Toxic metal ions present in environmental water samples and other samples need to be detected for their removal. The detection of trace metal ions using an ion selective electrode (ISE) holds great significance in analytical chemistry. A 4-vinyl pyridine-ethyl acrylate copolymer-polyvinyl chloride (VE-PVC) based polymeric matrix (electrode) has been fabricated by free radical bulk polymerization method which is an example of a green and sustainable method capable of detecting Ni2+ ions even in trace amounts. To fabricate the polymeric matrix (electrode) (PME), VE has been used as an ionophore. Further, the effectiveness of Ni2+ ion ISE has also been investigated in the presence of surfactants and detergents. Its performance has also been analyzed in the presence of plasticizers. The electrode is found to be very useful for the estimation of Ni2+ ions using ethylenediaminetetraacetic acid by potentiometric titration and also in the estimation of presence of Ni2+ ions in water. Compared to other metal ions, the fabricated membrane electrode developed in this work has been found to show efficient and better selectivity towards Ni2+ ions.

Here in this work, two electrochromic systems have been prepared by functionalizing di-pentyl viologen (DPV) and di-heptyl viologen (DHV) with graphene quantum dots (GQDs). Strong molecular forces like cation pi interactions, 7C-7C stacking interactions, electrostatic interactions, etc., ensure an adequate interaction between GQDs and viologens, hence, responsible for stabilizing the electrochromic system. All solid electrolyte-free electrochromic devices have been fabricated by dispersing DPV-GQD and DHV-GQD in poly(vinyl)alcohol (PVA) gel. Electrochemical behavior and electrochromic responses of the fabricated devices were investigated using chronoamperometry, cyclic voltammetry and in situ UV-vis spectroscopy. Both devices were found to work efficiently without the help of supporting electrolytes. Both DPV-GQD and DHV-GQD devices exhibit high optical contrast of 53.4% and 60%, with superior coloration efficiency of 143.9 cm2/C and 66 cm2/C, respectively. Swift electrochromic responses of 4.4 s/3.5 s and 6.2 s/2.5 s have been recorded for coloration/bleaching for DPVGQD and DHV-GQD devices, respectively. Fabricated DPV-GQD device was found to retain 73% of its initial optical contrast while DHV-GQD depicts retention of only 63% after 3000 cycles. The superior coloration efficiency and balanced response time of DPV-GQD make it a potential material for the device application.

The photovoltaic (PV) for irrigation system is an emerging technology to harness the solar energy. The performance of the PV modules depends on the incident solar radiation, geographical location, and the surface temperature of the modules. The performance of the PV system needs to be monitored by manually or embedded controllers. The commercially available technologies for monitoring the system are costlier and need to be optimized. The Arduino controller is used to monitor the performance of the photovoltaic (PV) system in Coimbatore (11.016° N, 76.9558° E), Tamilnadu, India. The PV surface temperature is monitored and controlled by flowing the water above the module by setting the mean ambient temperature as a reference temperature 34 °C when the system exceeds the reference temperature. PV surface temperature is reduced up to 16°C thus improved the electrical efficiency by 17% compare to the reference module. The Arduino controller control the relay to switch on the motor to control the mass flow rate of the water at 0.0028kg/s. The various parameters are measured such as voltage, current, and solar radiation of the location and analyzed. The estimated cost of monitoring system and various sensor is 10$ which cost comparatively 50% lower than the other PV monitoring controllers. This method can be employed in the medium and large-scale irrigation system.

The Agri-voltaic (AV) is an emerging technology to harness the solar energy. The performance of the AV modules depends on the incident solar radiation, geographical location and the surface temperature of the modules. The performance of the AV system needs to be monitored by manually or embedded controllers. The commercially available technologies for monitoring the system is costlier and need to be optimised. The Arduino controller is used to monitor the performance of the photovoltaic (PV) system in Coimbatore (11.0160 N, 76.95580 E), Tamilnadu, India. The PV surface temperature is monitored and controlled by flowing the water above the module by setting the mean ambient temperature as a reference temperature 34 °C when the system exceeds the reference temperature. PV surface temperature is reduced up to 16°C thus improved the electrical efficiency by 17% compare to the reference module. The Arduino controller control the relay to switch on the motor to control the mass flow rate of the water at 0.0028kg/s. The various parameters are measured such as voltage, current and solar radiation of the location and analysed. The estimated cost of monitoring system and various sensor is 10$ which cost comparatively 50% lower than the other PV monitoring controllers. This method can be employed in the medium and large-scale irrigation system.

