The thermal performance of window glazing requires improvement for a sustainable built environment at an acceptable cost. This work has attempted to develop a smart composite coating that combines photosensitive metal oxide and phase change materials and investigate their thermal comfort performance as a glazed window. Current work demonstrates a multi-fold smart composite. consisting of an optimized In2O3:ZnO-polymethyl methacrylate-paraffin composite to reduce heat exchange through the combined self-cleaning and energy-saving envelope of the smart built environment. It is observed that the In2O3:ZnO (5 wt%) multi-fold composite film experienced better transmittance and thermal performance compared to its other wt% composite samples. Moreover, the multi-fold composite coated glass integrated into a prototype glazed window was further investigated for its thermal performance, where a steady average indoor temperature of ~30oC was achieved when the outside temperature reached ~55oC while maintaining good visibility. Interestingly, the transparency reached ~86% at 60oC and experienced a hydrophobic water contact angle (WCA) of ~138o. In contrast, a similar film exhibits ~64% transparency at 22oC, where the WCA becomes moderately hydrophilic (~68o). Temperature-dependent on transparency, and wettability properties were examined for up to 60 cycles, resulting in excellent indoor thermal comfort. In addition. a thermal simulation studywas executed for the smart multi-fold composite glazing. Moreover, tshis study offers dynamic glazing development options for energy saving in the smart built environment.

Highly efficient photocatalytic water reduction to evolve hydrogen can be achieved by the construction of Z-scheme systems that mimics natural photosynthesis. However, coupling appropriate semiconductors with suitable water reduction potential still remains challenging. Herein, we report a novel Z-scheme system, based on the Au decorated 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin tetra(p-toluene sulfonate) functionalized iron-doped carbon nitride. We prepared carbon nitride by varying the amount of iron dopant and then functionalized with porphyrin to obtain heterostructure photocatalyst. Owing to the strong interfacial contact and proper band alignment, a Z-scheme system is fabricated. Finally, we deposited Au nanoparticles over the surface of the as-fabricated Z-scheme system to promote the surface redox properties via efficient charge carrier's separation and transfer. The 3Au-3 P/30Fe-CN photocatalyst achieved excellent H2 evolution activity by producing 3172.20 µmol h−1 g−1 under UV–visible irradiation. The calculated quantum efficiencies for 3Au-3 P/30Fe-CN photocatalyst at 365 and 420 nm irradiation wavelengths are 7.2% and 3.26%, respectively. The experimentally observed efficiency of our photocatalyst is supported by the density functional theory simulations in terms of the lowest work function and strong electrostatic interaction among the constituents of Z-scheme system.

Synthesis of noble-metal-free electrocatalysts for green hydrogen production is crucial to overcoming the energy demand of modern society. One of the most competitive and alternative noble-metal-free electrocatalysts for HER is Molybdenum disulfide (MoS2) based composites. Herein, MoS2 nanosheets grow on FeNi@N-doped graphene nanoparticles/N-doped carbon matrix (FeNi@NG/NCM@MoS2), using the hydrothermal method. FeNi@NG/NCM@MoS2 hybrid displays outstanding HER performance with a low overpotential of 79 mV at 10 mA cm-2, a small Tafel slope of 40.2 mV dec-1, and high durability. First-principles density functional theory (DFT) simulations confirm the electron transformation from FeNi alloy to NG surface of FeNi@NG particle and subsequently further transfer to MoS2 nanosheets which decrease the Gibbs free energy (ΔGH. ≈ -0.08 eV) and local work function for enhanced HER activities. Our work highlights the understanding of electron transfer in demonstrating the kinetic reaction of the HER process and offers a new avenue for constructing efficient MoS2-based electrocatalysts.

As an important energy storage and transportation carrier, hydrogen has the advantages of high combustion heat, non-toxic, and pollution-free energy conversion process. Bimetallic sulfide composites are one of the emerging catalysts for hydrogen evolution reactions (HER) during water splitting. Herein, a hydrothermal method has been employed for the in-situ synthesis of NiS2 nanoparticles/MoS2 nanosheets (NiS2/MoS2) hierarchical sphere anchored on reduced graphene oxide (RGO) for enhanced electrocatalytic HER activity. The NiS2/MoS2/RGO composite displays improved HER activity compared to MoS2/RGO and NiS2/RGO. The optimized NiS2/MoS2/RGO-9 requires only an overpotential of 136 mV at a current density of 10 mA cm−2, a small Tafel slope of 53.4 mV dec-1, and good stability in acid solution. The synergetic effect between NiS2 nanoparticles and MoS2 nanosheets is responsible for enhanced HER performance. Moreover, RGO provides the substrate for NiS2/MoS2 species and maintains the overall conductivity of NiS2/MoS2/RGO composites. Finally, density functional theory (DFT) calculations justify and approve the efficient HER activity of NiS2/MoS2/RGO in terms of lower Gibbs free energy (0.07 eV) and lower work function (3.98 eV) that subsequently enhance the dissociation of H2O.

