UV Vis NIR Spectroscopy Research Articles

Controllable Synthesis of Sc3N@C78 Microspindles with Excellent Electrophotonic Properties

Single-crystalline structures of fullerenes have attracted tremendous interest due to their promising physiochemical properties. However, research on the morphology and performance of endohedral metallofullerenes is still rare, due to the limited amount of samples. Herein, Sc3N@C78 microspindles are obtained for the first time by regulating the volume ratio of toluene to isopropyl alcohol (IPA) and the concentration of Sc3N@C78 solution as well. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) studies indicate that the crystalline structure of Sc3N@C78 microspindles belongs to the hexagonal system. UV–vis–NIR spectroscopy reveals that absorption of Sc3N@C78 microspindles is stronger than that of the Sc3N@C78 solution in the ultraviolet and visible regions, suggesting strong intermolecular π–π interactions. In addition, Sc3N@C78 microspindles exhibit excellent photoconductivity, as evidenced by the photoelectrochemical measurements. Our results provide new insight into the exploration of novel structures of metallofullerenes for optoelectronic applications.

Inclusion of an anionic dye in the molecular structure of potassium dihydrogen phosphate crystal for SSDL applications

Single crystals of pure potassium dihydrogen phosphate (KDP) and Reactive Orange 16 or Remazol Brilliant Orange dye-doped (0.1, 0.2 and 0.3 mol%) KDP single crystals were grown by slow evaporation method with the vision to improve the properties of pure KDP crystal. Enhanced dielectric, optical, thermal and NLO properties have been achieved by dye doping. The crystallinity and phase purity of the grown crystals were analysed by PXRD. The identification of various functional groups and dye incorporation in the grown crystals was confirmed qualitatively by FTIR analysis. The linear optical study on pure and dye-doped crystals was carried out using UV–Vis–NIR spectroscopy. The optical band gap, extinction coefficient, refractive index and optical conductivity were calculated using the transmittance spectra for all the samples. The thermal stability and the decomposition temperature were found to increase with the concentration of the dopant. This indicates the high quality of the crystal as well as its perfection. The SHG efficiency measurements were taken for the grown crystals and found that the SHG efficiency increases with doping concentration. The enhanced optical constants, thermal stability and second harmonic generation ability confirm the suitability of the grown crystals for solid-state laser materials.

Photo and thermal induced Bi2Se3 formation from Bi/GeSe2 hetero junction layer for topological insulator

In the present paper, we report the evolution of Bi2Se3 topological phase from the Bi diffusion into GeSe2 layer in the Bi/GeSe2 hetero junction film with light and thermal energy. The photo and thermal induced changes in the structural and optical properties of thermally evaporated Bi/GeSe2 bilayer film has been studied by various characterization techniques. The amorphous to crystalline phase transition and the formation of Bi2Se3 topological phase was confirmed from the X-ray diffraction analysis. The deposition as well as diffusion of Bi into GeSe2 layer changed the optical constants like transmitivity, absorption power, optical band gap, Urbach energy, Tauc parameter as studied from UV–Vis–NIR spectroscopy. The transmission power decreased after thermal annealing and laser irradiation where the reverse effect was found in case of absorption coefficient. The optical band gap decreased after diffusion which can be explained on the basis of density of defect states with an increase in disorder. Scanning electron microscopy investigations showed that the surface morphology was influenced by the diffusion phenomena. The Raman analysis also confirms the Bi2Se3 phase evolution with appropriate vibrational peaks. The modifications in optical parameters with thermal and light induced diffusion can be used in various optical applications using such metal/chalcogenides heterojunction layers.

