Enhanced visible transmittance and reduced transition temperature for VO2 thin films modulated by index-tunable SiO2 anti-reflection coatings

The low visible transmission is one of the bottleneck problems for the application of vanadium dioxide films since the high refractive index (RI) of VO₂ films results in strong reflection in the visible wavelength. To address this problem, in this paper, high-purity VO₂ films were deposited on fused silica by DC reactive magnetron sputtering at low temperature of 320 °C. Silica sol–gel coatings with tunable refractive index (RI) coated onto VO₂ films have been fabricated to enhance visible transmittance with the potential application in the field of smart windows. SiO₂ coatings with tunable RI (1.16–1.42 at λ = 700 nm) were prepared by sol–gel dip-coating technique. The double structure SiO₂/VO₂ films were characterized through several techniques, including X-ray diffraction, UV-VIS-NIR spectrophotometry and scanning electron microscopy. Compared with the single-layer VO₂ film (ΔT_sol of 6.25% and T_lum of 38.58%), the three kinds of SiO₂/VO₂ bilayer films had higher T_lum (41.93–50.44%) and larger ΔT_sol (8.15–8.51%) simultaneously due to significantly decreased reflectance. Moreover, the crystallization properties of VO₂ films are essentially unchanged by applying a SiO₂ top layer, while the phase transition temperature and thermal hysteresis width of sample S116 are lower than those of pure VO₂ film. The presented RI-tunable SiO₂ coatings, can regulate optical properties continuously for various VO₂ substrates, paving the way for practical applications of VO₂ films in the field of smart windows or others.

Index-tunable anti-reflection SiO₂ coatings prepared on the surface of VO₂ films by sol–gel dip-coating technique to enhance the visible and infrared transmittance of SiO₂/VO₂ films.     

Denaturation of proteins: electrostatic effects vs. hydration

The unfolding transition of proteins in aqueous solution containing various salts or uncharged solutes is a classical subject of biophysics. In many cases, this transition is a well-defined two-stage equilibrium process which can be described by a free energy of transition ΔG_u and a transition temperature T_m. For a long time, it has been known that solutes can change T_m profoundly. Here we present a phenomenological model that describes the change of T_m with the solute concentration c_s in terms of two effects: (i) the change of the number of correlated counterions Δn_ci and (ii) the change of hydration expressed through the parameter Δw and its dependence on temperature expressed through the parameter dΔc_p/dc_s. Proteins always carry charges and Δn_ci describes the uptake or release of counterions during the transition. Likewise, the parameter Δw measures the uptake or release of water during the transition. The transition takes place in a reservoir with a given salt concentration c_s that defines also the activity of water. The parameter Δn_ci is a measure for the gain or loss of free energy because of the release or uptake of ions and is related to purely entropic effects that scale with ln c_s. Δw describes the effect on ΔG_u through the loss or uptake of water molecules and contains enthalpic as well as entropic effects that scale with c_s. It is related to the enthalpy of transition ΔH_u through a Maxwell relation: the dependence of ΔH_u on c_s is proportional to the dependence of Δw on temperature. While ionic effects embodied in Δn_ci are independent of the kind of salt, the hydration effects described through Δw are directly related to Hofmeister effects of the various salt ions. A comparison with literature data underscores the general validity of the model.

A phenomenological approach to the unfolding transition of proteins is given. The model treats quantitatively the effect of electrostatics as well as of hydration (Hofmeister effects).     

Sr9In(VO4)7 as a model ferroelectric in the structural family of β-Ca3(PO4)2-type phosphates and vanadates

