PL Studies Research Articles

Integrating instructional designs of personalized learning through the lens of universal design for learning

AbstractBackgroundPersonalized learning (PL), conceptualized as an education innovation that tailors learning to meet diverse student needs, has drawn increased attention from different fields of study, such as education, learning sciences, and computer science. Regardless, there is a lack of a comprehensive understanding of PL instructional designs supported by technology.ObjectivesThis systematic literature review aimed to provide an empirical integration of PL designs and implementation across disciplines through the lens of the universal design for learning (UDL) framework. As an instructional framework that guides the design to embrace learner variability, UDL holds the potential to provide foundational considerations for instructional design components of PL.MethodsWe used four databases including ERIC, OmniFile Full Text Select, Academic Search Complete, and Web of Science to search empirical studies investigating technology‐supported PL in PK‐12 school‐based settings. In total, 61 studies published between 2006 and 2020 were included in the review. We analysed PL design and implementation features and aligned these features to the UDL framework.Results and ConclusionsOur results indicated that current empirical PL design features were widely mapped onto the UDL framework. Most current PL studies investigated segmented aspects such as student attributes (e.g., interest, motivation, self‐regulation) and instructional practices (e.g., facilitating goal setting) that could contribute to PL design. Rarely did studies investigate how PL was operationalized in a system integrating various design components that consider learner characteristics, instructional support, and contextual implementation factors.ImplicationsThe analysis of alignment between PL designs within the UDL framework can serve as a starting point for stakeholders to take a more holistic approach to designing PL experiences for all learners.

Visible-light-induced photocatalytic response of easily recoverable Mn2O3/SiO2 monolith in centimeter-scale towards degradation of ofloxacin: Performance evaluation and product analysis

Monolithic-photocatalysts being easily recoverable are a suitable alternative to powdered materials for pollutant treatment. This study was conducted to prepare Mn2O3/SiO2 monoliths by wet-impregnating Mn(NO3)2․4H2O in SiO2 monoliths. The crystallinity of oxide was affirmed via XRD analyses, whereas EDS and elemental-mapping, and XPS studies revealed the constituent elements and their oxidation states. FESEM images confirmed porous morphology, while BET-analysis confirmed its mesoporous nature (∼8.44 nm) and enormous surface area (∼241 m2/g). The DRS and PL studies disclosed that Mn2O3/SiO2 monoliths consisted of narrow band-gap of ∼2.14 eV and had suitable electron/hole separation. The photocatalytic effectiveness of the monolith had been checked by degrading model dye methylene blue (MB) and antibiotic ofloxacin (OF). The influence of various reaction parameters for degradation, i.e., monolith dose, solution-pH, illumination-area, scavengers, etc., was noted. At optimal reaction conditions, outstanding competence was achieved for MB (95.23%; 0.0225 min−1) and decent results were obtained for OF-degradation (73.2%; 0.0096 min−1). The recyclable nature of the catalyst (∼12.7%-reduction in effectiveness after 10 successive cycles) was vindicated by several characterization studies after reusability. The O2•−radicals participated majorly in the degradation reaction. The reaction intermediates plus products, generated after the degradation of had been identified via LC/MS study. The mineralization extent of the OF and MB was also gauged through TOC analyses. The photocatalytic treatment of raw textile wastewater manifested ∼57.8% COD and 53% TOC-removal. This study emphasizes the competence of Mn2O3/SiO2 monoliths for the photocatalytic abatement of refractory organic contaminants.

Study of intrinsic point defects in γ-In2Se3 based on first principles calculations for the realization of an efficient UV photodetector

