Photoassisted Water Purification through an Electrochemically Artificially Adjusted p-Cu2O Light Absorption Layer.

The implementation of photoelectrochemical water purification technology can address prevailing environmental challenges that impede the advancement and prosperity of human society. In this study, Cu, which is abundant on Earth, was fabricated using an electrochemical deposition process, in which the preferential orientation direction and carrier concentration of the Cu-based oxide semiconductor were artificially adjusted by carefully controlling the OH- and applied voltage. In particular, Cu2O grown with a sufficient supply of OH- ions exhibited the (111) preferred orientation, and the (200) surface facet was exposed, independently achieving 90% decomposition efficiency in a methyl orange (MO) solution for 100 min. This specialized method minimizes the recombination loss of electron-hole pairs by increasing the charge separation and transport efficiency of the bulk and surface of the Cu2O multifunctional absorption layer. These discoveries and comprehension not only offer valuable perspectives on mitigating self-photocorrosion in Cu2O absorbing layers but also provide a convenient and expeditious method for the mass production of water purification systems that harness unlimited solar energy. These properties enable significant energy saving and promote high-speed independent removal of organic pollutants (i.e., MO reduction) during the water purification process.

Property Modulation of Graphene Oxide Incorporated with TiO2 for Dye-Sensitized Solar Cells.

Graphene oxide (GO) nano-powder is synthesized by the modified Hummer's method, and further thin films are deposited by using the water solution of GO through spin-coating. These films are thermally reduced along with the synthesized GO nano-powder at 50 to 200 °C in a high vacuum. Microstructural, electrical, and optical properties are expectedly controlled by thermal reduction. The electronic properties of GO are investigated by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure. The reduction is confirmed by Raman spectroscopy. The work function and band gap of GO are tuned with the thermal reduction. The changes in properties of GO are not linear, and anomalous changes are observed for the reduction around 150 °C. Pristine and reduced GO nano-powder is incorporated into TiO2 paste to be the photoanode for dye-sensitized solar cells (DSSCs). It is observed that the performance of the fabricated cells is significantly enhanced for the GO reduced at 150 °C, and the cell exhibited a significant increment of ∼23% for the power conversion efficiency in comparison to DSSC based on an unmodified TiO2 photoanode.

A study on structural, optical, and electrical characteristics of perovskite CsPbBr3 QD/2D-TiSe2 nanosheet based nanocomposites for optoelectronic applications.

Lead halide perovskite (CsPbBr3) quantum dots (QDs) and two-dimensional (2D) layered transition metal dichalcogenides have a significant application in solution-processed optoelectronic devices. Here, we report the oleylamine-assisted exfoliation of TiSe2 nanosheets (NSs) in dichlorobenzene with high concentration and stable dispersion. The functionalized TiSe2 NSs were used to synthesize the solution-processed perovskite CsPbBr3 QD/TiSe2 NS-based nanocomposite. The perovskite QDs and TiSe2 NSs were characterized by different techniques. The strong photoluminescence (PL) quenching and decreased lifetime decay of the nanocomposite indicates efficient charge transfer from photo-excited CsPbBr3 to TiSe2 NSs. The calculated charge-transfer rate constant (KET) from photo-excited CsPbBr3 to TiSe2 NSs increased from 1.50 × 108 to 2.79 × 108 s-1 in different concentrations of TiSe2 NSs (5 to 20 µg mL-1), respectively. Furthermore, the photo-currents of CsPbBr3 QD/TiSe2 NS nanocomposite devices were dramatically enhanced ∼2 times compared to pristine CsPbBr3 QD based devices, which supports the charge transfer and charge separation in nanocomposite devices.

A study on chemical exfoliation and structural and optical properties of two-dimensional layered titanium diselenide.

Titanium diselenide (TiSe2) is the least studied member of the transition metal dichalcogenide family due to a lack of available synthesis methodology, controlled bandgap engineering, and rapid characterization of layers. In this paper, we report the chemical exfoliation of TiSe2 platelets synthesized by the chemical vapor transport route in ortho-dichlorobenzene (o-DCB) functionalized with oleylamine (OLA), for the first time to the best of our knowledge. It is found that the addition of OLA supports the formation of a stable dispersion of a large area of the TiSe2 sheets due to surface capping with the OLA molecules indicating the importance of the ligand in dispersion behavior. The X-ray diffraction pattern confirms the hexagonal structure of the TiSe2 platelets with the space group P3[combining macron]m1 while Raman spectroscopy reveals that two modes of vibration i.e. A1g and E2g exist with layered structures having dimensions in micrometers as confirmed by scanning electron microscopy. Fourier transform infrared spectroscopy confirms the successful functionalization of chemically exfoliated TiSe2 nanosheets. Field-emission scanning electron microscopy reveals that exfoliated TiSe2 has a thickness of 15-55 nm whereas high-resolution transmission electron microscopy indicates thicker sheets for ligand-free exfoliated TiSe2 which are crystalline. Atomic force microscopy confirms the formation of nanosheets. UV-Visible, photoluminescence, and time-resolved PL spectroscopy showed an enhanced effect and better average lifetime of excitation for the exfoliated sheets with OLA than those without OLA. The C-V studies reveal that with increasing scan rate, the corresponding current also increases. The present study offers the possibility of their utilization in optoelectronics, advanced low-power electronics, voltage-controlled oscillators, ultra-fast electronics, and electrochemical devices.