Sr₉In(VO₄)₇ was prepared by a solid-state method at 1270 K in air. This vanadate has the β-Ca₃(PO₄)₂-type structure and crystallizes in polar space group R3c. The structural parameters of Sr₉In(VO₄)₇ were refined by the Rietveld method from laboratory powder X-ray diffraction data (XRD): the lattice parameters are a = 11.18016(9) Å and c = 39.6170(3) Å with Z = 6. In³⁺ cations occupy the octahedral M5 site, Sr²⁺ cations occupy the M1, M2, and M3 sites of the β-Ca₃(PO₄)₂-type structure, and the M4 site remains vacant. Sr₉In(VO₄)₇ was characterized by differential thermal analysis (DTA), optical second-harmonic generation (SHG), high-temperature XRD, and dielectric measurements. All these methods prove the existence of a ferroelectric–paraelectric phase transition at T_c = 974 K. This transition is compared with a similar transition in Ca₉In(PO₄)₇ with lower T_c = 902 K. The polar-to-centrosymmetric phase transition in such compounds has a quite unique mechanism of the order–disorder type. The structural transition involves slight shifts of the M1, M2, M3 cations and the E2O₄, E3O₄ tetrahedra, while half of the E1O₄ tetrahedra (E = P or V) statistically reverse their orientation along the three-fold axis, so that the centre of symmetry appears in the structure as a whole. To invert the E1O₄ tetrahedron, one oxygen anion should pass a large neighbouring cation (Sr²⁺ or Ca²⁺) that is only possible when intense rotational vibrations of the tetrahedra are excited at high temperatures. The lower Curie temperature in Ca₉In(PO₄)₇ corresponds to the smaller rotational vibration amplitude of the P1O₄ tetrahedron required to reverse this tetrahedra at T_c in comparison with V1O₄ in Sr₉In(VO₄)₇.

Novel structural mechanism of ferroelectric phase transition was discovered in Sr₉In(VO₄)₇.     

Construction of 1T-MoS2 quantum dots-interspersed (Bi1−xFex)VO4 heterostructures for electron transport and photocatalytic properties

The present study reports trigonal phase molybdenum disulfide quantum dots (MoS₂/QDs)-decorated (Bi_1−xFe_x)VO₄ composite heterostructures. Initially, (Bi_1−xFe_x)VO₄ heterostructure nanophotocatalysts were synthesized through the hydrothermal method decorated with 1T-MoS₂via a sonication process. 1T-MoS₂@(Bi_1−xFe_x)VO₄ heterostructures were characterized in detail for phase purity and crystallinity using XRD and Raman spectroscopy. The Raman mode evaluation indicated monoclinic, mixed monoclinic-tetragonal and tetragonal structure development with increasing Fe concentration. For physiochemical properties, SEM, EDX, XPS, PL, EPR, UV-visible and BET techniques were applied. The optical energy band gaps of 1T-MoS₂@(Bi_1−xFe_x)VO₄ heterostructures were calculated using the Tauc plot method. It shows a blue shift initially within a monoclinic structure then a red shift with an increase of Fe concentration. 1T-MoS₂@(Bi₄₀Fe₆₀)VO₄ with 2 wt% of 1T-MoS₂-QDs carrying a mixed phase exhibited higher photocatalytic activity. The enhanced photocatalytic activity is attributed to the higher electron transportation from (Bi_1−xFe_x)VO₄ surface onto 1T-MoS₂ surface, consequently blocking the fast electron–hole recombination within (Bi_1−xFe_x)VO₄. 1T-MoS₂ co-catalyst interaction with (Bi_1−xFe_x)VO₄ enhanced the light absorption in the visible region. The close contact of small 1T-MoS₂-QDs with (Bi_1−xFe_x)VO₄ develops a high degree of crystallinity, with fewer defects showing mesoporous/nanoporous structures within the heterostructures which allows more active sites. Herein, the mechanism involved in the synthesis of heterostructures and optimum conditions for photocatalytic degradation of crystal violet dye are explored and discussed thoroughly.

The present study reports trigonal phase molybdenum disulfide quantum dots (MoS₂/QDs)-decorated (Bi_1−xFe_x)VO₄ composite heterostructures.     

Temperature effects on the C–H symmetric stretching vibrational frequencies of guest hydrocarbon molecules in 512, 51262 and 51264 cages of sI and sII clathrate hydrates

C–H symmetric stretching vibrational frequencies of CH₄, C₂H₄ and C₂H₆ molecules encapsulated in 5¹², 5¹²6² and 5¹²6⁴ cages of structures I (sI) and II (sII) clathrate hydrates measured by Raman spectroscopy in the temperature range of 93–183 K was analysed. The slopes of the symmetric stretch vibrational frequencies under changing temperatures (Δv/ΔT) for CH₄, C₂H₄ and C₂H₆ molecules encapsulated in sII 5¹²6⁴ cages were smaller than those for molecules in sI 5¹²6² cages, although sI 5¹²6² cages are smaller than sII 5¹²6⁴ cages. We compared the results of Δv/ΔT in this study with the geometrical properties of each host water cage, and these comparisons suggest that the geometry of host water cages affects Δv/ΔT.

