Showing papers in "Journal of Photochemistry and Photobiology A-chemistry in 2023"

Visible light activated MoS2/ZnO composites for photocatalytic degradation of ciprofloxacin antibiotic and hydrogen production

Abstract: In the photocatalysis process, photon energy is mainly converted into chemical energy with the help of both light and catalyst. This process can be used in different applications like photocatalytic degradation of hazardous compounds, fixation of nitrogen, hydrogen production, air purification, water splitting, carbon dioxide reduction etc. In this research work, multiplicative ZnO and MoS2/ZnO (MZ) composites were synthesized using green chemical methods like the hydrothermal process and used in two different applications i) photocatalytic degradation of ciprofloxacin (CIP) antibiotic and ii) hydrogen production. CIP is not easily biodegradable and is mainly used in various antibacterial treatments. The photocatalytic activity was tested for ZnO and different MoS2/ZnO composites along with this the effect of different amounts of catalysts doses was studied. MoS2/ZnO composites exhibit superior photocatalytic performance than ZnO for photocatalytic degradation of CIP. Using the LC-MS technique possible degradation pathways are proposed. The same photocatalyst materials were used to test the photocatalytic H2 production activity. H2 production rates were found to be 22, 39 and 235 µmol/g/h for ZnO, MoS2 and MZ-30 composite respectively. Superior photocatalytic activity of MZ-30 composite than ZnO is chiefly attributed to the extended light absorption capacity, effective charge transfer, suitable band alignment between the ZnO and MoS2, minimum recombination of charge carriers etc.

Fabrication of g-C3N4 nanosheets immobilized Bi2S3/Ag2WO4 nanorods for photocatalytic disinfection of Staphylococcus aureus cells in wastewater: dual S-scheme charge separation pathway

Abstract: In this work, graphitic carbon nitride (g-C3N4) immobilized Bi2S3/Ag2WO4 (BS/AW/CN) heterojunction was successfully fabricated using a facile multi-step approach. The fabricated nanomaterials were characterized using different sophisticated technologies. The morphological investigations revealed the existence of g-C3N4 nanosheets loaded with Ag2WO4 and Bi2S3 in a nanorod-like structure. The BS/AW/CN nanocomposite exhibited improved surface area, which was attributed to the regular deposition of Bi2S3/Ag2WO4 on the surface of g-C3N4 nanosheets. The obtained BS/AW/CN heterojunction displayed excellent light absorption ability with promoted photoelectrochemical properties, which was attributed to the lower band gap energy of Bi2S3 species. The BS/AW/CN (0.25 g/L) showed superior photocatalytic antimicrobial activity against Staphylococcus aureus cells (∼1 × 107 CFU/mL) under 140 W of visible-light illumination, where complete inactivation activity was observed in 90 min. The disinfection kinetics verified the faster photoreaction process over BS/AW/CN compared with single and binary catalysts. The inactivated bacterial cells were further elucidated by fluorescence spectroscopy and electron microscopy techniques. The photocatalytic disinfection activity was also investigated under different operating conditions like pH, catalyst loading, and bacterial density. The stability studies verified the high photostability of the obtained heterojunction in five photoreaction runs, suggesting its potential applicability in wastewater disinfection systems. The electronic characteristics and radical trapping results were considered in justifying the dual-S-scheme heterojunction mechanism in the presence of BS/AW/CN. In conclusion, this work demonstrates the feasibility of an efficient visible-light responsive photocatalyst for Staphylococcus aureus cells disinfection in wastewater treatment systems.

Photochromic polymer nanoparticles as highly efficient anticounterfeiting nanoinks for development of photo-switchable encoded tags

Abstract: • Synthesis of colloidal nanoparticles with different polarity and particle size, • Preparation of spiropyran-containing photochromic colloidal nanoparticles, • Effect of polarity on the fluorescence emision and photochromism of colloidal nanoparticles, • Development of the photochromic colloidal nanoparticles as anticounterfeiting nanoinks, • Application of the smart nanoinks for encrypting security documents. Dual photochromic and photoluminescent latex nanoparticles were synthesized to develop innovative anticounterfeiting nanoinks with applications in encryption technology. The colloidal nanoparticles bearing hydroxyl groups were resulted from semi-continuous miniemulsion copolymerization of 2-hydroxyethyl methacrylate and methyl methacrylate. Investigation of the particle size determination and microscopic analysis results demonstrated spherical morphologies for the latex nanoparticles with a mean size of about 80 nm and narrow size distribution. Modification of the polymer nanoparticles with hydroxyl functional groups led to the formation of a high level of hydrogen bonding between the hydroxyl groups and spiropyran chromophore, which is an advantage in the preparation of security anticounterfeiting nanoinks. In addition, optical analysis of the photochromic latex samples showed various UV-vis spectra, fluorescence emission, kinetics of isomerization, and photo-fatigue resistance depending on different amounts of the polar monomers. Further investigations on optical properties exhibited that reducing the size of the colloidal samples can affect their photoluminescence characteristics. This is an efficient way to provide remarkable photoreversible anticounterfeiting inks for different applications, such as printed photo-marking, rewritable handwriting patterns, security encoded tags, and labeling.

AIEE active stilbene based fluorescent sensor with red-shifted emission for vapor phase detection of nitrobenzene and moisture sensing

Abstract: A unique π-electron rich stilbene-based sensor with significantly enhanced red-shifted fluorescence emission has been synthesized via a Mizoroki-Heck cross-coupling reaction. The strong fluorescence properties of stilbene derivative as a potential fluorescent sensor have been investigated for sensitive and selective detection of hazardous and threatening nitrobenzene (NB) in both solution and vapor phase. The fluorescence emission intensity of stilbene sensor 1 at 474 nm was quenched upon interaction with NB. The fluorescence quenching was attributed to the combined effect of dominant smaller and adjustable size of NB and photo-induced electron transfer (PET) process. Stilbene sensor 1 is the first active bathochromic shifted fluorescent sensor with AIEE property was developed for both solution and vapor phase detection of NB. Possible interactions of stilbene sensor 1 with NB was evaluated by UV–vis., fluorescence, density functional theory (DFT) calculations, and 1H NMR titration experiment. Additionally, non-covalent interaction (NCI), Frontier molecular orbitals (FMOs) and interaction energy were studied by using Gaussian 09 software. Moreover, test strips were fabricated to accomplish contact mode detection of NB. Further, stilbene sensor 1 was successfully applied for trace detection of NB in real water samples.

