Small Band Gap Energy Research Articles

The impact of sintering temperature on structural properties, optical and dielectric parameters under photon energy of Ni0.6Cd0.4FeAl0.5Cu0.5O4 for optoelectronic devices

The impact of calcination temperature on the structural and optical properties of Ni0.6Cd0.4FeAl0.5Cu0.5O4 spinel ferrites was investigated in this work. These samples were prepared using sol-gel method and sintered at two different temperatures (950 °C and 850 °C). The X-ray diffraction analysis and Rietveld refinement confirm that the sample were well crystallized in the cubic spinel structure (Fd3¯m space group). With increasing sintering temperature, unit cell parameters and crystallites size show an increasing trend. The values of optical band-gap energy were calculated using absorbance, reflectance, and Tauc's method. These measurements confirm the direct optical transitions for the prepared samples. The direct bandgap energy calculated, respectively for S950 and S850 are EgTau = 2.6 eV, EgTau = 2.41 eV, EgDRS = 2.41 eV and 2.39, EgdrivAbso = 2.45 eV and 2.47 eV and EgdrivRefel = 2.382 eV and 2.377 eV. This shift of Eg value between Tauc method, spectra diffuse reflectance spectroscopy (DRS) is related to the lack of precision of Tauc method. Furthermore, the obtained low Urbach energies confirm the high quality of the prepared samples and imply that the degree of disorder and defects decreases as the sintering temperature rises. The Cauchy parameters were determined from the variation of the refractive index. In the other hand, the dispersion energy parameters were evaluated from the Wemple–Didomenico relation. The variations with wavelength of optical constants such as penetration depth, extinction coefficient, conductivity, and dielectric constants have also investigated. The low dielectric value and the relatively small bandgap energy show that this compound can be proposed as a good candidate for optical and optoelectronic applications.

Evaluation of physicochemical and biocompatibility characteristics of gadolinium oxide nanoparticles as magnetic resonance imaging contrast agents

The attractive properties of gadolinium-based nanoparticles as a positive contrast agent for magnetic resonance imaging (MRI) have piqued the interest of both researchers and clinicians. Nonetheless, due to the biotoxicity of gadolinium (III) ions' free radicals, there is a need to address this issue. Therefore, this research aimed to develop and evaluate of physicochemical and biocompatibility characteristics of gadolinium oxide nanoparticles (Gd2O3-NPs) as MRI contrast agents. Whereby, the Gd2O3-NPs were synthesized via sol-gel method at various annealing temperatures of (500 °C−1100 °C). The results showed that the Gd2O3-NPs annealed at a temperature of 1000 °C exhibited prominent physicochemical properties in comparison to other annealing temperatures such as high saturation magnetization, colloidal stability with a highly positive surface charge, high crystallinity percentage, high weight percentage of gadolinium Gd and small energy band gap of 4 eV. Moreover, during the heating process, the complete decomposition of gadolinium hydroxide (Gd(OH)3) resulted in a significant increase in signal intensity in T1-weighted MRI images. The enhanced signal intensity in MRI is caused by structural changes in tissues or the contrast agent, which affect their interaction with the magnetic field, leading to the increased signal due to molecular conformation, aggregation, and mobility influencing T1 relaxation properties. Furthermore, the biocompatibility of Gd2O3-NPs synthesized at 1000 °C was assessed through MTT assay tests on Hep G2 cells, which demonstrated good biocompatibility without any cytotoxic effects. The sol-gel technique shows promise in synthesizing Gd2O3-NPs with remarkable properties for various applications, including MRI contrast agents, by controlling annealing temperature.

Structure, chemical reactivity, NBO, MEP analysis and thermodynamic parameters of pentamethyl benzene using DFT study

This study explores the structural, molecular and electronic properties of the pentamethyl benzene (PMB) using quantum chemical calculations employing DFT/ B3LYP/6–311++G(d,p) level of theory. Structural parameters, HOMO-LUMO energies, chemical reactivity descriptors and molecular electrostatic potential (MEP) were evaluated from the optimized molecular geometry. The computed small band gap energy, correlated with the UV–visible spectrum, demonstrates that the test molecule has good biological activity. NLO activity of the molecule was also studied by evaluating dipole moment and first order hyperpolarizability values. Intra-molecular charge transfer, donor-acceptor transitions and stabilizations energies were determined from the analyses of natural bond orbital (NBO) and natural population. 1H and 13C chemical shifts were computed from the simulated NMR spectrum following GIAO approach in DMSO‑d6 solvent at the same level of DFT. Furthermore, thermodynamic parameters and rotational constants were also calculated for this molecule.