Benzoyl Halide as Alternative Precursor for Synthesis of Lead Free Double Perovskite Cs3Bi2Br9 Nanocrystals.

Ternary bismuth halides are interesting functional materials closely related to Pb halide perovskite photovoltaic material, and are widely sought after due to reduced toxicity of Bi compared to Pb. There are several reports on synthesis of Cs3Bi2Br9 nanocrystals (NCs) due to its being relatively stable compared to lead perovskite. Cs3Bi2Br9 nanocrystals have been synthesised using benzoyl bromide as an precursor using hot injection process at two different temperatures of 120 °C and 160 °C. Samples have been characterized for its structural, optical, microstructural and luminescent properties using X-ray diffraction, (XRD) UV-Vis spectroscopy, high resolution transmission electron microscopy and photoluminescent spectroscopy. XRD showed formation of Cs3Bi2Br9 phase with mono-crystalline structure. UV-Vis showed two types of band gap in the visible region which shows that the material can be used for photovoltaic applications. HRTEM confined the particles to be composed of nanocrystals with ˜5 nm particles in the samples grown at 120 °C and it the particles joined together yield various structures composed of nanoparticles. The time resolved photoluminescence shows average life times of 3.067 ns and 4.761 ns for samples grown at two different temperatures. To the best of our knowledge, this is the first report where benzoyl halide has been used as alternative precursor for the synthesis of lead free double perovskite Cs3Bi2Br9 nanocrystals which have many applications.

Mitogen-Activated Protein Kinase Phosphatase 1 (MKP1) Negatively Regulates the Production of Reactive Oxygen Species During Arabidopsis Immune Responses.

Genetic ablation of the ß subunit of the heterotrimeric G protein complex in agb1-2 confers defective activation of microbe-associated molecular pattern (MAMP)-triggered immunity, resulting in agb1-2 enhanced susceptibility to pathogens like the fungus Plectosphaerella cucumerina BMM. A mutant screen for suppressors of agb1-2 susceptibility (sgb) to P. cucumerina BMM identified sgb10, a new null allele (mkp1-2) of the mitogen-activated protein kinase phosphatase 1 (MKP1). The enhanced susceptibility of agb1-2 to the bacterium Pseudomonas syringae pv. tomato DC3000 and the oomycete Hyaloperonospora arabidopsidis is also abrogated by mkp1-2. MKP1 negatively balances production of reactive oxygen species (ROS) triggered by MAMPs, since ROS levels are enhanced in mkp1. The expression of RBOHD, encoding a NADPH oxidase-producing ROS, is upregulated in mkp1 upon MAMP treatment or pathogen infection. Moreover, MKP1 negatively regulates RBOHD activity, because ROS levels upon MAMP treatment are increased in mkp1 plants constitutively overexpressing RBOHD (35S::RBOHD mkp1). A significant reprograming of mkp1 metabolic profile occurs with more than 170 metabolites, including antimicrobial compounds, showing differential accumulation in comparison with wild-type plants. These results suggest that MKP1 functions downstream of the heterotrimeric G protein during MAMP-triggered immunity, directly regulating the activity of RBOHD and ROS production as well as other immune responses.

Enhancement of Y123 dye-sensitized solar cell performance using plasmonic gold nanorods.

The role of the surface plasmon resonance (SPR) of gold nanorods (Au NRs) on the performance of Y123 dye-sensitized solar cells (DSSC) was investigated. DSSCs were fabricated by incorporating different concentrations (0.6 to 3.0 wt%) of Au NRs into TiO2 photoanodes. With an increase in the concentration of the Au NRs, the light absorption by the Y123 dye loaded photoanodes enhanced linearly, but the charge extraction was susceptible to the concentration of the Au NRs. With optimized concentrations (∼1.8 wt%) of the Au NRs, the photocurrent of the DSSC enhanced from 12.45 to 15.74 mA cm-2, and the power conversion efficiency (PCE) improved from 5.31 to 8.86%. The DSSC performance was also verified using Au nanoparticles (the PCE was enhanced from 5.31 to 7.72%) for comparison with the Au NR DSSC performance, which demonstrated the advantage of the Au NRs' shape effect with longitudinal SPR due to the modified light interaction. To explain the experimental observations of the plasmonic DSSC, the Au NRs' extinction efficiency and spatial distribution of the near-fields in complete and porous TiO2 media were also estimated using the finite-element method.