Structural, spectral, thermal and nonlinear optical analysis of 4-fluoro salicylideneaniline crystal

4-fluoro salicylideneaniline (4FSA) (IUPAC Name: 4-Fluoro-2-[(phenylimino)methyl]phenol) crystals were grown by condensation reaction. The lattice constants and crystal system were determined from X-ray diffraction (XRD) analysis. 4FSA crystallizes in monoclinic centrosymmetric space group P21/c. The chemical composition of 4FSA was confirmed by carbon, hydrogen and nitrogen (CHN) elemental study. The vibrational frequencies of the crystal were identified by Infrared and Raman spectra. NMR spectroscopy was employed to ascertain the molecular structure. Thermogravimetric (TG) / Differential scanning calorimetry (DSC) analysis reveals that 4FSA is melting at 75 °C. The region of optical transmission of 4FSA has been studied by UV–Vis–NIR spectroscopy. The nonlinear refractive index (n2), nonlinear absorption coefficient (β) and the third-order nonlinear optical (NLO) susceptibility (χ(3)) were calculated by Z-scan analysis.

Uniform Sb2S3 optical coatings by chemical spray method.

Antimony sulfide (Sb2S3), an environmentally benign material, has been prepared by various deposition methods for use as a solar absorber due to its direct band gap of ≈1.7 eV and high absorption coefficient in the visible light spectrum (1.8 × 105 cm−1 at 450 nm). Rapid, scalable, economically viable and controllable in-air growth of continuous, uniform, polycrystalline Sb2S3 absorber layers has not yet been accomplished. This could be achieved with chemical spray pyrolysis, a robust chemical method for deposition of thin films. We applied a two-stage process to produce continuous Sb2S3 optical coatings with uniform thickness. First, amorphous Sb2S3 layers, likely forming by 3D Volmer–Weber island growth through a molten phase reaction between SbCl3 and SC(NH2)2, were deposited in air on a glass/ITO/TiO2 substrate by ultrasonic spraying of methanolic Sb/S 1:3 molar ratio solution at 200–210 °C. Second, we produced polycrystalline uniform films of Sb2S3 (Eg 1.8 eV) with a post-deposition thermal treatment of amorphous Sb2S3 layers in vacuum at 170 °C, <4 × 10−6 Torr for 5 minutes. The effects of the deposition temperature, the precursor molar ratio and the thermal treatment temperature on the Sb2S3 layers were investigated using Raman spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and UV–vis–NIR spectroscopy. We demonstrated that Sb2S3 optical coatings with controllable structure, morphology and optical properties can be deposited by ultrasonic spray pyrolysis in air by tuning of the deposition temperature, the Sb/S precursor molar ratio in the spray solution, and the post-deposition treatment temperature.

Lightweight SrM/CCTO/rGO nanocomposites for optoelectronics and Ku band microwave absorption

In this research, nanocomposites comprising M-type strontium hexaferrites (SrM) SrFe12−xCsxO19 (x = 0.0, 0.05, 0.10), calcium copper titanate (CCTO) CaCu3Ti4−yAlyO12 (y = 0.0, 0.1, 0.2) and reduced graphene oxide (rGO) have been prepared. XRD patterns shows the presence of single phase nanocrystalline SrM and CCTO which is further supported by Raman spectroscopy and FTIR analysis. The presence of secondary phase such as α-Fe2O3, CaTiO3, and CuO has not been observed. Characteristics absorption bands of Cs-substituted SrM and Al-substituted CCTO were observed at 446, 551 and 605 cm−1, these peaks gives the idea of the formation of SrM and CCTO phase. The D and G bands of GO were observed at 1358 and 1604 cm−1 respectively, while that of the rGO were respectively observed at 1351 and 1595 cm−1. FESEM micrograph show the incorporated SrM nanoparticles, CCTO nanoparticles and rGO sheets, reduction in surface energy and magnetic dipolar interaction prompt the SrM nanoparticles to surround the CCTO nanoparticles and decorate the surface of the rGO sheets. The non-magnetic CCTO phase in the nanocomposites causes the tuning of the magnetic properties. The band gap obtained from UV–vis NIR spectroscopy is within the range of UV-blue LED application. The sample SCR3 shows a maximum reflection loss of − 16.0 dB at 18.0 GHz and matching thickness of 2 mm. The obtained reflection loss is attributed to multiple absorption mechanism as a result of improved impedance matching between the dielectric and magnetic loss absorbents.

