Mechanistic investigation, kinetic modeling and analysis parameters of poly(3-hexylthiophene) degradation to fullerenes

Thermal degradation of Poly (3-hexylthiopene) (P3HT) was studied under nitrogen environment. Kinetic parameters of thermal degradation were determined using Vyazovkin model free method and model fitting method. Vyazovkin model free kinetic analysis is carried out to understand the variation of activation energy (E_α) required for degradation of polymer with conversion (α). Various reaction models have been tested for probable reaction mechanism using hybrid genetic algorithm (HGA). Diffusion model and nucleation & growth with n = 2/3 has prominent role in thermal decomposition of P3HT. A plausible degradation route is proposed based on the experimental details acquired from gas chromatography (GC), Raman spectroscopy, FTIR spectroscopy, powder X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Degradation of P3HT starts at around 195 °C with release of lighter units like CS. Further increase in the temperature results in detachment of the hexyl chain from P3HT and the residue obtained at 1050 °C contains fullerenes mixed with amorphous carbon.     

Uniform Ln (Eu, Tb) doped NaLa(WO4)2 nanocrystals: Synthesis, characterization, and optical properties

Uniform shuttle-like Ln³⁺ (Eu³⁺, Tb³⁺) doped NaLa(WO₄)₂ nanocrystals have been solvothermally synthesized, and the size of the nanocrystals could be easily controlled by adjusting the volume ratio of ethylene glycol (EG) to water. Doped with 5 mol% Eu³⁺ and Tb³⁺ ions, the NaLa(WO₄)₂ nanocrystals showed strong red and green emissions with lifetimes of 0.8 and 1.40 ms, respectively. A high quenching concentration of 15 mol% was observed in Eu³⁺-doped NaLa(WO₄)₂ nanocrystals and 35 mol% in Tb³⁺-doped NaLa(WO₄)₂ nanocrystals. The emission intensity measurements of Eu³⁺-doped NaLa(WO₄)₂ with different sizes indicated that the emission intensity of shuttles with length of 300 nm in average was stronger than that of shuttles with length of 900 nm in average, but was weaker than that of needles with length of 4 and 9 μm in average.     

Low temperature synthesis of Mn3O4 polyhedral nanocrystals and magnetic study

Manganese oxide (hausmannite) polyhedral nanocrystals were prepared by a microwave-assisted solution-based method using Mn(CH₃COO)₂ and (CH₂)₆N₄ at 80 °C. The as-prepared Mn₃O₄ nanocrystals were characterized by means of X-ray diffraction, field-emission transmission electron microscopy, field-emission scanning electron microscopy and Raman spectrum. Mn₃O₄ polyhedral nanocrystals prepared by microwave heating at 80 °C for 60 min were of cubic and rhombohedral shapes with the edge lengths in the range of 15-40 nm. Mn₃O₄ nanocrystals grew following the Ostwald ripening mechanism with increasing reaction time. High-resolution transmission electron microscopy and selected area electron diffraction confirm that the as-obtained polyhedral nanocrystals were single-crystalline. The magnetic behavior of Mn₃O₄ nanocrystals was studied. Mn₃O₄ nanocrystals show an obvious ferromagnetic behavior at low temperatures. The magnetic behavior of Mn₃O₄ nanocrystals was sensitive to crystal size. Ferromagnetic onset temperatures (T_c) of samples 1 and 3 are 40.6 and 41.1 K, respectively, lower than that observed for bulk Mn₃O₄ (42 K).     

Ion-exchange synthesis and improved photovoltaic performance of CdS/Ag2S heterostructures for inorganic-organic hybrid solar cells

A facile ultrasound-assisted ion exchange route was developed for the synthesis of CdS/Ag₂S heterojunctions by ion exchange between the nanostructured CdS film and [Ag(NH₃)₂]⁺ under ultrasonication. The CdS/Ag₂S heterojunction film was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis DRS spectroscopy, photoelectrochemical measurements, and the transient photovoltage (TPV) technique. CdSAg₂S heterojunctions exhibit a dense morphology, enhanced visible light absorption and stronger photocurrent response than the pure CdS films. Poly(3-hexylthiophene) (P3HT) was then spin coated into the CdS/Ag₂S framework. Hybrid solar cells constructed with FTO/CdS/Ag₂S/P3HT/Au display relatively higher power conversion efficiency than FTO/CdS/P3HT/Au.     