Building's energy conservation signifies a lowering in building energy consumption without sacrificing thermal comfort. Window glazing is the most suitable approach to the built environment that can be controlled through its sustainable development for global energy consumption. In this work, for the first time, paraffin incorporated SnO2-Al2O3 composite coating is developed on a 5 cm × 5 cm glass using a screen-printing method, which signifies an intelligent cooling behaviour for a comfortable indoor environment irrespective of their emplacement. The composite energy-saving properties exhibit less transmission of infra-red light while keeping high visible light transmittance behaviour resulting superior heat-shielding performance. The composite coated glass's average indoor temperature profile remains at ∼30 °C when the outside temperature reaches a maximum of 45 °C during outdoor testing. While the same composite film is set inside, the indoor average temperature maintains ∼30 °C, whereas outside temperature reaches a maximum of 80 °C. The distinct temperature profile for composite coated glass indicates high transparency of 80% throughout the experiment. Interestingly paraffin has been incorporated into the composite, offering no leakage, translucent characteristics, and limited water ingress. In comparison, non-coated glass is failed to provide them with a comfortable, stable indoor temperature. We believe this study envisages the recent technological innovations combined with phase change material and transparent infrared absorber together as a composite for window glass for warmer climates, which further leads to significant energy savings compared with plain glass.

Supercapacitors (SCs) have received much interest due to their enhanced electrochemical performance, superior cycling life, excellent specific power, and fast charging–discharging rate. The energy density of SCs is comparable to batteries; however, their power density and cyclability are higher by several orders of magnitude relative to batteries, making them a flexible and compromising energy storage alternative, provided a proper design and efficient materials are used. This review emphasizes various types of SCs, such as electrochemical double-layer capacitors, hybrid supercapacitors, and pseudo-supercapacitors. Furthermore, various synthesis strategies, including sol-gel, electro-polymerization, hydrothermal, co-precipitation, chemical vapor deposition, direct coating, vacuum filtration, de-alloying, microwave auxiliary, in situ polymerization, electro-spinning, silar, carbonization, dipping, and drying methods, are discussed. Furthermore, various functionalizations of SC electrode materials are summarized. In addition to their potential applications, brief insights into the recent advances and associated problems are provided, along with conclusions. This review is a noteworthy addition because of its simplicity and conciseness with regard to SCs, which can be helpful for researchers who are not directly involved in electrochemical energy storage.

Recently, polymeric carbon nitride (g-C3 N4 ) as a proficient photo-catalyst has been effectively employed in photocatalysis for energy conversion, storage, and pollutants degradation due to its low cost, robustness, and environmentally friendly nature. The critical review summarized the recent development, fundamentals, nanostructures design, advantages, and challenges of g-C3 N4 (CN), as potential future photoactive material. The review also discusses the latest information on the improvement of CN-based heterojunctions including Type-II, Z-scheme, metal/CN Schottky junctions, noble metal@CN, graphene@CN, carbon nanotubes (CNTs)@CN, metal-organic frameworks (MOFs)/CN, layered double hydroxides (LDH)/CN heterojunctions and CN-based heterostructures for H2 production from H2 O, CO2 conversion and pollutants degradation in detail. The optical absorption, electronic behavior, charge separation and transfer, and bandgap alignment of CN-based heterojunctions are discussed elaborately. The correlations between CN-based heterostructures and photocatalytic activities are described excessively. Besides, the prospects of CN-based heterostructures for energy production, storage, and pollutants degradation are discussed.

Photocatalysis is a classical solution to energy conversion and environmental pollution control problems. In photocatalysis, the development and exploration of new visible light catalysts and their synthesis and modification strategies are crucial. It is also essential to understand the mechanism of these reactions in the various reaction media. Recently, bismuth and graphene’s unique geometrical and electronic properties have attracted considerable attention in photocatalysis. This review summarizes bismuth-graphene nanohybrids’ synthetic processes with various design considerations, fundamental mechanisms of action, heterogeneous photocatalysis, benefits, and challenges. Some key applications in energy conversion and environmental pollution control are discussed, such as CO2 reduction, water splitting, pollutant degradation, disinfection, and organic transformations. The detailed perspective of bismuth-graphene nanohybrids’ applications in various research fields presented herein should be of equal interest to academic and industrial scientists.

