Diffuse Reflectance Spectra Research Articles

2D/1D nested hollow porous ZnIn2S4/g-C3N4 heterojunction based on morphology modulation for photocatalytic CO2 reduction

The two-dimensional (2D) composite one-dimensional (1D) heterojunction structure is one of the main strategies for constructing composite photocatalysts for photocatalytic reduction of carbon dioxide (CO2). However, morphology modulation for 2D/1D heterojunction is an important way to enhance performance. In this study, a unique 2D/1D ZnIn2S4/g-C3N4 nested hollow porous heterojunction structure was constructed by an in-situ growth method with spatial confinement effect. The synergy between 1D g-C3N4 and 2D ZnIn2S4, achieved through advanced morphology modulation at an optimal ratio of 3:1, results in the formation of the CZ-3 photocatalyst. This unique configuration enables a simultaneous high yield of carbon monoxide (CO) and methane (CH4), achieving 79.96 μmol/g and 17.33 μmol/g respectively, under visible light irradiation without the need for sacrificial agents. The core of this enhanced photocatalytic performance is attributed to the employment of a type-II heterojunction mechanism, which optimizes the transfer of photogenerated carriers. Ultraviolet-visible diffuse reflection spectrum, photoluminescence spectrum and photoelectrochemical analysis reveal the effect of morphology on photocatalytic performance in terms of visible light absorption, photogenerated carrier pairs separation and electronic band structure of heterojunction. By combining the advantages of 2D/1D structural benefits with the efficient charge dynamics of a type-II heterojunction, this work provides new ideas for improving the morphology of composite heterojunction photocatalysts with 2D/1D structure to enhance the photocatalytic CO2 reduction performance.

Internal quality evaluation of ‘Fuji’ apples during storage based on bulk optical properties or diffuse reflection and transmission spectra

The purpose of this study is to compare the performance of prediction models based either on the bulk optical properties (BOP) or with models based on the diffuse reflection and transmission spectra to assess the soluble solids content (SSC) or fruit firmness (FF) of ‘Fuji’ apples. Diffuse reflection and transmission spectra of 240 apples in 500-1000 nm were acquired using a self-constructed single integrating sphere system, from which the absorption coefficient (μa) and reduced scattering coefficient (μ's) were determined. The relationships of μa, μ's, and the reflection and transmission spectra with the SSC and FF were analyzed, and detection models were established using partial least squares regression coupled with characteristic wavelength selection. Results showed that neither the SSC nor the FF changed obviously during 80-days storage, and the μa and μ's showed no monotonic increase or decrease pattern. The SSC prediction model based on μa spectra combined with the baseline correction method performed the best (R2p=0.79, RMSEP=0.62), while the model based on μ's spectra was the best for FF (R2p=0.67, RMSEP=0.35 N). Overall, the accuracy of the model based on BOP in predicting internal quality was better than that based on reflection and transmission spectra from the same measurement.

Structural, Optical, and Magnetic Properties of Mn Doped Zn3P2 Diluted Magnetic Semiconductor Nanoparticles

Mn-doped Zn3P2-diluted magnetic semiconducting nanoparticles (Zn0.98Mn0.02P2, Zn0.96Mn0.04P2, Zn0.94Mn0.06P2, and Zn0.92Mn0.08P2) were synthesized by a conventional solid-state reaction followed by a subsequent vacuum annealing process. The formation of a tetragonal structure of pure and Mn-doped Zn3P2 was confirmed by X-ray diffraction studies, with no evidence of any further phases. Lattice parameters dicrease from a = b = 8.133 Å, c = 11.459 Å to a = b = 8.041 Å, c = 11.410 Å with increasing dopant concentration. Scanning electron microscpy analysis indicated that all samples that underwent doping exhibited agglomeration in the scanned range of 500 nm. Energy-dispersive X-ray analysis confirmed the presence of Zn, P, and Mn in the samples, and all of the synthesized samples achieved a nearly atomic ratio. In the diffused reflectance spectra, the optical band gap increases from 1.398 to 1.418 eV with increasing dopant concentration. PL has provided evidence indicating that the emission intensity of all doped samples remains constant with increasing dopant content from x = 0.02 to 0.08, with different excitation wavelengths (215 and 290 nm). Vibrating sample magnetometer tests confirmed the presence of ferromagnetic behavior at room temperature, and a positive correlation between saturation magnetization and Mn content, with the magnetic moment increasing from 0.0640 to 0.1181 emu g−1 with an increase in dopant content.

