Visible-light-mediated synthesis of α,ß-diamino esters via coupling of N,N-dimethylanilines and glyoxalic oxime ethers.

A visible-light-mediated synthesis of α,ß-diamino esters has been developed via the cross coupling of N,N-dimethylanilines with glyoxalic oxime ethers. This protocol involves the generation of α-aminoalkyl radicals under mild reaction conditions, provides α,ß-diamino esters in good to excellent yields, and can be performed on a gram-scale.

TiO2 nanoflower photocatalysts: Synthesis, modifications and applications in wastewater treatment for removal of emerging organic pollutants.

Titanium dioxide (TiO2) has been considered as one of the most promising photocatalysts nanomaterials and is being used in a variety of fields of energy and environment under sunlight irradiation via photocatalysis. Highly efficient photocatalytic materials require the design of the proper structure with excellent morphology, interfacial structures, optical and surface properties, etc. Which are the key points to realize effective light-harvesting for photocatalytic applications. Hierarchical TiO2 based nanoflower structures (i.e., 3D nanostructures) possess such characteristics and have attracted much attention in recent years. The uniqueness of TiO2 nanoflowers (NFs) with a coarse texture and arranged structures demonstrates higher photocatalytic activity. This review deals with the hydrothermal synthesis of 3D TiO2 NFs and effect of shape/size as well as various key synthesis parameters to improve their optoelectronic and photocatalytic properties. Furthermore, to improve their photocatalytic properties, various strategies such as doping engineering and heterojunction/nanocomposite formation with other functional nanomaterials have been discussed followed by their potential applications in photocatalytic degradation of various emerging pollutants discharged into the wastewater from various sources. Importance of such 3D nanoarchitecutres and future research in other fields of current interest in environments are discussed.

Stabilization of a Highly Concentrated Colloidal Suspension of Pristine Metallic Nanoparticles.

A colloidal suspension containing a high concentration of metallic nanoparticles (NPs) finds potential applications in flexible electronic printing, nanofluids, healthcare, antifouling coating, and so on. Here, we demonstrate a generic, easily scalable, simple, and contamination-free cryogenic temperature grinding method, which can effectively be used to prepare pristine NPs that can be stabilized in polar liquids in high concentrations. These surfactant-free pristine NPs have been found to remain dispersed in different polar liquids (CH3OH, C2H5OH, glycol, etc.) for weeks. The long-term stability of the NPs in these liquids has been investigated using zeta potential, in situ Fourier transform infrared spectroscopy, indicating electrostatic stabilization for ultrapure, surfactant-free NPs. Furthermore, stabilization of the NPs has been probed with detailed calculations using the Derjaguin Landau Verwey Overbeek theory as well as atomistic molecular dynamics simulation (MD). Experimental measurements along with theoretical calculations categorically indicate that the electrostatic energy is helping these NPs to be stabilized in a polar liquid.

Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers or polymer matrix help in further improving the dielectric properties as compared to two-phase nanocomposites. Recent research has been focused on altering the dielectric properties of different materials while also maintaining their superior flexibility. Flexible polymer nanocomposites are the best candidates for application in various fields. However, certain challenges still present, which can be solved only by extensive research in this field.

Highly efficient visible light active doped metal oxide photocatalyst and SERS substrate for water treatment.