Studies on structural and optical properties of pure and transition metals (Ni, Fe and co-doped Ni–Fe) doped tin oxide (SnO2) nanoparticles for anti-microbial activity

In this present work, pure and transition metal ions (Ni, Fe and co-doped Ni–Fe) doped SnO2 nanoparticles (NPs) were synthesized using a simple chemical co-precipitation method. Transition metal ions (Ni, Fe and co-doped Ni–Fe) were doped in order to study the influence of structural and optical properties. The synthesized samples were analyzed by using powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, UV–Visible spectroscopy, FT-IR, and photoluminescence spectroscopic techniques. SnO2 crystallites were found to exhibit tetragonal rutile structure with space group P42/mnm (136) with average particle size in the range of 20–30 nm. Also confirmed that all the doped metal ions were incorporated to SnO2. The UV–Vis-NIR spectroscopy revealed a significant red shift in the absorbing band edge due to increase in the amount of Ni, Fe and co-doped Ni–Fe contents. The SEM image shows the morphology of pure and doped (Fe, Ni and Fe–Ni co-doped) SnO2 NPs with large spherical shapes. In FT-IR spectra, the strong peaks are attributed to the antisymmetric stretching mode of O-Sn-O. The PL spectrum exhibits a strong blue emission peak. The antimicrobial studies were investigated against standard bacterial strains and enhanced anti-bacterial activity in doped and co-doped samples was observed, which can be attributed to the ROS and the particles were in the nanoscale regime.

Synthesis of Au/Si nanocomposite using laser ablation method

Production and characterization of gold/silicon nanocomposites have been investigated experimentally, using laser ablation method. Firstly Si nanoparticles and Au nanoparticles were synthesized by ablation of their bulk in deionized water with the fundamental wavelength of Nd:YAG pulsed laser separately. Then the produced Au nanoparticles and Si nanoparticles suspensions were mixed and irradiated with the second harmonic of the pulsed Nd:YAG laser operating at 532 nm. Effects of the volumetric ratio of Au and Si nanoparticle suspensions in the characteristics of Au/Si nanocomposite have been studied in this research. A variety of analytical techniques such as UV–Vis-NIR spectroscopy, X-ray diffraction, DLS measurement, FTIR spectrum, photoluminescence spectroscopy, and TEM and SEM imaging were applied to characterize the products. Strong plasmonic absorption band of Au nanoparticles around 530 nm made them to be heated and melted by the green laser irradiation to form nanocomposite with Si nanoparticles nearby.

Strontium doping and impregnation onto alumina improve the NOx storage and reduction capacity of LaCoO3 perovskites

Here we report the effects of strontium doping of perovskites (La1-xSrxCoO3) on NOx storage and reduction (NSR) as well as the effects of supporting the perovskite onto an alumina support. The NSR capacity of La0.7Sr0.3CoO3 improved with strontium doping: this material displayed a good balance between NO oxidation capacity and adsorption sites accessibility. Increased accessibility was mainly due to the strontium oxide segregates. In addition, different loadings of La0.7Sr0.3CoO3 perovskite (10, 20, 30, 40 and 50%) were impregnated onto alumina in order to increase the exposed surface area of the perovskite. This had the effect of increasing the NSR capacity of the perovskite. The results of X-Ray diffraction, UV–vis–NIR spectroscopy, N2 adsorption-desorption, electron microscopy, and temperature programmed techniques, demonstrated that the cobalt ions preferably formed cobalt aluminate (CoAl2O4) in the case of low perovskite loadings (<20%). Meanwhile, a well-developed perovskite phase was observed with the higher loadings (>30%). The specific NO oxidation rate per gram of perovskite increased dramatically with the incorporation onto an alumina support. 30% LSCO/Al2O3 sample had an oxidation rate of 138 μmol min-1 (g LSCO)-1 at 350 °C, more than double the rate of the bulk La0.7Sr0.3CoO3 (49 μmol min−1 (g LSCO)−1). Likewise, the 30% LSCO/Al2O3 sample had a higher NOx storage capacity than its bulk counterpart at 400 °C: 306 vs. 115 μmol (g LSCO)−1. The higher oxidation capacity of the alumina-supported samples also facilitated the diffusion of the intermediate compounds from oxidation to adsorption sites. Impregnating alumina with perovskite could be used to improve the efficiency of perovskite mediated NOx removal in automobile applications. Furthermore, adding palladium onto optimum alumina-supported perovskite sample, i.e. 1.5% Pd-30% LSCO/Al2O3, resulted in a clear improvement in NOx storage and reduction capacity. This last sample demonstrated a nitrogen yield as high as 65%, an improvement over the model Pt-based NSR catalyst.

