Optoelectronic Properties of Self-Assembled Nanostructures of Polymer Functionalized Polythiophene and Graphene

Supramolecular Self-Assembled Nanostructures Derived from Amplified Structural Isomerism of Zn(II)-Sn(IV)-Zn(II) Porphyrin Triads and Their Visible Light Photocatalytic Degradation of Pollutants

Two structural isomeric porphyrin-based triads (Zn(II)porphyrin-Sn(IV)porphyrin-Zn(II)porphyrin) denoted as T1 and T2 were prepared from the reaction of meso-[5-(4-hydroxyphenyl)-10,15,20-tris(3,5-di-tert-butylphenyl)porphyrinato]zinc(II) (ZnL) with trans-dihydroxo-[5,10-bis(3-pyridyl)-15,20-bis(phenyl)porphyrinato]tin(IV) (SnP1) and trans-dihydroxo-[5,15-bis(3-pyridyl)-10,20-bis(phenyl)porphyrinato]tin(IV) (SnP2), respectively. All the compounds were characterized using UV-vis spectroscopy, emission spectroscopy, ESI-MS, 1H NMR spectroscopy, and FE-SEM. Most importantly, the two structurally isomeric porphyrin-based triads supramolecularly self-assembled into completely different nanostructures. T1 exhibits a nanosphere morphology, whereas T2 exhibits a nanofiber morphology. The amplified geometric feature in the structural isomeric porphyrin-based triads dictates the physical and chemical properties of the two triads. Both compounds showed the morphology-dependent visible light catalytic photodegradation of rhodamine B dye (74-97% within 90 min) and tetracycline antibiotic (44-71% within 45 min) in water. In both cases, the photodegradation efficiency of T2 was higher than that of T1. The present investigation can significantly contribute to the remediation of wastewater by tuning the conformational changes in porphyrin-based photocatalysts.

A Review on Self-Assembly Driven Optoelectronic Properties of Polythiophene-Peptide and Polythiophene-Polymer Conjugates

Polythiophene (PT) is an important conducting polymer for its outstanding optoelectronic properties. Here, we delineate the self-assembly-driven optoelectronic properties of PT-peptide and PT-polymer conjugates, taking examples from recent literature reports. PT-peptide conjugates made by both covalent and noncovalent approaches are discussed. Poly(3-thiophene acetic acid) (P3TAA) covalently coupled with Gly-Gly-His tripeptide, C-protected and deprotected tripeptide H2N-F-F-V-OMe, etc. exhibits self-assembly-driven absorbance, fluorescence, photocurrent, and electronic properties. Noncovalent PT-peptide conjugates produced via ionic, H-bonding, and π-stacking interactions show tunable morphology and optoelectronic properties by varying the composition of a component. PT conjugated with Alzheimer's disease peptide (KLVFFAE, Aβ16-22) shows enhanced photocatalytic water splitting, cationic PT(CPT-I)-perylene bisimide-appended dipeptide (PBI-DY), and anionic PT-perylene diimide-appended cationic peptide (PBI-NH3+) conjugates and exhibits self-assembly-driven enhanced photoswitching and organic mixed electronic and ionic conductivity (OMEIC) properties. In the PT-polymer conjugates, self-assembly-driven optoelectronic properties of covalently produced PT-random copolymers, PT-block copolymers, PT-graft-random copolymers, and PT-graft-block copolymer conjugates are discussed. The HOMO-LUMO levels of hyperbranched polymers are optimized to obtain better power conversion efficiency (PCE) in the bulk heterojunction (BHJ) solar cell than in linear polymers, and P3TAA-ran-P3HT (43 mol % P3TAA) conjugated with MAPbI3 perovskite exhibits higher PCE (10%) than that with only P3TAA hole-transporting material. In the ampholytic polythiophene (APT), on increasing pH, the morphology changes from the vesicle to fibrillar network for the dethreading of the PT chain, resulting in a red shift of the absorbance peak, an enormous increase in PL intensity, lowering of the charge transfer resistance, and an induction of Warburg impedance for the release of quencher I- ions. The PT-g-(PDMAEMA-co-PGLU-HEM) graft copolymer self-assembles with Con-A lectin, causing fluorescence quenching, and acts as a sensor for Con-A with a LOD of 57 mg/L. Varying sequences of the block copolymer containing pH-responsive PDMAEMA and temperature-responsive PDEGMEM grafted to the PT backbone shows different self-assembly, optical, electronic, and photocurrent properties depending on the proximity and preponderance of the block sequence on the PT backbone.