The development of efficient nanomaterials with promising optical and surface properties for multifunctional applications has always been a subject of novel research. In this work, the study of highly efficient TiO2 nanorods (NRs) and Ta-doped TiO2 NRs (Ta-TiO2 NRs) synthesized by alkaline hydrothermal treatment followed by soaking treatment has been reported. NRs were investigated for their potential applications as recyclable/reproducible visible light active photocatalysts and surface-enhanced Raman scattering (SERS) substrates in wastewater treatment. NRs were characterized by various microscopic (scanning and transmission electron microscopy), spectroscopic (X-ray diffraction, X-ray photoelectron, UV-visible, photoluminescence, and Raman spectroscopy), and surface (Brunauer-Emmett-Teller) techniques. The NRs exhibited promising optical properties with a band gap of 2.95 eV (TiO2 NRs) and 2.58 eV (Ta-TiO2 NRs) showing excellent photo-degradation activities for methylene blue (MB) dye molecules under natural sunlight. Particularly, Ta-TiO2 NRs showed enhanced response as visible light active photocatalysts in normal sunlight and also as SERS substrate attributed to the additional defects introduced by Ta doping. It could be explained by the combined effect of doping-induced enhanced visible light absorption and charge transfer (CT) properties of Ta-TiO2 NRs. Furthermore, Ta-TiO2 NRs were investigated for their long-term stability, reproducibility of the data, and recyclability in view of their potential applications in water treatment.

Sustainable Nanoparticles from Stephania glabra and Analysis of Their Anticancer Potential on 2D and 3D Models of Prostate Cancer.

In pursuit of a novel effective treatment for prostate cancer, methanolic extract of Stephania glabra tubers (Sg-ME) was utilized to fabricate silver (Sg-AgNP), copper oxide (Sg-CuONP), and silver-copper bimetallic nanoparticles (Sg-BNP). The characterization of the nanoparticles confirmed spherical shape with average diameters of 30.72, 32.19, and 25.59 nm of Sg-AgNP, Sg-CuONP, and Sg-BNP, respectively. Interestingly, these nanoparticles exhibited significant cytotoxicity toward the prostate cancer (PC3) cell line while being non-toxic toward normal cells. The nanoparticles were capable of inducing apoptosis in PC3 cells by enhancing reactive oxygen species (ROS) generation and mitochondrial depolarization. Furthermore, the shrinkage of 3D prostate tumor spheroids was observed after 4 days of treatment with these green nanoparticles. The 3D model system was less susceptible to nanoparticles as compared to the 2D model system. Sg-BNP showed the highest anticancer potential on 2D and 3D prostate cancer models.

Functionality Tuning in Hierarchically Engineered Magnetoelectric Nanocomposites for Energy-Harvesting Applications.

The ß-phase of the copolymer poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) possesses the highest dipole moment among all the functional polymers. It remains a key component of flexible energy-harvesting devices based on piezoelectricity and triboelectricity in the last decade. However, the quest for P(VDF-TrFE)-based magnetoelectric (ME) nanocomposites with enhanced ferroelectric, piezoelectric, and triboelectric properties remains elusive. The magnetostrictive inclusion in the copolymer matrix forms electrically conducting pathways and degrades ß-phase crystallinity significantly, deteriorating the functional properties of the nanocomposite films. To address this issue, we report the synthesis of magnetite (Fe3O4) nanoparticles on micron-scale magnesium hydroxide [Mg(OH)2] templates. These hierarchical structures were incorporated within the P(VDF-TrFE) matrix rendering composites with enhanced energy-harvesting capability. The Mg(OH)2 template prevents the formation of a continuous network of magnetic fillers, leading to lower electrical leakage in the composite. The addition of dual-phase fillers with 5 wt % only increases remanent polarization (Pr) values by ∼44%, owing to the presence of the ß-phase with significant crystallinity and increased interfacial polarization. The composite film exhibits a quasi-superparamagnetic nature and a significant magnetoelectric coupling coefficient (αME) of 30 mV/cm Oe. The film was also employed for triboelectric nanogenerator applications, exhibiting five times higher power density than the pristine film. We finally explored the integration of our ME devices with an internet of things platform to monitor the operational status of electrical appliances remotely. In light of these findings, the present work opens the path for future self-powered, multifunctional, and flexible ME devices with new application domains.

Visible-Light-Mediated Three-Component Cascade Sulfonylative Annulation.

Visible-light-promoted cascade radical cyclization for the synthesis of sulfonylated benzimidazo/indolo[2,1-a]iso-quinolin-6(5H)-ones has been reported. The reaction provides transition-metal-free and expeditious access to sulfonylated polyaromatics. The use of sodium metabisulfite as a SO2 surrogate and the rapid generation of molecular complexity using a three-component photochemical protocol are the salient features of this reaction manifold.

