Improved Efficiency and Stability in 1,5-Diaminonaphthalene Iodide-Passivated 2D/3D Perovskite Solar Cells.

Engineering multidimensional two-dimensional/three-dimensional (2D/3D) perovskite interfaces as light harvesters has recently emerged as a potential strategy to obtain a higher photovoltaic performance in perovskite solar cells (PSCs) with enhanced environmental stability. In this study, we utilized the 1,5-diammonium naphthalene iodide (NDAI) bulky organic spacer for interface modification in 3D perovskites for passivating the anionic iodide/uncoordinated Pb2+ vacancies as well as facilitating charge carrier transfer by improving the energy band alignment at the perovskite/HTL interface. Consequently, the NDAI-treated 2D/3D PSCs showed an enhanced open-circuit voltage and fill factor with a remarkable power conversion efficiency (PCE) of 21.48%. In addition, 2D/3D perovskite devices without encapsulation exhibit a 77% retention of their initial output after 1000 h of aging under 50 ± 5% relative humidity. Furthermore, even after 200 h of storage in 85 °C thermal stress, the devices maintain 60% of their initial PCE. The defect passivation and interface modification mechanism were studied in detail by UV vis absorption, photoluminescence spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), solid-state NMR, space-charge-limited current (SCLC) mobility measurement, and impedance spectroscopy. This study provides a promising path for perovskite surface modification in slowing their degradation against external stimuli, providing a future direction for increasing the perovskite device efficiency and durability.

An efficient strategy to assemble water soluble histidine-perylene diimide and graphene oxide for the detection of PPi in physiological conditions and in vitro.

A strategy to develop water soluble, biocompatible nanocomposite probe for the detection of pyrophosphate (PPi) in physiological conditions and in in vitro live melanoma cancer cells (B16F10) is reported. The self-assembled nanocomposite probe comprised of amino acid (histidine) functionalized perylenediimide (PDI-HIS), copper ion and graphene oxide (GO) and that could be utilized as a highly effective sensing platform in biological conditions and cellular environment via fluorescence "turn-on" for PPi detection. This controlled fabrication of metal organic self-assembled spheres along with GO proved very valuable for the detection of PPi in unprecedented sensitivity over other competing ions. The PDI-HIS-Cu-GO (PCG) nanocomposite sensor provides a unique platform for the fluorogenic detection of PPi having a very low limit of detection (LOD) of 0.60×10-7M based on the strong affinity (1.0×106M-1) between the copper complex of PDI-HIS receptor and PPi. The intracellular detection of PPi using PCG also carried out in B16F10 cells where >10 times observed as compared to the PDI-HIS+Cu2+ complex. Thus early cancer detection via PPi recognition in physiological conditions and in live cells was possible using PCG. Furthermore, the fabrication of PDI-HIS and PCG with PVA hydrogel films and on thin layer chromatography plates demonstrated the practical utility for the detection of PPi anions by "off-on" response rapidly in a label free manner.

Modulation of Amyloid-ß Fibrils into Mature Microrod-Shaped Structure by Histidine Functionalized Water-Soluble Perylene Diimide.

Alzheimer's disease (AD) is associated with different types of amyloid peptide aggregates including senile plaques, fibrils, protofibrils, and oligomers. Due to these difficulties, a powerful strategy is needed for the disaggregation of amyloid aggregates by modulating their self-aggregation behavior. Herein, we report a unique approach toward transforming the aggregated amyloidogenic peptides using an amino acid functionalized perylene diimide as a molecular modulator, which is a different nondestructive approach as compared to inhibiting the aggregation of peptides. The histidine functionalized perylenediimide (PDI-HIS) molecule could coassemble with amyloid ß (Aß) peptides via hydrogen bonding that leads to the enhancement in the π-π interactions between Aß and PDI-HIS moieties. The Thioflavin T (ThT) assay and various spectroscopic and microscopic techniques establish that the PDI-HIS molecules accelerate the Aß1-40 and the amyloid aggregates in CSF into micro size coassembled structures. These results give rise to a new and unique complementary approach for modulating the biological effects of the aggregates in amyloidogenic peptides.

An anionic conjugated polymer as a multi-action sensor for the sensitive detection of Cu(2+) and PPi, real-time ALP assaying and cell imaging.

A Cu(2+) ensemble polyfluorene derivative, poly[5,5'-(((9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(oxy))diisophthalate] sodium salt (PFT), displays unprecedented selectivity for PPi (LOD = 2.26 ppb) in aqueous solution as well as in random urine samples at physiological pH vis-a-vis monitoring ALP activity. Furthermore, intracellular imaging of Cu(2+) and PPi in mouse macrophage (J774A.1) and human breast cancer cells (MDA-MB231) was achieved to confirm the viability of PFT in biological systems.

Enhanced environmental stability induced by effective polarization of a polar dielectric layer in a trilayer dielectric system of organic field-effect transistors: a quantitative study.

We report a concept fabrication method that helps to improve the performance and stability of copper phthalocyanine (CuPc) based organic field-effect transistors (OFETs) in ambient. The devices were fabricated using a trilayer dielectric system that contains a bilayer polymer dielectrics consisting of a hydrophobic thin layer of poly(methyl methacrylate) (PMMA) on poly(vinyl alcohol) (PVA) or poly(4-vinylphenol) (PVP) or polystyrene (PS) with Al2O3 as a third layer. We have explored the peculiarities in the device performance (i.e., superior performance under ambient humidity), which are caused due to the polarization of dipoles residing in the polar dielectric material. The anomalous behavior of the bias-stress measured under vacuum has been explained successfully by a stretched exponential function modified by adding a time dependent dipole polarization term. The OFET with a dielectric layer of PVA or PVP containing hydroxyl groups has shown enhanced characteristics and remains highly stable without any degradation even after 300 days in ambient with three times enhancement in carrier mobility (0.015 cm(2)·V(-1)·s(-1)) compared to vacuum. This has been attributed to the enhanced polarization of hydroxyl groups in the presence of absorbed water molecules at the CuPc/PMMA interface. In addition, a model has been proposed based on the polarization of hydroxyl groups to explain the enhanced stability in these devices. We believe that this general method using a trilayer dielectric system can be extended to fabricate other OFETs with materials that are known to show high performances under vacuum but degrade under ambient conditions.