Designing of dimethylfluorene-based hole transport materials for high-performance organic/perovskite solar cells

In this study, we present the design of five new hole-transporting materials (ZM1, ZM2, ZM3, ZM4, and ZM5) based on dimethylfluorene through end-capped acceptors via thiophene linkers. We aimed to enhance the photovoltaic properties of hole-transporting materials (HTMs) for potential use in high-efficiency perovskite solar cells (PSCs). We employed density functional theory (DFT) based calculations to investigate the electronic and photovoltaic properties of the designed HTMs. Our results demonstrated that designed HTMs possess superior planarity, deeper HOMOs energies, and high solubility with small energy band gap (Eg) compared to the reference (ZR) and Spiro-OMeTAD HTMs, leading hole extraction and efficacious solution processing properties. This effectively drives the transport of holes from the perovskite layer with high open-circuit voltages (1.15 V to 1.25 V). The results of the hole charge transfer integral of the designed HTMs (0.244 eV to 0.346 eV) indicate their improved hole mobility rate for PSCs. Additionally, all designed HTMs exhibited superior anticipated power conversion efficiency (25.87% to 28.33%) with a higher fill factor (0.8948 to 0.9014) compared to the reference molecule (13.22%). Our findings suggested that ZM1-ZM5 molecules are advantageous HTMs for the fabrication of high-performance PSCs, which may have the potential for future commercial use in the solar industry.

Experimental Investigation of Pure Spinel Mn3O4 Properties Synthesized through Chemical Spray Pyrolysis for Future Gas Sensor Application

AbstractThe semiconductor realization is a very significant stage in gas sensor application. Herein, the Mn3O4 semiconductor was deposited using chemical spray pyrolysis. The effect of deposition temperature on structural, vibrational optical and electrical Mn3O4 thin layers properties were investigated through: X‐ray diffraction, Raman spectroscopy, UV‐visible spectrophotometer, and two points electrometers respectively. The X‐ray diffraction showed the appearance of spinel phase of tetragonal Mn3O4 with strong formation direction along (101) plan and without any secondary phase indicating the formation of pure Mn3O4. The Raman spectroscopy confirmed the results obtained in XRD and certified the high‐quality formation of Mn3O4. In addition, the crystallinity improvement (the increase of crystallite size and the decrease of dislocation density) was caused by the increasing of deposition temperature from 350 °C to 450 °C. Optical properties such as transmittance, absorbance and band gap energy were extracted by UV‐Visible spectrophotometer. Thus, low transmittance, high absorbance and small band gap energy were observed at the highest substrate temperature (450 °C). The electrical conductivity showed good values between 4.83 and 13.89 mS.cm−1. These properties make Mn3O4 an appropriate material to be used as a sensitive layer in gas sensors applications.

On the Su–Schrieffer–Heeger model of electron transport: Low‐temperature optical conductivity by the Mellin transform

AbstractWe describe the low‐temperature optical conductivity as a function of frequency for a quantum‐mechanical system of electrons that hop along a polymer chain. To this end, we invoke the Su–Schrieffer–Heeger tight‐binding Hamiltonian for noninteracting spinless electrons on a one‐dimensional (1D) lattice. Our goal is to show via asymptotics how the interband conductivity of this system behaves as the smallest energy bandgap tends to close. Our analytical approach includes: (i) the Kubo‐type formulation for the optical conductivity with a nonzero damping due to microscopic collisions, (ii) reduction of this formulation to a 1D momentum integral over the Brillouin zone, and (iii) evaluation of this integral in terms of elementary functions via the three‐dimensional Mellin transform with respect to key physical parameters and subsequent inversion in a region of the respective complex space. Our approach reveals an intimate connection of the behavior of the conductivity to particular singularities of its Mellin transform. The analytical results are found in good agreement with direct numerical computations.