Erbium-doped chalcogenide glass thin film on silicon using femtosecond pulsed laser with different deposition temperatures

The properties of Er3+-doped gallium lanthanum sulphide thin films prepared on a silicon substrate by femtosecond pulsed laser deposition were studied as a function of process temperature. The films were characterised using transition electron microscopy imaging, X-ray diffractometry, Raman spectroscopy, fluorescence spectroscopy, and UV–Vis–NIR spectroscopy. The results show that by increasing the substrate temperature, the deposited layer thickness increases and the crystallinity of the films changes. The room temperature photoluminescence and lifetimes of the 4I13/2→4I15/2 transition of Er3+ are reported in the paper.

CrAlSiN barrier layer to improve the thermal stability of W/CrAlSiNx/CrAlSiOyNx/SiAlOx solar thermal absorber

The influence of adding CrAlSiN barrier layer between the back-reflector tungsten (W) and stainless-steel substrate on thermal stability has been investigated. In previous work, after the annealing in vacuum at 600 °C, tungsten diffusion from the back-reflection layer towards the stainless-steel substrate was found. In this study, a barrier layer was added and its influence upon the W diffusion was studied. Several designs of multilayer solar selective absorber for high temperature applications were used to test the thermal and chemical stability and oxidation resistance after vacuum annealing. These samples were characterized by Scanning Electron Microscopy (SEM), Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Fourier-transform Infrared Spectroscopy (FTIR) and UV–VIS–NIR spectroscopy. All absorber tandems show good thermal stability after vacuum annealing at 600 °C and the changes in optical constants solar absorptance (α) and thermal emittance (ε) are negligible. In some cases, small changes in the reflectance curves after the first step of annealing were seen. Some changes were found in the oxide layer, due to the incomplete oxidized Si atoms, as confirmed by FTIR analyses. This cannot justify the increase of NIR reflectance observed in the optical stacks after annealing, which can be due to the phase changes of the back-reflector tungsten layer. All layers of stacks are amorphous, except the tungsten layer, which is polycrystalline and shows a columnar growth. The addition of a CrAlSiNP = 0.11 Pa barrier layer between tungsten and stainless-steel substrate proved to be a good solution to control the diffusion of W atoms towards the substrate, whereas using higher nitrogen partial pressure in the high and the low absorption layers reduce the diffusion of Cr from those layers to surface.

Classification of aflatoxin contaminated single corn kernels by ultraviolet to near infrared spectroscopy

