Solar Light Assisted Reductive Hydrogen Peroxide Production from Dioxygen and Water

Department of Chemical EngineeringThe finite nature of fossil fuel reserves and the increasing pace of climate change mean that we must find and harness clean and sustainable energy sources. H2O2 can be one such energy source as it generates more energy than any other fuel without generating any pollutant. Moreover, H2O2 has widespread applications in chemical industries, medicinal science, water treatment, etc. However, the commercial multistep anthraquinone (AQ) process for H2O2 production requires high energy input for hydrogenation/oxidation reaction, gases supply (H2 and O2), and noble metal catalysts. The usage of organic solvents and generation of by-products during extraction makes it non-eco-friendly process. However, photocatalytic H2O2 generation can be a potential replacement to AQ process, as it doesn???t require explosive hydrogen gas, expensive noble metals, etc. Considering, H2O2 as a potential future energy carrier, the research will be much focused on constructing an efficient and sustainable photochemical solar H2O2 production system capable of producing high concentrations of H2O2. In this dissertation, three different potential light absorbers (pristine as well as hybrid) have been synthesized directly/ indirectly to construct a sustainable powder based photocatalytic system capable of producing high concentrations of H2O2 under visible light irradiation at ambient conditions. In this reported research work, both organic as well as inorganic photocatalysts have been utilized to scale up the H2O2. In Chapter 2, to maximize the light harvesting efficiency over a wide range of the solar spectrum and enhancing the charge transfer efficiency by minimizing charge recombinations, polymer/TiO2 heterojunction photocatalyst has been synthesized. To find an ideal combination, and to construct an efficient heterojunction between poly (fluorene-benzothiadiazole) (PFBT) based polymeric photocatalyst and TiO2, three different fluorine substituted PFBT polymer (PFBT, PFFBT, and PF2FBT) have been synthesized and tested. Compared to bare TiO2, polymer/TiO2 heterojunction (polymer having 1 or 2 fluorine atom) generates nearly 80 times higher H2O2. The theoretical calculations corroborated by experimental results demonstrate that the hydrophobic character of the polymeric photocatalysts plays a key role in maximizing the performance of polymer/TiO2 hybrid catalyst. The hydrophobic character of fluorinated PFBT polymeric photocatalysts restricts the surface adsorption of photogenerated H2O2, which prevent the photodegradation of the same. Contrary to polymer/TiO2 heterojunction polymer, bare TiO2 show a high degree of H2O2 photodegradation which highlights its inability of H2O2 production in the absence of surface shielding. The hydrophobic nature of pristine polymeric, as well as hybrid photocatalysts, have been substantiated by contact angle measurement studies. As we highlighted earlier, one of the main challenges for scale up the photochemical H2O2 generation is the stabilization of photogenerated H2O2 in the reaction medium. In Chapter 3, the metal-organic framework (MOF) derived carbon encapsulated CdS (C@CdS) composite photocatalysts have been synthesized and tested for photochemical H2O2 generation. The C@CdS photocatalyst is synthesized by carbonization of cadmium and sulfur atoms containing MOF by annealing at the high temperature in different gases environment. The transformation of MOF structure to C@CdS photocatalyst has been confirmed by analysis-ray diffraction, and electron microscopic techniques. The carbon matrix on the surface of CdS photocatalyst act as a shield to inhibiting the H2O2 photodecomposition on its surface. The exciting feature of this reported work is the unassisted (i.e., in the absence of hole scavenger) H2O2 production under visible light irradiation. The encapsulation of CdS into the carbon matrix increases the H2O2 production (2 mM) by nearly 4 folds in comparison to commercialized CdS. The extended photochemical reaction studies demonstrate the absence of point of equilibration even after 24 h irradiation in the case of for C@CdS which further widened the difference in the photogenerated H2O2 concentration over C@CdS (2.09 mM) and commercial CdS (0.33 mM) after 24 h of visible light irradiation. In Chapter 4, organic photocatalyst graphitic carbon nitride (g-C3N4) has been utilized for photochemical production of H2O2. To carry out the photochemical reaction g-C3N4 was synthesized by ionothermal process. The optimized ionothermal method helps us in synthesizing triazine structured, highly photoactive g-C3N4. A comparison has also been drawn between the photochemical H2O2 generation efficiency of g-C3N4 sample synthesized by two different methods, i.e., thermal condensation, and ionothermal process. It was quite surprising that g-C3N4 synthesized by ionothermal process shows nearly 7 fold high H2O2 production (16 mM) after 24 h of visible light irradiation under ambient conditions. The H2O2 production rate over as-synthesized g-C3N4 is far higher than any of the photochemical processes reported so far, and even comparable to the electrochemical processes for H2O2 production.clos

Deep Learning-Generated Nighttime Reflectance and Daytime Radiance of the Midwave Infrared Band of a Geostationary Satellite