ZIF-8 derived porous C, N co-doped ZnO modified B-g-C3N4: A Z-Scheme charge dynamics approach operative towards photocatalytic hydrogen evolution and ciprofloxacin degradation

Abstract: Herein, the fabrication of a robust CNZ/BCN nanocomposite is achived by a facile in-situ calcination of ZIF-8 along with BCN precursors. Morphologically the dodecahedral ZIF-8 farmeworks are transformed into granular CNZ nanoparticles that were densely addhered to the BCN nanosheet surface with interfacial interactions. MOF derived statergy plays significant role in reducing the optical band gap via intorducing C, N into the ZnO lattice as known from UV-Vis-DRS as well as XPS studies. Additionally the composite formation lead to significantly enhanced exciton anti-recombination as suggested from EIS and PL analysis. The optimal CNZ/BCN (1:1) nanohybrid exhibits enhanced photocatalytic H2 evolution rate of 7020 µmolh-1g-1 which is nearly two and eight folds greater than that of pristine CNZ and BCN respectively along with maximal ciprofloxacin photo-degradation rate (86.7%). The radical trapping experiments deduced the formation of both superoxide and hydroxyl radicals that promts the nanocomposite to follow Z-scheme charge transfer pathway during photocatalysis. Intermediates formed during CIP photo-degradtion were identified by using LC-MS technique that showed ten intermediates formed through two differnet routes. Hence, MOF derived CNZ and BCN nanocomposite acts as a robust Z-scheme mediated photocatlyst that can be employed for varied energy and environmantal purposes.

Spectroscopic studies on binding of ibuprofen and drotaverine with bovine serum albumin

Abstract: The interaction between ibuprofen (analgesic) and drotaverine (smooth muscle relaxant) drugs with bovine serum albumin (BSA) was investigated using both experimental (UV–Vis, fluorescence, and circular dichroism spectroscopy) and theoretical (molecular mechanics) methods. Both drugs quench the intrinsic fluorescence of BSA through static processes. The binding constant of the BSA–drotaverine complex is found to be relatively higher than that of the BSA–ibuprofen complex. The binding distance between BSA and ibuprofen/drotaverine was calculated to be 1.7 and 3.1 nm, respectively. Both fluorescence and circular dichroism spectral studies confirmed conformational changes in the BSA upon binding with these drugs. From both displacement competition studies and molecular docking, it was found that drotaverine can displace ibuprofen at higher concentrations, but ibuprofen can bind to other sites on the BSA. Circular dichroism showed that drotaverine has a stabilizing effect on the secondary structure of BSA in the presence of ibuprofen, which on its own leads to an increase in the disordered fraction at high concentrations. These observations imply that concurrent administration of these two drugs can be effective as a combination therapy in the management of pain due to primary dysmenorrhea, even when the disease tends to gain resistance to the NSAIDs; their competition for the BSA binding sites should be taken into account.

Construction of 3D flower-like Bi5O7I/Bi/Bi2WO6 heterostructure decorated NiFe2O4 nanoparticles for photocatalytic destruction of Levofloxacin in aqueous solution: Synergistic effect between S-scheme and SPR action

Abstract: Promoting the separation activity of photo-induced carriers via the design of heterostructure photocatalysts remains a vital challenge. In the present study, multistep strategies were developed to construct the Bi5O7I/Bi/Bi2WO6/NiFe2O4 heterojunction by in situ growth of Bi/Bi2WO6 and NiFe2O4 species on the surface of Bi5O7I microspheres, forming a 3D flower-like structure as verified by characterization technologies. The developed heterojunction reflected superior photodegradation activity (97.5% in 90 min) toward levofloxacin (LEV) under visible light irradiation. The enhanced photodegradation activity of the Bi5O7I/Bi/Bi2WO6/NiFe2O4 nanocomposite could be attributed to the synergistic outcomes of the S-scheme mechanism and the plasmonic action of Bi metal in one system. Furthermore, the Bi metal can directly harvest the simulated sunlight under the surface plasmon resonance (SPR) action, which contributes to generating a large number of electron-hole pairs. Some influencing factors like pH, LEV concentration, and catalyst loading were also discussed. The photocatalytic degradation pathways of LEV were investigated depending on the detected intermediate products. The radical experiment and ESR results stated that the major contribution of •OH, •O2−, and h+ radicals in LEV destruction. The recyclability experiments indicated the excellent stability and facile reusability of the magnetic Bi5O7I/Bi/Bi2WO6/NiFe2O4 composite. Finally, the photocatalytic mechanism for LEV destruction was clarified in terms of trapping experiments and band-gap discussions. This work introduces a clear technology to fabricate a quaternary S-scheme heterojunction boosted by the plasmonic effect of Bi metal to accelerate the charge separation ability and create a powerful redox potential to achieve a desirable LEV treatment process.

