Blue Shift In Absorption Spectra Research Articles

Star-shaped benzotriindole-based donor-acceptor molecules: Synthesis, properties and application in bulk heterojunction and single-material organic solar cells

The search of the novel building blocks for π-conjugated donor-acceptor (D-π-A) molecules remains an urgent task to design promising materials for organic solar cells (OSCs) and other electronic devices. Here we report on the design and synthesis of two star-shaped D-π-A small molecules based on benzotriidole (BTI) electron-donating core, BTI(2T-DCV-Hex)3 and BTI(2T-CNA-EHex)3, end-capped with either hexyldicyanovinyl or 2-ethylhexylcyanoacetate acceptor groups. Comprehensive investigation and comparison of the optical, thermal and physicochemical properties of these molecules and their analogue with the triphenylamine (TPA) core, N(Ph-2T-DCV-Hex)3, revealed the effect of the electron-withdrawing groups and type of the donor core on their properties. The BTI-based material BTI(2T-DCV-Hex)3 differs from the amorphous TPA-based analogue by high crystallinity and blue-shifted absorption and luminescence spectra. The change of electron-withdrawing group from hexyldicyanovinyl to 2-ethylhexylcyanoacetate leads to a higher energy of the lowest unoccupied molecular orbital, lower solubility and several times higher photoluminescence quantum yield in solutions achieving 67%. Evaluation of the photovoltaic performance of these materials in single-material OSCs and as a donor material in bulk heterojunction OSCs with PC71BM as an acceptor revealed that the devices based on BTI(2T-DCV-Hex)3 are more efficient as compared to those based on BTI(2T-CNA-EHex)3. In comparison to N(Ph-2T-DCV-Hex)3, the photovoltaic devices based on BTI(2T-DCV-Hex)3 showed the comparable performance in bulk heterojunction OSCs and two times higher performance (about 1%) in single-material OSCs. As a result, we conclude that the BTI core is a promising block for the design of semiconducting materials for organic photovoltaics and other related applications.

Comparison of the Energy Transfer Dynamics in Structural and Spectral Variants of the Light-Harvesting Complex 2 of Purple Bacteria

Light-harvesting complex 2 (LH2) of purple bacteria is a well-known model to study the initial light-harvesting steps of photosynthesis. It is organized into two rings: eight or nine bacteriochlorophyll collectively absorb at 800 nm (the B800 ring), while sixteen or eighteen bacteriochlorophyll absorb at 850 nm (the B850 ring). LH2 is produced in several variants both within and across species. While the dynamics of some of these variants have been characterized, the energy transfer rates within many of these variants have not been measured. In this work, we utilize ultrafast transient absorption measurements to compare the energy transfer dynamics of three variants of LH2: LH2 R. sphaeroides, a nonamer, LH2 Ph. molischianum, an octamer, and LH3 Ph. molischianum, which has a blue-shifted absorption spectrum to 820 nm compared to the B850 ring of LH2 Ph. molischianum. These results provide insight into how variations between and within species impact energy flow in photosynthetic systems.

Colorimetric chemosensor based on a Ni2+ complex of a pyridylazo dye for detection of citrate in aqueous solution

We developed a colorimetric naked-eye chemosensor based on the complex between a pyridylazo dye and Ni2+ in a 2:1 stoichiometric ratio (BrPSAA2-Ni2+) for the selective detection of citrate in a pure aqueous solution via the indicator displacement assay. Upon the addition of citrate, BrPSAA2-Ni2+ exhibited a naked-eye detectable color change from red to orange over other anions including dicarboxylates with a blue shift in absorption spectra due to the regeneration of BrPSAA by the interaction of citrate with Ni2+. Furthermore, the citrate detection process was not significantly influenced by other coexisting anions. Therefore, BrPSAA2-Ni2+ can be utilized as a simple and practical colorimetric chemosensor for citrate with selectivity and fast response in aqueous solution.