The preparation and properties of bulk-heterojunction organic solar cells with indole-containing fulleropyrrolidine derivatives as acceptors

Two indole-containing fullerene derivatives, N-hydrogen-2-[3-(N-2-ethylhexylindolyl)][60]fulleropyrrolidine (EHIHC60P), and N-(2-ethylhexylindolyl))-2-[3-(N-2-ethylhexylindolyl)][60]fulleropyrrolidine (DEHIC60P) were synthesized by the typical Prato reaction. The absorption spectra, electrochemical properties of the two compounds were measured. Inverted solar cells were fabricated with the structure of ITO/ZnO/poly(3-hexylthiophene) (P3HT):fullerene derivatives/MoO₃/Ag. The highest power conversion efficiencies (PCEs) of 3.32% and 3.23% were obtained for P3HT/EHIHC60P and P3HT/DEHIC60P based solar cells at the composite ratio of 1:1 after the active layers were annealed at 150 °C under inert atmosphere, with a open-circuit voltage (V_oc) of 0.66 V and 0.74 V, respectively. For comparison, the device based on P3HT/PCBM at the same conditions showed the PCE of 3.28%, with a V_oc of 0.61 V. The influence on the photovoltaic property of the fullerene derivatives, which was induced by some subtle changes in the chemical structure was compared and discussed.     

2,6-Di(4-t-butylphenyl)phenyl-group 13 organometallic compounds

Reaction of MX₃ (M = Al, Ga, In; X = Br, Cl) with RLi (R = 2,6-(4-t-BuC₆H₄)₂C₆H₃) affords RGaCl₂ · OEt₂, 1, RAlBr₂ · OEt₂, 2, R₂GaCl, 3, and R₃In, 4. These sterically demanding compounds have been characterized by elemental analyses, ¹H NMR spectroscopy, and single crystal X-ray diffraction. The geometry about the metal centers in 1 and 2 is best described as distorted tetrahedral while the coordination about the gallium atom in 3 is distorted trigonal planar. Compound 4, with the indium atom in a trigonal planar environment, is noteworthy as the first example of a tris(m-terphenyl)group 13 metal compound. The propeller arrangement of the three ligands in compound 4 serves to virtually encapsulate the metallic center.     

退火处理提高P3HT:PCBM聚合物太阳能电池光伏性能

利用旋转涂膜方法制备了以P3HT:PCBM为有源层的聚合物太阳能电池, 器件结构为ITO/PEDOT:PSS/P3HT:PCBM/Al(氧化铟锡导电玻璃/聚二氧乙基噻吩:聚对苯乙烯磺酸/聚三已基噻酚:富勒烯衍生物/铝),研究了退火温度对聚合物太阳能电池性能的影响. 实验发现: 聚合物薄膜经过120 °C退火10 min处理后, 开路电压(V_oc)达到0.64 V, 短路电流密度(J_sc)为10.25 mA·cm^-2, 填充因子(FF) 38.1%, 光电转换效率(PCE)达到2.00%. 为了讨论其内在机制, 对不同退火条件下聚合物薄膜进行了各种表征. 从紫外-可见吸收光谱中发现, 退火处理使P3HT在可见光范围内吸收加强且吸收峰展宽, 特别是在560和610 nm处的吸收强度明显增大; X射线衍射(XRD)结果表明, 120 °C退火后P3HT在(100)晶面上的衍射强度是未退火薄膜的2.8倍, 有利于光生载流子的输运; 原子力显微镜(AFM)研究结果表明, 退火显著增大了P3HT与PCBM的相分离程度, 提高了激子解离的几率; 傅里叶变换红外(FTIR)光谱验证了退火并没有引起聚合物材料物性的变化.     

Synthesis of indium alkali-earth double borates M3In(BO3)3

Double borates of composition M₃In(BO₃)₃ (M = Ba, Sr) were prepared by solid-phase reactions and studied using X-ray diffraction powder analysis and IR spectroscopy. The compounds were shown to be isostructural and to crystallize in trigonal space group , Z = 6. Unit cell parameters were refined for both phases.     