Lecithin sensitized thermo-sensitive niosome using NIR-carbon dots for breast cancer combined chemo-photothermal therapy

Abstract: In this work, a new class of thermo-sensitive niosome (TS-Nio) was synthesized using lecithin and NIR-carbon dots, for combined chemo-photothermal therapy. TS-Nio (200 nm) and noisome (240 nm) were synthesized using thin layer method and were stable for 14 days in water, buffer, and cellular environment. CQDs with a hydrodynamic diameter of 2.0 ± 0.5 nm (during 14 days) were synthesized by the hydrothermal method, and their photothermal, and quantum efficiency were 24.3% and 67%, respectively. Synthesized CQDs had repeating maximum temperature of 55 ± 0.2 °C in four 10-min irradiation cycles (LASER 808 nm) and photothermal therapy effect of 40%, 46%, 44%, and 48% for MCF-10A, MCF-7, MDA-MB-231, SKBR-3 cells, respectively. Drug and CQDs were loaded in the niosomes, and the release difference between normal and cancer cell conditions were 55% and 21% for TS-Nio and niosome, respectively. The drug release kinetic model was Komsmeyer & Peppas. Chemotherapy on MCF-7 cancer cells using Dox-loaded niosomes showed the maximum toxicity of 46% and 37% for TS-Nio and niosome, respectively. The chemophotothermal therapy on MCF-10A, MCF-7, MDA-MB-231, SKBR-3 cells using drug and CQDs loaded niosomes with 10 min laser irradiation were 40%, 88%, 89%, 15% for TS-Nio, and 17%, 61%, 67%, 29% for niosome respectively. The results showed perfect targeting and effective chemophotothermal therapy of TS-Nio on MCF-7 and MDA-MB-231 cell lines.

2,1,3-Benzothiadiazole-based bis-silylated compounds: Synthesis and use in the preparation of highly fluorescent low-contend organic–inorganic hybrid materials

Abstract: • Synthesis of new fluorescent bis-silylated benzothiadiazoles by Sonogashira coupling; • Benzothiadiazoles with blue-cyan emission, high quantum yields and large Stokes shift. • Photoactive organic-inorganic hybrid materials from bis-silylated 2,1,3-benzothiadiazoles. • Highly fluorescent low-contend benzothiadiazole hybrid materials. Herein, we report the synthesis of bis-silylated 2,1,3-benzothiadiazole derivatives and their use in the preparation of photoactive organic-inorganic hybrid materials with extremely low fluorophore/tetraethylorthosilicate molar ratios. The organic compounds were synthesized in good to excellent yields (55%-94%) using Pd-catalyzed Sonogashira cross-coupling as the key step. The bis-silylated benzothiadiazoles exhibited absorption in the UV-A region (∼376 nm), attributed to fully spin- and symmetry-allowed π-π* electronic transitions. An emission located in the blue-cyan region with a high quantum yield and large Stokes shift was observed, most likely due to a charge-transfer mechanism in the excited state. BTD-containing hybrid materials were obtained through a sol-gel process, for which the dye loading and aging time were studied. Optimal reproducibility of the photophysical results was achieved when the sol-gel reaction was conducted for 10 d at 60 °C. In the solid state, the obtained hybrid materials exhibited fluorescence emission in the blue-cyan-green regions, with relatively high quantum yields (∼30%). The protocol allows for the preparation of analogous photoactive hybrid materials containing very low amounts of BTD, behaving as fluorescent fumed silica.

Facile synthesis of NiO-loaded g-C3N4 heterojunction photocatalyst for efficient photocatalytic degradation of 4-nitrophenol under visible light irradiation

Abstract: Finding acceptable noble-metal-free cocatalyst-modified photocatalysts has gotten a lot of interest in the field of photocatalysis. In this study, an environmentally friendly ultrasonic-assisted approach was used to make NiO-loaded g-C3N4. The crystal, morphological structure, surface analysis, and optical properties of the pure g-C3N4 and NiO-loaded g-C3N4 were characterized by PXRD, TEM, BET, XPS, and UV–vis (DRS), respectively. UV–vis (DRS) results investigated that NiO-loaded g-C3N4 photocatalysts exhibit a reduction in the optical band gap energy related to the bare g-C3N4 that is particularly good for visible light absorption. TEM images prove the existence of the NiO in the NiO-loaded g-C3N4 which is very beneficial for the enhancement of the charge separation and transfer that is revealed using the electrochemical methods. Furthermore, Mott-Schottky plots showed that both bare g-C3N4 and NiO-loaded g-C3N4 photocatalysts have negative flat band potential. Importantly, the photocatalytic activity of NiO-loaded g-C3N4 photocatalysts was evaluated for the photodegradation of 4-nitrophenol (4-NP) in an aqueous solution under visible light irradiation. The optimized ratio of NiO-loaded g-C3N4 (11 wt% loaded g-C3N4) displays the highest activity performance and is almost 4 times higher than that of bulk g-C3N4. The remarkable photocatalytic improvement of NiO-loaded g-C3N4 is mainly attributed to the decreased band gap energy and synergistically enhanced charge separation and transfer. Additionally, the proposed photodegradation mechanism of NiO-loaded g-C3N4 was also deliberated in more detail. Hence, the NiO-loaded g-C3N4 photocatalyst is an attractive photocatalyst for photocatalytic water treatment.

S-scheme AgIO4/CeO2 heterojunction nanocomposite photocatalyst for degradation of rhodamine B dye

Abstract: Photocatalysis is auspicious technology for transferring inexhaustible solar energy into storable chemical energy. In this novel research, an auspicious S-scheme heterojunction is constructed by hybridizing CeO2 nanoparticles with band gap energy [2.9 eV], surface area [75 m2/g], and negative conduction band potential (ECB = -0.38 eV) with AgIO4 nanorods with 22 m2/g surface area, band gap energy of 1.98 eV and valence band potential of + 3.27 eV. The novel AgIO4/CeO2 heterojunctions containing different compositions of CeO2 and AgIO4 are fabricated through coupled sol–gel and sonochemical route. SEM, XRD, BET, XPS, DRS, PL and HRTEM investigate the morphological, structural, textural and optical features of the solid specimens. Combined PL and DRS analysis have pointed out that AgIO4 prohibit the as-synthesized heterojunctions with strong visible light absorbability and highly separation efficiency of photogenerated electrons and holes. CeAg15 optimal catalyst decompose RhB dye with pseudo-first order rate of 0.024 min−1 which is tenfold higher than that of pristine CeO2. In the light of scrubber experimental results and PL analysis of terephthalic acid, S-scheme is proposed for analyzing the route of charge transportation and generation of charge carriers with strong redox power. The construction of S-scheme mechanism reveal the preservation of the positive holes of AgIO4 oxidative photocatalyst and negative electrons of CeO2 reductive photocatalyst for consuming in destruction of RhB dye into eco-friendly species as manifested from TOC analysis. This novel research work provide a clear insight on fabrication of S-scheme heterojunction with strong oxidative and reductive power for eradicate water pollutants.