Electrochemical CO2 reduction reaction (CO2RR) provides a promising approach to curbing harmful emissions contributing to global warming. However, several challenges hinder the commercialization of this technology, including high overpotentials, electrode instability, and low Faradic efficiencies of desirable products. Several materials have been developed to overcome these challenges. This mini-review discusses the recent performance of various cobalt (Co) electrocatalysts, including Co-single atom, Co-multi metals, Co-complexes, Co-based metal–organic frameworks (MOFs), Co-based covalent organic frameworks (COFs), Co-nitrides, and Co-oxides. These materials are reviewed with respect to their stability of facilitating CO2 conversion to valuable products, and a summary of the current literature is highlighted, along with future perspectives for the development of efficient CO2RR.

The photocatalytic performance of g-C3N4 for CO2 conversion is still inadequate by several shortfalls including the instability, insufficient solar light absorption and rapid charge carrier's recombination rate. To solve these problems, herein, noble metals (Pt and Au) decorated Sr-incorporated g-C3N4 photocatalysts are fabricated via the simple calcination and photo-deposition methods. The Sr-incorporation remarkably reduced the g-C3N4 band gap from 2.7 to 2.54 eV, as evidenced by the UV-visible absorption spectra and the density functional theory results. The CO2 conversion performance of the catalysts was evaluated under visible light irradiation. The Pt/0.15Sr-CN sample produced 48.55 and 74.54 µmol h-1 g-1 of CH4 and CO, respectively. These amounts are far greater than that produced by the Au/0.15Sr-CN, 0.15Sr-CN, and CN samples. A high quantum efficiency of 2.92% is predicted for the Pt/0.15Sr-CN sample. Further, the stability of the photocatalyst is confirmed via the photocatalytic recyclable test. The improved CO2 conversion performance of the catalyst is accredited to the promoted light absorption and remarkably enhanced charge separation via the Sr-incorporated mid gap states and the localized surface plasmon resonance effect induced by noble metal nanoparticles. This work will provide a new approach for promoting the catalytic efficiency of g-C3N4 for efficient solar fuel production.

Gold nanoparticles (Au NPs) play a significant role in science and technology because of their unique size, shape, properties and broad range of potential applications. This review focuses on the various approaches employed for the synthesis, modification and functionalization of nanostructured Au. The potential catalytic applications and their enhancement upon modification of Au nanostructures have also been discussed in detail. The present analysis also offers brief summaries of the major Au nanomaterials synthetic procedures, such as hydrothermal, solvothermal, sol-gel, direct oxidation, chemical vapor deposition, sonochemical deposition, electrochemical deposition, microwave and laser pyrolysis. Among the various strategies used for improving the catalytic performance of nanostructured Au, the modification and functionalization of nanostructured Au produced better results. Therefore, various synthesis, modification and functionalization methods employed for better catalytic outcomes of nanostructured Au have been summarized in this review.

Covalent organic frameworks (COFs) are emerging crystalline polymeric materials with highly ordered intrinsic and uniform pores. Their synthesis involves reticular chemistry, which offers the freedom of choosing building precursors from a large bank with distinct geometries and functionalities. The pore sizes of COFs, as well as their geometry and functionalities, can be pre-designed, giving them an immense opportunity in various fields. In this mini-review, we will focus on the use of COFs in the removal of environmentally hazardous metal ions and chemicals through adsorption and separation. The review will introduce basic aspects of COFs and their advantages over other purification materials. Various fabrication strategies of COFs will be introduced in relation to the separation field. Finally, the challenges of COFs and their future perspectives in this field will be briefly outlined.

A molecular cross-linking approach of the perovskite grains combined with amine-based surface passivation leads to hysteresis-free perovskite transistors.

An efficient, low cost and non-precious hybrid metal catalyst compound consisting of boron-doped graphene nanosheets (BGNSs) and manganese oxide (MnO2) nanotubes is used as a catalyst for the oxygen reduction reaction (ORR).

