Smaller Optical Band Gap Research Articles

Rational construction of S-doped FeOOH onto Fe2O3 nanorods for enhanced water oxidation

Hematite-based photoanode (α-Fe2O3) is considered the promising candidate for photoelectrochemical (PEC) water splitting due to its relatively small optical bandgap. However, severe charge recombination in the bulk and poor surface water oxidation kinetics have limited the PEC performance of Fe2O3 photoelectrodes, which is far below the theoretical value. Herein, a new catalyst, S-doped FeOOH (S-FeOOH), has been immobilized onto the surface of the Fe2O3 nanorod (NR) array by a facile chemical bath deposition incorporated thermal sulfuration process. The grown S-FeOOH layer acts not only as an efficient catalyst layer to accelerate the water oxidation on the surface of photoelectrode but also constructs a heterojunction with the light absorption layer to facilitate the interface charge carrier separation and transfer. As expected, the modified S-FeOOH@Fe2O3 photoanode achieves a remarkable increase in PEC performance of 2.30 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (VRHE) andan apparent negative shifted onset potential of 250 mV in comparison with pristine Fe2O3 (0.95 mA cm−2 at 1.23 VRHE). These results provide a simple and effective strategy to coupling oxygen evolution catalysts with photoanodes for practically high-performance PEC applications.

Rare earth metals co-doped ZnO/CNTs composite as high performance photocatalyst for hydrogen production from water_triethanolmine mixture

This study investigated the zinc oxide (ZnO) based heterojunction photocatalysts for improved hydrogen production from water splitting. A sol-gel route was adopted to produce terbium (Tb) and samarium (Sm) co-doped ZnO/CNTs composites where CNTs worked as a support material. The built-in redox couples of lanthanides in co-doped TS-ZnO/CNTs composite showed higher hydrogen evolution activity than Sm doped (Sm-ZnO/CNTs) and Tb doped (Tb–ZnO/CNTs) photocatalysts. When triethanolamine was utilized as a sacrificial agent, the TS-ZnO/CNTs photocatalyst result in a remarkable hydrogen evolution rate of 2683 molh −1 g −1 under visible light illumination. The optimum photocatalyst also showed high stability over five successive hydrogen evolution cycles. The better hydrogen evolution rate with TS-ZnO/CNTs was referred to its fine particle size, high reactive surface area, small optical band gap, suppressed reunification of charge carriers and built-in redox couples. The photocatalytic mechanism, involved in water splitting with TS-ZnO/CNTs photocatalyst, is also deduced in this study. This study can stimulate the attempts towards construction of lanthanides based co-doped semiconductor photocatalysts for efficient hydrogen evolution. • Tb and Sm co-doped ZnO/CNTs composite was prepared by sol-gel method. • The heterojunction increases the separation and transfer of charge carriers. • H 2 evolution of Tb and Sm co-doped ZnO/CNTs was 47 times higher than pure ZnO. • CNTs modified photocatalyst has abundant active sites and high conductivity. • H 2 evolution mechanism of CNTs modified photocatalyst is also proposed.

Short-wavelength infrared (SWIR) photodetector based on multi-layer 2D GaGeTe.

Recent theoretical studies proposed that two-dimensional (2D) GaGeTe crystals have promising high detection sensitivity at infrared wavelengths and can offer ultra-fast operation. This can be attributed to their small optical bandgap and high carrier mobility. However, experimental studies on GaGeTe in the infrared region are lacking and this exciting property has not been explored yet. In this work, we demonstrate a short-wavelength infrared (SWIR) photodetector based on a multilayer (ML) GaGeTe field-effect transistor (FET). Fabricated devices show a p-type behavior at room temperature with a hole field-effect mobility of 8.6 - 20 cm2 V-1s-1. Notably, under 1310 nm illumination, the photo responsivities and noise equivalent power of the detectors with 65 nm flake thickness can reach up to 57 A/W and 0.1 nW/Hz1/2, respectively, at a drain-source bias (Vds) = 2 V. The frequency responses of the photodetectors were also measured with a 1310 nm intensity-modulated light. Devices exhibit a response up to 100 MHz with a 3dB cut-off frequency of 0.9 MHz. Furthermore, we also tested the dependence of the device frequency response on the applied bias and gate voltages. These early experimental findings stimulate the potential use of multilayer GaGeTe for highly sensitive and ultrafast photodetection applications.