Temperature effects on the C–H symmetric stretch of hydrocarbons in various cages of sI and sII clathrate hydrates were observed.     

Renal Function Is Associated With Peak Exercise Capacity in Adolescents With Type 1 Diabetes

OBJECTIVE

Diabetic nephropathy and cardiovascular disease are strongly related in adults with type 1 diabetes, yet little is known about this relationship in adolescents prior to the onset of detectable clinical disease. We hypothesized that cardiopulmonary fitness would be directly associated with albumin-to-creatinine ratio (ACR) and inversely related to estimated glomerular filtration rate (eGFR) in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Sixty-nine adolescents with type 1 diabetes and 13 nondiabetic control subjects of similar pubertal stage and BMI had insulin sensitivity (glucose infusion rate [GIR]), measured by hyperinsulinemic-euglycemic clamp, and lean body mass, measured by DEXA. Cardiopulmonary fitness was measured by cycle ergometry to obtain peak volume of oxygen (VO₂peak), and renal function was measured by eGFR using the Bouvet equation (measuring creatinine and cystatin C levels) and ACR.

RESULTS

Adolescents (15.5 ± 2.2 years of age) with type 1 diabetes (6.3 ± 3.8 years diabetes duration) had reduced VO₂peak (31.5 ± 6.3 vs. 36.2 ± 7.9 mL/kg ⋅ min, P = 0.046) and VO₂peak/lean kg (43.7 ± 7.0 vs. 51.0 ± 8.6 mL/lean kg ⋅ min, P = 0.007) compared with nondiabetic control subjects. eGFR was inversely associated with VO₂peak and VO₂peak/lean kg after adjusting for sex, Tanner stage, GIR, HbA_1c level, systolic blood pressure, and LDL cholesterol level (β ± SE, VO₂peak: −0.19 ± 0.07, P = 0.02; VO₂peak/lean kg: −0.19 ± 0.09, P = 0.048). Moreover, participants in the highest tertile for eGFR had significantly lower sex- and Tanner-adjusted VO₂peak and VO₂peak/lean kg compared with participants in the lowest tertile.

CONCLUSIONS

Adolescents with type 1 diabetes had reduced exercise capacity, which was strongly associated with renal health, independent of insulin sensitivity. Future studies should examine the underlying interrelated pathophysiology in order to identify probable targets for treatment to reduce cardiovascular and renal complications.     

Highly efficient and giant negative electrocaloric effect of a Nb and Sn co-doped lead zirconate titanate antiferroelectric film near room temperature

Adiabatic temperature variation (ΔT), coefficient of performance (COP) and electrocaloric coefficient (ΔT/ΔE) play important roles in evaluating the comprehensive performance of solid-state cooling technology based on the electrocaloric effect (ECE). A Nb and Sn co-doped lead zirconate titanate antiferroelectric film, Pb_0.99Nb_0.02(Zr_0.85Sn_0.13Ti_0.02)O₃ (PNZST), shows a highly efficient and giant negative ECE. The ΔT, |ΔT/ΔE| and COP are about −9.8 K, 0.0488 K cm kV⁻¹ and 35.53 at around 50 °C, respectively. The full width at half maximum of the ΔT peak is about 37 °C. Phenomenological analysis indicates that the highly efficient and giant negative ECE is associated with the first-order transition that has a discontinuous polarization change with increasing temperature.

A giant negative ECE of a PNZST film with a high electrocaloric coefficient and coefficient of performance near room temperature.     

Influence of low Bi contents on phase transformation properties of VO2 studied in a VO2:Bi thin film library

A thin-film materials library in the system V–Bi–O was fabricated by reactive co-sputtering. The composition of Bi relative to V was determined by Rutherford backscattering spectroscopy, ranging from 0.06 to 0.84 at% along the library. The VO₂ phase M1 was detected by X-ray diffraction over the whole library, however a second phase was observed in the microstructure of films with Bi contents > 0.29 at%. The second phase was determined by electron diffraction to be BiVO₄, which suggests that the solubility limit of Bi in VO₂ is only ∼0.29 at%. For Bi contents from 0.08 to 0.29 at%, the phase transformation temperatures of VO₂:Bi increase from 74.7 to 76.4 °C by 8 K per at% Bi. With X-ray photoemission spectroscopy, the oxidation state of Bi was determined to be 3+. The V⁵⁺/V⁴⁺ ratio increases with increasing Bi content from 0.10 to 0.84 at%. The similarly increasing tendency of the V⁵⁺/V⁴⁺ ratio and T_c with Bi content suggests that although the ionic radius of Bi³⁺ is much larger than that of V⁴⁺, the charge doping effect and the resulting V⁵⁺ are more prominent in regulating the phase transformation behavior of Bi-doped VO₂.

