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We report the synthesis and characterization of Methyl Ammonium Lead Bromide perovskites and their quantum dots for efficient, colour tunable emitters that can be used as active materials in low-cost display, lighting applications and solar cells. In general, organic/inorganic perovskites are highly sensitive to atmospheric exposure limiting their commercial applications. In this work, a comparison on optical properties of Methyl Ammonium Lead Bromide Quantum Dots (MAPbBr3 QDs) synthesized by Ligand-assisted Re-precipitation (LARP) technique in the presence and absence of Poly(methyl methacrylate) (PMMA) as a base matrix material is reported. The size distribution and quantum confinement of the synthesized material was confirmed using Transmission Electron Microscopy (TEM). The optical absorption and photoluminescence studies of the samples show stability even after 4 months of preparation proving that the polymer encapsulated MAPbBr3 QDs are highly resistant to environmental degradation.

Two novel, soluble, semiconducting and light emitting segmented block copolymers, termed as NPPV1 and NPPV2 are synthesized using Horner-Emmons condensation polymerization. The chromophoric groups present in the copolymers are distyrylbenzene (DSB) units substituted with rigid, bulky cyclohexylmethoxy and cyclohexylethoxy groups. The rigid blocks are linked to flexible α,ω-nonamethylenedioxy chain spacer through ether linkage. The structural, morphological, thermal and photo-physical characteristics of the synthesized polymers are studied in detail. Noticeable differences in properties arising through the substituent effects are observed for both the polymers. Detailed studies bring out quite interesting structure-property relationships between the substituents introduced in the synthesized copolymers and their crystalline properties, thermal characteristics, optical properties, photoluminescence emission and fluorescence quantum yield. Polymer light emitting diodes (PLEDs) employing these segmented polymers as emissive layers are assembled and characterized to establish their suitability for lighting applications. Using the architecture, ITO/PEDOT:PSS/NPPV1/LiF-Al, polymer light emitting diodes (PLEDs) are assembled and as the first step of device characterization, their current-voltage characteristics are studied to establish the device behavior and find out the onset voltage. The emission characteristics of the devices are then studied using Ocean Optics USB 2000 spectrometer integrated to a computer using a dedicated program. The assembled devices show Schottky junction like behavior in the current-voltage characteristics and electroluminescence emission in the blue green region with appreciable intensity at the onset voltage of 8.8 V. It is highly desirable to develop polymers showing emission in the high frequency,blue region, using cost-effective synthesis routes. The novel approaches adopted in the synthesis of the monomers and the corresponding copolymers to achieve the anticipated structure-property relationships suitable for the effective designing of polymer light emitting diodes are the highlights of the present work.

Two novel, highly soluble and semiconducting thienylene–biphenylenevinylene hybrid polymers with excellent photoluminescence and thermal stability were synthesized via Stille coupling polymerization of two novel monomers 5,5′-(1 E ,1′ E )-2,2′-(4,4′-bis(octyloxy)biphenyl-3,3′-diyl)bis(ethene-2,1-diyl)bis(2-bromothiophene) and 5,5′-(1 E ,1′ E )-2,2′-(6,6′-bis(octyloxy)biphenyl-3,3′-diyl)bis(ethene-2,1-diyl)bis(2-bromothiophene), respectively. The structural, thermal, optical and electrical characteristics of the synthesized monomers and polymers were studied in detail. Both polymers exhibit good solubility in common organic solvents, high thermal stability and desirable photophysical characteristics. Slight differences in the optical and electrical properties were observed for both the polymers which arise as a result of the positional change introduced to the functional groups attached in the polymer backbones. Hybrid density functional theory was used to study the band structure of the polymers and the values agree with the experimental results. Polymer light emitting diodes (PLEDs) were assembled based on these hybrid polymers as emissive layers and characterized to establish the suitability of these materials for PLED application. The assembled PLEDs show excellent diode characteristics and good emission in the orange red region.