Midwave infrared (MWIR) band of 3.75 μm is important in satellite remote sensing in many applications. This band observes daytime reflectance and nighttime radiance according to the Earth’s and the Sun’s effects. This study presents an algorithm to generate no-present nighttime reflectance and daytime radiance at MWIR band of satellite observation by adopting the conditional generative adversarial nets (CGAN) model. We used the daytime reflectance and nighttime radiance data in the MWIR band of the meteoritical imager (MI) onboard the Communication, Ocean and Meteorological Satellite (COMS), as well as in the longwave infrared (LWIR; 10.8 μm) band of the COMS/MI sensor, from 1 January to 31 December 2017. This model was trained in a size of 1024 × 1024 pixels in the digital number (DN) from 0 to 255 converted from reflectance and radiance with a dataset of 256 images, and validated with a dataset of 107 images. Our results show a high statistical accuracy (bias = 3.539, root-mean-square-error (RMSE) = 8.924, and correlation coefficient (CC) = 0.922 for daytime reflectance; bias = 0.006, RMSE = 5.842, and CC = 0.995 for nighttime radiance) between the COMS MWIR observation and artificial intelligence (AI)-generated MWIR outputs. Consequently, our findings from the real MWIR observations could be used for identification of fog/low cloud, fire/hot-spot, volcanic eruption/ash, snow and ice, low-level atmospheric vector winds, urban heat islands, and clouds

Diversity and Physiological Characteristics of Antarctic Lichens-Associated Bacteria

The diversity of lichen-associated bacteria from lichen taxa Cetraria, Cladonia, Megaspora, Pseudephebe, Psoroma, and Sphaerophorus was investigated by sequencing of 16S rRNA gene amplicons. Physiological characteristics of the cultured bacterial isolates were investigated to understand possible roles in the lichen ecosystem. Proteobacteria (with a relative abundance of 69.7–96.7%) were mostly represented by the order Rhodospirillales. The 117 retrieved isolates were grouped into 35 phylotypes of the phyla Actinobacteria (27), Bacteroidetes (6), Deinococcus-Thermus (1), and Proteobacteria (Alphaproteobacteria (53), Betaproteobacteria (18), and Gammaproteobacteria (12)). Hydrolysis of macromolecules such as skim milk, polymer, and (hypo)xanthine, solubilization of inorganic phosphate, production of phytohormone indole-3-acetic acid, and fixation of atmospheric nitrogen were observed in different taxa. The potential phototrophy of the strains of the genus Polymorphobacter which were cultivated from a lichen for the first time was revealed by the presence of genes involved in photosynthesis. Altogether, the physiological characteristics of diverse bacterial taxa from Antarctic lichens are considered to imply significant roles of lichen-associated bacteria to allow lichens to be tolerant or competitive in the harsh Antarctic environment

Characterization of a Novel CaCO3-Forming Alkali-Tolerant Rhodococcus erythreus S26 as a Filling Agent for Repairing Concrete Cracks

Biomineralization, a well-known natural phenomenon associated with various microbial species, is being studied to protect and strengthen building materials such as concrete. We characterized Rhodococcus erythreus S26, a novel urease-producing bacterium exhibiting CaCO3-forming activity, and investigated its ability in repairing concrete cracks for the development of environment-friendly sealants. Strain S26 grown in solid medium formed spherical and polygonal CaCO3 crystals. The S26 cells grown in a urea-containing liquid medium caused culture fluid alkalinization and increased CaCO3 levels, indicating that ureolysis was responsible for CaCO3 formation. Urease activity and CaCO3 formation increased with incubation time, reaching a maximum of 2054 U/min/mL and 3.83 g/L, respectively, at day four. The maximum CaCO3 formation was achieved when calcium lactate was used as the calcium source, followed by calcium gluconate. Although cell growth was observed after the induction period at pH 10.5, strain S26 could grow at a wide range of pH 4–10.5, showing its high alkali tolerance. FESEM showed rhombohedral crystals of 20–60 µm in size. EDX analysis indicated the presence of calcium, carbon, and oxygen in the crystals. XRD confirmed these crystals as CaCO3 containing calcite and vaterite. Furthermore, R. erythreus S26 successfully repaired the artificially induced large cracks of 0.4–0.6 mm width

Nighttime Reflectance Generation in the Visible Band of Satellites

Visible (VIS) bands, such as the 0.675 μm band in geostationary satellite remote sensing, have played an important role in monitoring and analyzing weather and climate change during the past few decades with coarse spatial and high temporal resolution. Recently, many deep learning techniques have been developed and applied in a variety of applications and research fields. In this study, we developed a deep-learning-based model to generate non-existent nighttime VIS satellite images using the Conditional Generative Adversarial Nets (CGAN) technique. For our CGAN-based model training and validation, we used the daytime image data sets of reflectance in the Communication, Ocean and Meteorological Satellite / Meteorological Imager (COMS/MI) VIS (0.675 μm) band and radiance in the longwave infrared (10.8 μm) band of the COMS/MI sensor over five years (2012 to 2017). Our results show high accuracy (bias = −2.41 and root mean square error (RMSE) = 36.85 during summer, bias = −0.21 and RMSE = 33.02 during winter) and correlation (correlation coefficient (CC) = 0.88 during summer, CC = 0.89 during winter) of values between the observed images and the CGAN-generated images for the COMS VIS band. Consequently, our CGAN-based model can be effectively used in a variety of meteorological applications, such as cloud, fog, and typhoon analyses during daytime and nighttime