Electropolymerized poly(3,4-ethylenedioxyselenophene) on flexible substrate: A comparative study of electronic and electrochromic properties with sulfur analogue and rigid substrate

Recently, significant efforts have been devoted on poly(3,4-ethylenedioxyselenophene) (PEDOS) and its derivatives due to their promising properties for various optoelectronic applications. Surprisingly, no study has been reported on electrochemical synthesis of PEDOS on flexible substrate, and its optoelectronic properties. In this work, electropolymerization of 3,4-ethylenedioxyselenophene (EDOS) on flexible (ITO/PET) as well as rigid (ITO/glass) substrates, followed by cyclic voltammetry, electrochemical stability, morphology, spectroelectrochemical, and electrochromic properties of the PEDOS films were studied. For comparison purpose, poly(3,4-ethylenedioxythiophene) (PEDOT) films were also prepared on both flexible and rigid substrates and a throughout comparison was made. It has been observed that the polymer films on flexible substrates are relatively more stable, rough, and show blue shift in absorption spectra as compared to the polymer films on rigid substrates. On repeated bending, polymers films on flexible substrate exhibits good mechanical stability. Moreover, polymer film on flexible substrate has improved contrast ratio than that of polymer film on rigid substrate, whereas no significant change of response time has been observed. To the best of our knowledge, electropolymerization of EDOS on flexible substrate has been reported for the first time.

Effect of Li doping and point vacancy on photocatalytic properties and mechanism of ZnO

Controlling the point defect in Li-doped ZnO is difficult. In addition, the absorption spectrum distribution in Li-doped ZnO with O vacancy (VO) has two reports of red- and blue-shift experimental predictions. The photocatalytic properties of Li doping and point defect on ZnO was studied using first-principles method based on generalized gradient approximation (GGA) plane-wave super-soft pseudopotential + U (GGA + U) to solve this problem. Compared with undoped ZnO, ZnO supercell with Li replacing Zn (LiZn) and VO, LiZn and Zn vacancy (VZn), interstitial Li (Lii) and VZn, and ZnO supercell with LiZn, Lii, and VZn have a narrower band gap and a red-shifted absorption spectrum distribution. By contrast, ZnO supercell with Lii and VZn have a wider band gap and a blue-shifted absorption spectrum distribution. The effective mass calculations show that the ZnO supercell with LiZn and VO has the smallest effective mass of carriers and can thus accelerate the separation of electron–hole pairs, thereby improving photocatalytic activity. The analysis of the electric dipole moment showed that ZnO supercell with LiZn and VO has the strongest activity of carries. This condition is advantageous for designing and preparing novel photocatalysts.

Curcumin/beta-cyclodextrin inclusion complex as a new “turn-off” fluorescent sensor system for sensitive recognition of mercury ion

The formation of supramolecular complex between the curcumin (CC or probe L) and β-cyclodextrin (β-CD) (CC: β-CD or probe LC) was confirmed using absorption and emission spectroscopy. The binding properties of probe LC with cations in water were observed for the first time via absorption and emission spectroscopies. The selectivity and sensitivity of fluorescence chemosensors have been studied using probe LC. The probe LC showed selective binding to Hg2+ and afforded new absorbance and fluorescence peaks at 379 nm and 502 nm, additionally to the prevailing bands of LC at 432 nm and 535 nm. It additionally showed apparent color change from yellow to colourlessness and strong fluorescent to weak fluorescent owing to selective binding of Hg2+ ion, which was detected by naked eyes. No noticeable changes of color and spectra were observed upon the addition of other metal cations such as [Ag+, K+, Na+, Cs+, Ba2+, Fe2+, Mg2+, Pb2+, Mn2+, Ni2+, Cd2+, CO2+, Cr3+, Sn2+ and Zn2+. Hg2+ produced blue shift in absorption spectra and quenching in emission spectra which suggested a likelihood of strong binding of Hg2+ ions with probe LC. The fluorescence response was concentration-dependent and can be well described by the typical Stern–Volmer model. Compared with prior reports, this method is very cheap, selective, sensitive and easily biodegradable of probe LC.