First-principles calculation of the electronic, optical, and photo-electrochemical properties of CaM2S4 (M = Sc, Y) compounds

The orthorhombic CaM2S4 (M = Sc, Y) structures were investigated in the present work by first-principles calculations. CaM2S4 (M = Sc, Y) compounds are found to be mechanically stable with the anisotropic elastic constants that make them to be stable with respect to uniaxial deformation (Young’s moduli are 73.724 and 57.441 GPa for CaSc2S4 and CaY2S4, respectively) but easy to be undergone to shear deformation (Poisson’s ratios are 0.352 and 0.371 for CaSc2S4 and CaY2S4, respectively). Due to their relatively small direct energy band gaps (1.89 eV for CaSc2S4 and 2.26 eV for CaY2S4), the two compounds are intriguing candidates for long-wave transparency applications. The high hybridization degree of Ca-d, Y/Sc-d and S-p orbitals results in a wide energy range between the valence highest band and the conduction lowest band enabling these compounds to interact actively with visible and ultra-violet waves. The high absorption rate of 12–18 × 105 cm−1 and good hole-electron separation make CaM2S4 (M = Sc, Y) compounds to consider them good candidates for optoelectronic materials. Moreover, CaM2S4 (M = Sc, Y) compounds show good ability in the process of photo-driven photocatalyst water splitting.

Enhanced hydrogen production from cracking of liquid toluene by applying liquid plasma and perovskite catalysts

In this study, a process for producing hydrogen from liquid hydrocarbons by applying plasma is proposed. Toluene was decomposed by discharging a pulse-type plasma into liquid toluene directly. The changes in the rate of hydrogen production and reaction characteristics owing to injecting a perovskite catalyst were also investigated. A high hydrogen production rate of approximately 130 NL/h·g was obtained from the liquid–phase plasma reaction of toluene using the BiFeO3 catalyst. The investigation into the reaction characteristics based on the plasma generation conditions indicated that the reaction was mainly affected by the plasma voltage. When titanium dioxide and perovskite (SrTiO3, BiFeO3) photocatalysts were applied to this reaction, the reaction activities also varied depending on the light-absorption capacity of the catalysts. The highest hydrogen evolution rate was obtained using the BiFeO3 catalyst, which absorbs visible light as well as UV light, compared with the TiO2 photocatalyst, which absorbs only UV light. Because the plasma emission from toluene is predominantly in the visible region, the reaction activity was also determined to be the highest for the BiFeO3 catalyst. The BiFeO3 absorbs visible light up to about 550 nm, and it has a small bandgap energy of about 2.15 eV. This led to high photocatalytic degradation activity in visible light generated by plasma discharge in toluene. The carbon obtained had a particle size of less than 20 nm and purity of approximately 99%.

Synthesis and Characterization of New Tetradentate N2O2-Based Schiff’s Base Cu (II) Complexes for Dye Photodegradation

We have reported tetradentate ligands (salophen) coordinated with N and O atoms that led to the Cu (II) complexes. These Cu (II) complexes (C-1 and C-2) were firstly established by using elemental analysis and confirmed by mass spectra. At the same time, the characterization of C-1 and C-2 complexes is performed by using several spectroscopic methods and morphological analysis. The bandgap values of the C-1 and C-2 complexes are evaluated with UV-vis DRS spectra. The PL spectral data and photocurrent curves clearly indicated the small recombination rate of the hole–electron pair. The synthesized C-1 and C-2 complexes’ photocatalytic properties were examined for the degradation of cationic dyes such as methylene blue (MB λmax.= 654 nm) and methyl violet (MV λmax.= 590 nm) below visible-light action. The C-2 complex is more active than the C-1 complex because of its high photostability, small band-gap energy, and low recombination rate for hole–electron pair separation, and improved visible-light character, which encourages the generation of hydroxyl radical species throughout the photodegradation process. Scavenger probes were used to identify the dynamic species for the photodegradation of dyes, and a mechanism investigation was established.