Effect of hetero-valence ions on structural and electrical properties of La2Ni(Mn0.5Ti0.5)O6 ceramics

The study of powder X-ray diffraction of La2Ni(Mn0.5Ti0.5)O6 (0.5LNMT) confirms a multi-phasic composition. The monoclinic P21/n phase content dominates. Occurrence of minor rhombohedral R3‾c phase and precipitates of MnO2 and La2MnO4 were detected. The morphology was analyzed using a SEM test and ceramics showed a porous structure and variation in the grain size below 4 μm. Dielectric permittivity of marked magnitude varies from ∼30 to ∼100 000 when temperature increases. Dielectric loss coefficient frequency dependence exhibits well-defined dielectric relaxation peaks, which were found to obey the Arrhenius law with the activation energy of 0.29 eV, below the presumed phase transition. Two sets of relaxation peaks in the imaginary part of electric modulus spectra relate to relaxations of different activation energies of 0.28 eV and 0.38 eV. An optical gap magnitude of 0.8 eV was determined from the diffuse reflectance spectrum in the Vis-NIR range. It compares with the band gap estimated from the X-ray photoelectron spectroscopy test. We also compare the influence of doping ions on the crystal lattice of the surface and the bulk ceramics. Electrical conductivity relaxation processes were attributed to the electron hopping mechanism between multi-valence Mnk+ and Nin+ ions’ states, which were determined from XPS analysis. The dc resistivity shows thermally generated dependence. Activation energy Edc magnitude varies between 0.27 and 0.37 eV which indicates the occurrence of defects and structural disorder. Such disorder correlates to the variable range hopping of small polarons involved in electrical conductivity. The density of states near Fermi energy was estimated N(EF) = 2.1 × 1025 eV−1 m−3. The 0.5LNMT application prospects were discussed.

Rational sonochemical engineering of Ag2CrO4/g-C3N4 heterojunction for eradicating RhB dye under full broad spectrum

In this novel research, S-scheme Ag2CrO4/g-C3N4 heterojunctions were generated by sonochemical hybridization of different compositions of Ag2CrO4 nanoparticles [EVB=+2.21 eV] and g-C3N4 sheets [ECB=-1.3 eV] for destructing RhB dye under artificial solar radiation. The as-synthesized nanocomposites were subjected to X-ray diffraction [XRD], diffuse reflectance spectrum [DRS], X-ray photoelectron spectroscopy [XPS], N2-adsorption-desorption isotherm, photoluminescence [PL] and high resolution transmission electron microscope [HRTEM] analysis to explore the interfacial interactions between g-C3N4 sheets and Ag2CrO4 nanoparticles. Spherical Ag2CrO4 nanoparticles deposited homogeneously on the wrinkles points of g-C3N4 sheets at nearly equidistant from each other facilitating the uniform absorption of solar radiations. The absorbability of solar radiations was enhanced by introducing 20 wt % Ag2CrO4 on g-C3N4 sheets. The surface area of g-C3N4 sheets was reduced from 37.5 to 16.4 m2/g and PL signal intensity diminished by 80 % implying the successful interfacial interaction between Ag2CrO4 nanoparticles and g-C3N4 sheets. The photocatalytic performance of heterojunctions containing 20% Ag2CrO4 and 80 % g-C3N4 destructed 96 % of RhB dye compared with 60 and 33 % removal on the surface of pristine g-C3N4 sheets and Ag2CrO4, respectively. Benzoquinone and ammonium oxalate are strongly scavenged the dye decomposition revealing the strong influence of valence band holes of Ag2CrO4 and superoxide radicals in destructing RhB dye under solar radiations. S-scheme charge transportation mechanism was suggested rather than type II heterojunction on the light of scavenger trapping experiments results and PL spectrum of terephthalic acid. Overall, this research work illustrated the manipulation of novel S-scheme heterojunction with efficient redox power for destructing various organic pollutants persisted in water resources.