In 2 Se 3 have attracted researcher’s attention due to its potential optoelectronic and memory device applications, having various polymorphs with few of them having layered structure. There exists a non-layered phase with vacancy ordered in screw form known as γ-In 2 Se 3 , whose properties are found to get affected majorly by the presence of defects. Here, the first principles calculations based on the density functional theory are performed to study the intrinsic point defects in defect wurtzite structure of γ-In 2 Se 3 using GGA-PBE approximations. Thermodynamic charge transitions based on the formation energy of the defects are determined for all native defects, V In , V Se , In i , Se i , Se In , In Se , under In-rich and Se-rich experimental growth conditions. The charge transition remains the same but transition energies differ for possible coordination of Se vacancies, whereas the charge transition as well as transition energy vary for different coordination sites of In vacancies. The In interstitial, In i is the most favourable defect site under In-rich conditions whereas Se In at the VBM and V In1 near CBM are dominating under Se-rich conditions. The origin of n-type conductivity of γ-In 2 Se 3 is found to be the presence of In i interstitials and In Se antisite in the defect wurtzite γ-In 2 Se 3 . Further, the films grown using PLD shows an n-type conductivity under In-rich conditions leading to a good performance with photo responsivity and specific detectivity of 5.22 × 10 2 A/W and 5.08 × 10 13 Jones. The understanding of these vacancies determines their thermodynamic behaviour which can help for the controlled growth of γ-In 2 Se 3 which leads to better device performance. • Thermodynamic transition states are predicted for γ-In 2 Se 3 under In-rich and Se-rich growth conditions using first principles study. • Origin of n-type conductivity of γ-In 2 Se 3 is found to be the presence of In i and In Se and V Se is observed to introduce the in-gap states. • Highly crystalline n-type γ-In 2 Se 3 thin films are optimized under the In-rich growth conditions using PLD technique. • High concentrations of In i and In Se are identified using PL studies. • High responsivity and detectivity is achieved for the prepared device indicating low trap states due to V Se .

Synthesis, characterization, and thermoluminescence‐based high‐dose neutron and gamma dosimetry study of Al5BO9: Mn, Li nanophosphor

AbstractA near tissue equivalent (Zeff = 10.8) and wide bandgap (Eg = 5.95 eV) Al5BO9: Mn, Li nanophosphor was synthesized by facile gel‐combustion (GC) method, and structural characterizations were performed by XRD, infra‐red, transmission electron microscopy, energy‐dispersive spectra, diffuse reflectance UV–visible spectra, and PL studies. Thermoluminescence (TL) study of Al5BO9: Mn, Li revealed the dosimetry glow peak at 542 K, which was absent in undoped Al5BO9 indicating the importance of Mn dopant. The highest TL response was obtained for the lowest studied dopant concentration (0.1 mol% Mn) that was attributed to the concentration quenching phenomenon. The material is highly reusable with low fading (<10%) up to 110 days. TL response for both thermal neutron and gamma radiations showed excellent linearity within 5 × 109–3 × 1011 n/cm2 and 30–5000 Gy, respectively. These studies suggested promising potential of Al5BO9: Mn, Li nanophosphor in clinical neutron dosimetry and food irradiation dosimetry applications. Based on the variation of calcination temperature, strategy toward dual application, namely, radiation dosimeter and red‐light emitting phosphor of the material was established. For a better understanding of the TL process, various kinetic parameters like activation energy (E), order of kinetics (b), and frequency factor (s) were evaluated using different methodologies, and the results were found to be in good agreement.

Morphological guided sphere to dendrite BiVO4 for highly efficient organic pollutant removal and photoelectrochemical performance under solar light

Monoclinic BiVO4 (m-BiVO4) has been reported as promising phase for solar light driven photocatalysis. However, in the case of morphology guided BiVO4 with different synthetic conditions maintaining the m-BiVO4 phase remains a substantial challenge for achieving an efficient photocatalyst driven by solar light. Herein, a simple hydrothermal approach was used to produce well-defined template free m-BiVO4 dendrites with distinct branches for photo catalytically removal of organic pollutant and photocurrent generation. The development of monoclinic dendrite BiVO4 was confirmed after comprehensive structural, morphological, and optical examinations. FE-SEM images of m-BiVO4 revealed transformation of spherical to dendritic morphology with distinct branches by simply changing the HNO3 to NaOH ratios from 2:1 to 2:2, which are named as BVO 2-1 and BVO 2-2, respectively. The BVO 2-2 dendrites exhibited improved activity of 98% towards methylene blue (MB) photodegradation upon simulated solar light irradiation. The BVO 2-2 dendrites photoelectrode showed an outstanding photocurrent density of 1.4245 mAcm−2 than that of the BVO 2-1 spherical photoelectrode (0.7367 mAcm−2). Enhanced photocatalytic and photoelectrochemical action, could be ascribed to the unique morphological changes provides photoactive sites, harvest more light utilization together with higher separation of e−/h+ pairs. Furthermore, photocatalytic mechanism is investigated based on scavenger trapping agent, valence band XPS, UV Visible DRS and PL study. Our findings could pave the way for the development of dendritic nanostructure photocatalysts with improved photocatalytic activity.