Designing of phenothiazine-based hole-transport materials with excellent photovoltaic properties for high-efficiency perovskite solar cells (PSCs)

In this study, a series of highly efficient organic hole-transporting materials (HTMs) were designed using Schiff base chemistry by modifying a phenothiazine-based core with triphenylamine through end-capped acceptor engineering via thiophene linkers. The designed HTMs (AZO1-AZO5) exhibited superior planarity and greater attractive forces, making them ideal for accelerated hole mobility. They also showed deeper HOMO energy levels (−5.41 eV to −5.28 eV) and smaller energy band gaps (2.22 eV to 2.72 eV), which improved charge transport behavior, open-circuit current, fill factor, and power conversion efficiency of perovskite solar cells (PSCs). The dipole moments and solvation energies of the HTMs revealed their high solubility, making them suitable for the fabrication of multilayered films. The designed HTMs showed tremendous enhancements in power conversion efficiency (26.19 % to 28.76 %) and open-circuit voltage (1.43 V to 1.56 V), with higher absorption wavelength than the reference molecule (14.43 %). Overall, the Schiff base chemistry-driven design of thiophene-bridged end-capped acceptor HTMs is highly effective in enhancing the optical and electronic properties of perovskite solar cells.

Synthesis and Characterization of αFe2O4/g-C3N4 Materials for Treatment of Congo Red Dye in Water

In recent years, the problem of environmental pollution is becoming extremely serious. Especially, environmental pollution caused by textile dyes not only affects living organisms in the water but also affects human health. There are many methods applied to remove dyes in water; in which, photocatalysis has been proven to be an efficient method. The g-C3N4 is a polymer material with small bandgap energy (about 2,7 eV) as well as chemical and thermal stability in the ambient environment. In this study, the g-C3N4 material was successfully synthesized from urea calcined at 550 0C, and the modified materials αFe2O3/g-C3N4 were also successfully prepared by hydrothermal method. The synthesized materials were characterized by modern analytical techniques, such as SEM-EDX, XRD, UV-Vis, and FT-IR. The experimental results showed that synthesized materials have high efficiency in removing Congo Red dye in water under visible light irradiation. Especially, the 7% αFe2O3/g-C3N4 material had the best efficiency of Congo Red treatment, with an efficiency of up to 93.59% at pH 5 after 150 minutes.

FeSe2/TiO2 heterostructure as an efficient photocatalyst and their electrochemical energy storage applications

This paper reported the facile synthesis of FeSe2 and TiO2 and their different wt.% composites (75 and 50% of TiO2, here after FT-1 and FT-2) via solvothermal in/ex-situ sol-gel method for the first time efficient photocatalytic degradation of Rhodamine removal and supercapacitor applications. Small bandgap energy was obtained for FT-1 samples from the optical analysis, with a more negligible band edge absorption. The result shows that the composite of FeSe2 and TiO2 increases the absorption, which collectively enhances the separation of the charge carriers and redox activities. The photocatalytic activities analysis demonstrated that the FT-1 sample reveals the fastest removal of the RB dye in just 60 min (FT-2, FeSe2, and TiO2 = 90, 100, and 180 min) with good stability (98%) after several cycles. As supercapacitor electrode materials, all electrodes showed well-defined peaks in their CV loops and voltage plateaus in their charge/discharge profile, illustrating the pseudocapacitive charge storage mechanism. No voltage decay was observed during many discharge currents from the charge/discharge investigation, demonstrating the chosen potential frame is a suitable window for the FeSe2 and TiO2 nanomaterials. The higher capacity of 295 (FT-1) than other electrodes (FeSe2, TiO2, and FT-2 = 220, 115, and 240 C/g) at 1 A/g was obtained to reach 180 at 10 A/g, resulting in an enhanced rate capability of 82%. The high rate capability is the cause of its more minor charge transfer resistance, resulting in higher conductivity and supporting rapid charge transport kinetics. These outstanding properties open a new avenue for other FeSe2 and TiO2 nanomaterials for efficient energy storage technologies.

