Interplay between photoinduced charge and energy transfer in manganese doped perovskite quantum dots.

A comprehensive study on the photo-excited relaxation dynamics in semiconducting perovskite quantum dots (PQDs) is pivotal in realizing their extensive potential for optoelectronics applications. Among different competing photoinduced relaxation kinetics, energy transfer and charge transfer (CT) in PQDs need special attention, as they often influence the device efficacy, particularly with the donor-acceptor hybrid architecture. In this work, we explore a detailed investigation into photoinduced CT dynamics in mixed halide undoped CsPb(Br/Cl)3 and Mn2+ doped CsPb(Br/Cl)3 PQDs with a quinone molecule, p-benzoquinone (BQ). The energy level alignment of undoped PQDs with BQ allows an efficient CT, whereas Mn2+ doping reduces the CT efficiency, experiencing a competition between energy transfer from host to dopant and CT to BQ. The conductive atomic force microscopy measurements unveil a direct correlation with the spectroscopic studies by showing a significant improvement in the conductance of undoped PQDs in the presence of BQ, while an inappreciable change is observed for doped PQDs. A much-reduced transition voltage and barrier height in the presence of BQ further validate faster CT for undoped PQD than the doped one. Furthermore, Mn2+ doping in PQDs is observed to enhance their stability, showing better air and thermal stability compared to their undoped counterparts. These results reveal that doping strategy can regulate the CT dynamics in these PQDs and increase their stability, which will be beneficial for the development of desired optoelectronic devices with long-term stability.

Polyoxometalate nanocluster-infused triple IPN hydrogels for excellent microplastic removal from contaminated water: detection, photodegradation, and upcycling.

Microplastic (MP) pollution pervades global ecosystems, originating from improper plastic disposal and fragmentation due to factors like hydrolysis and biodegradation. These minute particles, less than 5 mm in size, have become omnipresent, impacting terrestrial, freshwater, and marine environments worldwide. Their ubiquity poses severe threats to marine life by causing physical harm and potentially transferring toxins through the food chain. Addressing this environmental crisis necessitates a sustainable strategy. Our proposed solution involves a highly efficient copper substitute polyoxometalate (Cu-POM) nanocluster infused triple interpenetrating polymer network (IPN) hydrogel, comprising chitosan (CS), polyvinyl alcohol (PVA), and polyaniline (PANI) (referred to as pGel@IPN) for mitigating MP contamination from water. This 3D IPN architecture, incorporating nanoclusters, also enhances the hydrogel's photodegradation capabilities. Our scalable approach offers a sustainable strategy to combat MPs in water bodies, as demostrated by the adsorption behaviors on the hydrogel matrix under varying conditions, simulating real-world scenarios. Evaluations of physicochemical properties, mechanical strength, and thermal behavior underscore the hydrogel's robustness and stability. Detecting minute MP particles remains challenging, prompting us to label MPs with Nile red for fluorescence microscopic analysis of their concentration and adsorption on the hydrogel. The catalytic properties of POM within the hydrogel facilitate UV-induced MP degradation, highlighting a sustainable solution. Our detailed kinetics and isotherm studies revealed pseudo-first-order and Langmuir models as fitting descriptors for MP adsorption, exhibiting a high maximum adsorption capacity (Qm). Notably, pGel@IPN achieved ∼95% and ∼93% removal efficiencies for polyvinyl chloride (PVC) and polypropylene (PP) MPs at pH ∼ 6.5, respectively, also demonstrating reusability for up to 5 cycles. Post-end-of-life, the spent adsorbent was efficiently upcycled into carbon nanomaterials, effectively removing the heavy metal Cr(VI), exemplifying circular economy principles. Our prepared hydrogel emerges as a potent solution for MP removal from water, promising effective mitigation of the emerging pollutants of MPs while ensuring sustainable environmental practices.

Modulation of carrier conduction in CsPbBr3 perovskite quantum dots with band-aligned electron and hole acceptors.

The lead halide perovskites have emerged as promising materials with intriguing photo-physical properties and have immense potential for photovoltaic applications. A comprehensive study on the kinetics of charge carrier (electron/hole) generation and transfer across the interface is key to realizing their future scope for efficient device engineering. Herein, we investigate the interfacial charge transfer (CT) dynamics in cesium lead halide (CsPbBr3) perovskite quantum dots (PQDs) with energetically favorable electron acceptors, anthraquinone (AQ) and p-benzoquinone (BQ), and hole acceptors such as pyrene and 4-(dimethylamino)pyridine (DMAP). With various steady-state and time-resolved spectroscopic and microscopic measurements, a faster electron transfer rate is estimated for CsPbBr3 PQDs with BQ compared to that of AQ, while a superior hole transfer for DMAP is divulged compared to pyrene. In concurrence with the spectroscopic measurements, conducting atomic force microscopic studies across the electrode-PQD-electrode junction reveals an increment in the conductance of the PQD in the presence of both the electron and hole acceptors. The variation of the density of states calculation in the presence of the hole acceptors offers strong support and validation for faster CT efficiency. The above findings suggest that a careful selection of simple yet efficient molecular arrangements can facilitate rapid carrier transfer, which can be designed as auxiliary layers for smooth CT and help in the engineering of cost-effective photovoltaic devices.