Exploring optical properties of Gd doped zincblende GaN for novel optoelectronic applications (A DFT+U study)

In current research, we investigate optical properties of Gd doped zincblende GaN using Wien2K code, by employing DFT+U. We consider pure GaN and we dope various Gd concentrations 3.12%, 6.25% and 12.5% into the host GaN lattice while supercell size is kept fixed (1 × 2 × 2) for all cases. We elaborate and present a detailed comparison among optical and electronic properties of pure GaN with various Gd concentrations. Interaction of Gd and N atoms and localization of d and f states of dopant are remarked near Fermi level or maxima of valence band. In comparison to pure GaN, absorption spectra for 3.12% Gd concentration shows redshift but for highest Gd concentration (6.25% 12.5%), a blueshift in absorption spectrum is noted. Absorption is pronounced and enhanced in the UV region. Study of optical spectra for various optical properties suggest that Gd:GaN system is mostly suitable for UV optoelectronics. Results for optical properties have great similarity with the existing literature works. Our unprecedented and first ever reported results on optical properties of Gd:GaN system, direct future path of this material for its potential uses in UV optoelectronic, photonic, LEDs, UV sterilization application, photosensors, thermochromic solar cells and biochemical sensing industries.

Longer Cations Increase Energetic Disorder in Excitonic 2D Hybrid Perovskites.

We synthesize and characterize derivatives of the two-dimensional hybrid perovskite (2DHP) phenethylammonium lead iodide ((PEA)2PbI4) in which the para H on the cation is replaced with F, Cl, CH3, or Br. These substitutions increase the length of the cation but leave the cross-sectional area unchanged, resulting in structurally similar PbI42- frameworks with increasing interlayer spacing. Longer cations result in broader, blue-shifted excitonic absorption spectra with reduced or eliminated structure, indicating greater energetic disorder. Photoluminescence spectra are largely invariant and insensitive to cation length, suggesting polaron formation stabilizes a structural and electronic minimum. Temperature-dependent line width analysis reveals excitons couple to a vibration on the organic framework that is weakly sensitive to these cation substitutions, and Raman spectra and electronic structure calculations support the presence of such a cationic mode. Despite carriers being confined to the inorganic framework, the length of the organic cation alters the optical and electronic properties of 2DHPs.

Side-chain effect in ethenylene fused thiophene-vinylene-thiophene (ETVT) based photovoltaic polymers

To investigate side chain effect of ETVT based photovoltaic polymers, we designed and synthesized the polymers with different solubilizing substituents. The impact of side chains on the solubility, planarity, optical and electronic properties of these ETVT based conjugated polymers was systematically studied. Extending the intrinsic alkyl group or adding new alkyl substituent to the polymer obviously increased the solubility of the resulting polymers. Thus, the polymerization reaction yield was improved to 88% and 81%, for PETVT-TBT24 and PETVT8-TBT, compared to that of 39% for PETVT-TBT. PETVT8-TBT showed blue-shifted absorption spectrum, reduced hole mobility and consequently inferior photovoltaic performance, owing to the steric hindrance caused by redundant octyl group on ETVT unit. However, the introduction of alkyl substitutes in ETVT remarkably increases the open-circuit voltage of PETVT8-TBT based PSCs to 1.03 V, by both decreasing HOMO of the polymer and reducing the energy losses. Extending the intrinsic alkyl group resolved the problem of low solubility of PETVT-TBT, and furthermore, was benefit to improve charge carrier mobility in the resulting polymer based solar cells. As a result, PETVT-TBT24 basically maintained the advantages of ETVT based photovoltaic polymers, realizing a moderate PCE of 7.8% when paired with the non-fullerene acceptor of ITIC.

Selective Protonation of Unbounded Sodium Cholates for Reversible Blue-Shift Absorption Spectra of Single-Chirality Single-Walled Carbon Nanotube in Solution

In contradiction to the long-standing optical depletion of single-walled carbon nanotubes (SWCNT) by acid doping, this work reports the blue-shifted and optical density-increased S11 (the first Van Hove singularity transition) peak absorption spectra of single-chirality (6,5) SWCNT dispersed in specific surfactant compositions such as 1% SDS (sodium dodecyl sulfate) /1% SC (sodium cholate) and 2% SDS/0.5% SC, which were caused by addition of acid. These anomalous optical changes can be reversed by adding base, and they are discussed on the basis of surfactant arrangements on SWCNT sidewalls, which arose from the selective protonation of unbounded SC to shift the thermodynamic equilibrium of SC adsorbed SWCNT to the desorption of SC from SWCNT surface. The spectroscopic interpretation obeys the dipole moment transition related energy level variation and oscillator strength change.