Red-emitting polyaniline-based nanoparticle probe for pH-sensitive fluorescence imaging.

Fluorescent probes based on semiconducting polymer nanoparticles (NPs) such as polyaniline (PANI) usually require external fluorophore doping to provide fluorescence function. Direct use of PANI-based NPs for bioimaging applications has been limited by PANI's weak blue fluorescence and aggregation-induced quenching in physiological medium. In this report, we developed a facile solid-state synthesis method to produce fluorescent polyaniline nanoparticles (FPNs) that are not only water-soluble but also exhibit high intensity and pH-sensitive red fluorescence. The FPNs showed high photoluminescence quantum yield (PLQY) of 19.3 % at physiological pH, which makes FPNs ideal for application as fluorescent nanoprobes in bioimaging. Moreover, we performed an in-depth study of photoluminescence dependence on pH and the phenomena of exciton-polaron quenching at low pH was highlighted. We also found that the ratio of emission intensity at 600 nm and 650 nm increased from 0.04 to 1.65 as pH was raised from 2.6 to 11.8, which could find its application in ratiometric pH sensing. FPNs exhibited excellent biocompatibility with >85 % cell viability for fibroblasts NIH/3 T3 and prostate cancer 22RV1 cells even at concentrations as high as 1000 µg/mL. In addition, fluorescence microscopy demonstrated concentration-dependent red fluorescence in the cytoplasm owing to the cellular uptake of FPNs in prostate cancer cells.

Insights and Perspectives Regarding Nanostructured Fluorescent Materials toward Tackling COVID-19 and Future Pandemics.

The COVID-19 outbreak has exposed the world's preparation to fight against unknown/unexplored infectious and life-threatening pathogens. The unavailability of vaccines, slow or sometimes unreliable real-time virus/bacteria detection techniques, insufficient personal protective equipment (PPE), and a shortage of ventilators and many other transportation equipments have further raised serious concerns. Material research has been playing a pivotal role in developing antimicrobial agents for water treatment and photodynamic therapy, fast and ultrasensitive biosensors for virus/biomarkers detection, as well as for relevant biomedical and environmental applications. It has been noticed that these research efforts nowadays primarily focus on the nanomaterials-based platforms owing to their simplicity, reliability, and feasibility. In particular, nanostructured fluorescent materials have shown key potential due to their fascinating optical and unique properties at the nanoscale to combat against a COVID-19 kind of pandemic. Keeping these points in mind, this review attempts to give a perspective on the four key fluorescent materials of different families, including carbon dots, metal nanoclusters, aggregation-induced-emission luminogens, and MXenes, which possess great potential for the development of ultrasensitive biosensors and infective antimicrobial agents to fight against various infections/diseases. Particular emphasis has been given to the biomedical and environmental applications that are linked directly or indirectly to the efforts in combating COVID-19 pandemics. This review also aims to raise the awareness of researchers and scientists across the world to utilize such powerful materials in tackling similar pandemics in future.

Antibacterial and Antiviral Functional Materials: Chemistry and Biological Activity toward Tackling COVID-19-like Pandemics.

The ongoing worldwide pandemic due to COVID-19 has created awareness toward ensuring best practices to avoid the spread of microorganisms. In this regard, the research on creating a surface which destroys or inhibits the adherence of microbial/viral entities has gained renewed interest. Although many research reports are available on the antibacterial materials or coatings, there is a relatively small amount of data available on the use of antiviral materials. However, with more research geared toward this area, new information is being added to the literature every day. The combination of antibacterial and antiviral chemical entities represents a potentially path-breaking intervention to mitigate the spread of disease-causing agents. In this review, we have surveyed antibacterial and antiviral materials of various classes such as small-molecule organics, synthetic and biodegradable polymers, silver, TiO2, and copper-derived chemicals. The surface protection mechanisms of the materials against the pathogen colonies are discussed in detail, which highlights the key differences that could determine the parameters that would govern the future development of advanced antibacterial and antiviral materials and surfaces.