Unraveling the Relevance of Electron and Hole Transfer in Lead Halide Perovskite Nanocrystals on Current Conduction.

Optimization of perovskite-based optoelectronic performance demands prudent engineering in the device architecture with facile transport of generated charge carriers. Herein, we explore the charge transfer (CT) kinetics in perovskite nanocrystals (PNCs), CsPbBr3, with two redox-active quinones, menadione (MD) and anthraquinone (AQ), and its alteration in halide exchanged CsPbCl3. With a series of spectroscopic and microscopic measurements, we infer that both electron and hole transfer (ET-HT) prevail in CsPbCl3 with quinones, resulting in a faster CT, while ET predominates for CsPbBr3. Furthermore, current-sensing atomic force microscopy measurements demonstrate that the conductance across a metal-PNC-metal nanojunction is improved in the presence of quinones. The contributions of ET and HT to current conduction across PNCs are well supported and validated by theoretical calculations of the density of states. These outcomes convey a new perspective on the relevance of ET and HT in the optimal current conduction and optoelectronic device engineering of perovskites.

Deciphering the Relevance of Quantum Confinement in the Optoelectronics of CsPbBr3 Perovskite Nanostructures.

Perovskites (PVKs) have emerged as an exciting class of semiconducting materials owing to their magnificent photophysical properties and been used in solar cells, light-emitting diodes, photodetectors, etc. The growth of multidimensional nanostructures has revealed many exciting alterations in their optoelectronic properties compared to those of their bulk counterparts. In this work, we have spotlighted the influence of quantum confinement in CsPbBr3 PVKs like the quantum dot (PQD), nanoplatelet (PNPL), and nanorod (PNR) on their charge transfer (CT) dynamics with 1,4-naphthoquinone (NPQ). The energy band alignment facilitates the transfer of both electrons and holes in the PNPL to NPQ, enhancing its CT rate, while only electron transfer in the PQD and PNR diminishes CT. The tunneling current across a metal-nanostructure-metal junction for the PNPL is observed to be higher than others. The higher exciton binding energy in the PNPL results in efficient charge transport by enhancing the mobility of the excited-state carrier and its lifetime compared to those of the PNR and PQD.

Interpenetrating polymer networks for desalination and water remediation: a comprehensive review of research trends and prospects.

Interpenetrating polymer network (IPN) architectures have gained a lot of interest in recent decades, mainly due to their wide range of applications including water treatment and environmental remediation. IPNs are composed of two or more crosslinked polymeric matrices that are physically entangled but not chemically connected. In polymer science, the interpenetrating network structure with its high polymer chain entanglement is commonly used to generate materials with many functional properties, such as mechanical robustness and adaptable structure. In order to remove a targeted pollutant from contaminated water, it is feasible to modify the network architectures to increase the selectivity by choosing the monomer appropriately. This review aims to give a critical overview of the recent design concepts of IPNs and their applications in desalination and water treatment and their future prospects. This article also discusses the inclusion of inorganic nanoparticles into traditional polymeric membrane networks and its advantages. In the first part, the current scenario for desalination, water pollution and conventional desalination technologies along with their challenges is discussed. Subsequently, the main strategies for the synthesis of semi-IPNs and full-IPNs, and their relevant properties in water remediation are presented based on the nature of the networks and mechanism, with an emphasis on the IPN membrane. This review article has thoroughly investigated and critically assessed published works that describe the latest study on developing IPN membranes, hydrogels and composite materials in water purification and desalination. The goal of this critical analysis is to elicit fresh perspectives regarding the application and advantages of IPNs in desalination and water treatment. This article will also provide a glimpse into future areas of research to address the challenges relating to advanced water treatment as well as its emerging sustainable approaches. The study has put forward a convincing justification and establishes the relevance of IPNs being one of the most intriguing and important areas for achieving a sustainable generation of advanced materials that could benefit mankind.

Fractal Dimension-Based Infection Detection in Chest X-ray Images.

The current ongoing trend of dimension detection of medical images is one of the challenging areas which facilitates several improvements in accurate measuring of clinical imaging based on fractal dimension detection methodologies. For medical diagnosis of any infection, detection of dimension is one of the major challenges due to the fractal shape of the medical object. Significantly improved outcome indicates that the performance of fractal dimension detection techniques is better than that of other state-of-the-art methods to extract diagnostically significant information from clinical image. Among the fractal dimension detection methodologies, fractal geometry has developed an efficient tool in medical image investigation. In this paper, a novel methodology of fractal dimension detection of medical images is proposed based on the concept of box counting technique to evaluate the fractal dimension. The proposed method has been evaluated and compared to other state-of-the-art approaches, and the results of the proposed algorithm graphically justify the mathematical derivation of the box counting approach in terms of Hurst exponent.

Hollow Polyaniline Microsphere/MnO2/Fe3O4 Nanocomposites in Adsorptive Removal of Toxic Dyes from Contaminated Water.