Demystification of luminescence properties and the near imperceptible thermal quenching of Sm3+-doped tungstate phosphors.

Ultra-high thermally stable Ca2MgWO6:xSm3+ (x = 0.5, 0.75, 1, 1.25, and 1.5mol%) double perovskite phosphors were synthesized through solid-state reaction method. Product formation was confirmed by comparing the X-ray diffraction (XRD) patterns of the phosphors with the standard reference file. The structural, morphological, thermal, and optical properties of the prepared phosphor were examined in detail using XRD, Fourier transform infrared spectra, scanning electron microscopy, diffused reflectance spectra, thermogravimetric analysis (TGA), photoluminescence emission, and temperature-dependent PLE (TDPL). It was seen that the phosphor exhibited emission in the reddish region for the near-ultraviolet excitation with moderate Colour Rendering Index values and high colour purity. The optimized phosphor (x = 1.25mol%) was found to possess a direct optical band gap of 3.31 eV. TGA studies showed the astonishing thermal stability of the optimized phosphor. Additionally, near-zero thermal quenching was seen in TDPL due to elevated phonon-assisted radiative transition. Furthermore, the anti-Stokes and Stokes emission peaks were found to be sensitive toward the temperature change and followed a Boltzmann-type distribution. All these marked properties will make the prepared phosphors a suitable candidate for multifield applications and a fascinating material for further development.

Optimization of preparation conditions of Bi-doped TiO2/montmorillonite composites and its photodegradation of Rhodamine B

In order to improve the photocatalytic degradation performance of titanium intercalated montmorillonite composites, the sol-gel method was used to intercalate bismuth/titanium polymerized hydroxyl cations into the interlayer of sodium-based montmorillonite (Na-MMT). The optimum synthesis conditions of Bi-doped TiO2/montmorillonite composite photocatalytic material (Bi/Ti-MMT) were investigated. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and UV–vis diffusion reflectance spectrum (UV-Vis DRS) had been used to study the formation of Bi/Ti-MMT. Under the conditions of Bi/Ti molar ratio of 7 %, montmorillonite suspension mass fraction of 2 %, calcination temperature of 600 ℃ and calcination time of 3 h, the Bi/Ti-MMT had the highest photocatalytic activity, the degradation rate of Rhodamine B (RhB) was 88.16 %. In Bi/Ti-MMT composites, TiO2 existed in anatase phase. Bi3+ replaced Ti4+ and was doped into the TiO2 lattice, which can inhibit the growth of TiO2 crystals and reduce the band gap. The photoresponse range of the composite material was broadened to visible light, which improved the utilization of light.

Construction of Bi2WO6/g-C3N4/Cu foam as 3D Z-scheme photocatalyst for photocatalytic CO2 reduction

Photocatalytic CO2 reduction to hydrocarbon fuels represents a promising solution to CO2 emission challenges. However, photocatalytic CO2 reduction systems face hurdles in practical utilization for the low efficiency of photocatalysts and challenge in catalyst immobilization. Therefore, a novel monolithic three-dimensional Z-scheme photocatalyst was synthesized by fabricating Bi2WO6/g-C3N4 heterojunction on Cu foam substrate (Bi2WO6/g-C3N4/Cu foam) via thermal polymerization and electrophoresis deposition. A series of characterization results, including X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and N2 adsorption–desorption, illustrate the crystalline properties, pore structure, and morphology of the composite photocatalyst. Consequently, Bi2WO6/g-C3N4/Cu foam achieved CO production yield of 33.84 μmol/g cat under visible light illumination for 6 h and retained 96.2 % of initial photocatalytic activity after 30 h of reaction. UV–Vis diffuse reflection spectra, photoluminescence spectra and photoelectrochemical analysis was involved to reveal the mechanism of the photocatalytic activity of composite photocatalyst.The synergistic effect of the Z-scheme mechanism and the hierarchical macroporous structure improves the light absorption, light-induced electron-hole pair separation, and charge transmission. This catalyst construction strategy provides a viable approach for facilitating practical photocatalytic CO2 reduction.