Novel S-scheme 2D/2D Bi4O5Br2 nanoplatelets/g-C3N5 heterojunctions with enhanced photocatalytic activity towards organic pollutants removal

Removal of organic pollutants and pharma products in waste water using semiconductor photocatalysts has gained huge interest among recent days. However, low visible light absorption, recombination rate of charge carriers and less availability of reaction sites are still major obstacles for the photocatalysis process. Herein, an in situ-forming Bi4O5Br2 nanosheets decorated on the surface g-C3N5 were prepared via simple hydrothermal method under ambient temperature. The basic pH condition plays a vital role in growing for Bi4O5Br2 nanosheets. Various characterization studies such as TEM, SEM, PL and UV-DRS studies confirmed the formation of close contact between the Bi4O5Br2 and g-C3N5 nanosheets. The construction of Bi4O5Br2 nanoplatelets/g-C3N5 nanocomposite increases the surface-active sites and improving the separation efficiencies of excitons, which is greatly influenced in the degradation of ciprofloxacin and bisphenol-A pollutants. Meanwhile, the flow of electrons from the layered structured graphite carbon of g-C3N5 which enables excellent electrical contact in the heterojunction. Besides, the main free radicals were determined as e− and •O2−, and production level of free radicals were confirmed by radical trapping experiments. The possible degradation mechanism was proposed and discussed. Finally, this work provides a unique approach to in-situ preparation of heterojunction photocatalysts and demonstrates the prepared Bi4O5Br2 nanoplatelets/g-C3N5 photocatalysts have great potential in the waste water management.

Enhancement Photocatalytic Activity of Mn Doped Cds/Zno Nanocomposites for the Degradation of Methylene Blue Under Solar Light Irradiation

Abstract In this study, Mn doped CdS/ZnO nanocomposites synthesized by co-precipitation method and its photocatalytic activity was tested using methylene blue under solar light irradiation. The prepared hybrid nanocomposites are characterized by using different physicochemical techniques including XRD, FESEM, EDX, TEM, UV-vis DRS and PL analysis. From the XRD analysis, Mn doped ZnO/CdS nanocomposite diffraction peaks only reflect the binary crystalline structures of ZnO and CdS. However, there is no characteristic peak of Mn is found that may be because of low content of Mn doped on ZnO/CdS. But Mn (2.9 wt%) was detected in the Mn doped ZnO/CdS nanocomposite, which was measured by EDX analysis. The FESEM and TEM results exhibit the surface particle of Mn doped ZnO/CdS nanocomposite which have spherical nature and confirmed the formation of Mn doped ZnO/CdS nanocomposites. The photocatalytic degradation results have revealed that the Mn doped CdS/ZnO nanocomposites exhibit admirable activity toward the photocatalytic degradation of the MB. The reason for excellent photocatalytic activity of Mn doped CdS/ZnO nanocomposites indicates the absorbance band shifted to red region and reduction of recombination of photogenerated electron-hole, which is in good agreement with UV-visible DRS analysis and PL study results. The fitted kinetic plots showed a pseudo-first-order reaction model and the appropriate rate constants were found to be 0.0068 min−1, 0.00846 min−1, and 0.0188 min−1, for ZnO, 25 % CdS/ZnO, and 0.8 mol% Mn doped CdS/ZnO nanocomposites, respectively. The maximum photocatalytic activity was achieved by 0.8 mol% Mn doped CdS/ZnO nanocomposites with a 95% degradation efficiency of MB. Hydroxyl and superoxide radicals, having a vital role in the degradation of MB, confirmed scavenging experiments. In addition, the recycling tests displays that the Mn doped CdS/ZnO nanocomposites have shown good stability and long durability. The enhanced photodegradation activity of Mn doped CdS/ZnO nanocomposites indicates the potential of the nanocomposite for the treatment of organic pollutants from the textile wastewater.