Adverse cardiac events are a major cause of late-stage drug development withdrawals. Improved in vitro systems for predicting cardiotoxicity are of great interest to prevent these events and to reduce the expenses involved in the introduction of cardiac drugs into the marketplace. Interdigitated electrodes (IDEs) affixed with a culture well provide a simple, suitable solution for in vitro analysis of cells because of their high sensitivity, ease of fabrication, and label-free, nondestructive analysis. Culturing human pluripotent stem cell differentiated cardiomyocytes onto these IDEs allows for the use of the IDE–cell combination in predictive toxicity assays. IDEs with smaller interdigitated distances allow for greater sensitivity, but typically require cleanroom fabrication. In this communication, we report the definition of a simple IDE geometry on a printed nanostructured substrate, demonstrate a Cellular Index (CI) increase from 0 to 7.7 for human cardiomyocytes, and a decrease in CI from 2.3 to 1 with increased concentration of the model drug, norepinephrine. The nanostructuring results in an increased sensitivity of our 1 mm pitch IDEs when compared to traditionally fabricated IDEs with a pitch of 10 μm (100 times larger electrode gap). The entire nanostructured IDE (nIDE) is fabricated and assembled in a rapid nanofabrication environment, thus allowing for iterative design changes and robust fabrication of devices.

Wearable electronic devices represent a paradigm change in consumer electronics, on-body sensing, artificial skins, and wearable communication and entertainment. Because all these electronic devices require energy to operate, wearable energy systems are an integral part of wearable devices. Essentially, the electrodes and other components present in these energy devices should be mechanically strong, flexible, lightweight, and comfortable to the user. Presented here is a critical review of those materials and devices developed for energy conversion and storage applications with an objective to be used in wearable devices. The focus is mainly on the advances made in the field of solar cells, triboelectric generators, Li-ion batteries, and supercapacitors for wearable device development. As these devices need to be attached/integrated with the fabric, the discussion is limited to devices made in the form of ribbons, filaments, and fibers. Some of the important challenges and future directions to be pursued are also highlighted.

Conducting polyaniline (PANi)–graphene (G) free standing, hybrid films were obtained by a solution intercalation method suitable for electromagnetic interference (EMI) shielding applications. The films were characterized structurally using Fourier transform infrared spectroscopy, micro-Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The electrical characterization was done using Hall measurement setup to estimate the dc electrical conductivity and establish the charge carrier type and mobility and investigate the possibility of using the hybrid films in other applications. The thermal stability of the films was investigated using thermo gravimetric analysis. The EMI shielding effectiveness (SE) of the composite films was tested over a broad microwave frequency range covering 4–12 GHz (C and X bands) by waveguide transmission line technique. The films exhibit very high values of reflected power (Pr) in the range of 85–90% in the C-band and 75–80% in the X-band, respectively. A maximum total shielding effectiveness value of SET ∼ 42 dB could be observed in the frequency range of 4–8 GHz and SET ∼ 32 dB could be observed in the frequency range of 8–12 GHz, corresponding to more than 99.99% microwave attenuation in both the C and X bands. In the entire frequency range of analysis, contributions from reflection to the total EMI SE is very high compared to that of absorption. The results suggest that the hybrid film may be used as effective, lightweight and flexible, reflection dominated EMI shielding material in a broad range of electromagnetic spectrum.

Two dimensional (2D) graphene and transition metal dichalcogenides are an emerging class of extremely interesting materials showing unique physical properties, such as large third-order optical nonlinearity, offering potential applications in optical limiting. Here we report the optical limiting properties of Titanium disufide (TiS2), and Graphene sheets measured using open aperture and photo-acoustic z-scan techniques. Our best results were observed in TiS2 Sheets, yielding an optical limiting of 77% at an irradiance of 0.713 GW/cm2with 2PA and 3PA absorption coefficient to be 80cm/GW and 2000 cm3/GW2 respectively.Also, TiS2 sheets show improved shelf life and stability upon irradiation with higher laser powers. This demonstrates the feasibility of using them as a potential candidate for optical limiting applications.