A typical Z-scheme system is composed of two photocatalysts which generate two sets of charge carriers and split water into H2 and O2 at different locations. Scientists are struggling to enhance the efficiencies of these systems by maximizing their light absorption, engineering more stable redox couples, and discovering new O2 and H2 evolutions co-catalysts. In this work, Au decorated WO3/g-C3N4 Z-scheme nanocomposites are fabricated via wet-chemical and photo-deposition methods. The nanocomposites are utilized in photocatalysis for H2 production and 2,4-dichlorophenol (2,4-DCP) degradation. It is investigated that the optimized 4Au/6% WO3/CN nanocomposite is highly efficient for production of 69.9 and 307.3 µmol h−1 g−1 H2 gas, respectively, under visible-light (λ > 420 nm) and UV–visible illumination. Further, the fabricated 4Au/6% WO3/CN nanocomposite is significant (i.e. 100% degradation in 2 h) for 2,4-DCP degradation under visible light and highly stable in photocatalysis. A significant 4.17% quantum efficiency is recorded for H2 production at wavelength 420 nm. This enhanced performance is attributed to the improved charge separation and the surface plasmon resonance effect of Au nanoparticles. Solid-state density functional theory simulations are performed to countercheck and validate our experimental data. Positive surface formation energy, high charge transfer, and strong non-bonding interaction via electrostatic forces confirm the stability of 4Au/6% WO3/CN interface.

In the present work, 10 to 14 nm titania nanoparticles with high-packing density are synthesized by the soft-template method using a range of cationic surfactants including cetyl trimethylammonium bromide (CTAB), Sodium dodecyl sulfate (SDS), and dodecyl trimethylammonium bromide (DTAB). The synthesized nanoparticles are used as a photoanode material in dye solar cells. Density functional theory (DFT) simulations reproduce our experimental results of charge transfer and strong interaction between the TiO2 and N719. N719-TiO2 complex establishes strong electrostatic bonding through H of the dye with the O of TiO2 surface. Solar cell efficiency of 6.08% with 12.63 mA/cm2, 793 mV, and 48.5% for short circuit current density, open circuit voltage, and fill factor, respectively, are obtained under 1 sun illumination for the dye-sensitized solar cell (DSSC) using a film of mesoporous TiO2 synthesized from the SDS surfactant. On the other hand, the 21 nm commercial TiO2 powder (P25) device results in 4.60% efficiency under similar conditions. Electrochemical impedance spectroscopic studies show that the SDS device has lesser charge transport resistance than the other devices because of its higher surface area, packing density, and dye loading capacity. Our results show that employing high packing density-based TiO2 nanoparticles represents a commercially viable approach for highly beneficial photoanode development for future DSSC applications.

Recently, oxynitrides materials such as β-TaON has been using as a photoanode material in the field of photocatalysis and is found to be promising due to its suitable band gap and charge carrier mobility. Computational study of the crystalline β-TaON in the form of primitive unit cell, supercell and its N, Ta, and O terminated surfaces are carried out with the help of periodic density functional theory (DFT). Optical and electronic properties of all these different species are simulated, which predict TaON as the best candidate for photocatalytic water splitting contrast to their Ta2O5 and Ta3N5 counterparts. The calculated bandgap, valence band, and conduction band edge positions predict that β-TaON should be an efficient photoanodic material. The valence band is made up of N 2p orbitals with a minor contribution from O 2p, while the conduction band is made up of Ta 5d. Turning to thin films, the valence band maximum; VBM (−6.4 eV vs. vacuum) and the conduction band minimum; CBM (−3.3 eV vs. vacuum) of (010)-O terminated surface are respectively well below and above the redox potentials of water as required for photocatalysis. Charge carriers have smaller effective masses than in the (001)-N terminated film (VBM −5.8 and CBM −3.7 eV vs. vacuum). However, due to wide band gap (3.0 eV) of (010)-O terminated surface, it cannot absorb visible wavelengths. On the other hand, the (001)-N terminated TaON thin film has a smaller band gap in the visible region (2.1 eV) but the bands are not aligned to the redox potential of water. Possibly a mixed phase material would produce an efficient photoanode for solar water splitting, where one phase performs the oxidation and the other reduction.

Abstract
Photoelectrochemical water splitting (PEC) offers a promising path for sustainable generation of hydrogen fuel. However, improving solar fuel water splitting efficiency facing tremendous challenges, due to the energy loss related to fast recombination of the photogenerated charge carriers, electrode degradation, as well as limited light harvesting. This review focuses on the brief introduction of basic fundamental of PEC water splitting and the concept of various types of water splitting approaches. Numerous engineering strategies for the investgating of the higher efficiency of the PEC, including charge separation, light harvesting, and co-catalysts doping, have been discussed. Moreover, recent remarkable progress and developments for PEC water splitting with some promising materials are discussed. Recent advanced applications of PEC are also reviewed. Finally, the review concludes with a summary and future outlook of this hot field.

