is found to be 3.6 × 107 s-1. The enhancement of photocurrent (11 fold) under solar light irradiation of the C dot-ZnO NP heterostructure opens up new possibilities to design efficient light harvesting systems.

The development of graphene oxide (GO)/semiconductor quantum dots (QDs) hybrid composite remains a frontier area of research to design optoelectronic, photovoltaic, and light harvesting devices based on an electron transfer process. Therefore, the examination of the electron transfer process from QDs to GO as a function of the number of sites of QD and the mean fractional surface coverage of QD by GO sheet with changing the size of QD and concentration of GO is an important issue to manipulate the performance of devices. Here, we have assembled graphene oxide-CdTe QD composite by the attachment of positively charged cysteamine capped CdTe QDs with negatively charged GO. The structural changes due to electronic interaction of graphene oxide with QDs have been evaluated using Raman spectroscopy. The shifting of G-band and increase of ID/IG intensity ratio reveal the electron transfer from excited QDs to GO. The fluorescence dynamics of QD has been investigated by time-resolved fluorescence spectroscopy, and...

A new Co(III) Schiff-base complex, [Co(HL)2]NO3·H2O (1) (H2L = 1-(N-3-methoxy-salicylideneimino)-ethane-2-ol), has been synthesized and characterized by several physicochemical methods. X-ray crystal structure analysis revealed that complex 1 features a distorted octahedral coordination geometry and the metal center is surrounded by two tridented N,O,O-donor Schiff base ligands (HL−). [Co(HL)2]NO3·H2O (1) is capable of activating dioxygen in air to catalyze the epoxidation of various alkenes using isobutraldehyde as a co-reductant under homogeneous conditions. It was observed that the yield of the epoxides and their selectivity is highest in acetonitrile medium.

Wavelet Mutation based Novel Particle Swarm Optimization (NPSOWM) technique is applied for the comparison of the performances of Circular array (CA), Hexagonal Array (HA) and Elliptical Array (EA) of isotropic antenna elements which can produce array pattern with maximum reduced Side-Lobe Level (SLL). Novel Particle Swarm Optimization (NPSO) explores the solution space more effectively for a better solution when the wavelet theory is applied in terms of mutation. Syntheses of 24-element single ring planar antenna arrays are presented which illustrate the effectiveness of the NPSOWM algorithm to achieve the optimization goal. As Compared with conventional PSO and NPSO methods, NPSOWM outperforms with the goal of maximum SLL suppression with improvement of directivity and that too for elliptical array of eccentricity 0.4. Numerical results for synthesizing three different array geometries have demonstrated the superiority of EA over the CA and EA.

Particle Swarm Optimization with Aging Leader and Challengers (ALC-PSO) method, which represents a novel approach for optimization problems, is applied for radiation pattern synthesis of a three ring Concentric Elliptical Array Antenna (CEA) of isotropic elements which can generate beam pattern with maximum reduced Side Lobe Level (SLL). This paper introduces a recently developed metaheuristic algorithm, known as ALC-PSO, to the pattern synthesis of recently proposed configured planar array, CEA, with desired SLL by amplitude-only optimization. To overcome the problem of premature convergence characteristic of PSO, ALC-PSO is designed without significantly impairing the fast converging property of PSO. To improve the radiation pattern in terms of minimum relative SLL, a set of antenna designed parameters as excitation weights of the elements and eccentricity of the elliptical shaped rings are to be developed. The variation of SLL with eccentricity of synthesized array is also reported. Compare with conventional PSO method, ALC-PSO outperform with the goal of maximum SLL suppression.