Enhanced visible light photocatalytic degradation of rhodamine B using Ni1-xCaxFe2O4 (0 ≤ x ≤ 0.5) nanoparticles: Performance, kinetics and mechanism

In this study we have synthesized calcium doped nickel ferrite (Ni1-xCaxFe2O4 (0 ≤ x ≤ 0.5)) nanoparticles by microwave combustion technique. The prepared nanoparticles and its degradation have been studied using one of the most harmful dye rhodamine B (RhB), by means of enhanced visible light photocatalytic degradation. The structural characteristics of the sample was analysed using XRD, FT-IR, HR-SEM, TEM and XPS. Those were utilised to observe the structure, vibrations and surface morphology of the calcium doped nickel ferrite sample. UV-DRS, PL and VSM studies, give optical and magnetic properties of obtained samples. From XRD the crystallite size obtained were in the extent of 44–20 nm. The energy gap of NF1 was noticed to be improved between 3.05 eV and 2.11 eV with calcium doping. Agglomerated coalescence and recombination of electron-hole pairs were observed from HR- SEM and PL spectroscopy respectively. RhB dye degradation performance, mechanism and kinetics of prepared Ca doped Ni ferrite has been studied in detail. The efficiency of photocatalyst increased with doping. The PCD efficiency for NCF5 is 99.69% compared to NF1 which is mainly because of active parting along with prohibition of photo electron-hole pair recombination.

Visible light driven robust photocatalytic activity in vanadium-doped ZnO/SnS core-shell nanocomposites for decolorization of MB dye towards wastewater treatment

Vanadium metal oxide (V2O5) doped ZnO/SnS core-shell nanocomposites are fabricated by hydrothermal method at 2200C for 10 hours. All synthesized Nanocomposites were optically, structurally, morphologically and magnetically examined by different techniques such as UV-DRS, XRD, TEM, electron paramagnetic resonance (EPR), XPS and PL techniques. The photocatalytic activity (PCA) was studied for methylene blue (MB) model pollutant dye under 300 W visible light illumination. XRD peaks confirmed the mixed phase abundance with hexagonal ZnO and orthorhombic SnS. TEM micrographs inferred uneven surface with more agglomeration. XPS conclude V4+ oxidation state for vanadyl atoms along with constitutes elements. The UV-DRS inferred red shift in bandgap. EPR argued that vanadyl ions perform tetragonal compression distorted octahedral site symmetry. PL study described quantum confinement effect. The achieved MB dye degradation under visible light illumination is more than 96% in 2 hours. Enhanced PCA argued owing to plasmonic effect and tunable energy bandgap nature of heterogeneous semiconducting materials.

Optical and magnetic properties of fluoride-doped CeO2 obtained by an oxidative insertion method

• CeO 2 : F sample is synthesized using molten flux promoted oxidative insertion method. • PXRD and Raman spectral measurements confirmed the fluorite structure of CeO 2 :F. • Besides Ce and O, EDX analysis also revealed the presence of 18 at. % of fluoride. • PL and magnetic studies revealed a lower concentration of O vacancies in CeO 2 :F. • The F-doped sample had a higher concentration of Ce 3+ in CeO 2 :F. In the present study, we generated a fluoride-doped CeO 2 sample through the molten hydroxide flux promoted oxidative insertion approach using CeF 3 as the precursor. We analyzed the results and compared them with pure CeO 2 prepared by the same approach starting from Ce(NO 3 ) 3 . High-resolution powder X-ray diffraction, FTIR, and Raman spectral measurements confirmed both samples’ fluorite structure. The CeO 2 resulted from the oxidative flux treatment of CeF 3 had 18 at.% of fluoride ion-doped in it. The optical band gap narrowed marginally from 2.98 to 2.88 eV upon fluoride doping in CeO 2 . The blue emission intensity decreased with fluoride doping, indicating a reduction in oxygen vacancies compared to undoped CeO 2 . F-doped CeO 2 showed ferromagnetic behavior with magnetization, H c, and M r values higher than the undoped sample. A higher concentration of Ce 3+ and a lower concentration of oxygen vacancies were the consequences of fluoride doping in CeO 2 by this synthetic method.

An intriguing Z-scheme titania loaded on fibrous silica ceria for accelerated visible-light-driven photocatalytic degradation of ciprofloxacin