Preparation and characterizations of TiO2/ZnO nanohybrid and its application in photocatalytic degradation of tetracycline in wastewater

Abstract: The photodegradation of tetracycline antibiotics (TC) in an aqueous solution, using the TiO2 nanoparticles, ZnO microparticles, and TiO2/ZnO composite under the UV lamp in a continuous reactor, was performed. The effects of different parameters, such as the initial TC concentration, medium pH, ratio of each photocatalyst, and the flow rate were comprehensively studied. SEM, EDX, and XRD characterization techniques were employed to study the morphology and structure features of the prepared composite. The results revealed that a more significant amount of TC is not easily removed from wastewater. Furthermore, by increasing the pH of the medium to 11, the efficiency of TC degradation was increased, while the amount of removal remained stable at higher pH values. As the flow rate increased up to 190 mL/min, the removal efficiency increased; however, at higher flow rates, lower efficiency was obtained. Moreover, using multivariate analysis and response surface methodology (RSM), a model for removing TC and the effect of experimental parameters on removal efficiency was proposed. The optimal conditions using the RSM method were found to be the reduction efficiency of 78.94 % in pH = 11 (flow rate of 132 mL/min, and TiO2 concentration of 323 mg) and reduction efficiency of 75.89% in pH = 9 (flow rate of 143.19 mL/min and TiO2 concentration of 312.73 mg).

Hydrophilic hydrogen-bonded organic frameworks/g-C3N4 all-organic Z-scheme heterojunction for efficient visible-light photocatalytic hydrogen production and dye degradation

Abstract: • A novel all-organic Z-scheme HOFs/g-C3N4 heterojunction photocatalyst is fabricated. • A new strategy to improving the photochemcial stability of unstable HOFs. • Samples show efficient photocatalytic activity. • Mechanism and pathways of photocatalytic are revealed. Herein, a novel all-organic Z-scheme hydrogen-bonded organic frameworks (HOFs)/g-C 3 N 4 nanosheets (CNNS) heterojunction photocatalyst is synthesized through an in-situ electrostatic method. Characterization and density functional theory studies together verify that the band structures with staggered alignment between HOFs and CNNS can induce a rapid Z-scheme interfacial charge-transfer pathway. Combing the complementary advantages of HOFs and CNNS, the fabricated Z-scheme HOFs/CNNS heterojunction inhibits photoinduced electron-hole recombination and more charge carriers are accumulated to produce highly reactive substances (•O 2 - , •OH and h + ). In addition, the superior hydrophilicity of HOFs can enhance the interaction of HOFs/CNNS heterojunction with water molecules and methyl orange pollutant, which is beneficial to boosting photocatalytic activity. Therefore, in contrast to inactive pure HOFs, the novel Z-scheme HOFs/CNNS heterojunction exhibits a high photocatalytic hydrogen evolution rate of 4450 μmol h -1 g -1 with an apparent quantum efficiency (AQY) of 22% at 450 nm, which is approximately 11 times higher than that of pure CNNS. Additionally, such heterojunction enables 100% degradation of methyl orange within 60 min.

Economically viable multi-responsive probes for fluorimetric detection of trace levels of Ga3+, Al3+ and PPi in near aqueous medium

Abstract: Gallium compounds are commonly used in cancer treatment and are known to be compounds with minimal toxicity. On the other hand, aluminium has procured extensive significance in modern lifestyle as well as industrial applications. Both these Group III metal ions, irrespective of their amicable properties and applications, in their excesses harm human and ecological health. We report in this work two tailor-made reversible chemosensors c towards the end of achieving recognition of these relevant metal ions. H3L1 was sensitive to both Ga3+ and Al3+ while H4L2 was highly selective towards Ga3+. They exhibited sensing of these ions via a turn-on strategy. Both these ligands sequentially detected pyrophosphate ion in an off-on-off manner. Very low detection levels were achieved for all the targeted analytes in near-aqueous medium. Fluorescence experiments, HR-MS data, NMR titrations were used to speculate the binding mode of the probes and the prevalent mechanisms. Both the probes could detect P2O74− in a sequential, manner. Apart from paper strip tests, cytotoxic studies and bio-imaging of Ga3+ and Al3+ were conducted in Vero cells in an effort to explore the practical applications of probes.

Efficient photocatalytic oxidation of VOCs using ZnO@Au nanoparticles

Abstract: The emission of toxic VOCs (Volatile Organic Compounds) in the environment causes serious problems and, if from one side there are directives to reduce this threat, from the other side there are stringent necessities for their removal. Several methods have been proposed to remove toxic VOCs, but little attention has been paid towards their photooxidation using materials with improved photodetection. For these reasons, we account here on the good photocatalytic performance of semiconducting [email protected] nanostructures that revealed to be excellent for both ultraviolet and visible light detection, thanks to the wide ZnO band gap and visible Au surface plasmon resonance, towards the photooxidation of some toxic Volatile Organic Compounds. In particular, we tested these peculiar materials for the removal of some common VOCs as toluene, ethanol and formaldehyde under solar light irradiation. The [email protected] showed excellent performance in the total oxidation of toluene (95% of conversion) and formaldehyde (85%) with the consequent formation of only CO2 and water as by-products. This good activity was also confirmed in the photooxidation of ethanol that allowed to obtain the 72% of CO2 selectivity. Furthermore, in all tests the catalysts showed a good stability after several consecutive runs. The efficient electronic communication between the gold core and the zinc oxide shell permitted to enhance the overall photodetection of the solar irradiation, improving also the charge carriers separation. The [email protected] nanostructures can be considering promising candidates as photocatalysts for air purification.