A VO₂:Bi thin-film library was fabricated by reactive co-sputtering. The phase transformation temperature of VO₂:Bi increases from 74.7 to 76.4 °C by 8 K/at% Bi in the range of 0.08–0.29 at% suggesting an effect of charge doping from Bi³⁺.     

New wide-stability four-ring azo/ester/Schiff base liquid crystals: synthesis,mesomorphic, photophysical,and DFT approaches

New four-groups-based azo/ester/Schiff base liquid crystals, ((4-substitutedphenylimino)methyl)phenyl 4-[2-(4-alkoxyhenyl)diazenyl]benzoate, In_a–d, were synthesized and analyzed for their mesomorphic stability and optical activity. In these compounds, a terminal alkoxy group of variable chain length from n = 6 to n = 16 carbons is attached to the end of a phenylazo benzoate moiety and the other end of the molecules is connected to a different polar compact substituent X (CH₃O, CH₃, H, and Cl). FT-IR, ¹H NMR, mass spectroscopy and elemental analysis were carried out for molecular structure confirmation of the prepared compounds. The mesomorphic properties were confirmed using a combination of differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The photophysical property was studied by UV-vis spectroscopy. All the prepared homologous series exhibited high thermal stability with a wide-temperature mesomorphic range. The thermal and geometrical parameters of the investigated compounds were estimated by density functional theory (DFT). The results revealed that all the compounds were not completely planar with a relatively high twisting moiety at the CH N part and their twist angles were affected by the electronic nature of the attached X group. Moreover, the calculated quantum chemical parameters as determined by the DFT approach of the investigated compounds were related to the experimentally determined values of the mesophase thermal stability (T_c) and mesophase temperature ranges (ΔT_SmA and ΔT_N) as well as the type of the mesophase.

DSC thermograms of some prepared compounds: (a) recorded from second heating and (b) from cooling at a rate of ±10 °C min⁻¹.     

Synthesis of cyanooxovanadate and cyanosilylation of ketones

The cyanosilylation was performed by using metavanadate catalysts, and in situ measurements revealed the formation of [VO₂(CN)₃]²⁻ and [VO₄TMS₂]⁻ under reaction conditions. The reaction of [VO₂(CN)₃]²⁻, trimethylsilyl cyanide (TMSCN), and water afforded [VO₄TMS₂]⁻ and CN⁻, which reacted with ketones to yield the corresponding cyanohydrin trimethylsilyl ethers over [VO₂(CN)₃]²⁻. Compound [VO₂(CN)₃]²⁻ showed high catalytic performance for cyanosilylation of various carbonyl compounds. In the case of n-hexanal, turnover frequency reached up to 250 s⁻¹.

Two key catalytic vanadium species involved in cyanosilylation of ketones were observed by in situ measurement.     

Theoretical design and characterization of new terpolymer donors based on PTB7Ir for high-efficiency triplet-material-based organic photovoltaics

In the current work, eleven terpolymer donors with different electron-withdrawing groups were designed and investigated based on the reported PTB7Ir to screen outstanding donors for triplet-material-based organic photovoltaics (T-OPVs). Geometry structures, frontier molecular orbital energy levels, energy driving forces (ΔE_L–L), absorption spectra, energy differences between S₁ and T₁ states (ΔE_ST), and driving forces of the triplet charge recombination (−ΔG_CRT) of PTB7Ir and designed 1–11 systems were evaluated by DFT and TD-DFT methods to estimate the light absorption abilities and the charge transfer dynamics. The results show that designed 5, 8, 10 and 11 possess larger spin–orbit couplings (SOC) affinity and smaller ΔE_ST and −ΔG_CRT values, which could effectively suppress the triplet charge recombination process at the donor/acceptor interface. Excitingly, the designed terpolymer 10 presents enhanced light absorption, revealing that it will be a promising donor candidate for high-performance T-OPV devices. Moreover, the results can provide theoretical guidelines to predict new terpolymer donors of T-OPVs.

