Recent Advances in Quantum Dots for Photocatalytic CO2 Reduction: A Mini-Review

Solar energy–driven carbon dioxide (CO2) reduction to valuable solar fuels/chemicals (e.g., methane, ethanol, and carbon monoxide) using particulate photocatalysts is regarded as one of the promising and effective approaches to deal with energy scarcity and global warming. The growth of nanotechnology plays an eminent role in improving CO2 reduction (CO2R) efficiencies by means of offering opportunities to tailor the morphology of photocatalysts at a nanoscale regime to achieve enhanced surface reactivity, solar light absorption, and charge separation, which are decisive factors for high CO2R efficiency. Notably, quantum dots (QDs), tiny pieces of semiconductors with sizes below 20 nm, offering a myriad of advantages including maximum surface atoms, very short charge migration lengths, size-dependent energy band positions, multiple exciton generation effect, and unique optical properties, have recently become a rising star in the CO2R application. In this review, we briefly summarized the progress so far achieved in QD-assisted CO2 photoreduction, highlighting the advantages of QDs prepared with diverse chemical compositions such as metal oxides, metal chalcogenides, carbon, metal halide perovskites, and MXenes. © Copyright © 2021 Park, Murali, Modigunta, In and In.1

pH-Responsive NIR-Absorbing Fluorescent Polydopamine with Hyaluronic Acid for Dual Targeting and Synergistic Effects of Photothermal and Chemotherapy

In cancer therapy, optimizing tumor-specific delivery, tumor distribution, and cellular uptake of a drug is important for ensuring minimal toxicity and maximum therapeutic efficacy. This study characterized the therapeutic efficacy of a stimulus responsive and dual targeting nanocarrier for a bioimaging-guided photothermal and chemotherapeutic platform. Hyaluronic acid (HA) conjugated with triphenylphosphonium (TPP) and boronic acid (BA) diol-linked β-cyclodextrin (β-CD) forms an inclusion complex with paclitaxel (PTX), creating a shell-like composite on a core of carbonized fluorescent polydopamine nanoparticles (FNPs-pDA) applicable for photothermal therapy as well as bioimaging. The successful diol cross-linking between core@shells generates nanocarriers [FNPs-pDA@HA-TPP-CD-PTX] that can be used as an extracellular HA- and intracellular TPP-mediated dual targeting system. The carbonized FNPs-pDA was cross-linked with the boronic acid groups of HA-TPP-CD-PTX to promote the formation of boronate esters for pH-mediated photothermal activity, which have shown time dependent complete PTX release along with a photothermal mediated response. The in vitro dual bioimaging and photothermal-chemotherapeutic activities were compared between cancer and normal cells. Lysosomal escape and live/dead cells staining confocal images highlight the promise of this system, which might open up a new approach, a simple and versatile method for site-specific synergetic drug delivery

Triggered pH/redox responsive release of doxorubicin from prepared highly stable graphene with thiol grafted Pluronic

Strategy, to develop stable graphene and well control hydrophobic drug release from the prepared graphene, is reported to achieve a biomedical platform in drug delivery system. Reduced graphene oxide (rGO) has been prepared using quaternized 2-chloro-3',4'-dihydroxyacetophenone to poly(ethylene glycol)-g-poly(dimethylaminoethyl methacrylate) [PEG-g-PDMA, QC-PEG] following catechol chemistry which exhibited excellent dispersibility in water. Installation of thiol grafted Pluronic (Plu-SH) results formation of disulfide bonds surrounding rGO/QC-PEG matrix and further aids to achieve high DOX loading efficiency as well as trigged responsive controlled release behavior of DOX from the matrixes by redox responsive Plu-SH and pH sensitive. The rGO/QC-PEG with Plu-SH matrix showed significant stability under different physiological conditions. In vitro DOX release was conducted against different reductive environment and at different pH to figure out the release kinetics. Investigation from MTT assay assures more biocompatible behavior of rGO/QC-PEG/Plu-SH than prepared reduced graphene oxide. Effects of introducing Plu-SH was flashed when QDs loaded rGO/QC-PEG was applied to cell and examining the emitted fluorescence behavior from the cell by confocal images. The confocal investigation showed that high quenching effect of graphene is an obstacle to trace their position if it is used in cell tracking where application of Plu-SH could minimize this. (C) 2013 Elsevier B.V. All rights reserved

Phase-controlled 1T/2H-MoS2interaction with reduced TiO2for highly stable photocatalytic CO2reduction into CO

Photocatalytic CO2 reduction is a potential technique for converting solar energy and greenhouse gases into value-added-chemicals. However, limited light absorption and poor charge separation of electron-hole pairs are the main obstacles. Here, we have developed a highly stable, phase-controlled heterostructured photocatalyst of molybdenum sulfide with reduced titania (1T/2H-MoS2@RT) for CO2 reduction into CO. The optimized 1T/2H-MoS2@RT produced 1.02 μmol g-1 h-1 (1480.1 ppm g-1 h-1) of CO. The catalyst showed ∼5 and ∼19 times higher activity than RT and MoS2, respectively, and excellent stability over 48 h (8 cycles). Our investigation revealed that the combination of phase-controlled MoS2 with RT synergizes the selective conversion of CO2 to CO. MoS2 acts as a visible light sensitizer and electron transport bridge; however, RT extracts electrons from MoS2 because of its lower energy potential. Improved light absorption, CO2 adsorption, and rapid electron-hole separation are responsible for the increased catalytic activity and stability. © 2022 The Authors.TRU