Nanoparticle Assembly: From Self-Organization to Controlled Micropatterning for Enhanced Functionalities

Nanoparticles form long-range micropatterns via self-assembly or directed self-assembly with superior mechanical, electrical, optical, magnetic, chemical, and other functional properties for broad applications, such as structural supports, thermal exchangers, optoelectronics, microelectronics, and robotics. The precisely defined particle assembly at the nanoscale with simultaneously scalable patterning at the microscale is indispensable for enabling functionality and improving the performance of devices. This article provides a comprehensive review of nanoparticle assembly formed primarily via the balance of forces at the nanoscale (e.g., van der Waals, colloidal, capillary, convection, and chemical forces) and nanoparticle-template interactions (e.g., physical confinement, chemical functionalization, additive layer-upon-layer). The review commences with a general overview of nanoparticle self-assembly, with the state-of-the-art literature review and motivation. It subsequently reviews the recent progress in nanoparticle assembly without the presence of surface templates. Manufacturing techniques for surface template fabrication and their influence on nanoparticle assembly efficiency and effectiveness are then explored. The primary focus is the spatial organization and orientational preference of nanoparticles on non-templated and pre-templated surfaces in a controlled manner. Moreover, the article discusses broad applications of micropatterned surfaces, encompassing various fields. Finally, the review concludes with a summary of manufacturing methods, their limitations, and future trends in nanoparticle assembly.

Facile Synthesis and Electrochemical Characterization of Polyaniline@TiO2-CuO Ternary Composite as Electrodes for Supercapacitor Applications

This research reports the facile, controlled, low-cost fabrication, and evaluation of properties of polyaniline matrix deposited on titanium dioxide and copper(II) oxide ternary-composite (PANI@TiO2-CuO)-based electrode material for supercapacitor application. The process involves the preparation of CuO in the presence of TiO2 to form TiO2-CuO by a facile method, followed by in-situ oxidative polymerization of aniline monomer. The structural and physical properties were evaluated based on the results of FTIR spectroscopy, X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), transmission electron (TEM) and scanning electron (SEM) microscopy, thermogravimetric analysis (TGA), and BET surface areas analysis. The results indicated that TiO2-CuO was dispersed uniformly in the PANI matrix. Owing to such dispersion of TiO2-CuO, the PANI@TiO2-CuO material exhibits dramatic improvements on thermal stability in comparison with the pure PANI. The cyclic voltammetry (CV) confirms the reversibility of PANI redox transitions for this optimized electrode material. Moreover, the results reveal that the specific capacitance of PANI@TiO2-CuO reaches 87.5% retention after 1500 cycles under 1.0 A g-1, with a better charge storage performance as compared to pure PANI and PANI@TiO2 electrodes. The preparation of PANI@TiO2-CuO with enhanced electrochemical properties provides a feasible route for promoting its applications in supercapacitors.