Development of Thiol–Ene Reaction-Based HA Hydrogel with Sustained Release of EGF for Enhanced Skin Wound Healing

This study develops a novel drug delivery system using a hyaluronic acid (HA) hydrogel for controlled release of epidermal growth factor (EGF) to enhance skin wound healing. Conventional hydrogel-based methods suffer from a burst release and limited drug delivery times. To address this, we employ bioconjugation to introduce an acrylate group to EGF, enabling chemical bonding to the HA hydrogel matrix through thiol–ene cross-linking. This approach results in sustained-release delivery of EGF based on the degradation rate of the HA matrix, overcoming diffusion-based limitations. We confirm the introduction of the acrylate group using matrix-assisted laser desorption ionization–time-of-flight (MALDI-TOF) mass spectrometry. We evaluated the hydrogel morphology and rheological properties following binding of acrylate-conjugated EGF to the HA matrix. Assessment of the EGF release profile demonstrates delayed release compared to unconjugated EGF. We evaluate the impact on cells through cell proliferation and scratch assays, indicating the system’s efficacy. In a rat wound healing model, the sustained release of EGF from the hydrogel system promotes appropriate tissue healing and restores it to a normal state. These findings suggest that this practical drug delivery system, involving the modification of growth factors or drugs to chemically bind healing factors to hydrogels, can achieve long-lasting effects

Statins Decrease Programmed Death-Ligand 1 (PD-L1) by Inhibiting AKT and β-Catenin Signaling

Retrospective observational studies have reported that statins improve clinical outcomes in patients previously treated with programmed cell death protein 1 (PD-1)-targeting monoclonal antibodies for malignant pleural mesothelioma (MPM) and advanced non-small cell lung cancer (NSCLC). In multiple mouse cancer models, de novo synthesis of mevalonate and cholesterol inhibitors was found to synergize with anti-PD-1 antibody therapy. In the present study, we investigated whether statins affect programmed death-ligand 1 (PD-L1) expression in cancer cells. Four statins, namely simvastatin, atorvastatin, lovastatin, and fluvastatin, decreased PD-L1 expression in melanoma and lung cancer cells. In addition, we found that AKT and β-catenin signaling involved PD-L1 suppression by statins. Our cellular and molecular studies provide inspiring evidence for extending the clinical evaluation of statins for use in combination with immune checkpoint inhibitor-based cancer therapy

High performance H2O2 production achieved by sulfur-doped carbon on CdS photocatalyst via inhibiting reverse H2O2 decomposition

Solar production of hydrogen peroxide (H2O2) from oxygen gas and water using photocatalysts is a safe, cost-effective, and eco-friendly method. However, the development of efficient photocatalysts has been impeded by their high decomposition rate of photogenerated H2O2 on the surface of photocatalysts. Here we report CdS/sulfur-doped carbon nanocomposites prepared by adopting a Cd- and S-containing metal-organic framework as a precursor. The intimate contact between the two components provoked their synergetic effect for much better H2O2 production performance than that of commercial CdS, where the hydrophobic sulfur-doped carbon prevent the approach of H2O2 and suppress its decomposition. Resultingly, it recorded H2O2 concentration of 17.1 mM under visible light irradiation in KOH solution with 2-propanol as a hole scavenger, which is the highest value among all the reported photocatalysis systems. This value is sufficiently high to be directly utilized in area of bleaching and acidic waste treatments

Peli3 ablation ameliorates acetaminophen-induced liver injury through inhibition of GSK3β phosphorylation and mitochondrial translocation

Abstract The signaling pathways governing acetaminophen (APAP)-induced liver injury have been extensively studied. However, little is known about the ubiquitin-modifying enzymes needed for the regulation of APAP-induced liver injury. Here, we examined whether the Pellino3 protein, which has E3 ligase activity, is needed for APAP-induced liver injury and subsequently explored its molecular mechanism. Whole-body Peli3 −/− knockout (KO) and adenovirus-mediated Peli3 knockdown (KD) mice showed reduced levels of centrilobular cell death, infiltration of immune cells, and biomarkers of liver injury, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST), upon APAP treatment compared to wild-type (WT) mice. Peli3 deficiency in primary hepatocytes decreased mitochondrial and lysosomal damage and reduced the mitochondrial reactive oxygen species (ROS) levels. In addition, the levels of phosphorylation at serine 9 in the cytoplasm and mitochondrial translocation of GSK3β were decreased in primary hepatocytes obtained from Peli3 −/− KO mice, and these reductions were accompanied by decreases in JNK phosphorylation and mitochondrial translocation. Pellino3 bound more strongly to GSK3β compared with JNK1 and JNK2 and induced the lysine 63 (K63)-mediated polyubiquitination of GSK3β. In rescue experiments, the ectopic expression of wild-type Pellino3 in Peli3 −/− KO hepatocytes restored the mitochondrial translocation of GSK3β, but this restoration was not obtained with expression of a catalytically inactive mutant of Pellino3. These findings are the first to suggest a mechanistic link between Pellino3 and APAP-induced liver injury through the modulation of GSK3β polyubiquitination