Aflatoxin contamination in corn poses threats to consumer food safety and grower economic stability. Current industrial methods for aflatoxin management in corn focus on the bulk aflatoxin level, which can lead to either acceptance of lots with contaminated corn kernels (consumer food safety risk) or rejection of lots with mostly harmless corn kernels (grower economic loss). This dilemma may be resolved by utilizing spectroscopy to classify single corn kernels. Hence, our research aims to investigate the potential of using a custom-built UltraViolet-Visible-Near InfraRed spectroscopy system (UV–Vis–NIR) to classify single corn kernels by aflatoxin level. Single kernels from cobs inoculated with aflatoxin-producing Aspergillus flavus (240 kernels) and uninoculated cobs (240 kernels) were i) scanned individually for reflectance from 304 nm to 1086 nm by an increment of 0.5 nm; ii) ground; iii) measured for aflatoxin by ELISA. Using the spectra and the aflatoxin concentration, a random forest model was trained on 80% of the kernels to classify single corn kernels above or below 20 ppb of aflatoxin and was tested on the remaining 20% of the kernels. Among 480 kernels, 374 kernels had <20 ppb of aflatoxin and 106 kernels had ≥20 ppb of aflatoxin. The random forest model had a sensitivity of 87.1% and specificity of 97.7% in the training set and a sensitivity of 85.7% and specificity of 97.3% in the test set, which is higher than previous models where kernels were in motion and comparable to models where kernels were stationary. Spectral regions around 390, 540, and 1050 nm are found to be important for classification. This study demonstrated the custom-built UV–Vis–NIR spectroscopy system showed considerable potential in classifying single corn kernels by aflatoxin level while the kernels are in motion.

Study of indium and antimony incorporation into SnS2 single crystals

Pure SnS2, 5% In-doped SnS2, 15% In-doped SnS2, 5% Sb-doped SnS2 and 15% Sb-doped SnS2 single crystals are grown in closed sealed quartz ampoule by direct vapour transport technique. The energy dispersive analysis of X-rays analysis of all the five as-grown single crystals showed them to be stoichiometric. The X-ray diffraction analysis showed that all the crystals are single phase possessing a hexagonal structure with (0 0 1) preferential orientation. The surface morphology of as-grown single crystals studied by scanning electron microscopy and optical microscopy showed crystal growth is by layer growth mechanism supported by screw dislocation. Selected area electron diffraction showed hexagonal spot pattern confirming the single crystalline nature of the crystals. Optical bandgap of the as-grown crystals determined by UV–Vis-NIR spectroscopy showed that the single crystals possess direct optical bandgap and the value varied between 1.89 and 2.31 eV. The photoluminescence spectra study showed the presence of six peaks. The Raman spectra showed SnS2 type the A1g vibrational mode and shifting in A1g vibrational mode with In and Sb doping. The results are elaborated in details.

Solid-State Preparation, Structural Characterization, Physical Properties, and Theoretical Studies of a Series of Novel Rare-Earth Metal Chalcogenides with Unprecedented Closed-Cavities

Multinary rare-earth metal chalcogenides have aroused great concern owing to their special structure characteristics and diverse physical functions. In this work, five novel rare-earth chalcogenides adopt the formula Cs2[RE8InS14] (where RE = Ho–Lu), obtained by the elemental mixture in CsCl flux at 1273 K. They are isotype and belong to orthorhombic Cmca (no. 64) [a = 15.711(7)–15.385(2) A, b = 22.232(2)–21.786(2) A, c = 15.483(5)–15.244(2) A, V = 5408.4(4)–5130.1(7) A3 and Z = 8], exhibiting a dense 3D [RE8InS14] framework consisting of RES6 octahedron and discrete InS4 tetrahedron. The large closed-cavities of Cs4@S26 are far apart and embedded within the network along bc-plane, which was discovered for the first time. The band gaps from 2.45 to 2.72 eV for Cs2[RE8InS14] were deduced from the UV–Vis–NIR spectroscopy based on the Kubelka–Munk function. A magnetic test indicates that the Cs2[RE8InS14] (RE = Ho–Yb) compounds possess paramagnetism above 50 K. In addition, the solid-state preparation, struc...