Oleic acid capped zinc oxide (ZnO) nanoparticles have been synthesized by a wet chemical route. The chemical oxidative method is employed to synthesize polyaniline (PANI) and PANI/ZnO nanocomposites doped with four different dopants such as orthophosphoric acid (H 3 PO 4 ), hydrochloric acid (HCl), naphthalene-2-sulphonic acid and camphor sulphonic acid (CSA). The samples have been structurally characterized by X-ray diffraction (XRD), field emission scanning electron microscopy and Fourier transform infrared (FT-IR) spectroscopic techniques. A comparison of the photoluminescence (PL) emission intensity of PANI and PANI/ZnO nanocomposites is attempted. The enhanced PL intensity in PANI/ZnO nanocomposites is caused by the presence of nanostructured and highly fluorescent ZnO in the composites. It has been observed that, among the composites, the H 3 PO 4 doped PANI/ZnO nanocomposite is found to exhibit the highest PL intensity because of the higher extent of (pi) conjugation and the more orderly arrangement of the benzenoid and quinonoid units. In the present work, transparent thin films of PANI and PANI/ZnO nanocomposite for which PL intensity is found to be maximum, have been prepared after re-doping with CSA by the spin-coating technique. The XRD pattern of the PANI/ZnO film shows exceptionally good crystallanity compared to that of pure PANI, which suggests that the addition of ZnO nanocrystals helps in enhancing the crystallanity of the PANI/ZnO nanocomposite. There is a significant increase in the PL emission intensity of the PANI/ZnO nanocomposite film making it suitable for the fabrication of optoelectronic devices.

Polypyrrole has drawn a lot of interest due to its high thermal and environmental stability in addition to high electrical conductivity. The present work highlights the enhanced crystallinity of polypyrrole films prepared from the redoped sample solution. Initially hydrochloric acid doped polypyrrole was prepared by chemical oxidative polymerization of pyrrole using ammonium peroxidisulphate as oxidant. The doped polypyrrole was dedoped using ammonia solution and then redoped with camphor sulphonic acid. Films were coated on ultrasonically cleaned glass substrates from the redoped sample solution in meta-cresol. The enhanced crystallinity of the polypyrrole films has been established from X-ray diffraction (XRD) studies. The room temperature electrical conductivity of the redoped polypyrrole film is about 30 times higher than that of the hydrochloric acid doped pellet sample. The results of Raman spectroscopy, Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) of the samples support the enhancement in crystallinity. Percentage crystallinity of the samples is estimated from XRD and DSC data. The present work is significant, since crystallinity of films is an important parameter for selecting polymers for specific applications.

Polyaniline (PANI) is well-known for its remarkable electrical and optical properties which find immense applications in polymer optoelectronics. Though extensive work has been reported in polyaniline samples both in bulk and thin film forms, much attention has not been paid to investigate the quantum confinement effects in ultrathin polyaniline films. The present work is devoted to the search for quantum confinement effects in ultrathin polyaniline films having nanometer thickness, prepared from m-cresol, through conventional and less sophisticated spectroscopic techniques. Remarkable blue-shift has been observed in the absorption spectrum of these samples. Much intense photo-luminescent emission with considerable blue-shift observed in these ultrathin films is cited as the clear evidence for confinement effects.

Highly crystalline camphor sulfonic acid (CSA)-doped polyaniline (PANI) thin films cast from m-cresol and N-methylpyrrolidone (NMP) were investigated. PANI powder prepared by chemical oxidative polymerization subjected to doping–de-doping–re-doping procedures was cast into thin films using NMP and m-cresol as solvents. X-ray diffraction (XRD) reveals the presence of exceptionally highly crystalline or rather ordered regions in the PANI film samples prepared from m-cresol. Atomic force microscopy (AFM) images also support the presence of crystalline regions on the surface of these films. The DC electrical conductivity of m-cresol-cast PANI is found to be quite high, and much higher than that of NMP-cast PANI. The free-carrier absorption tail extending to the near-infrared region observed in the optical absorption spectrum of the m-cresol-cast PANI films suggests a metallic nature and regular structural arrangement in these films. Both inter-chain and intra-chain ordering brought about as a result of CSA doping, secondary doping effect of m-cresol and ultrasonication are suggested to be the prime factors contributing towards the observed excellent crystallinity of these PANI films as evident from the XRD and AFM studies. The marked thermal stability of the m-cresol-cast PANI films is also established based on the variation of DC electrical conductivity with temperature and on thermogravimetric analysis. Copyright © 2012 Society of Chemical Industry