Theoretical Approach to Evaluate the Gas-Sensing Performance of Graphene Nanoribbon/Oligothiophene Composites

Composite formation with graphene is an effective approach to increase the sensitivity of polythiophene (nPT) gas sensors. The interaction mechanism between gaseous analytes and graphene/nPT composite systems is still not clear, and density functional theory calculations are used to explore the interaction mechanism between graphene/nPT nanoribbon composites (with n = 3-9 thiophene units) and gaseous analytes CO, NH₃, SO₂, and NO₂. For the studied analytes, the interaction energy ranges from -44.28 kcal/mol for (C₅₄H₃₀-3PT)-NO₂ to -2.37 kcal/mol for (C₅₄H₃₀-3PT)-CO at the counterpoise-corrected ωB97M-V/def2-TZVPD level of theory. The sensing mechanism is further evaluated by geometric analysis, ultraviolet-visible spectroscopy, density of-states analysis, calculation of global reactivity indices, and both frontier and natural bond orbital analyses. The variation in the highest occupied molecular orbital/lowest unoccupied molecular orbital gap of the composite indicates the change in conductivity upon complexation with the analyte. Energy decomposition analysis reveals that dispersion and charge transfer make the largest contributions to the interaction energy. The graphene/oligothiophene composite is more sensitive toward these analytes than either component taken alone due to larger changes in the orbital gap. The computational framework established in the present work can be used to evaluate and design graphene/nPT nanoribbon composite materials for gas sensors.

DFT study on some polythiophenes containing benzo[d]thiazole and benzo[d]oxazole: structure and band gap

The content of this paper focuses/shed light on the effects of X (X = S in P1 and X = O in P2) in C11H7NSX and R (R = H in P3, R = OCH3 in P4, and R = Cl in P5) in C18H9ON2S2-R on structural features and band gaps of the polythiophenes containing benzo[d]thiazole and benzo[d]oxazole by the Density Function Theory (DFT) method/calculation. The structural features including the electronic structure lattice constant (a), shape, total energy (Etot) per cell, and link length (r), are measured via band gap (Eg) prediction with the package of country density (PDOS) and total country density (DOS) of material studio software. The results obtained showed that the link angle and the link length between atoms were not changed significantly while the Etot was decreased from Etot = - 1904 eV (in P1) to Etot = - 2548 eV (in P2) when replacing O with S; and the Etot of P3 was decreased from Etot = - 3348 eV (in P3) when replacing OCH3, Cl on H of P3 corresponding to Etot = - 3575 eV (P4), - 4264 eV (P5). Similarly, when replacing O in P1 with - S to form P2, the Eg of P1 was dropped from Eg = 0.621 eV to Eg = 0.239 eV for P2. The Eg of P3, P4, and P5 is Eg = 0.006 eV, 0.064 eV, and 0.0645 eV, respectively. When a benzo[d]thiazole was added in P1 (changing into P3), the Eg was extremely strongly decreased, nearly 100 times (from Eg = 0.621 eV to Eg = 0.006 eV). The obtained results serve as a basis for future experimental work and used to fabricate smart electronic device.

Effect of doped H, Br, Cu, Kr, Ge, As and Fe on structural features and bandgap of poly C13H8OS-X: a DFT calculation

Structural features such as the shape, the lattice constant, the bond length, the total energy per cell, and the energy bandgap (Eg) of C13H8OS-X are studied by the calculating Partial Density Of States (PDOS), and DOS package of the Material Studio (MS) software. Calculations show that the bond length and the bond angle between atoms insignificant change as 1.316 Å to 1.514 Å for C-C, 1.211 Å for C-O, 1.077 Å to 1.105 Å for C-H; bond angle of round one changes from 118.883° to 121.107° for C-C-C, from 117.199° to 122.635° for H-C-C, from 119.554° to 123.147° for C-C-O and from 109.956° to 117.537° for C-C-H. When C13H8OS-X doped in the order of -Br, -Cu, -Kr, -Ge, -As, and -Fe then bond lengths, bond angles between atoms have a nearly constant value. Particularly for links C-X, there is a huge change in value, respectively 1.876, 1.909, 10.675, 2.025, 2.016, 2.014 Å; the total energy change from Etot = -121,794 eV to Etot = -202,859 eV, and the energy band gap decreases from Eg = 2.001 eV to Eg = 0.915 eV. The obtained results are useful and serve as a basis for future experimental research.