Dyes are considered as recalcitrant compounds and are not easily removed through conventional water treatment processes. The present study demonstrated the fabrication of polyaniline hollow microsphere (PNHM)/MnO2/Fe3O4 composites by in situ deposition of MnO2 and Fe3O4 nanoparticles on the surface of PNHM. The physicochemical characteristics and adsorption behavior of the prepared PNHM/MnO2/Fe3O4 composites towards the removal of toxic methyl green (MG) and Congo red (CR) dyes have been investigated. The characterization study revealed the successful synthesis of the prepared PNHM/MnO2/Fe3O4 adsorbent with a high Brunauer-Emmett-Teller (BET) surface area of 191.79 m2/g. The batch adsorption study showed about 88 and 98% adsorption efficiencies for MG and CR dyes, respectively, at an optimum dose of 1 g/L of PNHM/MnO2/Fe3O4 at pH ∼6.75 at room temperature (303 ± 3 K). The adsorption phenomena of MG and CR dyes were well described by the Elovich and pseudo-second-order kinetics, respectively, and Freundlich isotherm model. The thermodynamics study shows that the adsorption reactions were endothermic and spontaneous in nature. The maximum adsorption capacity (Qmax) for MG and CR dyes was observed as 1142.13 and 599.49 mg/g, respectively. The responsible adsorption mechanisms involved in dye removal were electrostatic interaction, ion exchange, and the formation of the covalent bonds. The coexisting ion study revealed that the presence of phosphate co-ion considerably reduced the CR dye removal efficiency. However, the desorption-regeneration study demonstrated the successful reuse of the spent PNHM/MnO2/Fe3O4 material for the adsorption of MG and CR dyes for several cycles. Given the aforementioned findings, the PNHM/MnO2/Fe3O4 nanocomposites could be considered as a promising adsorbent for the remediation of dye-contaminated water.

Hollow Polyaniline Microsphere/Fe3O4 Nanocomposite as an Effective Adsorbent for Removal of Arsenic from Water.

Polyaniline hollow microsphere (PNHM)/Fe3O4 magnetic nanocomposites have been synthesized by a novel strategy and characterized. Subsequently, PNHM/Fe3O4-40 (Fe3O4 content: 40 wt.%) was used as an adsorbent for the removal of arsenic (As) from the contaminated water. Our investigations showed 98-99% removal of As(III) and As(V) in the presence of PNHM/Fe3O4-40 following pseudo-second-order kinetics (R2 > 0.97) and equilibrium isotherm data fitting well with Freundlich isotherm (R2 > 0.98). The maximum adsorption capacity of As(III) and As(V) correspond to 28.27 and 83.08 mg g-1, respectively. A probable adsorption mechanism based on X-ray photoelectron spectroscopy analysis was also proposed involving monodentate-mononuclear/bidentate-binuclear As-Fe complex formation via legend exchange. In contrast to NO3- and SO42- ions, the presence of PO43- and CO32- co-ions in contaminated water showed decrease in the adsorption capacity of As(III) due to the competitive adsorption. The regeneration and reusability studies of spent PNHM/Fe3O4-40 adsorbent showed ~83% of As(III) removal in the third adsorption cycle. PNHM/Fe3O4-40 was also found to be very effective in the removal of arsenic (<10 µg L-1) from naturally arsenic-contaminated groundwater sample.

Alteration in branchial NKA and NKCC ion-transporter expression and ionocyte distribution in adult hilsa during up-river migration.

Hilsa (Tenualosa ilisha) is a clupeid that migrates from the off-shore area through the freshwater river for spawning. The purpose of this study was to investigate the involvement of branchial Na+/K+-ATPase (NKA) and Na+/K+/2Cl- cotransporter (NKCC) in maintaining ionic homeostasis in hilsa while moving across the salt barriers. Hilsa, migrating through marine and brackish waters, did not show any significant decline in NKA activity, plasma osmolality, and plasma ionic concentration. In contrast, all the parameters declined significantly, after the fish reached in freshwater zone of the river. Immunoblotting with NKA α antibody recognized two bands in gill homogenates. The intensity of the higher molecular NKA band decreased, while the other band subsequently increased accompanying the movement of hilsa from marine water (MW) to freshwater. Nevertheless, total NKA expression in marine water did not change prior to freshwater entry. NKCC expression was down-regulated in gill, parallel with NKA activity, as the fish approached to the freshwater stretch of river. The NKA α-1 and NKCC1 protein abundance decreased in freshwater individuals by 40% and 31%, respectively, compared to MW. NKA and NKCC1 were explicitly localized to branchial ionocytes and immunoreactive signal appeared throughout the cytoplasm except for the nucleus and the most apical region indicates a basolateral/tubular distribution. Immunoreactive ionocytes were distributed on the filaments and lamellae; lamellar ionocytes were more in number irrespective of habitat salinity. The decrease in salinity caused a slight reduction in ionocyte number, but not in size and the underlying distribution pattern did not alter. The overall results support previously proposed models that both the ion transporters are involved in maintaining ionic homeostasis and lamellar ionocytes may have the function in hypo-osmoregulation in migrating hilsa, unlike other anadromous teleosts.