Zinc oxide (ZnO) nanoparticles are synthesized using a simple chemical method at room temperature. A variation in molar concentration of the precursor, potassium hydroxide, from 0.25 to 0.01 mol L−1 is accompanied by a decrease in the average size of the nanoparticles. These nanoparticles are used for the preparation of polystyrene/ZnO nanocomposite films using the spin-coating technique. These films are found to be highly transparent throughout the visible region and absorb UV light in the region from 395 to190 nm, almost covering the near and middle UV ranges (400 to 200 nm). This observation highlights the possible prospects of these films in UV shielding applications. The wavelength corresponding to the onset of UV absorption is found to be blue shifted with a decrease in size of the ZnO particles in the composite films due to confinement effects. The photoluminescence spectra of the composite films also change as a function of particle size. The emissions at longer wavelength due to defects and impurity-related states in ZnO are almost quenched as a result of surface modification by the polymer matrix. The observed band-gap enlargement with a decrease in size of the ZnO particles in the composite films is significant for band-gap engineering of nanoparticles for various applications. Copyright © 2011 Society of Chemical Industry

Polyaniline (PANI) has been of great interest to many researchers because of its high electrical conductivity, environmental stability, ease of preparation, affordability and good redox properties compared to other conducting polymers. It has been reported that PANI doped with orthophosphoric acid exhibits quite high photoluminescence (PL) emission intensity. Orthophosphoric acid doped PANI exhibits good room temperature D.C electrical conductivity also. Thus orthophosphoric acid doped PANI has been found to be a suitable material for optoelectronic applications. In the present work, an attempt is made to develop highly luminescent orthophosphoric acid doped PANI by treating it with oleic acid and it is found that the PL emission intensity is significantly enhanced upon modification of PANI with oleic acid.

The advancement in high power lasers has urged the requisite of efficient optical limiting materials for both eye and sensor protection. The discovery of atomically thin 2D transition metal dichacogenides with distinctive properties has paved the way for a variety of applications including optical limiting. Until recently, the optical limiting effect exhibited by 2D materials is inferior to the benchmark materials fullerene (C60) and graphene. This article reports the optical limiting activity of the 2D transition metal dichalcogenide, titanium disulfide (TiS2) nanosheets, using optical and photoacoustic z-scan techniques. The 77% nonlinear optical limiting exhibited by the TiS2 sheets with 73% linear-transmittance is superior to that of any other existing 2D dichalcogenide sheets, graphene, and the benchmark optical limiting material, C60. The enhanced nonlinear response is attributed to the concerted effect of 2-photon and the induced excited state absorptions. By using photoacoustic z-scan, a unique tool developed to determine the nonlinear optical limiting mechanism in materials, it is found that the optical limiting exhibited by TiS2 2D sheets and graphene are mainly due to nonlinear absorption rather than scattering effects. These results have opened the door for 2D-dichalcogenide-materials-based highly efficient optical limiters, especially at low fluences.