The crystal structure, vibrational and luminescence properties of the nanocrystalline KEu(WO4)2 and KGd(WO4)2:Eu obtained by the Pechini method

The luminescent nanocrystalline KEu(WO₄)₂ and KGd_0.98Eu_0.02(WO₄)₂ have been prepared by the Pechini method. X-ray diffraction, infrared and Raman spectroscopy as well as optical spectroscopy were used to characterise the obtained materials. The crystal structure of KEu(WO₄)₂ was refined in I2/c space group indicating the isostructurality to KGd(WO₄)₂. The size of the crystalline grains depended on the annealing temperature, increasing with the increase of the temperature. The average size of crystallites of both crystals formed at 540 °C was about 50 nm. Vibrational spectra showed noticeable changes as a function of size due to, among others, phonon confinement effect. Luminescence studies did not reveal significant changes for the nanocrystallites with the lowest grain size in comparison with the bulk material. The differences observed in luminescence spectra in form of slight inhomogeneous broadening of the spectral lines and increase of the hypersensitive I_0-2/I_0-1 ratio point to very low symmetry of Eu³⁺ ions and change of the polarisation of the local vicinities of Eu³⁺. X-ray diffraction, vibrational and optical studies showed that the structure of the synthesised nanocrystalline KEu(WO₄)₂ and KGd(WO₄)₂:Eu is nearly the same as that found for the bulk material. The size-driven phase transitions were established for both compounds.     

Syntheses, X-ray structures and CVD studies of diorganoalkoxogallanes

Structural studies by X-ray crystallography have been carried out for a range of diorganoalkoxogallanes incorporating donor-functionalized ligands. The compounds [Et₂Ga(μ-OR)]₂ (1, R = CH₂CH₂NMe₂; 2, R = CH(CH₃)CH₂NMe₂; 3, C(CH₃)₂CH₂OMe; 4, R = CH(CH₂NMe₂)₂) adopt dimeric structures with a planar Ga₂O₂ ring, and each gallium atom is coordinated in a distorted trigonal bipyramidal geometry. Low pressure chemical vapor deposition (CVD) of 2 and 4 resulted in the formation of oxygen deficient gallium oxide thin films on glass. However, the reaction of Et₃Ga and ROH (R = CH₂CH₂NMe₂, CH(CH₃)CH₂NMe₂, C(CH₃)₂CH₂OMe, CH(CH₂NMe₂)₂) in toluene under aerosol assisted (AA)CVD conditions afforded stoichiometric Ga₂O₃ thin films on glass. This CVD technique offers a rapid, convenient route to Ga₂O₃, which involves the in situ formation of diethylalkoxogallanes, of the type [Et₂Ga(μ-OR)]₂, the structures of which are described in this paper. The gallium oxide films were deposited at 450 °C and analyzed by scanning electron microscopy (SEM), X-ray powder diffraction, wavelength dispersive analysis of X-rays (WDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.     

The reciprocal CuInS2+2CdSe⇔CuInSe2+2CdS system. Part I. The quasi-binary CuInSe2-CdSe system: Phase diagram and crystal structure of solid solutions

The type of interaction in quasi-binary system CuInSe₂ (CIS)-CdSe was investigated using differential thermal and X-ray phase analysis methods. The limits of existence of solid solutions based on low-temperature (α) and high-temperature (γ) CIS modifications and CdSe (β) with chalcopyrite, sphalerite and wurtzite structures, respectively, were established in sub-solidus region at 620 K and 870 K. For certain compositions of solid solutions, the structure was refined using powder X-ray diffraction. A phase diagram of the CIS-CdSe system was constructed. A peritectic process L+β⇔γ takes place in the system at 1260 K.     

Synthesis and characterization of organophosphine/phosphite stabilized silver(I) complexes bearing 2-acetyl-1,3-indandione ligand,crystal structure of [Ph3P·AgC11H7O3]

Six organophosphine/phosphite stabilized silver(I) complexes of 2-acetyl-1,3-indandione (2-AID) of type L_n·AgC₁₁H₇O₃ (L = PPh₃; n = 1, 2a; n = 2, 2b; L = P(OMe)₃; n = 1, 2c; n = 2, 2d; L = P(OEt)₃; n = 1, 2e; n = 2, 2f) have been prepared by reacting of [AgC₁₁H₇O₃], which could be obtained by reacting of 2-AID with AgNO₃, with triphenylphosphine, trimethylphosphite, or triethylphosphite in 1:1–2 M ratio. These complexes were obtained in high yields and characterized by elemental analysis, ¹H, ¹³C{H} NMR, IR spectroscopy, and thermal analysis (TG and DSC), respectively. The molecular structure of 2a has been determined by X-ray single crystal analysis in which the silver atom is in a distorted trigonal geometry.     