Photocatalytic Removal of Ciprofloxacin in Water by Novel Sandwich-like CuFe2O4 on rGO/Halloysite Material: Insights into Kinetics and Intermediate Reactive Radicals

In this study, the CuFe2O4 on rGO/halloysite material was made in an uncomplicated manner. The catalyst has a sandwich-like shape with a uniform coating of the active phase on the rGO sheets and halloysite tubes. The catalyst’s large specific surface area (130 m2/g) and small band gap energy (1.9 eV) allow it to adsorb photons and photocatalyze organic contaminants effectively. In approximately 1 h of light, the catalyst showed high performance in achieving almost complete conversion in photodegrading CIP for an initial CIP concentration of 20 ppm. A pseudo-first-order rate law was followed by the process, as revealed by the experimental results. In addition, the pH effect and the contribution of intermediate reactive radicals that emerged during the photochemical process were explored. The results indicated that hydroxyl radicals and holes had a major impact on CIP decomposition, suggesting that the addition of these radicals could enhance CIP degradation efficiency at a larger scale. This study also confirmed the superiority of catalysis and photochemical processes in environmental treatments by the neutral pH values.

Hydrothermal fabrication of novel nanocomposites Mx‐MoO3‐α‐NaFe2(MoO4)3‐α‐FeMoO4 (M = Al, Co, Ni, and Er) for highly efficient catalytic synthesis of 5‐aryl‐1H‐tetrazole analogs

Mx‐MoO3‐α‐NaFe2(MoO4)3‐α‐FeMoO4 (M = Al, Co, Ni, and Er) nanomaterials were fabricated by the hydrothermal method in the present study. XRPD, FESEM, TEM, BET‐BJH, UV‐Vis, and VSM analyses were used to characterize and study the physical attributes of the as‐synthesized samples. Rietveld analysis data illustrated that the products were a mixture of α‐NaFe2(MoO4)3, α‐FeMoO4, MoO3, and Fe2O3 crystal phases. UV‐Vis spectra indicated that the obtained samples had a small direct band gap energy amount at about 1.3–1.5 eV. VSM analysis confirmed that the as‐fabricated samples had magnetic properties. However, most ferromagnetic behaviors were observed by doping Ni into the host crystal system. Catalytic synthesis of some 5‐aryl‐1H‐tetrazole analogs was performed under heat, microwave, and ultrasonic conditions. Reaction time, temperature, and solvent type parameters were studied to find the optimum conditions. High efficiency was obtained when ethyl alcohol was used as the reaction mixture solvent.

The highly efficient green synthesis of nanostructured ZnFe2O4 photocatalysts by using Ziziphus mauritiana and Salvadora persica extracts for the photocatalytic degradation of crystal violet in sunlight

The current study is aimed to investigate the photocatalytic degradation of crystal violet dyes solution in the presence of modified ZnFe2O4 photocatalysts by Ziziphus mauritiana and Salvadora persica extracts in sunlight. Regardless of the extracts used, the modified ZnFe2O4 catalysts demonstrated excellent photocatalytic degradation. However, the catalysts modified using Salvadora persica extract achieved superior photocatalytic degradation of crystal violet dye. ZnFe2O4 with Salvadora persica yielded smaller particles with a larger surface area, smaller band gap energy and a better distribution of differently sized particles than by using Ziziphus mauritiana. This photocatalyst also demonstrated stability, being able to be reused at least five times with minimal loss of catalytic ability, falling from 91% at the first iteration to 85% by the fifth reuse. These materials were prepared easily using an environmentally friendly method.

Boosting photocatalytic Cr(VI) reduction activities of layered COF through regulating donor-acceptor units and the orientation of imine bonds

In this work, three isoreticular covalent-organic frameworks (COFs) were successfully synthesized at room temperature, namely C1, C2, and C3, respectively. Due to their wide absorption ranges and sufficient photoredox potentials, the constructed COFs exhibited good photocatalytic performance for reducing Cr(VI). Among them, C2 displayed the best photocatalytic performance, which may be attributed to the unique donor-acceptor structure, good light absorption, and excellent photoinduced carriers’ separation and migration efficiency. When the COFs were modified with gold nanoparticles (labeled as Au@C1, Au@C2, and Au@C3), their photocatalytic performance can be further improved. For Au@C2, 98.2% of Cr(VI) can be reduced within 120 min, and its photocatalytic activity can be maintained over five reaction cycles. The structure-activity correlation was studied via both experimental and DFT calculation methods. It is shown that although C3 displayed wider absorption range and smaller energy band gap, its photocatalytic activity was much lower than C2. This may be due to the rapid nonradiative electron-hole recombination in C3, leading to low light utilization. These results indicate that to construct excellent COF photocatalysts, it not only needs to pursue wider absorption range and smaller energy band gap, but also improve the utilization of light energy and photogenerated charge carriers. In addition, the active species and photocatalytic mechanism were also studied.