Density functional theory study has been carried out to design a new All-Solid-State dye-sensitized solar cell (SDSC), by applying a donor-acceptor conjugated polymer instead of liquid electrolyte. The typical redox mediator (I1−/I3−) is replaced with a narrow band gap, hole transporting material (HTM). The electronic and optical properties predict that donor and acceptor moieties in the polymeric body have increased the visible light absorption and charge transporting ability, compared to their parent polymers. A unique “upstairs” like band energy diagram is created by packing N3 between HTM and TiO2. Upon light irradiation on the proposed configuration, electrons will move from the dye to TiO2and from HTM to dye (to regenerate dye), simultaneously. Our theoretical simulations prove that the proposed configuration will be highly efficient as the HOMO level of HTM is 1.19 eV above the HOMO of sanitizer (dye); providing an efficient pathway for charge transfer. High short-circuit current density and power conversion efficiency is promised from the strong overlapping of molecular orbitals of HTM and sensitizer. A low reorganization energy of 0.21 eV and exciton binding energy of 0.55 eV, confirm the high efficiency of HTM. Finally, a theoretical open-circuit voltage of 1.49 eV would results high quantum yield while, the chemical stability of HTM towards oxidation can be estimated from its high ionization potential value (4.57 eV).

Density functional theory study of Polypyrrole/TiO2have been carried out at molecular level, to find its internal nature for the tuning of photocatalytic efficiency. Molecular isolated TiO2interacts with various pyrrole oligomers for the investigation of inter-molecular interaction. A narrowing in band gap and better visible light absorption are achieved compared to their individual constituents, based on electronic properties simulations. Electrostatic potential, the density of states, IP, EA, UV–vis spectra and band gap are also supportive to the composite formation. Inter-molecular interaction energy (−28 to −45 kcal mol−1), counterpoised corrected (BSSE), and ΔEgCP-D3methods are employed which confirm the existence of a strong covalent type of bonding between Py and TiO2in nPy-TiO2composites. Finally, Mulliken and natural bonding orbital analysis have pointed out that Py oligomers are p-type and donated electron cloud density to TiO2in all of the nPy-TiO2composites.

Monoclinic clinobisvanite BiVO4 is one of the most promising materials in the field of solar water splitting due to its band gap and suitable valence band maximum (VBM) position. We have carried out comprehensive experimental and periodic density functional theory (DFT) simulations of BiVO4 heterojunction with selenium (Se-BiVO4), to understand the nature of the heterojunction. We have also investigated the contribution of Se to higher performance by effecting morphology, light absorption, and charge transfer properties in heterojunction. Electronic properties simulations of BiVO4 show that its VBM and conduction band minimum (CBM) are comprised of O 2p and V 3d orbitals, respectively. The Se/BiVO4 heterojunction has boosted the photocurrent density by 3-fold from 0.7 to 2.2 mA cm–2 at 1.3 V vs SCE. The electrochemical impedance and Mott–Schottky analysis result in favorable charge transfer characteristics, which account for the higher performance in Se/BiVO4 as compared to the BiVO4 and Se. Finally, spectroscopic, photoelectrochemical, and DFT show that Se makes a direct Z-scheme (band alignments) with BiVO4 where the photoexcited electron of BiVO4 recombines with the VB of Se, giving electron–hole separation at Se and BiVO4, respectively; as a result, enhanced photocurrent is obtained.

Oligomeric synthesis of phenyl-end-capped oligoaniline (4PANI LB) has been carried out through a weak oxidizing agent, CuCl2, using chemical oxidative polymerization protocol. The sample was characterized by mass spectrometry, UV–vis, IR, and CHN elemental analysis. The experimental results are counterchecked with the aid of Quantum mechanical calculations such as density functional theory (DFT). DFT at B3LYP/6–31 G (d) level of theory was used for the geometric and electronic properties simulations which also confirm the existence of 4PANI LB. Excellent correlation is observed between the experiment and theory, particularly in the UV–vis spectra which conclude the formation of tetramer (fully reduced form) 4PANI LB (C24H20.06N4.07). Electronic properties such as Ionization Potential (I.P), Electron Affinities (E.A), the coefficient of highest occupied molecular orbital (HOMO), the coefficient of lowest unoccupied molecular orbital (LUMO) of 4PANI LB were evaluated at the above-mentioned level of theory.

A thin film of poly(o-aminophenol), POAP, has been used as a sensor for various types of toxic and nontoxic gases: a gateway between the digital and physical worlds. We have carried out a systematic mechanistic investigation of POAP as a humidity sensor; how does it sense different gases? POAP has several convenient features such as flexibility, transparency, and suitability for large-scale manufacturing. With an appropriate theoretical method, molecular oligomers of POAP, NH and O functional groups and the perpendicular side of the polymeric body, are considered as attacking sites for humidity sensing. It is found that the NH position of the polymer acts as an electrophilic center: able to accept electronic cloud density and energetically more favorable compared to the O site. The O site acts as a nucleophilic center and donates electronic cloud density toward H2Ovap. In conclusion, only these two sites are involved in the sensing process which leads to strong intermolecular hydrogen bonding, having a 1.96 a bond distance and δE ~ -35 kcal mol-1. The results suggest that the sensitivity of the sensor improved with the oxidization state of POAP.