A novel Z-scheme titania loaded on fibrous silica ceria (Ti-FSC) was triumphantly fabricated via hydrothermal followed by electrolysis method and evaluated for the visible-light degradation of ciprofloxacin (CIP). Noticeably, Ti-FSC exhibits as an efficient photocatalyst for CIP photodegradation with 95% as followed by titania loaded on fibrous silica (Ti-FS) (68%), Ti–CeO2 (35%), FSC (47%), FS (22%), and CeO2 (17%). The combination of the inherent merits of Ti loaded on FSC is able to realize the crucial role of Ce in harnessing the high dispersion of Ti, which could beneficial for improving the performance proven by XRD, FESEM, TEM and FTIR. Consequently, high dispersion of Ti on FSC has worthwhile towards the interaction of the Si–O–Ti, Ce–O–Ti, and Si–O–Ti, which could enhance the CIP photodegradation by providing more surface defects, narrowing the band gap, improving electron-hole separation and suppressing electron-hole recombination that revealed by XPS, UV–vis/DRS, Nyquist plots and PL studies, respectively. The scavenger study revealed that the controlling species in the system was hydroxyl radical and holes. A potential Z-scheme heterojunction mechanism for Ti-FSC was deduced from the band structure analysis. The possible photodegradation pathway was proposed based on GCMS analysis. Besides, the acceptable reusability, which exceeded 90% of degradation indicated the great application potential of Z-scheme Ti-FSC in wastewater treatment and others application.

Structural, optical and enhanced antibacterial activities of ZnO and (Co, Fe) co-doped ZnO nanoparticles by sol-gel combustion method

Zn1-x(Co, Fe)xO nanoparticles (NPs) were synthesized by sol-gel combustion method.XRD pattern confirmed the formation of single-phase hexagonal (wurtzite) structure in all samples withP63mcspace group.The average crystallite sizes varied between 20 and 28 nm. All samples were optically activated under ultraviolet light. The optical band gap values varied between 3.33 and 3.82 eV. The PL study revealed the reduction of the recombination of charge carriers due to (Co,Fe) co-doping into ZnO. Enhancement of the antibacterial activity was observed due to (Co,Fe) co-doping. Zn0.95Co0.025Fe0.025NPs exhibited excellent antibacterial activity against E. coli and S. aureus bacteria.

Photocatalytic and antibacterial activities of green synthesized Ag doped MgO nanocomposites towards environmental sustainability

The utilization of MgO nanoparticles (NPs) for Photocatalytic and antimicrobial activities has gained lots of attention in recent years. Since silver is an expensive material, it's of interest to check that doping of very small concentration of silver will increase the pollutant degradation efficiency of composites. Here Aloe Vera plant extract was used for synthesis of MgO, Ag NPs and Ag/MgO-nanocomposites (NCs). Green synthesized NPs and NCs were confirmed by using different techniques like UV–Vis, BET, TGA, FTIR, PL, XRD (optical, functional, Thermal, Structural) EDX, TEM, SEM, XPS, EIS and EPR (morphological, elemental, photoelectrical and ROS) studies respectively. Then NPs and NCs were applied for the photocatalytic activity of methylene blue (MB), phenol and antimicrobial studies of E. coli bacteria. Ag/MgO–NCs showed 90.18% dye and 80.67% phenol degradation in 120 min which killed E. Coli pathogenic bacteria in 25 min under solar light irradiations. In disk diffusion methods, it inactivates 24 mm area of bacterial cell growth. Thus, among these green synthesized NPs and NCs, Ag/MgO–NCs exhibited enhanced photocatalytic and antimicrobial activities.

Surfactant induced copper vanadate (β-Cu2V2O7, Cu3V2O8) for different textile dyes degradation

In this study, pristine β-Cu2V2O7, CTAB-β-Cu2V2O7 and PVP–Cu3V2O8 were synthesized via hydrothermal method. The synthesized brown powder samples were exemplified using XRD, UV, PL, Raman and SEM studies. Further with XRD, we confirmed that the impurities were eradicated in addition of surfactant PVP. The bandgap obtained were 3.09 eV, 2.97 eV and 2.28 eV for β-Cu2V2O7, CTAB-β-Cu2V2O7 and PVP–Cu3V2O8. The morphology of β-Cu2V2O7 was found to be cluster of nanoparticles with high level of agglomeration. While adding the surfactants (CTAB, PVP) the nano platelets were grown and uniformly arranged. The PVP-Cu3V2O8 sample exhibited 96%, 77% and 96% efficiency on reducing Methylene Blue, Rhodamine B and Malachite Green dyes. The enhancement of attaining complete efficiency by the PVP–Cu3V2O8 photocatalyst is attributed by the appropriate phase of host material and the PVP itself acted as a trapper for electron and hole which induced the rate of degrading toxic pollutants. The PVP–Cu3V2O8 photocatalyst will be enthusiastic and optimized aspirant for reducing organic pollutants and for wastewater management in future days.