Fault tolerance is one of the main issues in Wireless Sensor Networks (WSNs) since it becomes critical in real deployment environment where reliability and reduced inaccessibility times are important. In this paper, we propose a fault- tolerance technique for coverage area of the sensor network that enhances the energy efficiency by reducing the communication, with the help of Constrained Delaunay Triangulation intersect line. Further by applying the above approach, we reduce the energy consumption and congestion in the network. In last, we describe our approach with a case study that our approach is better in fault tolerance and energy saving. sensor networks, coverage is classified in several ways based on different criteria. Area coverage is one of the classifications. Area coverage deals with the entire geographical region being monitored, and that every location in the region is monitored by at least one sensor node. Each node monitors an area of geographical region within its boundary, also known as the sensing region and the distance from the node to the boundary is known as the sensing radius. It is essential for a wireless sensor network to monitor every location in the region to provide sensing information, proving the importance of coverage in a sensor network. All locations in geographical region are 1-covered when each location in the region is within the sensing range of at least one sensor node.

Tungsten oxide incorporated mesoporous molecular sieve (WO3–SBA-15) composite was successfully synthesized via one-step hydrothermal process using tetraethylorthosilicate (TEOS) as the silica source, sodium tungstate as the tungsten precursor, and pluronic P123 triblock polymer (EO20PO70EO20, Mav = 5800) as a structure-directing agent. The material was characterized by small angle X-ray diffraction (SAX), transmission electron microscopy (TEM), nitrogen sorption measurement and Fourier transform infrared spectroscopy. The catalyst showed excellent catalytic efficiency in epoxidation reactions with various olefinic compounds using H2O2 as oxidant and NaHCO3 as co-catalyst. The solid catalyst can be recovered after reaction and can be reused for several times in catalytic reactions without any significant loss of activity.

A new azido derivative of a NNO donor tridentate Schiff-base copper(II) complex, [CuL(μ1,1-N3)]n (1) (HL = 1-(N-ortho-hydroxyacetophenimine)-2-(N-ethyl)aminoethane), containing a single end-on μ1,1-azido bridged 1D infinite chain has been synthesized and characterized. X-ray single crystal structure analysis reveals that the complex [CuL(μ1,1-N3)]n (1) is a 1D chain in which neighboring Cu(II) chromophores are related by glide planes and linked by single azido bridges in the EO mode. No measurable magnetic interaction was evidenced in the complex [CuL(μ1,1-N3)]n (1) through variable temperature magnetic susceptibility measurements (10–300 K). The complex was used as an active catalyst for the epoxidation of cyclooctene using tert-butyl-hydroperoxide as an oxidant. The catalytic activity of the complex has been compared in a series of solvents. The results show that in acetonitrile medium, the epoxide was produced in high yield with high selectivity.

A layered oxo-vanadium(IV) dihydrogen phosphate, {VO(H2PO 4)2} n has been synthesized hydrothermally and characterized by several physicochemical methods. Single-crystal X-ray analysis (crystal system, tetragonal; space group, P4/ ncc; unit cell dimensions, a = b = 8.9632(4), c = 7.9768(32) A) of {VO(H2PO4) 2} n reveals that the compound has an extended two-dimensional structure. The VO2+ moieties are connected through bridging H 2PO4 (-) ions, and this type of connection propagates parallel to the crystallographic ab plane which gives rise to a layered structure. The layers are staked parallel to the crystallographic c axis with a separation between the layers of ca. 4.0 A. Magnetic susceptibility of {VO(H2PO4)2} n has been measured in the temperature range 2-300 K on a SQUID magnetometer. The magnetic property of {VO(H2PO4)2} n is explicable in the light of a two-dimensional quantum Heisenberg antiferromagnet model. Magnetic pathways are available through the dihydrogen-phosphato bridges within the layer and provide for weak antiferromagnetic interactions. Notably {VO(H2PO4)2} n catalyzes the epoxidation reaction of alkenes with tert-BuOOH in acetonitrile medium under heterogeneous condition.