Two-dimensional metal organic frameworks for biomedical applications.

Two-dimensional (2D) metal organic frameworks (MOFs), are an emerging class of layered nanomaterials with well-defined structure and modular composition. The unique pore structure, high flexibility, tunability, and ability to introduce desired functionality within the structural framework, have led to potential use of MOFs in biomedical applications. This article critically reviews the application of 2D MOFs for therapeutic delivery, tissue engineering, bioimaging, and biosensing. Further, discussion on the challenges and strategies in next generation of 2D MOFs are also included. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Graphite modified sodium alginate hydrogel composite for efficient removal of malachite green dye.

Herein, porous sodium alginate/graphite based hybrid hydrogel was fabricated as an effective adsorbent for organic pollutant. Sodium alginate was modified through graft polymerization of acrylic acid and subsequently loaded with graphite powder to enhance its adsorption capability. The synthesized sodium alginate cross-linked acrylic acid/graphite (NaA-cl-AAc/GP) hydrogel composite was utilized in the removal of malachite green (MG) dye from aqueous solution using batch adsorption experiments. The NaA-cl-AAc/GP hydrogel composite was characterized by infrared spectroscopy, Raman spectroscopy, thermo-gravimetric analysis, scanning electron microscopy, x-ray photoelectron spectroscopy and x-ray diffraction. Under optimized experimental conditions, a maximum adsorption capacity of 628.93 mg g-1 was attained for malachite green dye. Moreover, the adsorption process could be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. The hydrogel composite also showed 91% adsorption after three consecutive cycles of dye adsorption-desorption. Therefore, the NaA-cl-AAc/GP hydrogel composite is a potentially favourable material towards dye pollution remediation owing to its better swelling rate, environment friendliness, high adsorption potential and regeneration capability.

Effect of NiO Precursor Solution Ageing on the Perovskite Film Formation and Their Integration as Hole Transport Material for Perovskite Solar Cells.

Exceptional progress in the performance of perovskite solar cells in a very short time has made it a potential photovoltaic technology for future deployment. The compositional engineering in perovskite materials and other buffer layers makes it a feasible candidate for commercial applications in the near future. However, there are certain challenges associated with these devices which need to be addressed such as device stability, process dependent device efficiency, hole transport layer (HTL) etc. The device performance is highly dependent on the processing parameters of the precursors. Understanding the origin of this challenge is very crucial for reproducible device performance. In this work, we have focused on utilizing NiO as a HTL in planar perovskite solar cells and studied the ageing effect of NiO precursor solution on the perovskite film quality in terms of crystallinity, grain growth, surface morphology, and overall device performance. It is observed that the ageing of NiO precursor promotes the formation of NiO films with increased roughness which improves the perovskite film quality. Structural and morphological studies revealed that the perovskite films formed on aged NiO films were highly crystalline in nature, uniform and with larger grain size. Current- voltage characteristics under illumination show that the films casted from NiO aged solution are better for perovskite solar cell applications and result in reduced parasitic resistances and enhanced charge transport.

Significantly Enhanced Energy Density by Tailoring the Interface in Hierarchically Structured TiO2-BaTiO3-TiO2 Nanofillers in PVDF-Based Thin-Film Polymer Nanocomposites.