Tuning optical properties of CsPbBr3 by mixing Nd3+ trivalent lanthanide halide cations for blue light emitting devices

In recent years, significant progress has been made in the red and green perovskite quantum dots (PQDs) based light-emitting devices. However, a scarcity of blue-emitting devices that are extremely efficient precludes their research and development for optoelectronic applications. Taking advantage of tunable bandgaps of PQDs over the entire visible spectrum, herein we tune optical properties of CSPbBr3 by mixing Nd3+ trivalent lanthanide halide cations for blue light-emitting devices. The CsPbBr3 PQDs doped with Nd3+ trivalent lanthanide halide cations emitted strong photoemission from green into the blue region. By adjusting their doping concentration, a tunable wavelength from (515 nm) to (450 nm) was achieved with FWHM from (37.83 nm) to (16.6 nm). We simultaneously observed PL linewidth broadening thermal quenching of PL and the blue shift of the optical bandgap from temperature-dependent PL studies. The Nd3+ cations into CsPbBr3 PQDs more efficiently reduced non-radiative recombination. As a result of the efficient removal of defects from PQDs, the photoluminescence quantum yield (PLQY) has been significantly increased to 91% in the blue-emitting region. Significantly, Nd3+ PQDs exhibit excellent long-term stability against the external environment, including water, temperature, and ultraviolet light irradiation. Moreover, we successfully transformed Nd3+ doped PQDs into highly fluorescent nanocomposites. Incorporating these findings, we fabricate and test a stable blue light-emitting LED with EL emission at (462 nm), (475 nm), and successfully produce white light emission from Nd3+ doped nanocomposites with a CIE at (0.32, 0.34), respectively. The findings imply that low-cost Nd3+ doped perovskites may be attractive as light converters in LCDs with a broad color gamut.

Enhanced photocatalytic behavior of ZnO nanorods decorated with a Au, ZnWO4, and Au/ZnWO4 composite: Synthesis and characterization

The present work studied ZnO nanorod (ZnO NRs) enhanced with ZnWO4 and gold (Au) nanoparticles. The ZnO NRs were successfully synthesized by the hydrothermal method. Subsequently, the hydrothermal method was used to load ZnWO4 on the ZnO surface to form the ZnWO4/ZnO NRs heterostructure. Furthermore, Au nanoparticles were coated on the ZnO NRs and ZnWO4/ZnO NRs to achieve the Au/ZnO NRs and Au/ZnWO4/ZnO NRs heterostructures, respectively. The samples were charactered by XRD, SEM, EDX, TEM, UV–Vis, and XPS techniques. The photocatalytic behavior of ZnO and the various enhancements was investigated. The results showed that the as mentioned coating materials can enhance the photocatalytic properties of the ZnO material where the Au/ZnWO4/ZnO sample is the best photocatalyst compared to the others. According to the EIS and PL study, the Au/ZnWO4 decoration leads to the low e−/h+ pairs recombination rate which is attributed to the high photocatalytic performance.

Visible light active black TiO2 nanostructures and its RGO based nanocomposite for enhanced hydrogen generation and electrochemical potency

Hydrogen is considered to be a sustainable, clean form of energy and a fundamental pillar to combat global warming. Hence, it is necessary to develop an eco – friendly, efficient energy storage device for future generations. Herein, we have developed an effective, vacuum annealing synthetic protocol to prepare black TiO2 (BT), black-nitrogen doped TiO2 (BNT) and RGO composited black TiO2 (BTG) in the presence of ethanol for an efficient photocatalytic hydrogen generation. Change in the optical and electronic properties of black nanocomposites are examined by UV-vis and PL studies. Investigation of FTIR and XPS confirms the reduction of functional groups on the nanocomposites. Meanwhile, low photocatalytic efficiency and capacitance of BNT than expected has been associated with the formation of N-O moiety during the annealing process. Plausible mechanism has been proposed for the low efficiency of BNT to understand the electronic structures of black nanocomposite.