4,4′-Bipyridine-based Ni(ii)-metallogel for fabricating a photo-responsive Schottky barrier diode device

4,4′-Bipyridine-based Ni(ii)-metallogel has been implemented to execute a light-responsive semiconducting Schottky barrier diode device with advanced functionality.

State of the art: synthesis and characterization of functionalized graphene nanomaterials

Nanomaterials play nowadays a preponderant role in the field of materials science due to the wide range of applications and synergy with other fields of knowledge. Recently, carbonaceous nanomaterials, most notably bi-dimensional graphene (2D graphene), have been highlighted by their application in several areas: electronics, chemistry, medicine, energy and the environment. The search for new materials has led many researchers to develop new routes of synthesis and the expansion of the current means of production, by the anchoring of other nanomaterials on graphene surface, or by modifications of its hexagon sp2 structure, through the doping of heteroatoms. By adding functional groups to the graphene surface, it is possible to increase its affinity with other materials, such as polymers, magnetic nanoparticles and clays, leading to the formation of new nanocomposites. Several covalent and non-covalent functionalization processes, their advantages and disadvantages with respect to their interactions with other chemical species, are discussed in this review. The characterization of these materials is a sensitive topic, since the insertion of functional groups over the graphene basal plane causes changes in its morphology and the so-called chemistry of surface. In this sense, beyond the classical techniques, such as x-ray Diffraction (XRD), Infrared Spectroscopy (FTIR), Raman Spectroscopy and Transmission Electron Microscopy (TEM), modern characterization techniques of graphene-based nanomaterials are discussed, focusing on those more indicated according to the proposed modifications. A significant attention was driven to environmental applications of functionalized graphenes, specifically in the removal of pollutants from wastewaters.

Two-dimensional graphene-HfS2 van der Waals heterostructure as electrode material for alkali-ion batteries

Poor electrical conductivity and large volume expansion during repeated charge and discharge is what has characterized many battery electrode materials in current use. This has led to 2D materials, specifically multi-layered 2D systems, being considered as alternatives. Among these 2D multi-layered systems are the graphene-based van der Waals heterostructures with transition metal di-chalcogenides (TMDCs) as one of the layers. Thus in this study, the graphene–hafnium disulphide (Gr–HfS₂) system, has been investigated as a prototype Gr–TMDC system for application as a battery electrode. Density functional theory calculations indicate that Gr–HfS₂ van der Waals heterostructure formation is energetically favoured. In order to probe its battery electrode application capability, Li, Na and K intercalants were introduced between the layers of the heterostructure. Li and K were found to be good intercalants as they had low diffusion barriers as well as a positive open circuit voltage. A comparison of bilayer graphene and bilayer HfS₂ indicates that Gr–HfS₂ is a favourable battery electrode system.

A high rate capacity, moderate volume expansion and energetically stable alkali ion graphene–HfS₂ electrode material.

Mechanical and Self-Healing Behavior of Matrix-Free Polymer Nanocomposites Constructed via Grafted Graphene Nanosheets

Through molecular dynamics (MD) simulation, the structure and mechanical properties of matrix-free polymer nanocomposites (PNCs) constructed via polymer-grafted graphene nanosheets are studied. The dispersion of graphene sheets is characterized by the radial distribution function (RDF) between graphene sheets. We observe that a longer polymer chain length L_g leads to a relatively better dispersion state attributed to the formation of a better brick-mud structure, effectively screening the van der Waals interactions between sheets. By tuning the interaction strength ε_end-end between end functional groups of grafted chains, we construct physical networks with various robustness characterized by the formation of the fractal clusters at high ε_end-end values. The effects of ε_end-end and L_g on the mechanical properties are examined, and the enhancement of the stress-strain behavior is observed with the increase of ε_end-end and L_g. Structural evolution during deformation is quantified by calculating the orientation of the graphene sheets and their distribution, the stress decomposition, and the size of the clusters formed between end groups and their distribution. Then, we briefly study the effects of time and temperature on the self-healing behavior of these unique PNCs in the rubbery state. Lastly, the self-healing kinetics is quantitatively analyzed. In general, this work can provide some rational guidelines to design and fabricate matrix-free PNCs with both excellent mechanical and self-healing properties.