Dielectric polymer nanocomposites with a high breakdown field and high dielectric constant have drawn significant attention in modern electrical and electronic industries due to their potential applications in dielectric and energy storage systems. The interfaces of the nanomaterials play a significant role in improving the dielectric performance of polymer nanocomposites. In this work, polydopamine (dopa)-functionalized TiO2-BaTiO3-TiO2 (TiO2-BT-TiO2@dopa) core@double-shell nanoparticles have been developed as novel nanofillers for high-energy-density capacitor applications. The hierarchically designed nanofillers help in tailoring the interfaces surrounding the polymer matrix as well as act as individual capacitors in which the core and outer TiO2 shell function as a capacitor plate because of their high electrical conductivity while the middle BT layer functions as a dielectric medium due to high dielectric constant. Detailed electrical characterizations have revealed that TiO2-BT-TiO2@dopa/poly(vinylidene fluoride) (PVDF) possesses a higher relative dielectric permittivity (εr), breakdown strength ( Eb), and energy density as compared to those of PVDF, TiO2/PVDF, TiO2@dopa/PVDF, and TiO2-BT@dopa/PVDF polymer nanocomposites. The εr and energy density of TiO2-BT-TiO2@dopa/PVDF were 12.6 at 1 kHz and 4.4 J cm-3 at 3128 kV cm-1, respectively, which were comparatively much higher than those of commercially available biaxially oriented polypropylene having εr of 2.2 and the energy density of 1.2 J cm-3 at a much higher electric field of 6400 kV cm-1. It is expected that these results will further open new avenues for the design of novel architecture for high-performance polymer nanocomposite-based capacitors having core@multishell nanofillers with tailored interfaces.

Hydrothermally Tailored Three-Dimensional Ni-V Layered Double Hydroxide Nanosheets as High-Performance Hybrid Supercapacitor Applications.

Here, we report a facile and easily scalable hydrothermal synthetic strategy to synthesize Ni-V layered double hydroxide (NiV LDH) nanosheets toward high-energy and high-power-density supercapacitor applications. NiV LDH nanosheets with varying Ni-to-V ratios were prepared. Three-dimensional curved nanosheets of Ni0.80V0.20 LDH showed better electrochemical performance compared to other synthesized NiV LDHs. The electrode coated with Ni0.80V0.20 LDH nanosheets in a three-electrode cell configuration showed excellent pseudocapacitive behavior, having a high specific capacity of 711 C g-1 (1581 F g-1) at a current density of 1 A g-1 in 2 M KOH. The material showed an excellent rate capability and retained the high specific capacity of 549 C g-1 (1220 F g-1) at a current density of 10 A g-1 and low internal resistances. Owing to its superior performance, Ni0.80V0.20 LDH nanosheets were used as positive electrode and commercial activated carbon was used as negative electrode for constructing a hybrid supercapacitor (HSC) device, having a working voltage of 1.5 V. The HSC device exhibited a high specific capacitance of 98 F g-1 at a current density of 1 A g-1. The HSC device showed a higher energy density of 30.6 Wh kg-1 at a power density of 0.78 kW kg-1 and maintained a high value of 24 Wh kg-1 when the power density was increased to 11.1 kW kg-1. The performance of NiV LDHs nanosheets indicates their great potential as low-cost electrode material for future energy-storage devices.

Milli-Watt Power Harvesting from Dual Triboelectric and Piezoelectric Effects of Multifunctional Green and Robust Reduced Graphene Oxide/P(VDF-TrFE) Composite Flexible Films.

For a variety of mechanical energy harvesting as well as biomedical device applications, flexible energy devices are useful which require the development of environment-friendly and robust materials and devices. In this manuscript, we demonstrate a lead-free, facile, low-cost, sol-gel-processed reduced graphene oxide (rGO)/P(VDF-TrFE) nanocomposite with multipurpose capability demonstration as a piezoelectric nanogenerator (PENG) and hybrid piezoelectric triboelectric nanogenerator (HPTENG) devices. The structural analysis of the materials shows that the interactions between the rGO and P(VDF-TrFE) matrix help in breaking the centrosymmetry of rGO, resulting in a strong enhancement in the piezoelectric, ferroelectric, and triboelectric properties of composites over pristine P(VDF-TrFE) films. In the case of PENG, the composite devices showed >22 times improvement in the piezoelectric output voltage over the pristine P(VDF-TrFE) PENG device with the highest output voltage of 89.7 V for the 0.5 wt % rGO composite. Also, HPTENG devices based on composite films generated an average VOC of 227 V, much higher than the pristine P(VDF-TrFE)-based devices. Maximum output power densities measured were 0.28 W/cm3 and 0.34 mW/cm3 for hybrid piezoelectric-triboelectric and piezoelectric devices, respectively. The triboelectric devices demonstrated lighting of 45 blue light-emitting diodes directly, connected in series, by harvesting mechanical energy generated by repeated finger tapping. The study highlights the promise of rGO/P(VDF-TrFE) composites for PENG and HPTENG devices with dramatically improved electrical output.