Three copper(II) Schiff-base complexes, [Cu(L1)(H2O)](ClO4) (1), [Cu(L2)] (2) and [Cu(L3)] (3) have been synthesized and characterized [where HL1 = 1-(N-ortho-hydroxy-acetophenimine)-2-methyl-pyridine], H2L2 = N,N′-(2-hydroxy-propane-1,3-diyl)-bis-salicylideneimine and H2L3 = N,N′-(2,2-dimethyl-propane-1,3-diyl)-bis-salicylideneimine]. The structure of complex 1 has been determined by single crystal X-ray diffraction analysis. In complex 1, the copper(II) ion is coordinated to one oxygen atom and two nitrogen atoms of the tridentate Schiff-base ligand, HL1. The fourth coordination site of the central metal ion is occupied by the oxygen atom from a water molecule. All the complexes exhibit high catalytic activity in the oxidation reactions of a variety of olefins with tert-butyl-hydroperoxide in acetonitrile. The catalytic efficacy of the copper(II) complexes towards olefin oxidation reactions has been studied in different solvent media.

New zeolite-immobilized hybrid catalysts Cu(NO2-salen)–NaY have been prepared by encapsulating copper(II) Schiff base complexes [where NO2-salenH2 is N,N′-(ethylene)-bis-(5-nitro-salicylaldiimine)] in NaY zeolite matrix. The hybrid materials have been characterized by UV–vis, IR and EPR spectrometry and by X-ray powder diffraction analysis. The neat copper(II) Schiff base complex [Cu(NO2-salen)(EtOH)] (1) has also been synthesized and characterized. A brilliant color change (green–gray) has been observed when the complexes are immobilized in zeolitic matrix. X-ray powder diffraction analysis of Cu(NO2-salen)–NaY catalysts reveals that the structural integrity of the mother zeolite in the hybrid material remained intact upon immobilization of the complex. Spectroscopic studies indicate that coordination geometry of the complex undergoes a significant distortion when it is entrapped in the zeolite cavity. While Cu(NO2-salen)–NaY catalysts showed moderate to excellent catalytic activity and product selectivity in the oxidation reactions, the pure complexes Cu(NO2-salen) remained virtually catalytically inactive in these reactions. The efficiency of the catalysts depends on the stereo-electronic properties of the copper Schiff base moiety.

A new zeolite-immobilized hybrid catalyst Cu(MeO-salen)-NaY has been prepared by encapsulating [Cu(MeO-salen)(H2O)] (1) [where MeO-salenH2 = N,N′-(ethylene)-bis-(3-methoxysalicylaldimine)] in a NaY zeolite matrix. The hybrid material has been characterized by UV–Vis, IR and EPR spectrometry and by X-ray powder diffraction analysis. The pristine complex [Cu(MeO-salen)(H2O)] (1) has also been synthesized and characterized by all the spectrometric methods mentioned above as well as by single crystal X-ray diffraction analysis. A brilliant color change (green to red) has been observed when the complex [Cu(MeO-salen)(H2O)] (1) is immobilized in the zeolitic matrix. X-ray powder diffraction analysis of Cu(MeO-salen)-NaY reveals that the structural integrity of the mother zeolite in the hybrid material remains intact upon immobilization of the complex. The coordination geometry around the CuII ion in [Cu(MeO-salen)(H2O)] is found to be square pyramidal. Spectroscopic studies indicate that coordination geometry of the complex undergoes a significant distortion when it is entrapped in the zeolite cavity. While Cu(MeO-salen)-NaY shows excellent catalytic activity and product selectivity in the hydroxylation of phenol and 1-naphthol, [Cu(MeO-salen)(H2O)] (1) remains virtually catalytically inactive in these reactions.