High performance indoor light harvesters with a wide-gap donor polymer PBDB-T

Organic solar cells have received widespread attention with the development of indoor light harvesters. Due to the narrow emission spectra and weak light intensity of indoor emissions, the short-circuit current of indoor devices is largely restricted, and there would be an additional voltage loss around 0.15 V from the light intensity difference. However, most state-of-the-art cells cannot be adopted as indoor photovoltaics directly, because their small optical bandgaps lead to open-circuit voltage ( V OC ) values in the range of ~0.6 V in dim-lighting, which is difficult to drive most of internet of things. Herein, we revaluate the photovoltaic performance under indoor illuminances by combining a wide-gap polymer PBDB-T with various electron-accepting materials. The PBDB-T: BTA3 cell achieves an excellent efficiency higher than 25% under a 1000 lux 2700K LED illumination. The V OC value of such a device can still maintain close to 1 V under indoor cases. We then compare the underlying mechanism of the PBDB-T-based bulk heterojunctions (BHJs) with multiple techniques, and the results indicate the unchanged advantage of high V OC helps the BTA3-based cell shows the best indoor device performance when the light source is switched from AM1.5G to low illumination. This work revaluates the selection of state-of-the-art indoor light harvesters, and demonstrate an excellent optimal efficiency of the PBDB-T:BTA3 indoor cell up to 25.6%, with a desirable V OC of 0.99 V. In this work, we revaluate the relationship between high Voc and high performance of OPV devices for indoor light applications by combining a wide-gap polymer donor PBDB-T with a series of electron-accepting materials. We also demonstrate an excellent optimal efficiency of the PBDB-T: BTA3 indoor cell up to 25.6%, with a desirable Voc of 0.99 V.

Synergetic Effect of Side-Chain Engineering of Polymer Donors and Conformation Tuning of Small-Molecule Acceptors on Molecular Properties, Morphology, and Photovoltaic Performance

It is demonstrated that the side-chain engineering of polymer donors and molecular conformation of small-molecule acceptors (SMAs) plays a crucial role in the morphology and photovoltaic performance of polymer solar cells (PSCs). However, the synergetic effect of these two aspects has been rarely reported. Herein, two wide-band gap donor–acceptor (D–A) copolymers (PST-TTC and PSPT-TTC) featuring the same main-chain backbone but different conjugated side chains were developed and combined with three low-band gap symmetric SMAs (ITIC, DTCFO-ICCl, and Y6) with various molecular conformations (S-shape, C-shape, and U-shape) to investigate the synergetic effect of side-chain engineering of polymer donors and conformation manipulation of SMAs on molecular properties, device physics, film morphology, and photovoltaic performance. The results indicate that PST-TTC with an alkylthiothiophene side chain exhibits a broader absorption spectrum, a smaller optical band gap (1.95 vs 1.99 eV), and a deeper-lying highest occupied molecular orbital (HOMO) level (−5.39 vs −5.36 eV) as compared to PSPT-TTC with an alkylthiophenylthiophene side chain. The PSCs were constructed according to the different donor/acceptor combinations based on the two as-synthesized polymers and three selected SMAs. After optimization, PST-TTC paired with S-shaped ITIC provides a power conversion efficiency (PCE) of 10.10% and the PCE can be further improved up to 10.60% when C-shaped DTCFO-ICCl was used to replace ITIC as the acceptor. However, the device performance becomes worse, accompanied with a sharply reduced PCE of 7.36% after the substitution of ITIC for U-shaped Y6. On the contrary, when the paired donor was changed to PSPT-TTC, the PSPT-TTC:Y6-based PSC achieves a remarkably increased PCE of up to 11.46%. These delicate observations suggest that the polymer donor with different conjugated side chains should collaborate with symmetric SMAs possessing various molecular conformations to realize superior morphology and device performance.

Proton and Electron Transfer in the Formation of a Copper Dithiolene-Based Coordination Polymer.