Highly precise detection, discrimination, and removal of anionic surfactants over the full pH range via cationic conjugated polymer: an efficient strategy to facilitate illicit-drug analysis.

A water-soluble cationic conjugated polyelectrolyte (CPE), poly(1,4-bis(6-(1-methylimidazolium)-hexyloxy)-benzene bromide) (PMI) displays extraordinary stability over the full pH range of 1-14 as well as in seawater, brine, urine, and other solutions and carries out efficient detection, discrimination, and removal of moderately dissimilar anionic surfactants (viz., sodium dodecyl benzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS)) at very low levels (31.7 and 17.3 parts per billion (ppb), respectively). PMI formed stable hydrogels in the presence of SDS that remained unaffected by strong acids/bases, heating, ultrasonication, or exposure to light, whereas SDBS formed precipitate with PMI as a result of its different interpolymer cofacial arrangement via Columbic attraction. The complex-forming ability of PMI with SDS and SDBS facilitated their elimination from water or drug-doped urine samples without the use of any organic solvent, chromatographic technique, or solid support. This protocol, the first of its kind for the removal of anionic surfactants at very low concentrations from any type of solution and competitive environments, demonstrates an original application using a CPE. The surfactant-free sample solutions could be precisely analyzed for the presence of illicit drugs by any standard methods. Using PMI, a newly developed CPE, a rapid and practical method for the efficient detection, discrimination, and removal of SDS and SDBS at ppb levels from water and urine, under harsh conditions, and in natural chemical environments is demonstrated.

Therapeutic strategies to prevent Alzheimer's disease pathogenesis using a fluorescent conjugated polyelectrolyte.

Toxic metals accumulation in brain has a significant role in the pathogenesis of Alzheimer's disease (AD) by accelerating amyloid ß (Aß) peptide aggregation. Aß has high affinity for iron and copper resulting in the generation of neurotoxic hydrogen peroxide, oxidative stress and free radical formation. Water-soluble conjugated polyfluorene derivative poly(9,9-bis(6-sulphate hexyl) fluorene-alt-1,4-phenylene) sodium salt (P1) binds Fe(3+) heme proteins selectively in cerebrospinal fluid (CSF), including ferritin in the Aß fibrils and diminishes their accumulation. Hence, therapeutic strategies involving clearance of Aß from brain plaques, metal removal, structurally modifying the aggregates, and preventing them from aggregating again into toxic polypeptides are vital strategies to control AD pathogenesis.

Acetate recognition by 2,6-bis(2-benzimidazolyl)pyridine.

2,6-Bis(2-benzimidazolyl)pyridine, bbp, a simple tridentate ligand, is employed as a receptor for the recognition of anions. The binding of anionic guest species with bbp can be studied in short duration using UV/vis spectroscopy, fluorescence spectroscopy and (1)H NMR techniques at very low concentrations. The results obtained from the above spectroscopic techniques indicate that 2,6-bis(2-benzimidazolyl)pyridine is an efficient anion receptor providing chemical shift and optical modification based signals for the detection of acetate ions.

Enhancing the photostability of poly(3-hexylthiophene) by preparing composites with multiwalled carbon nanotubes.

Poly(3-hexylthiophene) (P3HT) degrades in organic solvents containing dissolved molecular oxygen when irradiated with ultraviolet light. Hence, it is important to develop strategies that can enhance the photostability of P3HT and enhance the device performance. In this work, we report that preparing composites of P3HT with appropriate amounts of multiwalled carbon nanotube (MWCNT) results in superior photostability of P3HT. UV-visible and fluorescence spectroscopy have been used as primary tools to study the photostability of P3HT and its composites. Scanning electron microscopy (SEM) images of the composites display dispersed CNTs being well coated by P3HT. Transmission electron microscopy (TEM) micrographs along with SAED patterns reveal that P3HT coats the CNTs, which is the reason for superior dispersion of the composite. ESR spectroscopy was also performed to pursue and follow the degradation of P3HT. Ten weight percent of MWCNTs in P3HT was found to be the optimum loading amount that results in maximum photostability of the P3HT as compared to the other ratios. This enhanced photostability of P3HT on preparing composites with MWCNT in addition to its easy processability directly from solution makes these composites immensely important for optoelectronic applications.

Facile C-H alkylation in water: enabling defect-free materials for optoelectronic devices.

A facile method for the alkylation of fluorene achieved via direct C-H alkylation under aqueous conditions is reported, wherein the formation of fluorenone is inhibited, resulting in the exclusive formation of the desired dialkyl-substituted fluorene monomer. As a proof of concept, this method has also been successfully extended to perform N-alkylation of carbazole, diphenylamine, and N,N-dialkylation of aniline in high yields.

Synthesis and optical properties of metallo-supramolecular polymers.

Metal-ligand interactions between metal ions, such as Zn2+, and ditopic low-molecular weight conjugated monomers, which utilize the 2,6-bis(1'-methylbenzimidazolyl)pyridine ligand, lead to the formation of supramolecular conjugated polymers with interesting optical properties.