First theoretical framework of superalkali metals [M3X(M=Li, Na, K; X= O, S, F, N)] doped all-boron B38 nanocluster: A promising class of nonlinear optical materials for optoelectronic applications

Abstract: Developing highly efficient nonlinear optical (NLO) materials is an area of frontier research. For the first time, all-boron fullerene analogue B38 nanocluster is utilized for creating highly efficient NLO materials. An effective computational design strategy of superalkali metals (Li3O, Na3O, K3O, Li3S, Na3S, K3S, Li3F, Li3N) doping is utilized on B38 nanocluster, and sixteen stable isomers (A-P) of M3[email protected] (M = Li, Na, K; X = O, S, F, N) are amplified for NLO properties. Potential utilization of superalkali metals doped B38 nanocluster for NLO response applications is confirmed through DFT and TD-DFT calculations executed for estimating NLO properties, photophysical features, interaction energies (Eint), vertical ionization energies (VIE), non-covalent interaction (NCI), natural bond orbitals (NBO), frontier molecular orbital (FMO), density of state (DOS) and molecular electrostatic potential (MEP) analysis. The VIE and Eint results indicate that [email protected] complexes are thermodynamically stable enough and show a strong interaction between B38 and doped superalkalis. Doping of superalkalis on B38 successfully lowers the energy gap from 1.99 (pristine B38) to 0.99 eV (doped B38). A triggering in dipole moment from 0.001924 D to 22.61 D is observed upon doping. NCI and NBO analysis confirmed the successful intermolecular charge transfer among superalkalis and B38. UV–Vis analysis showed that all [email protected] complexes are sufficiently transparent in the near-infrared (NIR) region. The NLO responses of developed complexes are evaluated by their polarizability and first hyperpolarizability (βo). Amplification in polarizability value from 413.69 a.u. to 865.60 a.u and in first hyperpolarizability from 0.71 a.u to 4.0 × 105 a.u. is achieved upon [email protected] doping. An eye-catching and highest NLO response (βo = 4.0 × 105 a.u) is exhibited by isomer E(K3[email protected]). The NLO response of all studied complexes is also found more significant than the standard prototype molecule. This report provides an efficient superalkali doping technique for creating highly effective future NLO systems and recommends superalkali-doped all-boron fullerene analogue B38 nanoclusters as ideal entrants for future NLO applications.

Photoluminescence and lifetime studies of C-dot decorated CdS/ZnFe2O4 composite designed for photoelectrochemical applications

Abstract: Cadmium sulphide (CdS) is a well-known material for photoelectrochemical water splitting as a photoanode. The valence and conduction band edges are well suited for both hydrogen and oxygen evolution reactions. However, a major drawback in the case of cadmium sulphide is its photocorrosion. In this regard, formation of a Type II heterostructure helps in well separation of the photogenerated charge carriers and reduces photocorrosion. Herein, we have incorporated a carbon dot layer (high conductivity) in between a CdS/ZnFe2O4 Type II composite heterostructure to further enhance the photoelectrochemical performance of the material. Steady state photoluminescence (PL) study revealed that maximum PL intensity is observed in the case of bare CdS while minimum intensity in the case of ternary composite after the incorporation of carbon dots. The inflation of PL intensity revealed the overall increase in the conductivity and enhanced charge separation at the interface after composite formation. The time-resolved photoluminescence (TRPL) decay dynamics have also been studied. The lifetime of the charge carriers for the ternary composite was found to be 2.41 ns, which is much higher than the bare (0.78 ns) and binary composite (0.85 ns), indicating the improved charge separation and the stability after composite formation (CdS/C-dot/ZnFe2O4). This further aids in the enhancement of photocurrent generation. The photocurrent density is enhanced by approximately 50 times compared to the bare material (CdS) and 5 times compared to the binary composite (CdS/ZnFe2O4).

A Comprehensive Study on RbGeI3 based Inorganic Perovskite Solar Cell using Green Synthesized CuCrO2 as Hole Conductor

Abstract: Though perovskite solar cell (PSC) is achieving an immense 25.7 % efficiency within a few years of extensive research, a shorter life span with organic part and charge transporting layers hinders their commercialization. So, inorganic perovskite aligned with the hole transporting layer (HTL) could be an alternative to achieve long-term device stability. The delafossite, CuCrO2 was prepared by the green synthesized method and then characterized. According to the X-ray diffraction (XRD) pattern, the crystallites are polycrystalline phases, and the average crystallite size is 159.3 nm. Spectrophotometric measurement was used to determine the bandgap (Eg), which is 3.0 eV. These results are applied for simulation study in Pb-free RbGeI3-based inorganic perovskite device using CuCrO2 as HTL. HTL thickness, diffusion length, interface defect, carrier concentration, activation energy, and temperature effects on the device performance have been explored by SCAPS-1D simulation software. In the optimized condition, the simulated result shows the maximum device efficiency is 23.8 %, corresponding open circuit voltage (Voc), short circuit current density (Jsc) and fill-factor (FF) of 0.89 V, 33.7 mA cm−2, and 79.2 %, respectively. A study of activation energy for the device elucidates that the significant recombination is Shockley Read Hall (SRH) type at the (RbGeI3/CuCrO2) interface layer. The result of temperature impact has supported better thermal stability. Indium tin oxide (ITO) is suitable front contact for the proposed p-i-n structure. The study reveals that the delafossite, CuCrO2 can be a potential HTL for Pb-free inorganic perovskite solar cells.