Graphene (GR) and its derivatives are promising materials on the horizon of nanotechnology and material science and have attracted a tremendous amount of research interest in recent years. The unique atom-thick 2D structure with sp2 hybridization and large specific surface area, high thermal conductivity, superior electron mobility and chemical stability has made GR and its derivatives extremely attractive components for composite materials for solar energy conversion, energy storage, environment purification and biosensor applications. This review gives a brief introduction of GR's unique structure, band structure engineering, physical and chemical properties, recent energy-related progress of GR-based materials in the field of energy conversion (e.g. photocatalytic, photoelectrochemical water splitting, CO2 reduction, dye sensitized and organic solar cells, and photosensitizer in photovoltaic devices) and energy storage (batteries, fuel cell and supercapacitors) applications. The vast coverage of advancements in environmental applications of GR-based materials for photocatalytic degradation of organic pollutants, gas sensing and removal of heavy metal ions is presented. Additionally, the presences of graphene composites in the bio-sensing field have been discussed in this review. We concluded the review with remarks on the challenges, prospective and further development of GR-based materials in the exciting field of energy, environment, and bioscience.

Abstract Quantum mechanical calculations are performed to establish the structure of an oligomer of aniline and pyrrole [Poly(Ani-co-Py)], through comparison of experimental and theoretically calculated properties, including conductivity. The copolymer was synthesized through chemical oxidative polymerization and then confirmed from the experimental IR, UV-vis, mass spectra, elemental, XRD, TGA, and SEM analysis. Quantum mechanical calculations are performed at Density Functional Theory (DFT) and Time dependent DFT (TD-DFT) methods for the electronic and spectroscopic properties of the oligomer. A very nice correlation is found between the theory and experiment which consequences the structure of Poly(Ani-co-Py). Poly(Ani-co-Py) is not explored like other conducting polymers; however, by tuning this molecular structure, the electro-active nature of this material can be enhanced adequately.

A series of four new porphyrin-furan dyads were designed and synthesized by having anchoring group either at meso-phenyl or pyrrole-β position of a zinc porphyrin based on donor-π-acceptor (D-π-A) approach. The porphyrin macrocycle acts as donor, furan hertero cycle acts as π-spacer and either cyanoacetic acid or malonic acid group acts as acceptor. These dyads were fully characterized by UV-Visible, 1H NMR, MALDI-MS and fluorescence spectroscopies and cyclic voltammetry. Both of the observed and TD-DFT simulated UV-vis spectra has strong correllation which validate and confirm the synthesiszed dyads and theoretical method for this type of compounds. Both soret and Q-bands are red shifted in the case of pyrrole-β substituted dyads. The redox potentials of all four dyads are not altered in comparison with their individual constituents. The dyads were tested in dye sensitized solar cells and found pyrrole-β substituted zinc porphyrins are showing better performance in comparison with the corresponding meso-phenyl dyads. Optical band gap, Natural bonding, and Molecular bonding orbital (HOMO-LUMO) analysis are in favour of pyrrole-β substituted zinc porphyrins contrast to meso-phenyl dyads.

Comprehensive theoretical and experimental studies of a natural product, 8-hydroxyisodiospyrin (HDO) have been carried out. Based on the correlation of experimental and theoretical data, an appropriate computational model was developed for obtaining the electronic, spectroscopic, and thermodynamic parameters of HDO. First of all, the exact structure of HDO is confirmed from the nice correlation of theory and experiment, prior to determination of its electroactive nature. Hybrid density functional theory (DFT) is employed for all theoretical simulations. The experimental and predicted IR and UV-vis spectra [B3LYP/6-31+G(d,p) level of theory] have excellent correlation. Inter-molecular non-covalent interaction of HDO with different gases such as NH3, CO2, CO, H2O is investigated through geometrical counterpoise (gCP) i.e. B3LYP-gCP-D3/6-31G∗ method. Furthermore, the inter-molecular interaction is also supported by geometrical parameters, electronic properties, thermodynamic parameters and charge analysis. All these characterizations have corroborated each other and confirmed the electroactive nature (non-covalent interaction ability) of HDO for the studied gases. Electronic properties such as Ionization Potential (IP), Electron Affinities (EA), electrostatic potential (ESP), density of states (DOS), HOMO, LUMO, and band gap of HDO have been estimated for the first time theoretically.