Generating pure red and near white light in NaLaF4 microcrystal by controlling site-selective luminescence of Eu3+ and Tb3+ dopant ions

Here in this work, we aim to develop both red and near white light emitting phosphor materials using Eu3+ and Tb3+ as co-dopant ions and NaLaF4 as host matrix. It was observed that both Na and La atom possess two different types of lattice sites having different co-ordination and symmetry. We have theoretically calculated the substitution energies for Eu3+ and Tb3+ ions for all the available lattice sites and found that the preference of distribution of the dopant ions into these lattice sites is different. While Eu3+ ion prefers 9-coordinated Na1/La2 site and 6-coordinated Na2 site, Tb3+ prefers 9-coordinated La1 site. This is also reflected in the PL study of both pure Eu3+ and Eu3+-Tb3+ co-doped compounds. Substitution of Eu3+ ion at Na2 site results in short-lifetime value and highly intense red ED line as observed from time resolved spectra analysis at different delay time. On contrary, its lifetime value was found to be higher at 9-coordinated La2 site and resulting higher intense orange MD line. Defect centres, which are being created due to charge imbalance during substitution at Na site, is solely responsible for such behaviour. Increasing concentration of Eu3+ ions also resulted in higher red colour purity of the Eu3+ doped compound due to more defect induced asymmetry surrounds Eu3+ ion. For the Eu3+-Tb3+ co-doped compounds, the Tb3+→Eu3+ energy transfer dynamic is responsible for tuneable emission colour characteristics from white light to red. From lifetime study with varied concentration of Tb3+ ion, we have observed that the possibility of charge transfer from Tb3+ ion at Na-site (Tb3+Na1) to Eu3+ ion at Na2 (Eu3+Na2) is more compared to that from Tb3+La2 to Eu3+Na2.

Hybrid magnetic core-shell TiO2@CoFe3O4 composite towards visible light-driven photodegradation of Methylene blue dye and the heavy metal adsorption: isotherm and kinetic study.

Magnetic core-shell TiO2@CoFe3O4 (TCM) composite photocatalytic particles with a core-shell structure were synthesized by the co-precipitation method as a novel catalyst for methylene blue (MB) dye degradation and adsorption efficiency of heavy-metal ion Pb(II) from aqueous solution. Various analytical techniques have verified the formation of the TCM core-shell through TEM, XRD, FT-IR, Raman, PL, and UV analysis. The presence of TiO2 and cobalt magnetite in the TCM core shell is confirmed by XRD analysis. The formation of a homogenous CoFe3O4shell on TiO2 spheres is confirmed by HR-TEM investigation. TiO2 nanoparticle has a rutile structure with an average crystallite size of about 57.44 and a TCM core-shell of about 64.62nm. From UV and PL studies, it was found that the core shell absorbs the visible range of the electromagnetic spectrum, which improves the effective separation between photo carriers. This study focused on several factors that influence metal ion adsorption, including initial concentrations, adsorbent dose, pH, and contact time. The TCM nanocomposite successfully separated the heavy metal ion Pb(II) from aqueous solutions, and the model predictions exactly matched the experimental results. For TCM material, the maximum adsorption efficiency for Pb(II) was 33.09mg/g. The photocatalytic performance of TiO2 and TCM is about 12% and 91% after 60min for MB dye degradation. It was found that TiO2@CoFe3O4 core-shell nanoparticles perform better as photo catalysts than pure TiO2 and CoFe3O4due to their high efficiency and reusability. Furthermore, the analysis revealed that heavy metal adsorption from aqueous solutions could be reused over seven cycles with no adsorption capacity modification.

PL study of Mn-doped ZnO nanowires

Mn-doped ZnO nanowires have been fabricated through a high temperature vapor-solid deposition process. The low-temperature photoluminescence spectra of the samples show that there are multipeak emissions at the ultra- violet (UV) region (about 3.4–3.0 eV). The excitonic and phonon-assisted transitions in Mn-doped ZnO nanowires were investigated. The results show that there is an obvious oscillatory structure emission at the UV region under low temperature from 12–125 K. The oscillatory structure has an energy periodicity about 70 meV and the oscillatory structure is mainly attributed to longitudinal optical (LO) phonon replicas of free excitons (FX). The multipeak emissions at 12 K are attributed to a donor-bound exciton (DBX, 3.3617 eV), 1LO-phonon replicas of a free exciton (FX- 1LO, 3.3105 eV), 2LO-phonon replicas of a free exciton (FX-2LO, 3.2396 eV), and 3LO-phonon replicas of a free exciton (FX-3LO, 3.1692 eV), respectively. The intensity of UV emission and the efficiency of emission from the Mn- doped ZnO nanowires are improved.