Water-soluble meso-thienyl BODIPY therapeutics: Synthesis, characterization, exploring photophysicochemical and DNA/BSA binding properties

Abstract: Recently, there is rising attention in photodynamic therapy (PDT) compared to traditional methods (immunotherapy, surgery, chemotherapy or radiotherapy) in the treatment of cancer. This method includes the sensitizers which are activated to generate cytotoxic reactive oxygen species (ROS). BODIPYs are known as one of the sensitizers used in PDT applications. Encouraged by these fact in this study, we present the synthesis of novel BODIPY derivatives with meso-thienyl segment, diiodine moieties at 2-,6-positions and distyryl structure at 3-,5-positions. The characterization of all compounds was performed by using various spectroscopic methods (UV–Vis, FT-IR, Mass, 1H-NMR and 13C-NMR spectroscopy). To assess the potentials of the synthesized compounds in PDT applications, fluorescence, singlet oxygen and photodegradation quantum yields were calculated. Singlet oxygen quantum yields are 0.03, 0.84, 0.13, 0.32 and 0.76 for BODIPY compounds 1–5, respectively. Besides the photophysicochemical studies, DNA/BSA binding experiments for water-soluble BODIPY derivative (5) were examined. For water-soluble BODIPY derivative 5, the DNA binding constant (Kb) is 1.75 × 105 and the BSA binding constant (KBSA) is 4.15 × 104.

Ag/TiNPS nanocatalyst: biosynthesis, characterization and photocatalytic activity

Abstract: Wastewater pollution by synthetic dyes has emerged as a serious environmental problem, causing a series of deleterious effects, since they have low biodegradability and considerable chemical stability, requiring advanced treatment technologies, such as Advanced Oxidative Processes (AOPs), such as heterogeneous photocatalysis. In this context, the present work aims to synthesize, characterize, and evaluate the photocatalytic activity of silver/titanium nanoparticles (Ag/TiNPs) using the biosynthesis method from Aloe vera extract for application in the removal of Rhodamine B dye (RhB) to propose an alternative to the problem of wastewater with dyes. Ag/TiNPs were characterized by N2 porosimetry (BET/BJ method), zeta potential (ZP), Field Emission Gun – Scanning Electron Microscope (FEG-SEM) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR). Ag/TiNPs showed SBET = 343 m2 g-1, Dp = 4.9 nm, Vp = 0.26 cm3 g-1, ZP = -15.1 mV and V-type isotherm with H1 hysteresis. ATR-FTIR showed the presence of characteristic functional groups of -OH, -C=O, -CH2, and -CH3. FEG-SEM micrographs presented a heterogeneous and porous surface with nanoparticle size around 12 nm. Regarding the heterogeneous photocatalysis, Ag/TiNPs showed 100% degradation of RhB (k = 0.0219 min-1) under visible irradiation after 120 minutes, with the possibility of reuse in 5 cycles and only 5% reduction in photocatalytic activity. Therefore, Ag/TiNPs showed promising characteristics for application as a nanocatalyst in the treatment of wastewater with dyes.

Photocatalytic degradation of phenol and its derivatives over ZnFe layered double hydroxide

Abstract: A simple co-precipitation method was employed for synthesizing ZnFe-CO3 layered double hydroxide (LDH) and characterized through powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), UV − visible diffused reflectance spectroscopy (UV–vis DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption–desorption measurement. The catalytic activity was then investigated for photodegradation of phenol and its derivatives under both visible and UV light irradiations. The catalyst exhibited enhanced photocatalytic activity towards the degradation of various phenolic compounds under visible light irradiation compared to UV light. The effect of various reaction parameters such as catalyst amount, initial concentration of phenolic compounds and pH of the solutions on the photodegradation process was also studied thoroughly. The reaction kinetics was analyzed by Langmuir-Hinshelwood first order kinetic model. The plausible mechanism and degradation pathway of photocatalytic degradation of phenolic compounds were also discussed in detail. In addition, we investigated reaction pathways and thermochemistry for the degradation of phenol initiated by OH radicals using Density Functional Theory. The photocatalyst was stable and active up to four successive cycles.

An Off-Off fluorescence sensor based on ZnS quantum dots for detection of glutathione

Abstract: Quantum dots (QDs) are excellent fluorescent indicators for chemical and biological analysis. In this paper, an Off-Off fluorescence sensor based on ZnS quantum dots was designed. It was found that Co2+ can quench the fluorescence of ZnS QDs, moreover glutathione (GSH) can further quench the fluorescence. Therefore, this method can be used for indirect detection of GSH. However, if change Co2+ into other metal ions, the system cannot be used to detect GSH indirectly. For direct detection GSH, that is adding GSH without Co2+, the fluorescence intensity changes little, while only amino acid or monosaccharide has no effect. When indirect detection of GSH based on this Off-Off fluorescent probe, the fluorescence quenching was linearly related to the concentration range of 1–300 μM GSH, and the detection limit could reach 0.48 μM, which can rival most Off-On and On-Off fluorescent probe. The relative standard deviation for parallel measurement of 300 μmol·L-1 GSH solution (for n = 10) was 1.43 %.

Oxazine as an efficient precursor for the development of photochromic spiropyrans

Abstract: Spiropyran derivatives were synthesized through an alternate synthetic route that passed through a photochromic [1,3]-oxazine. The structures of the new spiropyran derivatives were established with the assistance of spectroscopic methods and single-crystal X-ray crystallography. The photochemistry of the spiropyran derivatives was investigated using a suitable wavelength of UV and visible light. Density functional theory (DFT) was exploited as a predictive tool to understand the unique organic transformation, which supported the conversion of photochromic oxazine into the spiropyran through consideration of the stability of the intermediates, transition state, and H-bonds. A comparison of solvation energies calculated for different isomers suggested greater solvation of colored isomers of oxazine structure as compared to the colored isomers of spiropyran form.