In this work, the solar water collector flow tube geometry is modified as curved and spiral to enhance the system’s performance. The investigation is carried out experimentally under the meteorological conditions of the Kovilpatti region (9°10′0″N, 77°52′0″E), Tamil Nadu, India. The flow pipes of the solar water heater are made of copper material which has higher thermal conductivity to recover the water heat as thermal energy. The influence of the mass flow rate (MF) on the flow pipes with respect to the surface temperature for various configurations of the flow tubes is investigated. The two MFs of 0.0045 kg/s and 0.006 kg/s are tested. The MF of 0.006 kg/s yields the maximum efficiency of 73% compared to the other MF. The straight, curved, and spiral tubes yielded the maximum efficiency of 58%, 62%, and 69%, respectively, at 0.0045 kg/s. Similarly, the MF of 0.006 kg/s obtained an efficiency of 62%, 65%, and 73% for straight, curved, and spiral flow tubes, respectively. The economics and exergy of the system are analyzed. The maximum exergy efficiency of the collector is estimated to be 32% for the MF of 0.0045 kg/s for the spiral flow collector, and for the 0.006 kg/s MF, the obtained exergy efficiency is 27% for the spiral flow water heater. The economic analysis revealed that the expense is $0.0608 and $0.0512 worth of hot water produced for the domestic space heating.

We report for the first time, the effect of physicochemical properties of analyte on the selectivity of the polymethylmethacrylate: functionalized Multiwalled carbon nanotubes (PMMA: f-MWCNTs) composite sensor. In the present work, we have developed an optimized composite sensor and its selectivity was studied in detail. The sensor was exposed to various organic vapors and their response, response time and recovery time were recorded. It was found that the selectivity is jointly governed by the electronic and structural properties of both the species i.e. the sensing material and the vapor molecule. Also the discrimination towards different organic vapors strongly depends on the adsorption and chemical properties of the analyte. The sensor was observed to be highly selective for methanol vapor owing to its smallest molecular size and highest electronegativity.

The adverse impact of chemical and biochemical waste on the environment and human health poses a serious challenge in today's World. The best way to address these challenges is to reduce the waste by developing more efficient processes and technologies, based on the principles of "green chemistry". Some of these synthetic approaches involving the chemoenzymatic synthetic methodologies are discussed herein. These lead to the formation of unique nanomaterials with diverse applications, such as drugs/gene delivery systems, flame retardant materials, conducting polymers, controlled release systems, diagnostic agents, and polymeric electrolytes for nanocrystalline solar cells.

An efficient white polymer light-emitting diode (WPLED) with stable Commission Internationale de l’éclairage (CIE) coordinates is fabricated. A blue electroluminescence (EL)-emitting conducting polymer [poly(9,9-di-n-hexyl-fluorenyl-2,7-diyl)] is used as a host for red [Bis(1-phenyl-isoquinoline)(acetylacetonate)iridium(III)] and green [iridium(III)tris(2-(4-tolyl)pyridinato-N,C2)] phosphorescent dyes. Although efficient triplet energy transfer is not possible in the green phosphorescent dye, the self-trapping mechanism is utilized for the emission of EL in the green region while an efficient triplet exciton energy transfer from the host to the red dye is utilized for EL in the red wavelength region. Concentrations of the three constituents are optimized to obtain pure white light of appropriate CIE coordinates. An efficient electron-blocking layer based on a biomaterial (salmon-DNA) is also incorporated in the WPLED to improve the device performance. The WPLED shows three distinguished peaks for the primary colors and achieved a maximum luminance and luminous efficiency of 350 cd/m2 and 0.86 cd/A, respectively.

An efficient electron transporting layer (ETL) based on single walled carbon nanotube (SWCNT) composites has been developed for poly [2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) based orange polymer light emitting diodes (PLEDs) and its effect on the performance of PLEDs has been examined. It is observed that with increase in SWCNT concentration, in ETL, the luminance and luminous efficiency of the PLEDs increase (about 5 times increase in luminance is observed at 5%w/w SWCNT concentration). The SWCNTs present in the MEH-PPV ETL boost the mobility of electrons injected from the cathode towards the emissive layer by establishing highly conducting percolation paths. This balances the concentration of holes and electrons in the emissive layer, which leads to enhanced emission from the PLEDs.