Metal bis(dithiolene) complexes are promising building blocks for electrically conductive coordination polymers. N-Heterocyclic dithiolene complexes allow their cross-linking via the coordination of N-donor atoms to additional transition metal ions. In this study, we present the formal copper(II) and copper(III) 6,7-quinoxalinedithiolene complexes [Cu(qdt)2]- and [Cu(qdt)2]2- (qdt2-: 6,7-quinoxalinedithiolate), as well as the 2D coordination polymer Cu[Cu(Hqdt)(qdt)] (3). The dithiolene complexes were isolated as (Bu4N)2[Cu(qdt)2] (1), Na[Cu(qdt)2]·4H2O (2a), [Na(acetone)4][Cu(qdt)2] (2b), and [Ni(MeOH)6][Cu(qdt)2]2·2H2O (2c). Their crystal structures reveal nearly planar complexes with a high tendency of π-stacking. For a better understanding of their coordination behavior, the electronic properties are investigated by UV-vis-NIR spectroscopy, cyclic voltammetry, and DFT simulations. The synthesis of the 2D coordination polymer 3 involves the reduction and protonation of the monoanionic copper(III) complex. A combination of powder X-ray diffraction, magnetic susceptibility measurements, as well as IR and EPR spectroscopy confirm that formal [CuII(Hqdt)(qdt)]- units link trigonal planar copper(I) atoms to a dense 2D coordination polymer. The electrical conductivity of 3 at room temperature is 2 × 10-7 S/cm. Temperature dependent conductivity measurements confirm the semiconducting behavior of 3 with an Arrhenius derived activation energy of 0.33 eV. The strong absorption of 3 in the visible and NIR regions of the spectrum is caused by the small optical band gap of Eg,opt = 0.65 eV, determined by diffuse reflectance spectroscopy. This study sheds light on the coordination chemistry of N-heterocyclic dithiolene complexes and may serve as a reference for the future design and synthesis of dithiolene-based coordination polymers with interesting electrical and magnetic properties.

Synthesis of Amorphous Conjugated Copolymers Based on Dithienosilole-Benzothiadiazole Dicarboxylic Imide with Tuned Optical Band Gaps and High Thermal Stability

Two alternating copolymers of dithienosilole (DTS) were designed and synthesized with small optical band gaps, flanked by thienyl units as electron-donor moieties and benzothiadiazole dicarboxylic imide (BTDI) as electron-acceptor moieties. The BTDI moieties were anchored to two different solubilizing side chains, namely 3,7-dimethyloctyl and n-octyl chains. An analysis of the effect of the electrochemical, optical, thermal, and structural characteristics of the resulting polymers along with their solubility and molecular weight is the subject of this paper. The Stille polymerization was used to synthesize PDTSDTBTDI-DMO and PDTSDTBTDI-8. The average molecular weight of PDTSDTBTDI-DMO and PDTSDTBTDI-8 is 14,600 and 5700 g mol−1, respectively. Both polymers have shown equivalent optical band gaps around 1.4 eV. The highest occupied molecular orbital (HOMO) levels of the polymers were comparable, around −5.2 eV. The lowest unoccupied molecular orbital (LUMO) values were −3.56 and −3.45 eV for PDTSDTBTDI-DMO and PDTSDTBTDI-8, respectively. At decomposition temperatures above 350 °C, both copolymers showed strong thermal stability. The studies of powder X-ray diffraction (XRD) have shown that they are amorphous in a solid-state.

Polymer Composites with 0.98 Transparencies and Small Optical Energy Band Gap Using a Promising Green Methodology: Structural and Optical Properties.