Unravelling the effect of donor-π-acceptor architecture in designing 1,3-indanedione based sensitizers for DSSC applications

Abstract: • 1,3-indanedione-based electron-acceptor group has been employed in designing new sensitizers and theoretical calculations of the nine sensitizers, that are designed based on D-π-A architecture, were performed at DFT and TDDFT level. • HOMO-LUMO energy levels of the designed dyes are matching with the energy levels of titania and redox couples. • Frontier molecular orbital (FMO) analysis revealed intra-molecular charge transfer from the electron-donor to the 1,3-indanedione electron-acceptor. • Two-fold enhancement of dipole moment was observed in all sensitizers upon binding on (TiO 2 ) 9 nanocluster. • The simulated electronic spectra of free dyes and Dye@TiO 2 encompass the entire visible region. • Phenoxazine (POZ) and phenothiazine (PTZ) electron-donor moieties significantly improved the chemical reactivity and photophysical properties and therefore, corresponding RK4 and RK5 sensitizers are better than others. • The D-π-A architecture is found to be better than D-π-A-D architecture in the case of 1,3-indanedione-based sensitizers. Molecular engineering plays a vital role in the design of efficient organic sensitizers for DSSC applications. The study highlights the density functional theory calculations of nine organic sensitizers, designed based on a new 1,3-indanedione electron-acceptor cum anchoring group. The new sensitizers (RK1-9) have been designed by tailoring a modified 1,3-indanedione electron-acceptor with conventional electron-donors in the form of D-π-A architecture. Geometry optimization studies reveal that the RK7 & RK8 molecules have more twisted geometries. Similarly, the RK5 dye has the smallest energy gap of 2.34 eV compared to other dyes. LUMO energy levels of all the designed dyes are positive, found above the conduction band energy level, and the HOMO energy levels were more negative than the redox potentials. Calculated electrochemical parameters suggest that the dyes RK1-5 and RK9 inject the electrons efficiently into the conduction band of TiO 2 . Further, the Gibbs free energies of the dyes indicate that the RK4 and RK5 dyes regenerate much faster than the other dyes. The electronic absorption spectra of the RK dyes were steadily shifting towards the longer wavelength region with solvent polarity and further red-shifts upon adsorbing on the (TiO 2 ) 9 nanocluster. The LUMO and LUMO+1 wave functions of the RK dye@(TiO 2 ) 9 complexes are confined to the (TiO 2 ) 9 nanocluster, suggesting effective intramolecular charge transfer upon photo-excitation. Overall, the computational study demonstrates the significance of the 1,3-indanedione electron-acceptor and o the D-π-A architecture in the molecular design of new organic sensitizers for DSSC applications.

New photosensitizers that are based on carbazoles and have thiophene bridges with a low bandgap do 32% better than N719 metal complex dye

Abstract: • Highlights for publication in Journal of Photochemistry and Photobiology A: Chemistry • We present the results of a comprehensive photovoltaic analysis of four carbazole organic sensitizers with a D-π-A architecture in this study. • An effective ICT all over the structure of MES1-4 between the donors and the acceptors was demonstrated by the investigation of dihedral angle and NBO studies. • Using MES1-4 as sensitizers results in a broader light-harvesting ability (400-800 nm) and higher photovoltaic efficiency at a range of 6.06–9.55%. • The MES4 has the highest light harvesting ability owing to the existence of distinct functional groups that enhance the capacity to bind the dye with the semiconductor layer (TiO 2 ) and reflect on the device's efficiency. • The PCE of the DSSC based on MES4 yields an unexpected PCE of 9.55% and a score of 32% higher than that of the N719 metal complex dye. Synthesis of metal-free organic sensitizers is a promising route for obtaining low-cost, high-efficiency sensitizers for dye-sensitized solar cells (DSSCs). We present the results of a comprehensive photovoltaic analysis of four carbazole organic sensitizers with a D-A architecture in this study. MES 1-4 have been developed and used as sensitizers in DSSC applications. Using MES1-4 as sensitizers results in a broader light-harvesting ability ( 400–800 nm ) and higher photovoltaic efficiency at a range of 6.06–9.55% . Herein, the introduction of thiazolidine-4-one ring engineering into MES4 as a rich electron acceptor enhanced electron injection and inhibited electron recombination in thiazolidine-4-one sensitizers. The MES4 system has the highest light harvesting ability and reflectivity owing to the existence of distinct functional groups that enhanced the capacity to bind the dye with the semiconductor layer (TiO 2 device's efficiency). In conclusion, the DSSC using the novel electron acceptor thiazolidine-4-one ring sensitizer achieves an unexpected PCE of 9.55% and a 32% increase over using the N719 metal complex dye. All sensitizers based on carbazole compounds had good photovoltaic performance.

Preparation, Spectral and Judd Ofelt Analyses of Luminous Octa-coordinated Europium (III) Complexes

Abstract: Heteroleptic trivalent complexes of europium were prepared on reaction of EuCl3·6H2O, fluorinated 1,3-diketone and 2,2′-bipyridine or its derivatives in the molar ratio of 1:3:1 respectively. Structural analysis of prepared complexes was done via spectral study. Luminescence features of synthesized complexes have been explored by the photoluminescence and decay spectral profile. Strong emission in the red spectral region was observed for Eu3+ ion corresponding to the electric dipole 5D0 → 7F2 hypersensitive transition. The radiative transition probabilities as well as the Judd-Ofelt parameters were computed and discussed. Complexes emit red light in the visible spectrum as illustrated by their CIE color coordinates are essential for creating effective display and lighting devices.