Tracking the origin of photostability in purine nucleobases: the photophysics of 2-oxopurine.

This work scrutinizes the relaxation mechanism of 2-oxopurine. Contrary to its ancestor, purine, which is a UVC chromophore, 2-oxopurine shows a red-shifted absorption spectrum centered in the UVA region. In 2-oxopurine, relaxation along the ππ* spectroscopic state directs the population from the Franck-Condon (FC) region towards a minimum, which acts as a crossroad for the further decay of the system either to triplet states or, alternatively, to the ground state through a C6-puckered S1/S0 funnel. A comparison of the optical properties and excited state potential energy surfaces of purine, 2-oxopurine, 2-aminopurine, 6-oxopurine and adenine, allows establishing how the position and nature of substituent tune the photophysics of purine. For this series, we conclude that both C2 and C6 substitution redshift the absorption spectrum of purine, with 2-oxo substitution exhibiting the largest shift. An important exception is the canonical nucleobase adenine, which presents a blue shifted absorption spectrum. The topography of purine's ππ* potential energy surface experiences major changes when functionalized at the C6 position. In particular, the disappearance of the minimum along the ππ* potential energy surface efficiently funnels the excited state population from the FC region to the ground state and increases the photostability of 6-aminopurine (adenine) and 6-oxopurine (hypoxanthine) nucleobases.

A coumarin based fluorescent probe for rapidly distinguishing of hypochlorite and copper (II) ion in organisms.

A dual-functional fluorescent probe based on coumarin fluorophore for monitoring ClO- and Cu2+ was synthesized and characterized. The identification mechanisms for ClO- and Cu2+ induced different colorimetric and ratiometric changes. ClO- caused a colorimetric change from yellow to colorless and 120 nm blue-shifted emission spectra from red to blue. Besides, Cu2+ induced a remarkable fluorescence quenching behavior and 36 nm blue-shifted absorption spectra accompanied by the color change from yellow to luminous yellow. As expected, Probe 1 displayed excellent selectivity and sensitivity for detecting ClO- and Cu2+ over other competing ions in their respective systems. The limits of detection for ClO- and Cu2+ were 24.62 nM and 0.39 nM, respectively. The recognition mechanisms were proved by 1H NMR, mass spectrum and theoretical calculations. More importantly, the reversibility of Cu2+ could be applicable to rapid quantification for ClO-/Cu2+. Thus, the strategy for sensing ClO-/Cu2+ was carried out, which revealed broad applications of Probe 1 in multiple actual water and biology.

First-principle studies of optical properties of BexZn1-xO ternary mixed crystal

The optical properties of beryllium doped zinc oxide (BexZn1-xO) ternary mixed crystal are studied by the first-principles calculations within the framework of the density functional theory (DFT). It turned out that as the energy increases the real parεt ε1of the dielectric function of BexZn1-xO first reached a maximum peak and then gradually attenuated, the static dielectric constant of BexZn1-xO decreases as the Be component increases, the imaginary part ε2of the dielectric function represents light absorption, as the Be component increases, the three main peaks are constantly moving towards the high-energy tail. The refractive index and reflectivity of BexZn1-xO ternary mixed crystal are decreases with increasing Be concentrations, the blue shift of absorption spectrum of the system becomes more significant. Obtained smooth varying of the optical properties is related to the gradual decreasing of the lattice parameter of BexZn1-xO and increasing of the bandgap.

Structurally Precise Dichalcogenolate-Protected Copper and Silver Superatomic Nanoclusters and Their Alloys.