A Fruitful Usage of a Dialkylthiophene Comonomer for Redox Stable Wide-Gap Cathodically Coloring Electrochromic Polymers

A series of conjugated polymers are prepared via direct heteroarylation polymerization with the goal of yielding wide-gap, yellow and orange switching to transmissive cathodically coloring electrochromic polymers (ECPs). The polymers are based on repeat units of dialkylthiophene (DAT) in alternation with dioxythiophenes (DOTs) with various side chains to induce differing levels of inter-ring strain yielding 3,4-ethylenedioxythiophene (DAT-EDOT), 3,4-propylenedioxythiophene (DAT-ProDOT), 3,4-(1,3-dimethylpropylene)dioxythiophene (DAT-DMP), and 3,4-dimethoxythiophene (DAT-DMOT) structured polymers. Examination of the optoelectronic properties via UV–vis–NIR spectroscopy, differential pulse voltammetry, and spectroelectrochemistry shows that while increasing the inter-ring strain induced by the side chain of the DOT unit leads to an increased oxidation potential ranging from −122 to +288 mV relative to Fc/Fc+, this does not decrease the accessibility of the extreme charge states. Through subtle steric intera...

Radical Cations in Versatile High Performance Initiating Systems for Thermal, Redox, and Photopolymerizations

Highly versatile initiating systems for thermal, redox, and photopolymerization processes are proposed. The photopolymerization using the multifunctional amine tris[4-(diethylamino)phenyl]amine (t4epa) and iodonium salt (Iod) as photoinitiating system (PIS) is presented. Methacrylate function conversion up to 84% was reached under LED@850 nm using t4epa/Iod/phosphine PIS when only 60% was possible for the same resin using a commercial camphorquinone/amine/phosphines blue light (470 nm) PIS showing that longer wavelengths can be used with high final performances. Estimation of the balance between photothermal vs photoinduced electron transfer processes to initiate polymerization was performed exhaustively thanks to thermal imaging, Raman confocal microscopy, FTIR, cyclic voltammetry, UV–vis–NIR spectroscopy, ESR, ESR-ST photolysis, DSC, photo-DSC, and molecular modeling. This method can be used in further works interested in photochemical/thermal processes as it allowed to highlight two unusual reactivity ...

Kinetic study of single-walled carbon nanotube synthesis by thermocatalytic decomposition of methane using floating catalyst chemical vapour deposition

Single walled carbon nanotubes (SWCNTs) have been synthesized from thermocatalytic decomposition of methane by using ferrocene as the catalyst at atmospheric pressure. Floating catalyst chemical vapour deposition using a horizontal two zone reactor was employed to investigate the kinetics. The effects of temperature of synthesis (800–1000 °C), partial pressure (2–40 kPa) of reactant gas and catalyst concentration (0.2–4.6 mol m−3) on the rate of formation of SWCNTs have been studied. The rate is proportional to the partial pressure of methane indicating that the surface reaction of methane on the active site is the rate controlling step. The activation energy was found to be 80.16 kJ mol−1. Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, BET, UV–Vis-NIR and thermogravimetry have been used for the characterization of products. UV–Vis-NIR spectroscopy data reveals presence of 78–82% metallic SWCNTs (m-SWCNTs) in the synthesized samples. The BET surface area of purified SWCNTs were found to be 871 m2 g−1 with pore volume of 0.35 cc g−1 and electrical conductivity of 856–746 S cm−1.

Visible-Light-Driven Photocatalytic N-Doped TiO2 for Degradation of Bisphenol A (BPA) and Reactive Black 5 (RB5) Dye