In this work, a green approach was implemented to prepare polymer composites using polyvinyl alcohol polymer and the extract of black tea leaves (polyphenols) in a complex form with Co2+ ions. A range of techniques was used to characterize the Co2+ complex and polymer composite, such as Ultraviolet–visible (UV-Visible) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The optical parameters of absorption edge, refractive index (n), dielectric properties including real and imaginary parts (εr, and εi) were also investigated. The FRIR and XRD spectra were used to examine the compatibility between the PVA polymer and Co2+-polyphenol complex. The extent of interaction was evidenced from the shifts and change in the intensity of the peaks. The relatively wide amorphous phase in PVA polymer increased upon insertion of the Co2+-polyphenol complex. The amorphous character of the Co2+ complex was emphasized with the appearance of a hump in the XRD pattern. From UV-Visible spectroscopy, the optical properties, such as absorption edge, refractive index (n), (εr), (εi), and bandgap energy (Eg) of parent PVA and composite films were specified. The Eg of PVA was lowered from 5.8 to 1.82 eV upon addition of 45 mL of Co2+-polyphenol complex. The N/m* was calculated from the optical dielectric function. Ultimately, various types of electronic transitions within the polymer composites were specified using Tauc’s method. The direct bandgap (DBG) treatment of polymer composites with a developed amorphous phase is fundamental for commercialization in optoelectronic devices.

Fully Inorganic CsSnI3 Mesoporous Perovskite Solar Cells with High Efficiency and Stability via Coadditive Engineering

The small optical bandgap of a CsSnI3‐based inorganic perovskite film makes it a hopeful candidate as an absorber layer in solar cell applications. Herein, a coadditive 2‐aminopyrazine (APZ) in the precursor solution to form SnF2−APZ complex with the aim to restrain Sn2+ oxidation and thus improve the CsSnI3‐based device performance is proposed. It is found that the amino group of APZ significantly suppresses oxidation of Sn2+ through a Lewis acid–base addition reaction. Consequently, the CsSnI3‐based mesoporous perovskite solar cells that use a printable c‐TiO2/m‐TiO2/Al2O3/NiO/carbon framework with high reproducibility achieve a power conversion efficiency of 5.12%. This is a champion efficiency for fully inorganic CsSnI3‐based mesoporous devices reported up to now. Furthermore, after 60 days of storage in a N2‐filled glovebox, the device still maintains an initial efficiency of 92%.

TiO2/ZnO Nanocomposite Material for Efficient Degradation of Methylene Blue

In this research work, we have produced a composite material consisting titanium dioxide (TiO2) and zinc oxide (ZnO) nanostructures via precipitation method. Scanning electron microscopy (SEM) study has shown the mixture of nanostructures consisting nanorods and nano flower. Energy dispersive spectroscopy (EDS) study has confirmed the presence of Ti, Zn and O as main elements in the composite. X-ray diffraction (XRD) study has revealed that the successful presence of TiO2 and ZnO in the composite. The composite material exhibits small optical energy band gap which led to reduction of the charge recombination rate of electron–hole pairs. The band gap for the composite TiO2/ZnO samples namely 1, 2, 3 and 4 is 3.18, 3.00, 2.97 and 2.83 eV respectively. Small optical bandgap gives less relaxation time for the recombination of electron and hole pairs, thus favorable photodegradation is found. The degradation efficiency for the TiO2/ZnO samples for methylene blue in order of 55.03%, 75.7%, 85.14% and 90.08% is found for the samples 1, 2, 3 and 4 respectively. The proposed study of titanium dioxide addition into ZnO is facile and inexpensive for the development of efficient photocatalysts. This can be capitalized at large scale for the energy and

Highly controllable synthesis of MAPbI3 perovskite nanocrystals with long carrier lifetimes and narrow band gap for application in photodetectors

Low-dimensional organic-inorganic hybrid perovskite materials have attracted much attention in photoelectric devices due to their exotic performance in optoelectronics compared with their bulk and thin-film counterparts. In this article, using a simple ligand-assisted deposition method, we successfully synthesized uniform methylammonium lead iodide (MAPbI3) perovskite nanorods, nanotriangles and nanocubes, and investigated their photoelectric properties after fabricated into photodetectors (PDs) on SiO2/Si substrates. It is found that the synthesized MAPbI3 nanorods not only have extremely small optical band gap (minimum of ~1.36 eV), but also have long photoluminescence (PL) lifetime (longest of ~7.81 μs) and high absolute PL quantum yields (maximum of ~ 45%), and the PL lifetime is more than about one order of magnitude higher than that the reported previously. The PDs based on MAPbI3 nanorods presented a wide spectral response “window” from 350 to at least 950 nm, and exhibited a photoresponsivity of 12.2 mA/W, a detectivity of 2.67 × 1011 Jones, the on/off ratio of more than 800, the rise/decay time constants of 18/25 ms, under the excitation at 405 nm. Further analysis suggests that the dramatically improved photo-electric conversion properties of the nanorods PDs could be closely related with their morphology dependent properties, including bandgap, PL lifetime, trap density (ntrap) and carrier concentration. These results provide a simple and effective method for preparing different morphology low-dimensional MAPbI3, and discuss the mechanism of morphology-dependent photoelectric performance of PDs, which is of great significance for potential applications in the field of photoelectronic devices.