Controlling surface cation segregation in a nanostructured double perovskite GdBaCo2O5+δ electrode for solid oxide fuel cells.

Mechanistic studies, utilizing molecular dynamics (MD) and density functional theory (DFT) calculations, were undertaken to provide a molecular level explanation of Ba cation segregation in double perovskite GdBaCo2O5+δ (GBCO) electrodes. The energy (γ) of the terminal surface having only Ba cations, indicated the surface to be the most stable (γ = 6.7 kJ mol-1Å-2) as compared to the other surfaces. MD simulations elaborated on the cation disorder in the near surface region where Ba cations in the subsurface region were observed to migrate towards the surface. This led to a disruption in cation ordering with a propensity to form multiphases in the near surface region. In the near surface zone, oxygen anion diffusivity was observed to be reduced by an order of magnitude (D = 1.6 × 10-11 cm2 s-1 at 873 K) as compared to the bulk oxygen anion diffusivity value (D = 1.96 × 10-10 cm2 s-1 at 873 K). A novel idea was then proposed to control the degree of surface segregation of Ba cations by applying nanostructuring of the GBCO material in the form of nanoparticles. MD simulations elucidated that the near surface region having a high degree of cation disorder in the nanostructured GBCO may regain back the oxygen anion diffusivity value (D = 3.98 × 10-10 cm2 s-1, at 873 K) comparable to the bulk core region (D = 2.51 × 10-10 cm2 s-1, at 873 K). A proof of concept experiment was setup to test this hypothesis. The electrochemical performance of the electrode, fabricated using GBCO nanoparticles, was measured to improve by 15% as compared to the electrode synthesized with a bulk size GBCO material. This was attributed to the control in Ba-cation segregation, obtained on nanostructuring which resulted in higher oxygen anion transport in the near-surface region of the electrode material. XPS characterization of the surface of the nanostructured GBCO materials supported this assertion.

Three-dimensional nickel vanadium layered double hydroxide nanostructures grown on carbon cloth for high-performance flexible supercapacitor applications.

This study reports the synthesis of ultrathin Ni-V layered double hydroxide nanosheets on carbon cloth (NVL@CC) through adopting a facile and cost-effective method for flexible supercapacitor applications. The as-synthesized NVL@CC possesses a uniform, mechanically strong and highly ordered porous network with connected pores, ensuring high specific capacitance and enhanced cyclability. A high specific capacity of 1226 C g-1 (2790 F g-1) was obtained at 1 A g-1, and it remained at 430 C g-1 (1122 F g-1) even at a higher current density of 10 A g-1. A hybrid supercapacitor (HSC) was assembled with the NVL@CC electrode as the positive electrode and activated carbon coated carbon cloth as the negative electrode (NVL@CC//AC HSC). The devices showed an excellent energy density of 0.69 mW h cm-3 at a power density of 2.5 mW cm-3 with 100% of the original capacitance being retained at a current density of 5 mA cm-2. Furthermore, the devices exhibited an energy density of 0.24 mW h cm-3 even at a higher power density of 214.4 mW cm-3, surpassing the performances observed for many recently reported flexible supercapacitors. Importantly, the electrochemical performance of the solid-state flexible supercapacitors showed a negligible change upon bending and twisting of the devices. The devices showed no decay in specific capacitance and coulombic efficiency up to 5000 charge-discharge cycles, confirming the excellent cycle life of the HSC device. The performance of NVL@CC indicates the great potential of the material for future flexible energy storage devices.