Enhanced photoelectrochemical transient photoresponse properties of molybdenum oxide film deposited on black silicon

Nanostructured black silicon (b-Si) is widely deployed for different solar applications due to its novel light-harvesting characteristics, and large surface area-to-volume ratio. The present research work applies a novel approach via the chemical vapour deposition method to prepare molybdenum oxide (MoO3) film on a b-Si substrate for photoelectrochemical application. X-ray diffraction revealed α-MoO3 phase, with the MoO3/b-Si film exhibiting a relatively large crystallite size and improved crystalline quality. Optical reflectance measurements showed a relatively low reflectance and reduced optical bandgap energy for the MoO3/b-Si film. Chronoamperometric measurements showed an enhanced photocurrent density of 656.34 µA/cm2 at 1 V bias for the MoO3/b-Si photoanode measured in a 0.5 M H2SO4 solution. The enhanced photoelectrochemical activity could be attributed to an increase in light absorption, the relatively small bandgap energy, improved crystalline quality, and improved charge carrier separation and transfer at the interface.

Cs-Symmetric, Peripherally Fluorinated Boron Subphthalocyanine–Subnaphthalocyanine Hybrids: Shedding New Light on Their Fundamental Photophysical Properties and Their Functionality as Optoelectronic Materials

Hybridization of boron subphthalocyanine (BsubPc) and boron subnaphthalocyanine (BsubNc) has been modestly explored in the past, and was therefore carried out herein to access a subclass of these chromophores denoted as Ra-FxBsub(Pc3–p-Ncp) hybrids, where Ra is the axial halide substituent (axial chloride, Cl-, or axial fluoride, F-), x = 8, and p = 1. These chromophores were targeted as new candidate materials for organic electronic applications due to their Cs symmetry, in-plane dipole moment, and unique photophysical properties. Cl-/F- F8Bsub(Pc2-Nc1) hybrids were compared to Cl-/F- F8BsubPc hybrids, which are analogous compounds with an identical number of peripheral fluorine atoms but lower degree of π-conjugation. Upon photoexcitation of dilute toluene solutions and doped thin films with polystyrene as a nonemissive host, F8Bsub(Pc2-Nc1) hybrids exhibited distinctively broad absorption spectra and narrow emission profiles with red-shifted peak photoluminescence wavelengths in the 618–623 nm region compared to F8BsubPc hybrids (581–584 nm). Electroluminescence properties were probed in simple solution-cast organic light-emitting diodes (OLEDs) in which all four hybrids were diluted within an F8BT emissive polymer host. Upon electronic excitation, electroluminescence (EL) of Cs-symmetric hybrids followed the same trends as photoluminescence (PL), with OLED devices displaying narrow EL in the orange region (588–592 nm) for F8BsubPc hybrids and in the near-red region for F8Bsub(Pc2-Nc1) hybrids (627–632 nm). The photophysical processes important to OLEDs moderately improved with less π-conjugation in the periphery of the Cs-symmetric hybrids [F8Bsub(Pc2-Nc1) vs F8BsubPc; EQEMax: 0.099% vs 0.129%; luminance: 500 cd/m2 vs 1000 cd/m2 at maximum current density; relative PL quantum yields (QYs) ≈ 17–22% vs ≈ 35–44%]. Electrochemical data showed that Cs symmetry introduces reversibility or quasi-reversibility in the oxidation regime at potentials >1 V, and peripheral fluorination enables reversibility in the reduction process. Overall, F8Bsub(Pc2-Nc1) hybrids embody several unique physical characteristics into one: broad absorption spectra (full width at half-maximum height, FWHMsolabs = 53–55 nm, FWHMfilmabs = 71 nm), narrow near-red electroluminescence (FWHMOLEDEL = 33 nm), and photoluminescence (FWHMsolPL = 25–26 nm, FWHMfilmPL = 32 nm) emission, small energy band gaps (1.95–1.96 eV), high extinction coefficients (ε ≈ (5.65–6.16) × 104 M–1 cm–1), and dual electrochemical versatility. These results provide new physical insights into the material properties of Cs-symmetric macrocycles and advance the consideration of F8Bsub(Pc2-Nc1) and F8BsubPc hybrids for optoelectronic applications.