A novel iron metal organic framework-based nanocomposite for the synergistic degradation and adsorption of organic pollutants and Cr (Ⅵ) under visible light

In this work, a novel nitrogenous Fe-TPPE metal-organic-framework (MOF) with excellent visible light catalytic activity was successfully prepared, and a magnetic composite (Fe3O4@Fe-TPPE) with Z-type heterojunction structure was designed to synergistically treat organic pollutants and Cr(Ⅵ). The materials were carefully characterized by powder X-ray diffractometry, scanning electron microscope, Fourier transform infrared analysis, UV–visible diffuse reflectance spectra, X-ray photoelectron spectroscopy, thermogravimetric analysis, etc. The characterizations of photoelectric properties showed that the novel Fe-TPPE MOF exhibited strong response to visible light and Fe3O4@Fe-TPPE had even stronger response. Furthermore, the adsorption and photocatalytic degradation capabilities of Fe-TPPE and Fe3O4@Fe-TPPE, and the versatility as photocatalysts for aqueous pollutants were assessed through removal studies of the model pollutants tetracycline, rhodamine, methyl blue and Cr (VI). Additionally, the removal mechanism of the Fe3O4@Fe-TPPE for the above pollutants was explored. The high removal efficiency, fast magnetic separation, great recycling stability and minimal leak during application all demonstrate the good potential of Fe3O4@Fe-TPPE for practical and sustainable treatment of aqueous pollutants.

Construction of Zn0.5Cd0.5S/Bi4O5Br2 Heterojunction for Enhanced Photocatalytic Degradation of Tetracycline Hydrochloride

The development of efficient catalysts with visible light response for the removal of pollutants in an aqueous environment has been a hotspot in the field of photocatalysis research. A Zn0.5Cd0.5S (ZCS) nanoparticle/Bi4O5Br2 ultra-thin nanosheet heterojunction was constructed by ultrasound-assisted solvothermal method. The morphology, structure, and optoelectronic properties of the composite were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectra. Under simulated visible light illumination, the photocatalytic performance was evaluated through degradation of tetracycline hydrochloride. Results show that the degradation effect by the optimum ZCS/Bi4O5Br2 catalyst is superior to pure materials with the kinetic constant that is 1.7 and 9.6 times higher than those of Bi4O5Br2 and ZCS, and also has better stability and reusability. Trapping experiments and electron paramagnetic resonance tests find that free radicals in the photocatalytic system are superoxide radicals and holes. This work provides a referable idea for the development of more efficient and recyclable photocatalysts.

In-Line Chemical Composition Monitoring for the Injection Molding Process of Biodegradable Polymer Blends Using Simultaneous Measurement of Near-Infrared Diffuse Reflectance and Transmission Spectra.

In the processing of polymer blends and composites, in-line near-infrared (NIR) spectroscopy enables monitoring of the composition and its composite uniformity and contributes to rapid process development and quality control. However, in the injection molding process, the study of the composition of polymer materials has been delayed due to high-pressure conditions. Our research group developed NIR probes for transmission and diffuse reflectance measurements that can withstand high-pressure and temperature conditions up to 130 MPa and 200 °C. In this research, transmission and diffuse reflectance spectra were measured inline during the injection molding process of polymer blends of poly(lactic acid) and polybutylene succinate adipate. The intensity of each polymer band in the second-derivative spectra exhibited a monotonic increase or decrease in response to changes in the blend ratio. Using transmission and diffuse reflectance spectra as explanatory variables of the partial least squares regression model simultaneously, the model showed high estimation accuracy for the entire region of the blend ratio. Finally, this model was applied to monitor the polymer changeover operation, and the change in the blend ratio in the molded product was successfully estimated in line.