Femtomolar Detection of Spermidine Using Au Decorated SiO2 Nanohybrid on Plasmon-Coupled Extended Cavity Nanointerface: A Smartphone-Based Fluorescence Dequenching Approach

Coupling of photons with molecular emitters in different nanocavities have resulted in transformative plasmonic applications. The rapidly expanding field of surface plasmon-coupled emission (SPCE) has synergistically employed subwavelength optical properties of localized surface plasmon resonance (LSPR) supported by nanoparticles (NPs) and propagating surface plasmon polaritons assisted by metal thin films for diagnostic and point-of-care analysis. Gold nanoparticles (AuNPs) significantly quench the molecular emission from fluorescent molecules (at close distances <5 nm). More often, complex strategies are employed for providing a spacer layer around the AuNPs to avoid direct contact with fluorescent molecules, thereby preventing quenching. In this study we demonstrate a rapid and facile strategy with the use of Au-decorated SiO₂ NPs (AuSil), a metal (Au)-dielectric (SiO₂) hybrid material for dequenching the otherwise quenched fluorescence emission from radiating dipoles and to realize 88-fold enhancement using the SPCE platform. Different loading of AuNPs were studied to tailor fluorescence emission enhancements in spacer, cavity, and extended (ext.) cavity nanointerfaces. We also present femtomolar detection of spermidine using this nanohybrid in a highly desirable ext. cavity interface. This interface serves as an efficient coupling configuration with dual benefits of spacer and cavity architectures that has been widely explored hitherto. The multifold hot-spots rendered by the AuSil nanohybrids assist in augmented electromagnetic (EM)-field intensity that can be captured using a smartphone-based SPCE platform presenting excellent reliability and reproducibility in spermidine detection.

Light-Induced Conformational Change of Uracil-Anchored Polythiophene-Regulating Thermo-Responsiveness

Tuning the electronic structure of a π-conjugated polymer from the responsive side chains is generally done to get desired optoelectronic properties, and it would be very fruitful when light is used as an exciting tool that can also affect the backbone chain conformation. For this purpose, polythiophene- g-poly-[ N-(6-methyluracilyl)- N, N-dimethylamino chloride]ethyl methacrylate (PTDU) is synthesized. On exposure to diffuse sunlight, the uracil moieties of the grafted chains cause the absorption maximum of PTDU solution to show gradual blue shift of 87 nm and a gradual blue shift of 46 nm in the emission maximum, quenching its fluorescence with time. These effects occur specifically at the absorption range of polythiophene (PT) chromophore on direct exposure of light of different wavelengths, and the optimum wavelength is found to be 420 nm. Impedance study suggests a decrease in charge transfer resistance upon exposure because of conformational change of PTDU. Theoretical study indicates that on exposure to visible light, uracil moieties move toward the backbone to facilitate photoinduced electron transfer between the PT and the uracil, attributing to the variation in optoelectronic properties. Morphological and light-scattering studies exhibit a decrease in particle size because of coiling of the PT backbone and squeezing of the grafted chain on light exposure. The transparent orange-colored PTDU solution becomes hazy with a hike in emission intensity on addition of sodium halides and becomes reversibly transparent or hazy on heating or cooling. The screening of cationic centers of PTDU by varying halide anion concentration tunes the phase transition temperature. Thus, the light-induced variation in the backbone conformation is responsible for tuning the optoelectronic properties and regulates the thermos-responsiveness of the PTDU solution in the presence of halide ions.