Sensitivity and selectivity of polypyrrole (PPy) toward NH3, CO2, and CO have been studied at density functional theory (DFT). PPy oligomers are used both in the doped (PPy+) and neutral (PPy) form for their sensing abilities to realize the best state for gas sensing. DFT calculations are performed at the hybrid functional, B3LYP/6-31G(d), level of theory. Detection/interaction of CO is investigated from carbon [CO(1)] and oxygen termini of CO [CO(2)]. Interaction energies and charge transfer are simulated which reveal the sensing ability of PPy toward these gases. Furthermore, these results are supported by frontier molecular orbital energies and band gap calculations. PPy, in both the doped and neutral state, is more sensitive to NH3 compared to CO2 and CO. More interestingly, NH3 causes doping of PPy and dedoping of PPy+, providing evidence that PPy/PPy+ is an excellent sensor for NH3 gas. UV-vis and UV-vis-near-IR spectra of nPy, nPy+, and nPy/nPy+-X complexes demonstrate strong interaction of PPy/PPy+ with these atmospheric gases. The better response of PPy/PPy+ toward NH3 is also consistent with the experimental observations.

Density functional theory (DFT) and phytochemical study of a natural product, Diospyrin (DO) have been carried out. A suitable level of theory was developed, based on correlating the experimental and theoretical data. Hybrid DFT method at B3LYP/6-31G (d,p) level of theory is employed for obtaining the electronic, spectroscopic, inter-molecular interaction and thermodynamic properties of DO. The exact structure of DO is confirmed from the nice validation of the theory and experiment. Non-covalent interactions of DO with different atmospheric gases such as NH3, CO2, CO, and H2O were studied to find out its electroactive nature. The experimental and predicted geometrical parameters, IR and UV-vis spectra (B3LYP/6-31+G (d,p) level of theory) show excellent correlation. Inter-molecular non-bonding interaction of DO with atmospheric gases is investigated through geometrical parameters, electronic properties, charge analysis, and thermodynamic parameters. Electronic properties include, ionization potential (I.P.), electron affinities (E.A.), electrostatic potential (ESP), density of states (DOS), HOMO, LUMO, and band gap. All these characterizations have corroborated each other and confirmed the presence of non-covalent nature in DO with the mentioned gases.

We report here for the first time a comparative theoretical and experimental study of Pistagremic acid (P.A). We have developed a theoretical model for obtaining the electronic and spectroscopic properties of P.A. The simulated data showed nice correlation with the experimental data. The geometric and electronic properties were simulated at B3LYP/6-31 G (d, p) level of density functional theory (DFT). The optimized geometric parameters of P.A were found consistent with those from X-ray crystal structure. Differences of about 0.01 and 0.15 Å in bond length and 0.19-1.30 degree in the angles, respectively; were observed between the experimental and theoretical data. The theoretical vibrational bands of P.A were found to correlate with the experimental IR spectrum after a common scaling factor of 0.963. The experimental and predicted UV-Vis spectra (at B3LYP/6-31+G (d, p)) have 36 nm differences. This difference from experimental results is because of the condensed phase nature of P.A. Electronic properties such as Ionization Potential (I.P), Electron Affinities (E.A), co-efficient of highest occupied molecular orbital (HOMO), co-efficient of lowest unoccupied molecular orbital (LUMO) of P.A were estimated for the first time however, no correlation can be made with experiment. Inter-molecular interaction and its effect on vibrational (IR), electronic and geometric parameters were simulated by using Formic acid as model for hydrogen bonding in P.A. © 2013 Elsevier B.V. All rights reserved.

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations at the UB3LYP/6-31G(d) level have been performed to investigate the tunable nature, i.e. doping and dedoping processes, of polypyrrole (PPy). The calculated theoretical data show strong correlation with the recent experimental reports, which validates our computational protocol. The calculated properties are extrapolated to the polymer (PPy) through a second-order polynomial fit. Changes in band gap, conductivity, and resistance of nPy and nPy-X (where n = 1-9 and X = +, NH3, and Cl) were studied and correlated with the calculated vibrational spectra (IR) and electronic properties. Upon doping, bridging bond distance and internal bond angles decrease (decrease in resistance over polymer backbone), whereas dedoping results in increases in these geometric parameters. In the vibrational spectrum, doping is characterized by an increase in the band peaks in the fingerprint region and/or red shifting of the spectral bands. Dedoping (9Py+ with NH3), on the other hand, results in decreases in the number of vibrational spectral bands. In the UV-vis and UV-vis-near-IR spectra, the addition of different analytes (dopant) to 9Py results in the disappearance of certain bands and gives rise to some new absorbances corresponding to localized and delocalized polaron bands. Specifically, the peaks in the near-IR region at 1907 nm for Py+ and 1242 nm for 9Py-Cl are due to delocalized and localized polaron structures, respectively. Upon p-doping, the band gaps and resistance of nPy decrease, while its conductivity and π-electron density of conjugation increase over the polymeric backbone. However, a reversal of properties is obtained in n-doping or reduction of nPy+. In the case of oxidation and Cl dopant, the IP and EA increase, and consequently, there is a decrease in the band gap. NBO and Mulliken charges analyses indicate charge transferring from the polymer in the case of p-type dopants, while this phenomenon is reversed with n-type dopants. © 2014 American Chemical Society.