Electron Structure of α‐, β‐Te2MoO7 and Photocatalytic Decomposition of Antibiotics

Two modifications of Te2MoO7 oxide have been prepared by different synthetic methods. The crystal structure and composition have been studied by X‐ray diffraction analysis and X‐ray microanalysis. The phase of α‐Te2MoO7 has been synthesized by solid‐state reaction from ammonium salts and characterized by monoclinic structure with P21/c. The β‐Te2MoO7 compound has been formed in hydrothermal conditions and has amorphous nature. The thermal behavior of β‐Te2MoO7 modification is characterized by the phase transition into α‐form, however after melting the amorphous state has restored. The electron structure has been investigated experimentally by X‐ray photoelectron spectroscopy and UV‐vis diffusion reflectance spectra and theoretically by approximation using atomic electronegativity. Despite the same composition, the band gap of β‐Te2MoO7 corresponds to visible light, whereas α‐Te2MoO7 adsorbs light in UV region. The both modifications are able to generate superoxide radicals in vacuum or air and hydroxyl radicals in water under irradiation. The HPLC‐MS analysis has shown the quite deep decomposition of dye and antibiotics by α‐Te2MoO7, whereas amorphous phase almost does not lead to any oxidation.

2D Cadmium(II) Coordination Polymer Based on 2,5-Furandicarboxylate and 1,4-Bis(1H-imidazol-1-yl)butane Linkers: Synthesis, Characterization and DFT Studies

AbstractAs a result of hydrothermal synthesis of 2,5-furandicarboxylate (fdc2−), Cd(II) ion and bis(imidazole) derivative 1,4-bis(1H-imidazole-1-yl)butane (bib) ligand, a novel two-dimensional Cd(II) coordination polymer {[Cd(µ-fdc)(H2O)(µ-bib)]·H2O}n (1) was synthesized. According to the results of single crystal X-ray diffraction analysis, the complex was crystallized in the monoclinic system and in the P21/n space group. In addition, the thermal, luminescence and optical properties of the complex were investigated. The complex emits a maximum at 509 nm and also shows semi-conductor properties according to the solid-state UV–Vis diffuse reflection spectra results. To determine chemical structure, vibrational properties and some chemical properties of complex, theoretical calculations were carried out. All theoretical computations were performed using the DFT method at the B3LYP/LanL2DZ level of theory. The obtained experimental results were in good agreement with theoretical results. To calculate HOMO–LUMO energy values, which provided insights into the material's electronic properties, DFT calculations were used. Detailed information about the local and global chemical activity, as well as the electrophilic and nucleophilic nature of the complex, were also obtained.

Na3K6(CO3)3(NO3)2X·6H2O (X = NO3, Cl, Br): Exploring High-Performance UV Birefringent Crystals Induced by Coplanar π-Conjugated CO3 and NO3 Groups.

Planar π-conjugated groups, like CO3, NO3, and BO3 triangles, are ideal functional units for designing birefringent materials due to their large optical anisotropy and wide band gap. The key point for designing birefringent crystals is to select appropriate functional building blocks (FBBs) and the proper arrangement mode. It is well known that the substitution strategy has proven to be a promising and accessible approach. In this work, alkali metals were chosen to regulate and control two different π-conjugated groups, CO3 and NO3, to build new compounds with large birefringence. Subsequently, three new compounds, Na3K6(CO3)3(NO3)2X·6H2O (X = NO3, Cl, Br), were successfully synthesized using the hydrothermal method. The aliovalent substitution between the [NO3]- anionic group and halogen anions [Cl]-/[Br]- has been achieved in these compounds. Na3K6(CO3)3(NO3)2X·6H2O feature the well-coplanar CO3 and NO3 groups in their crystal structure. This coplanar arrangement mode may effectively enhance the anisotropic polarizability of Na3K6(CO3)3(NO3)2X·6H2O. And their experimental birefringence can reach 0.094-0.131 at 546 nm. Diffuse reflectance spectra demonstrate that these compounds exhibit short ultraviolet (UV) absorption edges of ∼235 nm. Meanwhile, Na3K6(CO3)3(NO3)2X·6H2O also have an easily grown capacity under facile conditions. This work not only reports three new potential UV birefringent crystals but also provides a strategy to make the π-conjugated MO3 group coplanar.