Spiropyran-conjugated Pluronic as a dual responsive colorimetric detector

Novel spiropyran-conjugated Pluronic [polyethylene oxide (PEO)-b-polypropylene oxide (PPO)-b-polyethylene oxide (PEO)] micelles are developed as a new colorimetric detector showing photo- or thermo-switchable behavior. Facile conjugation of spiropyran to Pluronic was confirmed by 1H NMR, UVVis, and Fluorescence spectroscopy. A switchable photoluminescence is found depending on the irradiation with either UV or visible light, and temperature resulting from structural isomerization of spiropyran between spiropyran (SP) and merocyanine (MC) form. Cytotoxicity of the spiropyran-conjugated Pluronic (SP-PL) was evaluated following an MTT assay, whereas photo responsiveness of spiropyran within the micelles was determined by confocal laser scanning microscopy

Iron Oxide@PEDOT-Based Recyclable Photothermal Nanoparticles with Poly(vinylpyrrolidone) Sulfobetaines for Rapid and Effective Antibacterial Activity

Growing microbial resistance that renders antibiotic treatment vulnerable has emerged, attracting a great deal of interest in the need to develop alternative antimicrobial treatments. To contribute to this effort, we report magnetic iron oxide (Fe₃O₄) nanoparticles (NPs) coated with catechol-conjugated poly­(vinylpyrrolidone) sulfobetaines (C-PVPS). This negatively charged Fe₃O₄@C-PVPS is subsequently encapsulated by poly­(3,4-ethylenedioxythiophene) (PEDOT) following a layer-by-layer (LBL) self-assembly method. The obtained Fe₃O₄@C-PVPS:PEDOT nanoparticles appear to be novel NIR-irradiated photothermal agents that can achieve effective bacterial killing and are reusable after isolation of the used particles using external magnetic fields. The recyclable Fe₃O₄@C-PVPS:PEDOT NPs exhibit a high efficiency in converting photothermal heat for rapid antibacterial effects against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i>. In this study, antibacterial tests for repeated uses maintained almost 100% antibacterial efficiency during three cycles and provided rapid and effective killing of 99% Gram-positive and -negative bacteria within 5 min of near-infrared (NIR) light exposure. The core–shell nanoparticles (Fe₃O₄@C-PVPS:PEDOT) exhibit the required stability, and their paramagnetic nature means that they rapidly convert photothermal heat sufficient for use as NIR-irradiated antibacterial photothermal sterilizing agents

Bi₂S₃ Nanorods Deposited on Reduced Graphene Oxide for Potassium-Ion Batteries

Hierarchical nanocomposites with surface active bonding features serve as an efficient electrode material for high-performance Li-/Na-/K-ion batteries. Tuning the physiochemical properties of these hierarchical nanocomposites has a great impact on the extremely improved electrochemical performance, and it is attributed to the synergistic effect of heterogeneous components. Herein, we report a hydrothermally synthesized bismuth sulfide (Bi2S3) nanorod bonding on the surface of the reduced graphene oxide (rGO) matrix and investigate it as an anode material for potassium-ion batteries. This hierarchical nanocomposite anode exhibits a high initial reversible capacity (586 mA h g–1 at 100 mA g–1), long-term cycling stability (410 mA h g–1 after 1000 cycles, 70% capacity retention), and an outstanding rate capability (140 mA h g–1 at 3 A g–1). This excellent electrochemical performance of the Bi2S3/rGO nanocomposite is attributed to the presence of active sites in rGO nanosheets that not only enhances the electrical conductivity of Bi2S3 nanorods but also prevents the shuttle effect of polysulfide through the formation of the in-built C–S bond, which is confirmed by X-ray photoelectron spectroscopy. Through the ex-situ X-ray diffraction patterns analysis at different voltage regions, a phase transformation mechanism has been proposed for K-ion storage in Bi2S3 nanorods. An ex-situ high-resolution transmission electron microscopy analysis reveals the structural and morphological stability of Bi2S3 nanorods. Further, the kinetic studies confirmed that the surface dominated pseudocapacitive K-ion storage also plays a major role in improving the electrochemical performance of the Bi2S3 nanorods/rGO nanocomposite. The K-ion full cell is successfully assembled, which exhibits stable cycling performance after 100 cycles at 1 C rate

Target delivery and cell imaging using hyaluronic acid-functionalized graphene quantum dots

This work demonstrates the way to achieve efficient and target specific delivery of a graphene quantum dot (GQD) using hyaluronic acid (HA) (GQD-HA) as a targeting agent. HA has been anchored to a GQD that accepts the fascinating adhesive properties of the catechol moiety, dopamine hydrochloride, conjugated to HA, which was confirmed by X-ray photoelectron spectroscopy. Transmission electron microscopy revealed a particle size of similar to 20 nm, and the fluorescence spectra revealed significant fluorescence intensity even after the anchoring of HA. The prepared GQD-HA was applied to CD44 receptor overexpressed tumor-bearing balb/c female mice, and the in vivo biodistribution investigation demonstrated more bright fluorescence from the tumor tissue. In vitro cellular imaging, via a confocal laser scanning microscope, exhibited strong fluorescence from CD44 overexpressed A549 cells. Both in vivo and in vitro results showed the effectiveness of using HA as targeting molecule. The loading and release kinetics of the hydrophobic drug doxorubicin from a GQD under mildly acidic conditions showed that a GQD can be considered as a novel drug carrier, while the nontoxic behavior from the MTT assay strongly supports the identification of GQD-HA as a biocompatible material