Density functional theory studies (DFT) have been carried out to evaluate the ability of polyaniline emeraldine salt (PANI ES) from 2 to 8 phenyl rings as sensor for NH3, CO2, and CO. The sensitivity and selectivity of nPANI ES among NH3, CO2, and CO are studied at UB3LYP/6-31G(d) level of theory. Interaction of nPANI ES with CO is studied from both O (CO(1)) and C (CO(2)) sides of CO. Interaction energy, NBO, and Mulliken charge analysis were used to evaluate the sensing ability of PANI ES for different analytes. Interaction energies are calculated and corrected for BSSE. Large forces of attraction in nPANI ES-NH3 complexes are observed compared to nPANI ES-CO2, nPANI ES-CO(1), and nPANI ES-CO(2) complexes. The inertness of +Cî - O- in nPANI ES-CO(1) and nPANI ES-CO(2) complexes are also discussed. Frontier molecular orbitals and energies indicate that NH3 changes the orbital energy of nPANI ES to a greater extent compared to CO2, CO(1), and CO(2). Peaks in UV-vis and UV-vis-near-IR spectra of nPANI ES are blue-shifted upon doping with NH3, CO2, CO(1), and CO(2) which illustrates dedoping of PANI ES to PANI emeraldine base (PANI EB). Finally, it is concluded that PANI ES has greater response selectivity toward NH3 compared to CO2 and CO and it is consistent with the experimental observations. © 2013 American Chemical Society.

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been performed to gain insight into the structure of poly(o-phenylenediamine) (POPD). Both reported structures of POPD, ladder (L)- and polyaniline (P)-like, are investigated theoretically through the oligomers approach. The simulated vibrational properties of 5POPD(L) and 5POPD(P) at B3LYP/6-31G (d) along with their assignments are correlated with experimental frequencies. Vibrational spectra show characteristic peaks for both POPD(L) and POPD(P) structures and do not provide any conclusive evidence. Excited-state properties such as band gap, ionization potential, electron affinities, and HOMO-LUMO gaps of POPD(L) and POPD(P) from monomers to five repeating units are simulated. UV-vis spectra are simulated at the TD-B3LYP/6-31+G (d, p) level of theory, supportive to the ladder-like structure as the major contributor. Comparison of the calculated data with the experimental one strongly suggests that the ladder-like structure is the predominant contributor to the molecular structure of POPD; however, a small amount of POPD(P) is also believed to be present. © 2013 American Chemical Society.

Density Functional Theory (DFT) and TD-DFT calculation have been performed to investigate the response mechanism of polypyrrole towards ammonia as sensor. Geometric and electronic properties of oligopyroles up to nine repeating units are evaluated theoretically, and the calculated properties are extrapolated for the polymer (polypyrole) through 2nd order polynomial fit. Hydrogen bonds between ammonia and oligopyrole are about 10-11 kcal mol-1 (7-8.5 kcal mol-1 BSSE corrected) in strength. Interaction of ammonia with the oligopyrrole causes certain geometric features to change (for example ∠C1C2N3C5) which results in decrease in resistance for the movement of electron over the oligomer backbone. The reduction in the resistance is also measured by perturbation in electronic properties including ionization potential (I.P), electron affinity (E.A.), HOMO, LUMO, band gap and λmax. E.A. and band gap (HOMO to LUMO) also support the sensing ability of nPy oligomers towards ammonia. Band gaps decrease while LUMO energies for oligopyroles increase upon interaction with NH3. Ammonia donates electron to the LUMO (electron acceptor) of nPy oligomers and increases its electronic clouds density therefore E.A. of nPy decreases. Moreover the extended conjugation in the oligopyrole backbone upon complexation with ammonia, combined with other electronic and geometric properties illustrate the potential of undoped oligopyrole as sensor for ammonia. © 2013 Elsevier B.V. All rights reserved.