The mechanism for exciting electroluminescence (EL) in a green phosphorescent dye, iridium(III)tris(2-(4-tolyl)pyridinato-N,C2) (Ir(mppy)3), doped in a host blue-emitting conducting polymer, poly[9,9-di-n-hexyl-fluorenyl-2,7-diyl] (PFO), has been studied. Photoluminescence measurements have been made on PFO/Ir(mppy)3 (0–12%) composites to rule out the possibility of singlet exciton energy transfer from the host polymer to the green dye. EL measurements have also been made to study the behavior of the composites in the presence of dc bias. The dominant mechanism for energy transfer from PFO to Ir(mppy)3 is found to be self-trapping of the charge carriers in the dye molecules, due to the extremely low LUMO and high HOMO levels as compared with PFO, thereby producing EL in the green region.

The effect of salmon DNA–CTMA as an electron blocking layer (EBL) has been examined on the performance of MEH–PPV and PFO-based light emitting diodes. Though the turn-on voltage increases with incorporation of EBL, a significant increase in luminance and luminous efficiency for both the devices is observed. The EBL improves the device performance by blocking electrons at the EBL–polymer interface, thereby increasing the recombination probability of electrons and holes. The luminance of the MEH–PPV based Bio-LED increases to 100cd/m2 from 30cd/m2 while a corresponding increase for the PFO based LED is to 160cd/m2 from 80cd/m2 with and without EBL, respectively.

The effect of change in the ratio of conduction band discontinuity to the valence band discontinuity (ΔE c /ΔE v ) on the electronic structures and conduction properties of model copolymers (A m B n ) x , belonging to the class of Type-I quasi-one-dimensional superlattices are reported. Six different systems of copolymers (A m B n ) x , differing in respect of the ratio ΔE c /ΔE v , have been modelled using the model band structure of constituent homopolymers (A) x and (B),. For each of these systems of copolymers the electronic density of states of the various periodic and aperiodic copolymer chains have been determined on the basis of negative factor counting method in tight binding approximation. The trends obtained in the electronic structures and conduction properties of these copolymers as a function of the ratio ΔE c /ΔE v are useful guidelines for designing copolymers with desired electronic and conduction properties.

Using the ab initio band structure results of three thiophene based donor-acceptor polymers, PHTH (A)(x), PFTH (B)(x) and PCNTH (C)(x), the electronic density of states of their various periodic and aperiodic copolymers (A(m)B(n))(x), (A(m)C(n))(x) and (BmCn), belonging to the class of Type-II staggered have been determined in tight binding approximation. The unit cell of these donor acceptor polymers consists of bicyclopentadithiophene unit bridged by an electron accepting group > C=CH2 in PHTH (A)(x), > C=CF2 in PFTH (B), and > C=C(CN)(2) in PCNTH (C)(x). The trends obtained in the electronic structures and conduction properties of these copolymers as a function of block size, composition and the arrangement of blocks in the copolymer chains are discussed. The results are important guidelines for designing novel polymers with desired conduction properties.

It has been found that insertion of a thin Ba buffer layer between the Al electrode and the MEH-PPV layer results in a significantly higher current density in ITO/MEH-PPV/Al polymer light-emitting diodes due to a reduction of the potential barrier at the cathode–polymer interface. The photoluminescence is found to increase with the addition of porphyrin-containing platinum as the central atom, showing that some of the triplet excitons decay radiatively as a result of mixing porphyrin.

The current-voltage characteristics of poly [2-methoxy-5-(2-ethylhexoxy)-1,4-phenylene vinylene] (MEH-PPV)-based hole-only light-emitting diodes are measured as a function of temperature. The hole current is found to be space-charge limited, providing a direct measure of the mobility as a function of temperature and electric field. A thermal activation energy of 0.2eV is obtained for the zero-field mobility, with a room-temperature low-field mobility value for holes of 3.3×10−7cm2∕Vs. The hole mobility exhibits field dependence in accordance with the Poole-Frenkel effect. The combination of space-charge effects and field-dependent mobility thus provides a consistent description of hole transport as a function of temperature and bias voltage in MEH-PPV films.