This chapter discusses the potential applications of graphene in the realization of efficient and stable organic optoelectronic devices, especially flexible solar cells. With the introduction of the prospects of graphene and functionalized graphene in modifying the performance characteristics of organic solar cells, the chapter evolves into assessing the prospects of realizing all carbon photovoltaic devices. The combination of unique, yet tunable, electrical and optical properties of graphene, makes it a highly sought after candidate for various technologically important applications in optoelectronics. Graphene has been identified as a suitable replacement for the highly expensive, brittle and less abundant indium tin oxide, as the transparent electrode material for optoelectronic device applications. The best graphene-based transparent conducting films show very low sheet resistance of 20 Ω/sq and high transparency around 90 % in the visible spectrum, making it a better choice compared to the commonly used transparent conductors including indium tin oxide (ITO) and zinc oxide (ZnO). The absence of energy band gap in graphene has originally limited its applications in optoelectronic devices. This problem has since been solved with the advent of graphene nanoribbons (GNRs) and functionalized graphenes. Functionalized graphenes and GNRs have extended the use of graphene as hole and electron transport layers in organic/polymer light emitting diodes and organic solar cells by the suitable tuning of the band gap energy. Blending dispersions of functionalised graphene with the active layers in photovoltaic devices has been found to enhance light absorption and enable carrier transport efficiently. Graphene layers with absorption in the entire visible region can be fine-tuned to be incorporated into the active layers of organic solar cells. Finally the synthesis conditions of GNRs and the functionalized graphenes can be optimized to achieve the required structural, optical and electrical characteristics for venturing into developing all carbon-based cost-effective organic solar cells with improved efficiency.

Numerous light emitting polymers and copolymers with excellent luminescence characteristics and thermal stability are being synthesized and extensively investigated for applications as emissive layers in polymer light emitting diodes. In the present study, three novel, thermally stable, segmented block copolymers (SBC) and two hybrid polymers with excellent photoluminescence (PL) and electroluminescence emission (EL) characteristics were subjected to spectroscopic investigations to explore the effect of various aromatic and non-aromatic solvents on the photoluminescence emission characteristics. Dilute solutions of the SBCs and the hybrid polymers were made from various solvents like dichloromethane, chlorobenzene, tetrahydrofuran, xylene, chloroform, etc. UV-Vis absorption and PL emission spectra of these polymer solutions were recorded simultaneously. No significant changes in the PL emission peaks were observed, depending on the nature of solvents. The effect of solvents in terms of aggregation effects in these polymers was studied. The low aggregation effects and solvent independent nature of the polymers offer very high prospects in various optoelectronic device applications. The present study can be of great use in designing efficient polymer LEDs based on these SBCs and hybrid polymers as emissive layers. The efficiency and stability of the polymer LEDs can be considerably improved by suitably choosing the solvent for the emissive polymers.

Emeraldine salt form of polyaniline (PANI) was synthesized by chemical oxidative polymerisation method using ammonium persulfate as oxidant. Resultant emeraldine salt form of PANI was dedoped using ammonia solution and then re-doped with camphor sulphonic acid (CSA), naphthaline sulphonic acid (NSA), hydrochloric acid (HCl), and m-cresol. Thin films of these doped PANI samples were deposited on glass substrates using solution casting method with m-cresol as solvent. A level surface was employed to get homogeneous thin films of uniform thickness. Detailed X-ray diffraction studies have shown that the films are exceptionally crystalline. The crystalline peaks observed in the XRD spectra can be indexed to simple monoclinic structure. FTIR and Raman spectroscopy studies provide convincing explanation for the exceptional crystallinity observed in these polymer films. FESEM and AFM images give better details of surface morphology of doped PANI films. The DC electrical conductivity of the samples was measured us...

Genetic Programming: Efficient Modeling Tool in Hydrology and Groundwater Management

This work highlights the prospects of applications of doped polyaniline (PANI) and Polyaniline–MultiWalled Carbon Nanotube (MWNT) composites with different dopants in pressure sensing devices. PANI and its nanocomposite samples in the form of pressed pellets show orders of change in electrical conductivity with applied pressure in the range 0–30 MPa, even for very small applied bias of a few milli-volts. The percentage variation of electrical conductivity with applied pressure is strikingly large for PANI and its composite samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The present work highlights the prospects of application of the nanocomposite, polyaniline (PANI) - polyvinylchloride(PVC)- Multi Walled Carbon Nanotube (MWNT), in pressure sensing devices. The above nanocomposite sample in the form of pressed pellet shows orders of change in electrical conductivity with applied pressure in the range 10E5 Pa to 10E9 Pa, even for very small applied bias of a few milli-volts. The percentage variation of electrical conductivity with applied pressure is strikingly large for this composite. There is ample scope for further investigations in this direction especially if the samples can be cast in the form of free-standing films.