1,2,3-Triazole-based conjugated porous polymers for visible light induced oxidative organic transformations

1,2,3-Triazole contained conjugated porous polymers (CPPs) have recently emerged as a new class of efficient photocatalysts. To gain more insight into the excellent photocatalytic activity of this kind of CPPs, herein, we report the design and preparation of a series of 1,2,3-triazole-based CPPs via oxidative coupling polymerization to study their photocatalytic performance. These CPPs have donor-acceptor properties and 1,2,3-triazole serves as an electron acceptor. The resulting CPPs with thiophene, carbazole and diphenylamine as electron donor units, respectively, have distinct porosities and optoelectronic properties, and showed effective photocatalytic performance towards oxidative hydroxylation of arylboric acids and alkylation of vinylarenes with diethyl bromomalonate or bromoacetonitrile. The thiophene contained CPP was a more efficient photocatalyst for the catalytic reactions, which can be attributed to its smaller optical band gap and greater charge separation efficiency. Furthermore, PTPT has shown reliable recyclability with no significant loss in its catalytic activity.

The influence of copper on the optical band gap of heterometallic iodido antimonates and bismuthates.

Halogenido metalates of heavy main group elements are versatile semiconductor materials with broad applications. Especially the iodido metalates generally show small optical band gaps, making them suitable for photovoltaics. However, the most promising results have been generated using toxic lead-based materials, raising environmental concerns, while the related and far less toxic bismuth compounds show band gaps too large for direct use in photovoltaics. The introduction of heterometals such as copper can significantly lower the band gap of iodido bismuthates and antimonates, but no clear trend could yet be established in this regard. In this work a short overview over all known copper iodido bismuthates and antimonates is given and this small family of compounds is expanded with nine charged as well as neutral complexes [EkMlIm(P(R)3)n]q- (E = Sb, Bi; M = Cu, Ag; R = Ph, o-tol). The compounds' crystal structures, stability and optical properties are investigated and compared to the findings of quantum chemical investigations. The main excitation is shown to be a copper to antimony or copper to bismuth charge transfer while the relative energetic position of the organic ligand orbitals influences the magnitude of the band gap. This reveals that the nature of the ligands and the coordination environment at the copper atom is crucial for designing new copper iodido antimonates and bismuthates with specific band gaps.

Semiconducting tailoring and electrical properties of A-site Co substituted Bi0·5Na0·5TiO3-δ ferroelectric ceramics

The new (1-x) Bi0·5Na0·5TiO3-xCoTiO3-δ ferroelectric semiconductor ceramics were prepared successfully by the solid-state method. The single perovskite structures and long-range polarity order of the (1-x) Bi0·5Na0·5TiO3-xCoTiO3-δ semiconductor ceramics were observed by X-ray diffraction (XRD) and Raman spectra, respectively. The typical relaxation behavior was founded in all the ceramics. The perfect ferroelectric loops and outstanding optical properties were achieved in the (1-x) Bi0·5Na0·5TiO3-xCoTiO3-δ ceramics. A very small optical bandgap (Eg = 1.44 eV) was obtained in the 0.94Bi0·5Na0·5TiO3-0.06CoTiO3-δ ceramic, which is approximately 55% lower than that of pure BNT (Eg = 3.2 eV). The Jsc and Voc of poled 0.94Bi0·5Na0·5 [Ti4+0.71, Ti3+0.29]O2.71-0.06Co [Ti4+0.71, Ti3+0.29]O2.71 ceramic can reach ~ 1.00 nA/cm2 and 0.13 V, respectively. The activation energies of the grains and grain boundaries were calculated to be 0.48 and 0.52 eV, respectively. These results show that the Co substation BNT ceramics highlight a promising candidate for multi-functional photoelectric applications.