Enhancing bio-aromatics yield in bio-oil from catalytic fast pyrolysis of bamboo residues over bi-metallic catalyst and reaction mechanism based on quantum computing

The high oxygen content and complicated compounds of pyrolysis bio-oil limit its application as a liquid fuel. In this study, bi-metallic modified HZSM-5 was used to enhance bio-aromatics yield in bio-oil from catalytic pyrolysis of bamboo residues. The catalytic pyrolysis behavior of bamboo residues over Fe and Zn co-modified HZSM-5 with different Fe to Zn mass ratios, loading rates, and different catalyst to biomass mass ratios towards the selectivity of aromatics was investigated using pyrolysis–gas chromatography/mass spectroscopy (Py-GC/MS). Quantum calculation of oxygen-containing products was used to infer the reaction mechanism. The results showed that Fe and Zn could adjust the strong acidity and pore size distribution of HZSM-5. The bi-metallic modified HZSM-5 promoted deoxygenation activity and monocyclic aromatic hydrocarbons yield. Zn modified HZSM-5 catalyst yielded higher aromatics than Fe modified HZSM-5. Maximum aromatics yield of 93.83 mg g−1 was obtained when the Fe to Zn mass ratio was 4:1 at a loading rate of 5 wt%(Fe and Zn). However when catalyst to biomass mass ratio exceeded 2:1, the yield of aromatics decreased. Quantum calculations showed that 2-Methoxy-4-vinylphenol had the largest dipole moment and the smallest energy band gap among the selected aromatic oxygen-containing compounds, indicating its weak molecular stability. Theoretical support for the hypothesis of the 2-Methoxy-4-vinylphenol pyrolysis pathway was provided by the analysis of the bond dissociation energy.

Development of new spiro[1,3]dithiine-4,11′-indeno[1,2-b]quinoxaline derivatives as S. aureus Sortase A inhibitors and radiosterilization with molecular modeling simulation

Multi-drug resistant microbes have become a severe threat to human health and arise a worldwide concern. A total of fifteen spiro-1,3-dithiinoindenoquinoxaline derivatives 2–7 were synthesized and evaluated for their biological activities against five standard and MDRB pathogens. The MIC and MBC/MFC for the most active derivatives were determined in vitro via broth microdilution assay. These derivatives showed significant activity against the tested strains with microbicidal behavior, with compound 4b as the most active compound (MIC range between 0.06 and 0.25 µg/mL for bacteria strains and MIC = 0.25 µg/mL for C. albicans). The most active spiro-1,3-dithiinoindenoquinoxaline derivatives were able to inhibit the activity of SrtA with IC50 values ranging from 22.15 ± 0.4 µM to 37.12 ± 1.4 µM. In addition, the active spiro-1,3-dithiinoindenoquinoxaline attenuated the in vitro virulence-related phenotype of SrtA by weakening the adherence of S. aureus to fibrinogen and reducing the biofilm formation. Surprisingly, compound 4b revealed potent SrtA inhibitory activity with IC50 = 22.15 µM, inhibiting the adhesion of S. aureus with 39.22 ± 0.15 % compared with untreated 9.43 ± 1.52 %, and showed a reduction in the biofilm biomass of S. aureus with 32.27 ± 0.52 %. We further investigated the effect of gamma radiation as a sterilization method on the microbial load and found that a dose of 5 kGy was sufficient to eradicate the microbial load. The quantum chemical studies exhibited that the tested derivatives have a small energy band gap (ΔE = −2.95 to −3.61 eV) and therefore exert potent bioactivity by interacting with receptors more stabilizing.