Compared with PTB7Ir, the designed terpolymer 10 will be a promising donor candidate for high-performance T-OPVs.     

Morphology and mechanical behavior of diamond films fabricated by IH-MPCVD

Morphology of diamond films has been controlled via intermediate frequency induction heated microwave plasma chemical vapor deposition (IH-MPCVD), which was transformed with various substrate temperatures (T_sub = 923–1123 K) and CH₄/H₂ ratios (η_c = 0.5–2 vol%). The coupling effects of T_sub and η_c on the structure of diamond films have been studied. At η_c = 0.5 vol%, the sp³/sp² ratio of diamond films reached 98% at 1073 K, surface roughness (R_ms) increased from 50 to 85 nm with increasing T_sub, the maximum hardness (H_a) reached 84 GPa at 973 K, and the maximum Young''s modulus (E) reached 642 GPa at 1023 K. The residual stress (σ) was calculated as a function of T_sub and η_c. The quality factor (Q), combining microstructure and mechanical behavior, has been creatively defined to evaluate the quality of diamond films.

Morphology of diamond films has been well controlled via intermediate frequency induction heated MPCVD.     

Metabolic Effects of Exercise Training Among Fitness-Nonresponsive Patients With Type 2 Diabetes: The HART-D Study

OBJECTIVETo evaluate the impact of exercise training (ET) on metabolic parameters among participants with type 2 diabetes mellitus (T2DM) who do not improve their cardiorespiratory fitness (CRF) with training.RESULTSA total of 202 participants (mean age 57.1 ± 7.9 years, 63% women) were included. Among the exercise groups (n = 161), there was substantial heterogeneity in ΔVO_2peak; 57% had some improvement in CRF (ΔVO_2peak >0), with only 36.6% having a ≥5% increase in VO_2peak. Both fitness responders and nonresponders (respectively) had significant improvements in hemoglobin A_1c and measures of adiposity (ΔHbA_1c: −0.26% [95% CI −0.5 to −0.01] and −0.26% [−0.45 to −0.08]; Δwaist circumference: −2.6 cm [−3.7 to −1.5] and −1.8 cm [−2.6 to −1.0]; Δbody fat: −1.07% [−1.5 to −0.62] and −0.75% [−1.09 to −0.41]). No significant differences were observed in the degree of change of these metabolic parameters between fitness responders and nonresponders. Control group participants had no significant changes in any of these metabolic parameters.CONCLUSIONSET is associated with significant improvements in metabolic parameters irrespective of improvement in cardiorespiratory fitness.     

Regional contrast agent quantification in a mouse model of myocardial infarction using 3D cardiac T1 mapping

Background

Quantitative relaxation time measurements by cardiovascular magnetic resonance (CMR) are of paramount importance in contrast-enhanced studies of experimental myocardial infarction. First, compared to qualitative measurements based on signal intensity changes, they are less sensitive to specific parameter choices, thereby allowing for better comparison between different studies or during longitudinal studies. Secondly, T₁ measurements may allow for quantification of local contrast agent concentrations. In this study, a recently developed 3D T₁ mapping technique was applied in a mouse model of myocardial infarction to measure differences in myocardial T₁ before and after injection of a liposomal contrast agent. This was then used to assess the concentration of accumulated contrast agent.

Materials and methods

Myocardial ischemia/reperfusion injury was induced in 8 mice by transient ligation of the LAD coronary artery. Baseline quantitative T₁ maps were made at day 1 after surgery, followed by injection of a Gd-based liposomal contrast agent. Five mice served as control group, which followed the same protocol without initial surgery. Twenty-four hours post-injection, a second T₁ measurement was performed. Local ΔR₁ values were compared with regional wall thickening determined by functional cine CMR and correlated to ex vivo Gd concentrations determined by ICP-MS.

Results

Compared to control values, pre-contrast T₁ of infarcted myocardium was slightly elevated, whereas T₁ of remote myocardium did not significantly differ. Twenty-four hours post-contrast injection, high ΔR₁ values were found in regions with low wall thickening values. However, compared to remote tissue (wall thickening > 45%), ΔR₁ was only significantly higher in severe infarcted tissue (wall thickening < 15%). A substantial correlation (r = 0.81) was found between CMR-based ΔR₁ values and Gd concentrations from ex vivo ICP-MS measurements. Furthermore, regression analysis revealed that the effective relaxivity of the liposomal contrast agent was only about half the value determined in vitro.