Direct extrapolation techniques on the energy band diagram of BiVO4 thin films

Bismuth vanadate (BiVO4) is one of the n-type semiconductors which has attracted attention as one of the promising photoanodes semiconductor for photoelectrochemical water splitting due to its small optical band gap, low cost, negative conduction band edge and good stability. In this work, BiVO4 thin films is fabricated by using electrodeposition method and the XRD spectra reveal that the sample crystallizes in monoclinic scheelite type. The optical bands show the bandgap energy of BiVO4 thin films is 2.40 eV as determined by Tauc plot and exhibits an anodic photocurrent. Further study is focusing on determination of the conduction band (CB) and valence band (VB) of BiVO4 thin films which is derived experimentally by using XPS analysis, Mott–Schottky plot and Cyclic Voltammetry (CV) technique. Based on the results, it is found that different analysis techniques exhibit almost similar values of CB and VB of BiVO4 thin films. All techniques give VB maximum in the range of 2.02 eV–2.05 eV and CB minimum in the range of −0.35 eV to −0.39 eV. However, the flat-band potential determined from Mott–Schottky plot is nearly 0.1 eV from CB potential caused by the presence of Fermi level and the effect of Helmholtz capacitance for dielectric semiconductors. These findings clearly show that the experimental values of different analysis techniques give comprehensive approach to understanding the energy band structure of the BiVO4 thin films.

Tea from the drinking to the synthesis of metal complexes and fabrication of PVA based polymer composites with controlled optical band gap

In the present study black tea extract (BTE) solution which is familiar for drinking was used to prepare cerium metal-complexes (Ce(III)-complex). The prepared Ce(III)-complex was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and UV–Vis spectroscopy. The results indicate that BTE solution is a novel green coordination chemistry approach for the synthesis of metal complexes. The outcomes signify that coordination occurs between cerium cations and polyphenols. The synthesis of metal-complexes with superior absorption performance in the visible region is a challenge for optoelectronic device applications. The suspended Ce(III)-complex in distilled water was mixed with poly (vinyl alcohol) (PVA) polymer to fabricate PVA/ Ce(III)-complex composites with controlled optical properties. The PVA/Ce(III)-complexes composite films were characterized by FTIR, XRD, and UV–Vis spectroscopy. The XRD findings confirms the amorphous structure for the synthesized Ce(III)-complexes. The addition of Ce(III)-complex into the PVA host polymer led to the growth of polymer composites with controllable small optical band gaps. It is shown by the FTIR spectra of the composite films that the functional groups of the host PVA have a vigorous interaction with the Ce(III)-complex. The XRD deconvolution on PVA composites reveals the amorphous phase enlargement with increasing Ce(III)-complex concentration. It is indicated in the atomic force microscopy (AFM) that the surface roughness in the doped PVA films increases with the increase of the Ce(III)-complex. There is a decrease in absorption edge from 5.7 to 1.7 eV. It becomes possible to recognize the type of electron transition by studying both the Tauc's model and optical dielectric loss (ɛi) parameter.

Crystal structure, linear and nonlinear optical properties of three thiophenyl chalcone derivatives: A combined experimental and computational study