In this paper, particle swarm optimization (PSO) method, which represents a recent approach for optimization problems in electromagnetic, is applied for array pattern synthesis of hexagonal array (HA) and concentric hexagonal array (CHA) of uniformly excited isotropic antennas which can generate directive beam with minimum relative side lobe level (SLL). Two examples has been presented and solved. In first example, the PSO is used to determine an optimal set of ‘ON-OFF’ elements in a 12-element thinned HA and 24-element thinned CHA, and in second example, PSO is used to determine an optimal set of amplitude distributions in a 12-element HA and a 24-element CHA that provide a radiation pattern with maximum SLL reduction. Optimization is done without significant change in the value of first null beam width (FNBW). Simulation results show that, in first example, the number of effective antenna elements can be brought down from 12 to 6 totals with simultaneous reduction in SLL by −23.85 dB for HA and from 24 to 11 totals with simultaneous reduction in SLL by −20.71 dB for CHA. In second example, SLL is reduced to less than −31 and −27 dB for HA and CHA, respectively, by optimizing inter-element spacing and inter-ring spacing along with amplitude using PSO.

In this paper, the optimal thinning of two-ring Concentric Hexagonal Array (CHA) of uniformly excited isotropic antennas which can generate directive beam with minimum relative Side Lobe Level (SLL) is described. The Improved Particle Swarm Optimization (IPSO) method, which represents a new approach for optimization problems in electromagnetic, is used in the optimization process. To determine an optimal set of ‘ON-OFF’ elements that provide a radiation pattern with maximum SLL reduction, the IPSO algorithm is used. The simulation results show that the number of antenna array elements can be brought down more than 50% of total isotropic elements with simultaneous reduction in Side Lobe Level (SLL) with an approximately fixed first null beam width (FNBW). Particle Swarm Optimization (PSO), as well is also adopted to compare the results of above IPSO.

In this paper, various swarm based algorithms like real coded genetic algorithm (RGA), conventional particle swarm optimization (PSO), a proposed novel particle swarm optimization (NPSO) have been applied for the optimal design of hyper beamforming of linear antenna array. Hyper beam is derived from sum and difference beam patterns each raised to the power of the hyper beam exponent parameter for the array. NPSO uses new definition for the velocity vector. The simulation results show NPSO outperforms RGA and PSO in the optimal hyper beamforming by achieving much greater reduction in sidelobe level (SLL) and much more improved first null beam width (FNBW) keeping the same value of hyper beam exponent. The optimized hyper beam is achieved by optimization of current excitation weights and uniform inter-element spacing. The approach is illustrated through 10-, 14-, and 20-element linear antenna arrays.

This paper describes optimal thinning of an Elliptical Cylindrical Array (ECA) of uniformly excited isotropic antennas which can generate directive beam with minimum relative Side Lobe Level (SLL). The Particle Swarm Optimization (PSO) method, which represents a new approach for optimization problems in electromagnetic, is used in the optimization process. The PSO is used to determine the optimal set of ‘ON-OFF’ elements that provides a radiation pattern with maximum SLL reduction. Optimization is done without prefixing the value of First Null Beam Width (FNBW). The variation of SLL with element spacing of thinned array is also reported. Simulation results show that the number of array elements can be reduced by more than 50% of the total number of elements in the array with a simultaneous reduction in SLL to less than -27dB. &nbsp

This paper describes optimal thinning of Concentric Hexagonal Array (CHA) of uniformly excited isotropic antennas which can generate directive beam with minimum relative Side Lobe Level (SLL). The Craziness Based Particle Swarm Optimization (CRPSO) method, which represents a new approach for optimization problems in electromagnetics, is used in the optimization process. The CRPSO is used to determine an optimal set of `ON-OFF' elements that provide a radiation pattern with maximum SLL reduction. The simulation results show that the number of antenna array elements can be brought down to 60% of total isotropic elements with simultaneous reduction in SLL with an approximately fixed first null beam width (FNBW). Conventional Particle Swarm Optimization (PSO) is also adopted to compare the results of above CRPSO.

Particle Swarm Optimization (PSO) is applied to the thinning of elliptical antenna arrays of uniformly excited isotropic antennas which can generate directive beam with minimum relative side lobe level (SLL). Thinning of elliptical antenna arrays using PSO are optimized with different values of eccentricity in all the cases and variation of side lobe level with eccentricity of thinned antenna array is also reported. It is found that changing eccentricity reduced values of side lobe level can be obtained.