Imidazole-derived new colorimetric/fluorometric chemosensor for the sensitive recognition of CN− ions: Real-time application in food samples and fluorescence bio-imaging

Abstract: On account of the supreme toxicity of CN− ions in the physiological systems, it is essential to develop a sensitive chemosensor to detect cyanide ions. Herein, we designed a new 5-(3-(4,5-diphenyl-1H-imidazol-2-yl)-2-hydroxybenzylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione (BMA) sensor, which exhibits tremendous colorimetric as well as fluorometric behaviour towards CN− ions. This could be due to the nucleophilic attack of CN− ions on the dione-vinyl site, which induces intramolecular charge transfer (ICT) capabilities. The cyanide recognition mechanism of BMA was verified by optical experiments such as UV–visible and fluorescence spectroscopy, NMR, and mass analysis. Moreover, the structural characterization was done by 1H NMR titration and HRMS analysis, and the molecular orbital interactions were studied by TDDFT calculations. The sensor BMA exhibited a rapid response towards CN− ions (10 sec) with low detection limit (7.87 nM), great pH stability in the physiologically applicable pH range (6–12) and had good sensitivity and selectivity towards CN− ions. Encouraged by these detection properties, we successfully used sensor BMA to determine CN− ions in real water and food samples. To validate the colorimetric behavior of the sensor BMA, test paper strip experiments were carried out in the laboratory. We also extensively studied the effect of the sensor in Escherichia coli (E.coli) bacterial cells.

A “turn-on” fluorescent chemosensor for the meticulous detection of gallium (III) ion and its use in live cell imaging, logic gates and keypad locks

Abstract: A pyrene-based fluorescence sensor PyAP [(Z)-2-((pyren-1-ylmethylene)amino)phenol] was developed by a simple Schiff base reaction. In the presence of other metal ions, the PyAP fluorescence chemosensor recognizes only Ga3+ ions. Additionally, PyAP showed good selectivity and sensitivity for the detection of Ga3+. In a solution containing DMSO/H2O (2:8, v/v) the binding constant for PyAP with Ga3+ was 7.03 × 104 M−1, and the detection limits were 3.35 nM. The quantum yield for PyAP and PyAP-Ga3+ was calculated and found to be 0.0006 and 0.227. This chemosensor PyAP was based on the photo-induced electron transfer (PET) mechanism, which was further validated by DFT studies. The capacity of PyAP to specifically detect Ga3+ in living cells and its cell permeability were both validated by live cell imaging in T24 cells. Finally, the chemosensor PyAP was offered applications for molecular logic gates and keypad locks.

Photovoltaic Characteristics of Organic Heterocyclic 2,9-dimethyl Quinacridone in Different Solvents Using DFT Approach

Abstract: In this work, efforts had been made to develop the photovoltaic utility of 2,9-dimethyl quinacridone (2,9-DMQA) using density functional theory (DFT). Initially, the structural analysis was done using the molecule's ground state geometry to study the molecule's structural characteristics. In particular, the global reactivity descriptors, density of states (DOS) analysis, molecular electrostatic potential (MEP), contour plot, and, ionization potential surface, dipole moment, Mulliken, and natural charge distribution, were computed and analyzed to identify the nucleophilic and electrophilic sites of the molecule. Considering N – H the donor and C = O the acceptor group, the intramolecular charge transfer (ICT) was established. Hirshfeld surfaces and fingerprint plots were also determined to explore intermolecular interactions. The electronic transitions were analyzed using the simulated absorption and emission spectra. To better understand the role of solvents in inducing the photovoltaic property, the light-harvesting efficiency of the molecules was computed in the considered solvents. The title molecule provided light harvesting efficiency in order of chloroform > ethanol > cyclohexane. Other photovoltaic properties were also computed to predict the power conversion efficiency of the molecule. Consequently, the title molecule offers a strong charge conduction ability and effective electron transport from the donor to the acceptor. The obtained results were favorable enough to test experimentally 2,9-DMQA which could be used as a photosensitizer in dye-synthesized solar cells and could enhance the performance of organic photovoltaic cells.

Different positions of cyano substitution controlled directionality of ESIPT processes with two asymmetric proton acceptors system: A TD-DFT study

Abstract: • The introduction of –CN group resulted in the obvious red-shift of the absorption and fluorescence peaks. • The more red-shift the absorption peak shows, the smaller the HOMO-LUMO energy gap is. • For BTHMB-1, BTHMB-2 and BTHMB-3, the ESIPT barriers increase with the weakening of IHB. • ESIPT process in BTHMB-2 prefers to occur toward O atom, while the ESIPT process in BTHMB-1 and BTHMB-3 prefer to occur toward N atom. In order to systematically investigate the effect of substitution position on excited state intramolecular proton transfer (ESIPT) process and photophysical properties, three 3-(benzo[ d ]thiazol-2-yl)-2-hydroxy-5-methoxy-benzaldehyde (BTHMB) derivatives (BTHMB-1, BTHMB-2 and BTHMB-3) were designed by introducing the strong electron-withdrawing group (–CN) at different positions. Based on the analyses of configurations, electron densities and infrared vibrational frequencies, the intramolecular hydrogen bond (IHB) of BTHMB derivatives are all enhanced in the excited state, which would promote the ESIPT process. All the BTHMB-1, BTHMB-2 and BTHMB-3 compounds can undergo ESIPT process via two possible pathways. The potential energy curves (PECs) showed that the ESIPT barriers decrease along the order of BTHMB-2-O > BTHMB-3-O > BTHMB-1-O, and BTHMB-3-N > BTHMB-2-N > BTHMB-1-N. Due to the lower energy barrier, the ESIPT process in BTHMB-2 tends to happen to the direction of proton acceptor O atom, while the ESIPT processes in BTHMB-1 and BTHMB-3 tend to happen to the direction of proton acceptor N atom. No matter where the substituted position was, the introduction of –CN group resulted in the obvious red-shift of absorption and fluorescence peaks. For BTHMB-1-O/BTHMB-2-O/BTHMB-3-O and BTHMB-1-N/ BTHMB-2-N/BTHMB-3-N, the red-shift values of absorption and fluorescence peaks in BTHMB-1-O and BTHMB-3-N are the largest, respectively. The more red-shift the absorption and emission peaks show, the smaller the S 0 and S 1 energy gap between HOMO and LUMO are.