The chalcogenolato silver and copper superatoms are currently a topic of cutting edge research besides the extensively studied Au n(SR) m clusters. Crystal structure analysis is an indispensable tool to gain deep insights into the anatomy of these sub-nanometer clusters. The metal framework and spatial arrangement of the chalcogenolates around the metal core assist in unravelling the structure-property relationships and fundamental mechanisms involved in their fabrication. In this Account, we discuss our contribution toward the development of dichalcogenolato Ag and Cu cluster chemistry covering their fabrication and precise molecular structures. Briefly introducing the significance of the single crystal structures of the atomically precise clusters, the novel dichalcogenolated two-electron superatomic copper and its alloy systems are presented first. The [Cu13{S2CNR}6{C≡CR'}4]+ is so far the first unique copper cluster having Cu13 centered cuboctahedra, which is a miniature of bulk fcc structure. The galvanic exchange of the central Cu with Ag or Au results in a similar anatomy of formed bimetallic [Au/Ag@Cu12(S2CN nBu2)6(C≡CPh)4][CuCl2] species. This is unique in the sense that other contemporary M13 cores in group 11 superatomic chemistry are compact icosahedra. The central doping of Ag or Au significantly affects the physiochemical properties of the bimetallic Cu-rich clusters. It is manifested in the dramatic quantum yield enhancement of the doped species [Au@Cu12(S2CN nBu2)6(C≡CPh)4]+ with a value of 0.59 at 77 K in 2-MeTHF. In the second part, the novel eight-electron dithiophosphate- and diselenophosphate-protected silver systems are presented. A completely different type of architecture was revealed for the first time from the successful structural determination of [Ag21{S2P(O iPr)2}12]+, [Ag20{S2P(O iPr)2}12] and [Au@Ag19{S2P(OPr)2}12]. They exhibit a nonhollow M13 (Ag or AuAg12) icosahedron, capped by 8 and 7 Ag atoms in the former and latter two species, respectively. The overall metal core units are protected by 12 dithiophosphate ligands and the metal-ligand interface structure was found to be quite different from that of Au n(SR) m. Notably, the [Ag20{S2P(O iPr)}12] cluster provides the first structural evidence of a silver superatom with a chiral metallic core. This chirality arises through the simple removal of one of capping Ag+ cations of [Ag21{S2P(O iPr)2}12]+ present on its C3 axis. Further, the effects of the ligand exchange on the structures of [Ag20{Se2P(O iPr)2}12], [Ag21{Se2P(OEt)2}12]+, and [AuAg20{Se2P(OEt)2}12]+ are studied extensively. The structure of the former species is similar to its dithiophosphate counterpart ( C3 symmetry). The latter two ( T symmetry) differ in the arrangement of 8 capping Ag atoms, as they form a cube engraving the Ag13 (AuAg12) icosahedron. The blue shifts in absorption spectra and photoluminescence further indicate the strong influence of the central Au atom in the doped clusters. Finally, the first paradigm of unusual heteroatom doping induced size-structure transformations is discussed by presenting the case of formation of [Au3Ag18{Se2P(O iPr)2}12]+ upon Au doping into [Ag20{Se2P(O iPr)2}12]0. Finally, before concluding this Account, we discuss the possibility of many unique structural isomers with different physical properties for the aforementioned Ag superatoms which need to be explored extensively in the future.

How to stabilize the HOMO levels and to improve the charge transport properties of hole-transporting materials? Probing the effects of molecular symmetry

Abstract Considering the effects of molecular symmetries, a series of novel organic small molecule hole-transporting materials are simulated by using density functional theory (DFT) and Marcus theory of electron transfer. As a fundamental understanding, the energy level alignments and the charge transport properties are explored for their potential applications. Our results show that, compared with the dissymmetric cases, the symmetric molecules exhibit obvious advantages with more deep energy levels, more delocalized frontier molecular orbitals, and more blue-shifted absorption spectra. By adding oxygen-bridge and sulfur-bridge in the core unit of spiro-OMeTAD, the highest occupied molecular orbital (HOMO) levels of new designed molecules are obviously down-shifted from −5.08 eV to −5.20 eV, whereas the linked nitrogen-bridge makes the HOMOs up-shifted due to its strong electron-donating capacity. Meanwhile, our results also indicate that the delocalized frontier molecular orbitals in symmetric cases can effectively enhance the electronic coupling between adjacent molecules, and coupled with the lower reorganization energies, the high hole mobilities are obtained. In addition, inserting linked atoms in core unit or changing molecular symmetry only have slightly influences on the aspects of electron-hole dissociation, solubility and stability. Through systemic investigations, several promising candidates are proposed toward more efficient PSCs, and we hope that our work could provide some clues for the experimentalists to design and synthesize new small molecule materials.