Construction of flexible BiOBr/W18O49/polyacrylonitrile discrete heterojunction nanofibers as a dual-functional photocatalyst for simultaneous hydrogen evolution and organic pollutant degradation

Dual-functional photocatalysis has attracted increasing attention due to its ability to achieve efficient synergistic hydrogen (H2) evolution and pollutant removal. Energy band structure engineering and surface morphology modification of photocatalysts is a useful strategy to improve the activity of photocatalysis. This paper uses a combination of electrospinning technology and hydrothermal method to prepare flexible BiOBr/W18O49/PAN discrete heterojunction flexible nanofibers (NFs) with staggered energy bands and spatially separated redox surfaces. The BiOBr/W18O49 heterojunction can improve carrier separation and migration, as evidenced by the photoluminescence and photoelectrochemical experiments. The localized surface plasmon resonance (LSPR) effect of W18O49 can achieve injection of “hot electrons” and lead to expanding the light absorption range according to the UV–visible-near infrared diffuse reflection spectra results. The discrete structure of BiOBr/W18O49/PAN NFs can provide spatially separated active sites for simultaneous photocatalytic redox reaction. As expected, the BiOBr/W18O49/PAN discrete heterojunction NFs greatly enhance the photocatalytic activity in simultaneous dual-functional reaction for H2 evolution and RhB degradation. The highest simultaneous H2 evolution rate and RhB degradation rate of BiOBr/W18O49/PAN NFs are 31.7 times and 34.1 times of BiOBr/PAN, respectively. The design and construction of this flexible discrete heterojunction NFs structures can provide novel ideas and directions for simultaneous dual-functional photocatalysts.

The subtle usage of NH4BF4: Facile and economical fabrication of Ti black surface for enhanced optical absorption performance

The Ti black surface has been widely used in aerospace and photocatalysis for many years. However, the preparation technique for the Ti black surface has several disadvantages, such as a complex process, high cost and safety concerns. In this study, a new chemical immersion method using the mixed aqueous solution of 0.715 mol/L NH4BF4 and 0.004 mol/L HF was proposed to prepare a uniform Ti black surface, which is very facile, economical and efficient. Due to the etching of HF, the light-trapping nanostructure was formed on Ti surface. Grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS) observations indicated that the black surface was covered by the film mainly composed of TiOx, Ti(OH)x, and TiH2. The diffuse reflectance spectra demonstrated that the black surface exhibited great optical absorption performance with the maximum reflectance of 7.6 % to the UV–visible light and 35.3 % to the near-infrared light. The as-fabricated TiOx film with narrower bandgap could be contributed to the doping of Ti3+ and F− ions. The presence of F− ions in the film prevented the Ti3+ ions in the bulk of TiOx from being oxidized. The combined contribution of light-trapping nanostructure and TiOx film enhanced the optical absorption performance of Ti surface.

Silver Sulfide Anchored Anatase TiO2 Nanoparticles for Ultrafast Degradation of Selective Textile Dyes

AbstractThe surface modification of the TiO2 with selective narrow band gap of metal or metal sulfide is an attractive attention in recent years. Herein, tiny Ag2S nanoparticles are well anchored on the TiO2 surface by a cost‐effective chemical precipitation method for efficient photocatalytic activity. The decoration of Ag2S nanoparticles is clearly identified through electron microscopy studies. The UV‐Vis diffuse reflection spectra (DRS) revealed that TiO2/Ag2S composites absorbed broad spectrum in the visible region. The reduced band‐gap of 2.41 eV by anchored the Ag2S on TiO2 may boosted the photocatalytic activity. Particularly, incorporation of Ag2S nanoparticles increased charge separation efficiency, lowering recombination, and improving photocatalytic performance. Because of their unique structural and optical properties, TiO2/Ag2S composites have increased photocatalytic activity. The photocatalytic performance of the pristine Ag2S and Ag2S anchored TiO2 are Crystal violet (CV) and Methyl orange (MO) dye molecules under same experimental condition. As expected, the TiO2/Ag2S showed highest photocatalytic degradation efficiency than alone TiO2.