YODA MAP3K kinase regulates plant immune responses conferring broad-spectrum disease resistance.

Mitogen-activated protein kinases (MAPKs) cascades play essential roles in plants by transducing developmental cues and environmental signals into cellular responses. Among the latter are microbe-associated molecular patterns perceived by pattern recognition receptors (PRRs), which trigger immunity. We found that YODA (YDA) - a MAPK kinase kinase regulating several Arabidopsis developmental processes, like stomatal patterning - also modulates immune responses. Resistance to pathogens is compromised in yda alleles, whereas plants expressing the constitutively active YDA (CA-YDA) protein show broad-spectrum resistance to fungi, bacteria, and oomycetes with different colonization modes. YDA functions in the same pathway as ERECTA (ER) Receptor-Like Kinase, regulating both immunity and stomatal patterning. ER-YDA-mediated immune responses act in parallel to canonical disease resistance pathways regulated by phytohormones and PRRs. CA-YDA plants exhibit altered cell-wall integrity and constitutively express defense-associated genes, including some encoding putative small secreted peptides and PRRs whose impairment resulted in enhanced susceptibility phenotypes. CA-YDA plants show strong reprogramming of their phosphoproteome, which contains protein targets distinct from described MAPKs substrates. Our results suggest that, in addition to stomata development, the ER-YDA pathway regulates an immune surveillance system conferring broad-spectrum disease resistance that is distinct from the canonical pathways mediated by described PRRs and defense hormones.

Alteration of cell wall xylan acetylation triggers defense responses that counterbalance the immune deficiencies of plants impaired in the ß-subunit of the heterotrimeric G-protein.

Arabidopsis heterotrimeric G-protein complex modulates pathogen-associated molecular pattern-triggered immunity (PTI) and disease resistance responses to different types of pathogens. It also plays a role in plant cell wall integrity as mutants impaired in the Gß- (agb1-2) or Gγ-subunits have an altered wall composition compared with wild-type plants. Here we performed a mutant screen to identify suppressors of agb1-2 (sgb) that restore susceptibility to pathogens to wild-type levels. Out of the four sgb mutants (sgb10-sgb13) identified, sgb11 is a new mutant allele of ESKIMO1 (ESK1), which encodes a plant-specific polysaccharide O-acetyltransferase involved in xylan acetylation. Null alleles (sgb11/esk1-7) of ESK1 restore to wild-type levels the enhanced susceptibility of agb1-2 to the necrotrophic fungus Plectosphaerella cucumerina BMM (PcBMM), but not to the bacterium Pseudomonas syringae pv. tomato DC3000 or to the oomycete Hyaloperonospora arabidopsidis. The enhanced resistance to PcBMM of the agb1-2 esk1-7 double mutant was not the result of the re-activation of deficient PTI responses in agb1-2. Alteration of cell wall xylan acetylation caused by ESK1 impairment was accompanied by an enhanced accumulation of abscisic acid, the constitutive expression of genes encoding antibiotic peptides and enzymes involved in the biosynthesis of tryptophan-derived metabolites, and the accumulation of disease resistance-related secondary metabolites and different osmolites. These esk1-mediated responses counterbalance the defective PTI and PcBMM susceptibility of agb1-2 plants, and explain the enhanced drought resistance of esk1 plants. These results suggest that a deficient PTI-mediated resistance is partially compensated by the activation of specific cell-wall-triggered immune responses.

Eu3+ doped down shifting TiO2 layer for efficient dye-sensitized solar cells.

Europium doped TiO2 (TiO2:Eu3+) down-shifting (DS) nanophosphors (NPrs) were synthesized by the solution-combustion method with different concentrations of Eu3+. The X-ray diffraction results confirmed the formation of a polycrystalline tetragonal structure of the TiO2. The emission of colour of the TiO2:Eu3+ DS NPr was tuned by varying the doping concentration of Eu3+. The photoluminescence results confirmed that the TiO2:Eu3+ DS NPrs converted the UV light into visible light by energy down-conversion process, i.e. down-shifting of high energy UV photons to low energy visible photons. These TiO2:Eu3+ DS NPrs were used to enhance the efficiency of the Dye sensitized solar cell from 8.32% to 8.80%.

Fabrication of perovskite films using an electrostatic assisted spray technique: the effect of the electric field on morphology, crystallinity and solar cell performance.