Abstract Three thiophenyl chalcone derivatives, (E)-1-(5-bromo-2-thienyl)-3-(4-bromophenyl)prop-2-en-1-one (B5B2SC), (E)-1-(5-bromo-2-thienyl)-3-(3-chlorophenyl)prop-2-en-1-one (3C5B2SC), and (E)-1-(5-bromo-2-thienyl)-3-(2-methoxyphenyl)prop-2-en-1-one (2M5B2SC), were successfully synthesized and crystallized. The structures were confirmed by experimental and theoretical FTIR and 1H NMR spectra. The crystal structures were determined by single-crystal XRD method. The B5B2SC, 3C5B2SC and 2M5B2SC crystallize in the monoclinic space groups P 21/c (centrosymmetric), P 2 (non-centrosymmetric) and triclinic space group P 1 ‾ (centrosymmetric), respectively. All these structures adopt trans configuration with respect to C6═C7 double bond. The chalcones have high thermal stability, a wide transparency in the visible region and small optical band gaps. The 3C5B2SC exhibits powder second-harmonic generation (SHG) intensity of about 1.7 times higher than Urea. From continuous wave (CW) laser (532 nm) Z-scan experimental data analyses, the third-order NLO parameters such as nonlinear absorption coefficient (β = ~10−4 cm/W), nonlinear refractive index (n2= ~10−9 cm2/W), third-order NLO susceptibility (χ(3) = ~10−7 esu), molecular hyperpolarizability (γh = ~10−27 esu), ground state absorption cross section (σg = ~10−22 cm2) and excited state cross sections (σex= ~10−20 cm2) were determined. The chalcones also exhibited optical limiting and all optical switching behaviour for CW laser operating at 532 nm wavelengths. The electric dipole moment, polarizability, hyperpolarizabilty, HOMO-LUMO energy gap, global chemical reactivity descriptors (GCRD), molecular electrostatic potentials (MEP) and natural bond orbital (NBO) analysis were computed theoretically (DFT). The results indicate that these three chalcones with thiophene moiety are potential materials for optical device applications.

Porphyrin-Ryleneimide Hybrids: Tuning of Visible and Near-Infrared Absorption by Chromophore Desymmetrization.

Unsymmetrically fused porphyrins containing one or two naphthalimide subunits were prepared in modular syntheses relying on electron-rich and electron-poor pyrrole building blocks. These new chromophores show progressive changes in their electron-deficient character, while retaining comparably small optical and electrochemical band gaps. The intrinsic curvature and extended optical absorption of these systems make them of interest as mono- and difunctional components of multichromophoric assemblies.

Iron-Intercalated Zirconium Diselenide Thin Films from the Low-Pressure Chemical Vapor Deposition of [Fe(η5-C5H4Se)2Zr(η5-C5H5)2]2.

Transition metal chalcogenide thin films of the type FexZrSe2 have applications in electronic devices, but their use is limited by current synthetic techniques. Here, we demonstrate the synthesis and characterization of Fe-intercalated ZrSe2 thin films on quartz substrates using the low-pressure chemical vapor deposition of the single-source precursor [Fe(η5-C5H4Se)2Zr(η5-C5H5)2]2. Powder X-ray diffraction of the film scraping and subsequent Rietveld refinement of the data showed the successful synthesis of the Fe0.14ZrSe2 phase, along with secondary phases of FeSe and ZrO2. Upon intercalation, a small optical band gap enhancement (Eg(direct)opt = 1.72 eV) is detected in comparison with that of the host material.

Formaldehyde sensor based on FSP-made AgOx-doped SnO2 nanoparticulate sensing films

In this research, 0–1 wt% AgOx-doped SnO2 nanoparticles were developed based on a single-step flame spray pyrolysis process and investigated for formaldehyde (HCHO)-sensing applications. The structural evaluations by X-ray diffraction, X-ray spectroscopy, electron microscopy, nitrogen adsorption and optical absorption indicated that Ag species containing Ag+ and Ag2+ oxidation states could be embedded in 5–20 nm tetragonal SnO2 nanoparticles as secondary AgOx crystals, leading to smaller crystallite size, larger surface area and smaller optical bandgap. From gas-sensing measurements at 200–400 °C, AgOx-doping with an optimal Ag content of 0.2 wt% enhanced HCHO response by more than one order of magnitude compared with that of undoped one. In particular, the 0.2 wt% AgOx-doped SnO2 sensing films exhibited a high response of ∼495–2000 ppm HCHO at 350 °C with high selectivity against NH3, NO, C2H2, C2H4, H2, CH4, C3H6O, C6H6, C2H6O, CH3OH, C7H8 and C8H10. Moreover, the AgOx doped SnO2 sensors displayed good stability and low dependencies of response on temperature and humidity. Thus, the FSP-made 0.2 wt% AgOx-doped SnO2 sensor could be a promising choice for selective and sensitive HCHO detections.