Bisphenol A (BPA) and reactive black 5 (RB5) dye are among the most persistent and non-biodegradable contaminants in water which require an urgent need for the development of effective removal method. The ubiquitous existence of both contaminants could interfere with the human health and aquatic environmental balance. Photocatalytic process as one of advanced oxidation processes (AOPs) has shown high performance for degradation of organic compounds to the harmless materials under sensible condition. Therefore, this study aims to develop a visible-light-driven photocatalyst that can efficiently degrade BPA and RB5 present in household water. N-doped TiO2 were successfully synthesized via simple and direct sol–gel method. The prepared TiO2 nanoparticles were characterized by field emission scanning microscope (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Brunauere Emmette Teller (BET) analysis. The incorporation of nitrogen in TiO2 lattice exhibited excellent optical responses to visible region as revealed by UV–Vis–NIR spectroscopy absorption capability at 400–600 nm. The photocatalytic activity of the N-doped TiO2 nanoparticles was measured by photocatalytic degradation of BPA and RB5 in an aqueous solution under visible-light irradiations. Degradation of BPA and RB5 was 91.3% and 89.1%, respectively after 360 min illumination. The degradation of BPA and RB5 by N-doped TiO2 was increased up to 89.8% and 88.4%, respectively under visible-light irradiation as compared to commercial TiO2 P25. This finding clearly shows that N-doped TiO2 exhibits excellent photocatalytic degradation of BPA and RB5 under visible irradiation, hence have a promising potential in removing various recalcitrant contaminants for water treatment to fulfill the public need to consume clean water.

Pillar[5]arene-Decorated Single-Walled Carbon Nanotubes.

Control of single-walled carbon nanotube dispersion properties is of substantial interest to the scientific community. In this work, we sought to investigate the effect of a macrocycle, pillar[5]arene, on the dispersion properties of a polymer–nanotube complex. Pillar[5]arenes are a class of electron-rich macrocyclic hosts capable of forming inclusion complexes with electron-poor guests, such as alkyl nitriles. A hydroxyl-functionalized pillar[5]arene derivative was coupled to the alkyl bromide side chains of a polyfluorene, which was then used to coat the surface of single-walled carbon nanotubes. Noncovalent functionalization of carbon nanotubes with the macrocycle-containing conjugated polymer significantly enhanced nanotube solubility, resulting in dark and concentrated nanotube dispersions (600 μg mL–1), as evidenced by UV–vis–NIR spectroscopy and thermogravimetric analysis. Differentiation of semiconducting and metallic single-walled carbon nanotube species was analyzed by a combination of UV–vis–NIR, Raman, and fluorescence spectroscopy. Raman spectroscopy confirmed that the concentrated nanotube dispersion produced by the macrocycle-containing polymer was due to well-exfoliated nanotubes, rather than bundle formation. The polymer–nanotube dispersion was investigated using 1H NMR spectroscopy, and it was found that host–guest chemistry between pillar[5]arene and 1,6-dicyanohexane occurred in the presence of the polymer–nanotube complex. Utilizing the host–guest capability of pillar[5]arene, the polymer–nanotube complex was incorporated into a supramolecular organogel.

Effect of Heteroatom and Doping on the Thermoelectric Properties of Poly(3‐alkylchalcogenophenes)

AbstractThis study reports on the thermoelectric properties of poly(3‐alkylchalcogenophene) thin films (500 nm) as a function of heteroatom (sulfur, selenium, tellurium), and how these properties change with dopant (ferric chloride) concentration. UV–vis–NIR spectroscopy shows that polaronic charge carriers are formed upon doping. Poly(3‐alkyltellurophene) (P3RTe) is most easily doped followed by poly(3‐alkylselenophene) (P3RSe) and poly(3‐alkylthiophene) (P3RT), where R = 3,7‐dimethyloctyl chain is the pendant alkyl group. Thermoelectric properties vary as functions of the heteroatom and doping level. At low dopant concentrations (≈1 × 10−3 m), P3RTe shows the highest power factor of 10 µW m−1 K−2, while, at higher dopant concentrations (≈5 × 10−3 m), P3RSe shows the highest power factor of 13 µW m−1 K−2. Most notably, it is found that the measured properties are consistent with Mott's polaron hopping model and not consistent with other transport models. Additionally, temperature‐dependent conductivity measurements show that for a given dopant concentration, the activation energies for electronic transport decrease as the heteroatom is changed from sulfur to selenium to tellurium. Overall, this work presents a systematic study of poly(chalcogenophenes) and indicates the potential of polymers beyond P3HT by tuning the heteroatom and doping level for optimized thermoelectric performance.