Visible and infrared luminescence properties of Er-doped Y2Ti2O7 nanocrystals

Er³⁺-doped Y₂Ti₂O₇ nanocrystals were fabricated by the sol-gel method. While the annealing temperature exceeds 757 °C, amorphous pyrochlore phase Er_xY_2−xTi₂O₇ transfers to well-crystallized nanocrystals, and the average crystal size increases from ∼70 to ∼180 nm under 800-1000 °C/1 h annealing. Er_xY_2−xTi₂O₇ nanocrystals absorbing 980 nm photons can produce the upconversion (526, 547, and 660 nm; ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2, respectively) and Stokes (1528 nm; ⁴I_13/2→⁴I_15/2) photoluminescence (PL). The infrared PL decay curve is single-exponential for Er³⁺ (5 mol%)-doped Y₂Ti₂O₇ nanocrystals but slightly nonexponential for Er³⁺ (10 mol%)-doped Y₂Ti₂O₇ nanocrystals. For 5 and 10 mol% doping concentrations, the mechanism of up-converted green light is the two-photon excited-state absorption. Much stronger intensity of red light relative to green light was observed for the sample with 10 mol% dopant. This phenomenon can be attributed to the reduced distance between Er³⁺-Er³⁺ ions, resulting in the enhancement of the energy-transfer upconversion and cross-relaxation mechanisms.     

Simple and low-temperature synthesis of NiO nanoparticles through solid-state thermal decomposition of the hexa(ammine)Ni(II) nitrate, [Ni(NH3)6](NO3)2, complex

NiO nanoparticles with an average size of about 12 nm were easily prepared via the thermal decomposition of hexa(ammine)Ni(II) nitrate complex, [Ni(NH₃)₆](NO₃)₂, at low temperature of 250 °C. The product was characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV-Vis spectroscopy, BET specific surface area measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and magnetic measurement. The magnetic measurement revealed a small hysteresis loop at room temperature, confirming a superparamagnetic (weak ferromagnetic) nature of the synthesized NiO nanoparticles. Indeed, the NiO nanoparticles prepared by this method could be an appropriate semiconductor material due to the optical band gap of 3.35 eV which shows a red shift in comparison with the previous reports. This method is simple, fast, safe, low-cost and also suitable for industrial production of high purity NiO nanoparticles for applied purposes.     

Morphological and phase evolution of TiO2 nanocrystals prepared from peroxotitanate complex aqueous solution: Influence of acetic acid

Nanosized anatase and rutile TiO₂ having different shape, phase and size have been prepared from aqueous solutions of peroxo titanium complex starting from titanium(IV) isopropoxide (TTIP), acetic acid and hydrogen peroxide (H₂O₂) in water/isopropanol media by a facile sol-gel process. The TiO₂ nanocrystals are characterized by powder X-ray diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, TEM, high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) techniques. The influence of pH and the sequence of addition of reaction contents on the phase and morphology of TiO₂ are studied. The reasons for the observation of only anatase and/or mixture of anatase and rutile are given.     

Syntheses, crystal structures and Raman spectra of Ba(BF4)(PF6), Ba(BF4)(AsF6) and Ba2(BF4)2(AsF6)(H3F4); the first examples of metal salts containing simultaneously tetrahedral BF4 and octahedral AF6 anions

In the system BaF₂/BF₃/PF₅/anhydrous hydrogen fluoride (aHF) a compound Ba(BF₄)(PF₆) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF₄)(PF₆) crystallizes in a hexagonal space group with a=10.2251(4) Å, c=6.1535(4) Å, V=557.17(5) Å³ at 200 K, and Z=3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF₄⁻ and PF₆⁻ anions. In the analogous system with AsF₅ instead of PF₅ the compound Ba(BF₄)(AsF₆) was isolated and characterized. It crystallizes in an orthorhombic Pnma space group with a=10.415(2) Å, b=6.325(3) Å, c=11.8297(17) Å, V=779.3(4) Å³ at 200 K, and Z=4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF₆⁻ and four F atoms from BF₄⁻ anions. When the system BaF₂/BF₃/AsF₅/aHF is made basic with an extra addition of BaF₂, the compound Ba₂(BF₄)₂(AsF₆)(H₃F₄) was obtained. It crystallizes in a hexagonal P6₃/mmc space group with a=6.8709(9) Å, c=17.327(8) Å, V=708.4(4) Å³ at 200 K, and Z=2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF₄⁻, three AsF₆⁻ and three H₃F₄⁻ anions. All F atoms, except the central atom in H₃F₄ moiety, act as μ₂-bridges yielding a complex 3-D structural network.     