Effects of the Substituents of Boron Atoms on Conjugated Polymers Containing B←N Units.

Organoboron chemistry is a new tool to tune the electronic structures and properties of conjugated polymers, which are important for applications in organic optoelectronic devices. To investigate the effects of substituents of boron atoms on conjugated polymers, we synthesized three conjugated polymers based on double B←N-bridged bipyridine (BNBP) with various substituents on the boron atoms. By changing the substituents from four phenyl groups and two phenyl groups/two fluorine atoms to four fluorine atoms, the BNBP-based polymers show blue-shifted absorption spectra, decreased LUMO/HOMO energy levels, and enhanced electron affinities, as well as increased electron mobilities. Moreover, these BNBP-based polymers can be used as electron acceptors for all-polymer solar cells. These results demonstrate that substituents of boron atoms can effectively modulate the electronic properties and applications of conjugated polymers.

Understanding the structure, reactivity and absorption spectra of borazine doped pillar[5]arene: A DFT study

Pillar[5]arene and its derivatives act as useful complexing agents and find utility in various fields of chemistry. Effects of doping of borazine unit in pillar[5]arene with respect to its geometry, reactivity and spectroscopic properties are discussed in the light of density functional theory and density functional reactivity theory. Reactivity parameters namely energy of the HOMO, global hardness and chemical potential are used to explain the reactivity of the undoped and doped pillar[5]arene. Aromaticity of the chosen molecule is determined by Nucleus Independent Chemical Shift (NICS) calculations. Absorption spectra of the chosen molecules are analyzed using time dependent density functional theory. Results suggest enhanced stability of pillar[5]arene system upon doping with of borazine unit. Blue shifts in absorption spectra of pillar[5]arene systems upon such doping are also evident which is remarkable from the viewpoint of its opto-electronic utility.

Synthesis of Polythiophene Derivatives with Oligoisobutylene Side Chains

In recent years, organic electronics including organic light emitting diode, organic photovoltaic cell and organic thin film transistor have received much attention due to their severals advantages based on organic materials, such as mechanical flexibility and solution-based low-cost processability. π-Conjugated polymers are known as mechanically soft and flexible material in organic semiconductors. However, their durability for stretched stress is not enough for practical application. Therefore, the molecular design is required for enabling stretchable organic semiconductor. The low strethcability of π-conjugated polymer is due to high crystallinity which induced their stiff main chain and strong intermolecular interactions. Here, we developed novel polythiophene derivatives, P3IBTs, which contain oligoisobutylene units in their side chains. We expect that several branched points on side chains weaken π-π stacking interaction and decrease crystallinity of the polymers. In addition, we tried to develop cross-linked P3IBT to realize the formation of an inherently stretchable π-conjugated polymer. We prepared the monomer of polythiophene derivatives with diisobutylene and triisobutylene side chains according to Scheme 1. The oligoisobutylene unit was synthesized based on a carbocationic addition reaction. Finally, polythiophene derivatives with diisobutylene sidechain (P3IB2T) (M n = 12,000, M w/M n = 1.17) and triisobutylene side chain (P3IB3T) (M n = 13,000, M w/M n = 1.21) could be synthesized by Kumada catalyst-transfer polycondensation. P3IB2T is dark red solid and P3IB3T is dark red chewing-gum like solid at room temperature. Subsequently, we characterized their thermal, optical properties and crystalline nature compared with poly(3-hexylthiophene)(P3HT) (M n = 10,000, M w/M n = 1.17). The thermal properties of the polymers were investigated by differential scanning calorimetry (DSC). The melting temperature of P3IB2T (T m = 130 ˚C) is lower than P3HT (T m = 242 ˚C). On the other hand, there are neigher endothermic nor exothermic peaks in the DSC curve of P3IB3T. Therefore, this polymer would be more amorphous-like than P3IB2T. These result suggests that oligoisobutylene side chains decrease crystallinity of polymers. The absorption spectrum of P3IB2T film showed lower absorption intensity around 620 nm than the P3HT film, indicating weaker π-π stacking interaction. Moreover, P3IB3T films showed the blue-shifted absorption spectrum compared to P3HT and P3IB2T ones probably due to larger torsion of main chains affected by triisobutylene side chain. Next, the crystalline nature was evaluated by Grazing incidence wide-angle x-ray scattering (GIWAXS). P3IB2T and P3IB3T films showed edge-on orientation similar to the P3HT ones, judged from the azimuth plots of (200) diffraction patterns. Moreover, (010) diffraction patterns were not observed for P3IB2T and P3IB3T films, probably due to less π-π stacking interaction by oligoisobutylene side chains. Finally, we cross-linked P3IB3T to realize the formation of an inherently stretchable p-conjugated polymer. 4,4’-Methylenebis(2,6-bis(methoxymethyl)phenol) and isopropyl p-toluenesulfonate were used as cross-linker and thermal acid generator, respectively. The cross-linking reaction was proceeded by heating at 200 ˚C for 3 h. The mechanical properties of the cross-linked P3IB3T was investigated by the tensile test using a TMA instrument. As a result, P3IB3T showed much lower tensile strength (0.68 MPa) and higher elongation at break (141%) than P3HT (984 MPa, 59 %). In conclusion, we have synthesized polythiophene derivatives with oligoisobutylene side chains. These polymer showed lower crystallinity and weaker π-π stacking interaction than P3HT. These properties might be caused by the effect of several branch points on oligoisobutylene side chains. In addition, the cross-linked P3IB3T film could be formed, possessing good mechanical durability. Figure 1