Conclusions

3D cardiac T₁ mapping by CMR can be used to monitor the accumulation of contrast agents in contrast-enhanced studies of murine myocardial infarction. The contrast agent relaxivity was decreased under in vivo conditions compared to in vitro measurements, which needs consideration when quantifying local contrast agent concentrations.     

Magnetocaloric study,critical behavior and spontaneous magnetization estimation in La0.6Ca0.3Sr0.1MnO3 perovskite

A detailed study of structural, magnetic and magnetocaloric properties of the polycrystalline manganite La_0.6Ca_0.3Sr_0.1MnO₃ is presented. The Rietveld refinement of X-ray diffraction pattern reveals that our sample is indexed in the orthorhombic structure with Pbnm space group. Magnetic measurements display a second order paramagnetic (PM)/ferromagnetic (FM) phase transition at Curie temperature T_c = 304 K. The magnetic entropy change (ΔS_M) is calculated using two different methods: Maxwell relations and Landau theory. An acceptable agreement between both data is noted, indicating the importance of magnetoelastic coupling and electron interaction in magnetocaloric effect (MCE) properties of La_0.6Ca_0.3Sr_0.1MnO₃. The maximum magnetic entropy change (−ΔS^max_M) and the relative cooling power (RCP) are found to be respectively 5.26 J kg⁻¹ K⁻¹ and 262.53 J kg⁻¹ for μ₀H = 5 T, making of this material a promising candidate for magnetic refrigeration application. The magnetic entropy curves are found to follow the universal law, confirming the existence of a second order PM/FM phase transition at T_c which is in excellent agreement with that already deduced from Banerjee criterion. The critical exponents are extracted from the field dependence of the magnetic entropy change. Their values are close to the 3D-Ising class. Scaling laws are obeyed, implying their reliability. The spontaneous magnetization values determined using the magnetic entropy change (ΔS_Mvs. M²) are in good agreement with those obtained from the classical extrapolation of Arrott curves (μ₀H/M vs. M²). The magnetic entropy change can be effectively used in studying the critical behavior and the spontaneous magnetization in manganites system.

A detailed investigation was conducted on the magnetocaloric properties of La_0.6Ca_0.3Sr_0.1MnO₃ and its potential application in cooling fields.     

Organic–inorganic hybrid [NH3(CH2)6NH3]ZnBr4 crystal: structural characterization,phase transitions,thermal properties,and structural dynamics

Organic–inorganic hybrid [NH₃(CH₂)₆NH₃]ZnBr₄ crystals were prepared by slow evaporation; the crystals had a monoclinic structure with space group P2₁/c and lattice constants a = 7.7833 Å, b = 14.5312 Å, c = 13.2396 Å, β = 90.8650°, and Z = 4. They underwent two phase transitions, at 370 K (T_C1) and 430 K (T_C2), as confirmed by powder X-ray diffraction patterns at various temperatures; the crystals were stable up to 600 K. The nuclear magnetic resonance spectra, obtained using the magic-angle spinning method, demonstrated changes in the ¹H and ¹³C chemical shifts were observed near T_C1, indicating changing structural environments around ¹H and ¹³C. The spin–lattice relaxation time, T_1ρ, increased rapidly near T_C1 suggesting very large energy transfer, as indicated by a large thermal displacement around the ¹³C atoms of the cation. However, the environments of ¹H, ¹⁴N, and C1 located close to NH₃ in the [NH₃(CH₂)₆NH₃] cation did not influence it significantly, indicating a minor change in the N–H⋯Br hydrogen bond with the coordination geometry of the ZnBr₄ anion. We believe that the information on the physiochemical properties and thermal stability of [NH₃(CH₂)₆NH₃]ZnBr₄, as discussed in this study, would be key to exploring its application in stable, environment friendly solar cells.

Organic–inorganic hybrid [NH₃(CH₂)₆NH₃]ZnBr₄ crystals were prepared by slow evaporation; the crystals had a monoclinic structure with space group P2₁/c and lattice constants a = 7.7833 Å, b = 14.5312 Å, c = 13.2396 Å, β = 90.8650°, and Z = 4.     