An electric field assisted spray deposition method is employed for improving the perovskite film morphology, crystallinity, and surface coverage, and for further fabricating an efficient solar cell. By applying different voltages ranging from 0.5 to 2.0 kV during spray deposition, we observed a large variation in the film morphology and surface coverage compared to those fabricated without an electric field, which is due to improved atomization from the Coulomb fission process. The optimized applied voltage of 1.5 kV during spraying led to completion of the reaction between CH3NH3I and PbI2 on a hot substrate for pure phase CH3NH3PbI3 thin film formation with improved grain growth and surface coverage. The cells fabricated using perovskite films showed clear applied voltage dependence in the energy conversion process and alleviation in J-V hysteresis; with 1.5 kV applied voltage the average cell efficiency of 8.9% was obtained compared to films fabricated without applying voltage providing only 6.5%. The best efficiencies are 10.9% and 7.37% for applied voltages of 1.5 kV and 0 kV, respectively. The enhancement in efficiency with applied voltage is due to the formation of more uniform and dense films with large perovskite crystals, which resulted in efficient electron transportation (enhanced photocurrent and modified series and shunt resistances) by minimizing the charge carrier recombination at grain boundaries (resulting in enhanced open circuit voltage). With further optimization of the perovskite film thickness by adjusting the CH3NH3I spray volume, the average cell efficiency of ∼11.0% was obtained.

Spray deposited copper zinc tin sulphide (Cu2ZnSnS4) film as a counter electrode in dye sensitized solar cells.

Stoichiometric thin films of Cu2ZnSnS4 (CZTS) were deposited by the spray technique on a FTO coated glass substrate, with post-annealing in a H2S environment to improve the film properties. CZTS films were used as a counter electrode (CE) in Dye-Sensitized Solar Cells (DSCs) with N719 dye and an iodine electrolyte. The DSC of 0.25 cm(2) area using a CE of CZTS film annealed in a H2S environment under AM 1.5G illumination (100 mW cm(-2)) exhibited a short circuit current density (JSC) = 18.63 mA cm(-2), an open circuit voltage (VOC) = 0.65 V and a fill factor (FF) = 0.53, resulting in an overall power conversion efficiency (PCE) = 6.4%. While the DSC using as deposited CZTS film as a CE showed the PCE = 3.7% with JSC = 13.38 mA cm(-2), VOC = 0.57 V and FF = 0.48. Thus, the spray deposited CZTS films can play an important role as a CE in the large area DSC fabrication.

Plasmonic effect of spray-deposited Au nanoparticles on the performance of inverted organic solar cells.

Gold nanoparticles with varying sizes were prepared by the spray process under an electric field (DC voltages of 0 V and 1 kV applied to the nozzle) for studying their role in inverted organic solar cells (ITO/Au/ZnO/P3HT:PCBM/Ag). The application of electric field during the spray process resulted in a smaller size (35 nm as compared to 70 nm without the electric field) of the nanoparticles with more uniform distribution. This gave rise to a difference in the surface plasmon resonance (SPR) effect created by the gold nanoparticles (Au NPs), which then affected the solar cell performance. The photovoltaic performances of plasmonic inverted organic solar cells (ITO/Au/ZnO/P3HT:PCBM/Ag) using spray-deposited Au and ZnO layers (both at 1 kV) showed improved efficiency. Fast exciton quenching in the P3HT:PCBM layer was achieved by using a spray-deposited Au layer in between ITO and ZnO layers. The absorption spectra and internal power conversion efficiency (IPCE) curve showed that the Au nanoparticles provide significant plasmonic broadband light absorption enhancement which resulted in the enhancement of the JSC value. Maximum efficiency of 3.6% was achieved for the inverted organic solar cell (IOSC) with an exceptionally high short circuit current density of ∼15 mA cm(-2) which is due to the additional photon absorption and the corresponding increase observed in the IPCE spectrum. The spray technique can be easily applied for the direct formation of Au nanoparticles in the fabrication of IOSC with improved performance over a large area.

Oxidative stress and antioxidant status in cervical cancer patients.

Cervical cancer (CaCx) is a global public health problem as it is the second most common cancer leading to the death of women worldwide. Many references revealed that the low levels of antioxidants induce the generation of free radicals leading to DNA damage and further mutations. In the present study attempt have been made to evaluate the levels of serum Lipid peroxide, Nitric Oxide (NO(.)) Erythrocytic-Superoxide Dismutase (RBC-SOD), Vitamin-C, serum Copper (Cu) and serum Zinc (Zn). 120 patients were divided in 4 groups according to the increasing CaCx stages i.e. stage I, II, III & IV respectively. All the patients were around the age group of 25-65 years. 30 healthy women between the same age group were treated as controls. Highly significant increased values of MDA, NO(.) and Cu were observed (p<0.001) whereas the activity of RBC-SOD, levels of Vitamin-C and Zn were significantly decreased in CaCx patients as compared with healthy controls (p<0.001). Cu/Zn ratio was found to be altered in CaCx patients. From our findings it can be concluded that the oxidative stress is induced among CaCx patients, which inturn increases the risk of CaCx.