RETRACTED: Microwave-assisted synthesis and characterization of WOx nanostructures for gas sensor application

Abstract Tungsten oxide (WO x ) nanoparticles were synthesized by a facile and eco-friendly microwave-assisted hydrothermal method without need for using any surfactant. A thorough investigation was performed in order to elucidate the effects of microwave irradiation time (10, 20 and 30 min) on the structural, morphological and optical properties of the as-prepared WO x . Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) of the samples revealed the presence of irregular nanosized particles containing some well-structured rod shape particles. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that these nanoparticles are crystallines with mean crystalline size of about 16 nm exhibiting both monoclinic and orthorhombic WO x crystal structures. The optical properties were investigated by using ultraviolet visible spectroscopy (UV-VIS) and photoluminescence (PL). A blue-shifted optical absorption spectrum with an enhanced defects emission was observed when it was compared to bulk spectrum of WO 3 . Thermal-aged WO x nanoparticles at mild temperature (350 °C) were also used to fabricate conductometric gas sensors Gas sensing tests showed excellent performance towards ethanol monitoring for each synthesized material. In particular, the highest sensitivity was obtained for the sensor based on WO x synthesized by 10 min irradiation time (S10). At the optimal operating temperature of 300 °C, the S10 sensor showed a response R a /R g = 8.5 towards 100 ppm ethanol with fast response time of 10 s, in addition to an excellent selectivity against common interfering gases.

A new carbazole-benzothiazole based chemodosimeter for chromogenic and fluorogenic detection of CN–

A hybrid carbazole-benzothiazole based chemodosimeter (CB) has been synthesized for the colorimetric and fluorogenic detection of cyanide ion (CN–). Intra-molecular charge transfer (ICT) played important role for the detection of CN– in DMSO-water (4/1, v/v, pH=7.2) solution. Upon treatment of CN– to the probe solution, results bleaching of the original yellow color of the probe with a large blue shift in absorption spectra. A large enhancement of the fluorescence intensity with a slight red shift is observed after addition of CN– to the probe (CB). Here, the nucleophilic addition of CN– inhibits the intra-molecular charge transfers (ICT) process responsible for the large enhancement of emission. The chemical reaction involved behind the sensing of CN– has been confirmed through 1H NMR and mass spectroscopic studies. The density function theory (DFT) and time-dependent density function theory (TDDFT) has also been conducted to support the experimental findings.