Tetraphenylantimony(V) O,O′-dialkyl dithiophosphates [Sb(C6H5)4{S2P(OR)2}] (R = s-C4H9, c-C6H11): Synthesis, structures, and 13C and 31P CP/MAS NMR spectra

Tetraphenylantimony(V) O,O′-di-sec-butyl dithiophosphate (I) and tetraphenylantimony(V) O,O′-dicyclohexyl dithiophosphate (II) [Sb(C₆H₅)₄{S₂P(OR)₂}] (R = sec-C₄H₉ or cyclo-C₆H₁₁) were obtained. Their structures and spectroscopic properties were studied by X-ray diffraction analysis and ¹³C and ³¹P CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in complexes I and II were found to be coordinated in S-monodentate and S,S′-bidentate fashions, respectively (MAS NMR data). According to X-ray diffraction data, the coordination polyhedron of antimony in molecular structure I is a trigonal bipyramid with unusual monodentate coordination of the Dtph group in the axial position.     

Flash microwave synthesis and sintering of nanosized La0.75Sr0.25Cr0.93Ru0.07o3-δ for fuel cell application

Perovskite-oxide nanocrystals of La_0.75Sr_0.25Cr_0.93Ru_0.07O_3-δ with a mean size around 10 nm were prepared by microwave flash synthesis. This reaction was performed in alcoholic solution using metallic salts, sodium ethoxide and microwave autoclave. The obtained powder was characterised after purification by energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), BET adsorption technique, photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM). The results show that integrated perovskite-type phase and uniform particle size were obtained in the microwave treated samples. At last the synthesised powder was directly used in a sintering process. A porous solid, in accordance with the expected applications, was then obtained at low sintering temperature (1000 °C) without use of pore forming agent.     

Synthesis of new nanocrystal-polymer nanocomposite as the electron acceptor in polymer bulk heterojunction solar cells

A hydroxyl-coated CdSe nanocrystal (CdSe-OH) and a CdSe-polymer nanocomposite were synthesized and used as the electron acceptors in polymer solar cells (PSCs). The CdSe-polymer composite was prepared via atom transfer radical polymerization (ATRP) of N-vinylcarbazole on functionalized CdSe quantum dots. Physical properties and photovoltaic characteristics of the CdSe-poly(N-vinylcarbazole) (CdSe-PVK) nanocomposite have been investigated. Thermogravimetric analysis (TGA) results displayed higher thermal stability for CdSe-PVK nanohybrid in comparison with the linear-type PVK polymer. Differential scanning calorimetry (DSC) studies indicated that CdSe-PVK had a lower glass-transition temperature (T_g) in comparison with PVK due to the branch effect of the star-shaped polymer hybrid. Cyclic voltammetric (CV) measurements were performed to obtain HOMO and LUMO values of PVK and CdSe-PVK. TEM and SEM micrographs exhibited CdSe nanoparticles were well coated with PVK polymer. Both CdSe-OH and CdSe-PVK were blended with poly(3-hexylthiophene) (P3HT) and used as the active layer in bulk heterojunction solar cells. Polymer solar cell based on CdSe-PVK as acceptor revealed that the photovoltaic properties can be significantly improved when PVK polymer chains were grafted on surfaces of CdSe nanocrystals. In comparison with the P3HT:CdSe-OH system, PSC based on P3HT:CdSe-PVK showed an improved power conversion efficiency (0.02% vs. 0.001%). Film topography studied by AFM further confirmed the better device performance was due to the enhanced compatibility between P3HT and CdSe-PVK.     

Er17Ru6Te3: A highly condensed metal-rich ternary telluride

Er₁₇Ru₆Te₃ is obtained from high-temperature solid-state reactions in tantalum ampoules. The structure according to single-crystal X-ray diffraction is monoclinic, C2/m (no. 12), Z=4, a=40.185(8) Å, b=3.9969(8) Å, c=16.037(3) Å, β=95.12(3)°, V=2565.5(9) Å³. The condensed structure consists of a complex intermetallic network of intergrown sheets of edge-sharing tetrakaidecahedra (tricapped trigonal prisms, TCTP), and pairs of rectangular-face-sharing bicapped trigonal prisms (BCTP) built of erbium and centered by ruthenium. This array also contains isolated columns of TCTP erbium normal to these sheets that contain tellurium. Basal face sharing of all Er polyhedra along the short b-axis gives rise to the three-dimensional network. Synthesis and the crystal structure of the compound are discussed.