Facile encapsulation of a cobalt complex inside the micropores of ZIF-8 through the bottle around the ship method: A novel heterogeneous catalyst for epoxidation of alkenes

A novel and stable heterogeneous catalyst for alkene epoxidation reaction, named as CoDMG@ZIF-8, has been synthesized by facile encapsulation of Co(III) complex i.e. [Co(DMGH)(DMGH2)Cl2] (abbreviated as CoDMG, DMGH2 denotes for dimethylglyoxime and DMGH denotes for dimethylglyoxime mono anion) inside the ZIF-8 micropores via a solvothermal process. Based on the results of fourier transform-infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) technique and field emission scanning electron microscopy (FE-SEM), it was observed that the catalyst has maintained the structure, crystallinity and morphology of the parent ZIF-8 as well. Furthermore, CHN, DRS (diffuse reflectance spectra), energy dispersive X-ray (EDX), induced coupled plasma (ICP-OES), thermal gravimetric (TGA) and nitrogen adsorption-desorption (BET method) analyses have confirmed the encapsulation of the CoDMG complex. The epoxidation reaction was performed using tert‑butyl hydroperoxide (TBHP) in CH3CN solvent in the presence of catalyst. By optimizing the reaction parameters, a total conversion of 96 % with 82 % selectivity towards the epoxide product, was achieved. It was found that both CoDMG complex and ZIF-8 exhibited lower efficiency individually, while the encapsulation of this complex inside the ZIF-8 micropores has resulted to superior activity. Finally, the epoxidation of various alkenes such as cyclohexene, 2-norbornene, α-pinene, styrene and 1-hexene under the optimized reaction condition, have been studied and the catalytic mechanism was also proposed.

Ba5Gd3(BO3)6F: A new alkaline earth-rare earth fluoroborate with magnetocaloric effect

A new alkaline-earth and Gd3+ borate, Ba5Gd3(BO3)6F, has been successfully grown through a high-temperature solution method employing a BaF2-NaF-B2O3 flux. This compound crystallizes in the monoclinic space group P21/c with lattice parameters of a = 13.679(4) Å, b = 8.694(3) Å, c = 7.664(2) Å, β = 99.116(7)°, V = 899.9(5) Å3, and Z = 1. Its three-dimensional structure consists of the [Ba/GdO] polyhedra and [FBa4Gd2] octahedra layers. Magnetic analysis reveals that Ba5Gd3(BO3)6F exhibits a magnetocaloric effect with a maximum −ΔSm of 29.86 J kg–1 K–1 at 3 K and 9 T. Additionally, the thermal stability, along with infrared (IR) and ultraviolet–visible–near-infrared (UV–Vis–NIR) diffuse reflectance spectra, were thoroughly examined. First-principles calculations further explored the electronic band structure and densities of states.

Empirical BRDF model for goniochromatic materials and soft proofing with reflective inks.

The commonly used analytic bidirectional reflectance distribution functions (BRDFs) do not model goniochromatism, that is, angle-dependent material color. The material color is usually defined by a diffuse reflectance spectrum or RGB vector and a specular part based on a spectral complex index of refraction. Extension of the commonly used BRDFs based on wave theory can help model goniochromatism, but this comes at the cost of significant added model complexity. We measured the goniochromatism of structual color pigments used for additive color printing and found that we can fit the observed spectral angular dependence of the bidirectional reflectance using a simple modification of the standard microfacet BRDF model. All we need to describe the goniochromatism is an empirically-based spectral parameter, which we use in our model together with a specular reflectance spectrum instead of the spectral complex index of refraction. We demonstrate the ability of our model to fit the measured reflectance of red, green, and blue commercial structural color pigments. Our BRDF model enables straightforward implementation of a shader for interactive preview of 3D objects with printed spatially and angularly varying texture.