Tetrathiafulvalene: effective organic anodic materials for WO3-based electrochromic devices

Finding a new, effective anodic species is a challenge for achieving simpler low-voltage tungsten trioxide (WO₃)-based electrochromic devices (ECDs). In this work, we utilize tetrathiafulvalene (TTF) and demonstrate its reversible redox behaviors as an electrolyte-soluble anodic species. The concentration of TTF in the electrolyte is varied to optimize device performance. When the TTF concentration is low (0.01 M), a smaller maximum transmittance difference (ΔT_max ∼ 34.2%) and coloration efficiency (η ∼ 59.6 cm² C⁻¹) are measured. Although a better performance of ΔT_max ∼ 93.7% and η ∼ 74.5 cm² C⁻¹ is achieved at 0.05 M TTF, the colored state could no longer return to its original form. We conclude that 0.03 M of TTF is the appropriate concentration for high-performance WO₃ ECDs with high optical contrast and reversible EC behaviors. The irreversible EC transition at high concentrations of TTF is attributed to the agglomeration of TTF molecules.

Tetrathiafulvalene (TTF) is employed as an effective electrolyte-soluble anodic species for achieving low-voltage tungsten trioxide (WO₃)-based electrochromic devices (ECDs).     

An indication of spin-transition accompanied by an order-disorder structural transformation in [Ni(phpyNO)2(NCS)2] (phpyNO = tert-butyl 5-phenyl-2-pyridyl nitroxide)

Reaction of nickel(ii) thiocyanate and tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO) afforded a 2p–3d–2p heterospin triad [Ni(phpyNO)₂(NCS)₂]. The compound crystallizes in the orthorhombic Pbcn space group. The whole molecule is crystallographically independent. The torsion angles around Ni–O–N–C_2py are 26.8(4) and 27.3(4)° at 400 K, indicating appreciable orbital overlaps of the radical π* and nickel(ii) 3d_x²−y²/3d_z² orbitals. In a low-temperature region, the torsion was enhanced, and the space group changed to monoclinic P2₁/c with a doubled asymmetric unit volume. The χ_mT value was practically null below ca. 140 K and, on heating to 400 K, gradually increased and reached 1.30 cm³ K mol⁻¹. A van''t Hoff analysis suggests a spin transition at T_1/2 = 530(20) K. Density functional theory calculation reproduced ground S_total = 0 with singlet-triplet gaps of 910 and 1263 K for the 140 K structure, and the gap was reduced to 297 K at 400 K. Consequently, the present compound can be considered as an incomplete spin-crossover material, as a result of T_1/2 located above the experimental temperature window.

The exchange coupling in [Ni(phpyNO)₂(NCS)₂] is strongly antiferromagnetic in a low-temperature structure whilst moderately antiferromagnetic in a high-temperature structure.     

Facile synthesis of novel calcium silicate hydrated-nylon 6/66 nanocomposites by solution mixing method

In this article a facile and green procedure for the synthesis of novel calcium silicate hydrated-nylon 6/66 nanocomposites is proposed. Calcium silicate hydrate (CSH) was synthesized by a hydrolysis technique assisted by ultrasound and using sodium dodecyl sulphate (SDS) as surfactant. CSH-nylon 6/66 nanocomposites were obtained by a solution mixing method at CSH loadings of 2.5, 25, 50 and 75 weight percent (samples CA, CD, CB and CC, respectively). The synthesis of CSH was confirmed by DRX and ATR-FTIR techniques; the CSH sample presents as mesoporous with a diameter between 3.34 nm and 52.68 nm and an average size of 27.07 nm; the specific surface area of the CSH sample was 343.99 m² g⁻¹. The formation of the CSH-nylon 6/66 nanocomposites was confirmed by ATR-FTIR, SEM, XRD, TGA, DSC and XPS techniques. The crystallization and melting temperatures (T_m and T_c, respectively) of CSH-nylon 6/66 nanocomposites occur at a slightly lower temperatures than those of neat Ny 6/66. These results suggest a slight decrease of the crystallite size and crystallization rate of nylon 6/66. The fusion enthalpy (ΔH_f) decreases with increase in CSH content in nylon 6/66, which can be associated to a good dispersion. The XRD peaks of the nylon 6/66 at 19.99° and 23.77° were displaced at slightly higher values of 2θ with the incorporation of CSH in the polymer forming nanocomposite materials.

In this work it was possible to synthesize novel CSH-nylon 6/66 nanocomposites using a simple and easy methodology such as the solution mixing method and using green solvents like water, formic acid and ethanol.