Carbon dots (CDs), versatile carbon-based luminescent nanomaterials, offer environmental friendliness, cost-effectiveness, and tunable optical properties for diverse optoelectronic applications, including light-emitting diodes, photodetectors, and flexible electronics. These nanoscale materials exhibit unique optical behaviors like highly tunable photoluminescence and efficient multiphoton up-conversion. Herein, it explores how precursor selection influences CDs’ sp2/sp3 hybridization ratios and their optoelectronic properties. CDs are synthesized from four distinct sources: polymeric polyvinylpyrrolidone, protein, biomass, and citric acid. Biomass- and protein-derived CDs display remarkable photocurrent enhancements under blue light, attributed to balanced sp2/sp3 ratios, while polymer-derived CDs show limited optoelectronic response. These findings reveal the critical role of precursor composition in tailoring the structural and electronic properties of CDs, offering sustainable pathways for their application in advanced optoelectronic devices.

The cofactors of proteins dictate the charge transport mechanism across molecular junctions when self-assembled protein monolayers are sandwiched between two metal electrodes. Here, we summarized how the chemical coordination nature of cofactors in various proteins modulates electrical conductance by investigating electronic transport studies across different protein-based molecular junctions under various forces applied under the AFM tip. We have utilized several numerical techniques of electronic transport to analyse the experimentally obtained current-voltage measurements across various protein-based molecular junctions and depicted the origin of electronic modulation in the electrical conductance under different external stimuli. We could also find the origin of electronic conductance modulation under external stimuli at various applied forces by obtaining several analytical transport parameters such as energy barrier, coupling strength, and electrical conductance values. Utilizing density-functional-theory calculations, we further validate that the electronic density of states present in the cofactors within the proteins dominates the electronic transport behaviours across protein-based molecular junctions. Our findings reveal the limiting factor for applying various external stimuli on different proteins, which could be further valuable in bioelectronic applications. We have also found that the organic cofactor containing protein follows all the tunneling mechanism-related numerical transport models and the electronic transport across proteins with pure inorganic cofactors follows Landauer transport formalism.

Here we report how the chemical functionalization of the bridge molecule influences the electronic properties of conjugated terthiophene and the electronic coupling, i.e., the linkage between molecule and electrode, using density functional theory (DFT) methods. Furthermore, we explore the modulation in electron transport properties of molecular junctions with various functional derivatives utilizing a combination of DFT and electron transport non-equilibrium Green’s function (NEGF) calculations.

Molecular junctions are formed by wedging molecules between two metal electrodes. In addition to the conventional parameters of the metal–molecule–metal junction, such as the work function of electrodes and the molecules' energy gap, molecule-electrode electronic coupling strength also plays a vital role in modulating the electronic properties of the molecular junction under external stimuli. We have examined the electron transport across bacteriorhodopsin molecular junction under various external forces applied at the AFM tip in the electrical characterization process with different humidity values under dark and illumination conditions. We have analyzed experimentally obtained I–V data under these external stimuli using tunneling-based transport modeling techniques such as differential conductance, law of corresponding states, normalized differential conductance, transition voltage spectroscopy, and Landauer transport formalism. We have also calculated several transport parameters which play a crucial role in finding the origin of conductance modulation under the external stimuli. We found that before particular humidity conditions, the modulation in the conductance is due to the variation in coupling strength, which is due to the modulation in the electrostatic environment of retinal chromophores of a protein by changing its structure under various external stimuli.

Sputter grown copper (Cu) and titanium dioxide (TiO2) based transparent solar heat rejecting film has been developed on glass substrates at room temperature for energy saving smart window applications. The performance of as-deposited ultra-thin TiO2/Cu/TiO2 multilayers was elucidated, wherein the visible transmittance of the multilayer significantly depends on the crystal quality of TiO2 layers. In-situ nanocrystal engineering of TiO2 films with optimized sputtering power improves crystallinity of nano-TiO2 domains. The transparent heat regulation (THR) coating with an average transmittance of ∼70% over the visible spectral regime and infra-red reflectance of ∼60% at 1200 nm was developed at room temperature. Optical characterization, X-ray diffraction (XRD), high resolution-transmission electron microscopy (HR-TEM) and atomic force microscopy (AFM) have been utilized to analyze the crystallinity of TiO2 and quality of the multilayered structure. TiO2/Cu/TiO2 based prototype device has been demonstrated for the energy saving smart windows application.

Proteins, a highly complex substance, have been an essential element in living organisms, and various applications are envisioned due to their biocompatible nature. Apart from proteins' biological functions, contemporary research mainly focuses on their evolving potential associated with nanoscale electronics. Here, we report one chemical doping process in model protein molecules (BSA) to modulate their electrical conductivity by incorporating metal (gold) nanoclusters on the surface or within them. The as-synthesized Au NCs incorporated inside the BSA (Au 1 to Au 6) were optically well characterized with UV-vis, time-resolved photoluminescence (TRPL), X-ray photon spectroscopy, and high-resolution transmission electron microscopy techniques. The PL quantum yield for Au 1 is 6.8%, whereas that for Au 6 is 0.03%. In addition, the electrical measurements showed ∼10-fold enhancement of conductivity in Au 6 (8.78 × 10-3S/cm), where maximum loading of Au NCs was predicted inside the protein matrix. We observed a dynamic behavior in the electrical conduction of such protein-nanocluster films, which could have real-time applications in preparing biocompatible electronic devices.

Two-dimensional molecular junctions (MJs) are mostly developed by sandwiching molecules between two metal electrodes. Charge transport in molecular junctions is not only determined by the difference between work function of electrodes and HOMO/LUMO of the molecule (≈ energy offset, ε), but also on molecule–electrode electronic coupling strengths (Γ g). Detailed knowledge of molecule–electrode coupling could reveal its effect on electron transport efficiency. We have examined the modulation of electronic conductance (G) across bio-molecule/protein-based MJs, where electronic coupling strengths were altered via applied mechanical forces on molecules with conducting-AFM probe. We have utilized numerical tunneling transport models which are developed for MJs and calculated G, ε, Γ g from experimentally obtained current–voltage data. We conclude that the modulation in electronic transport in bio-MJs under applied forces originates from the alteration of Γ g, which further incites the alteration of physical structure and variation of electrostatics environment around the chromophore of the protein.

We report the in-situ, room-temperature synthesis of methylammonium lead bromide CH3NH3PbBr3 crystals using N-methyl formamide as a source of methylammonium (MA+) ions during the crystallization process to explore the structural, dielectric, and electronic properties of CH3NH3PbBr3 crystals for optoelectronic applications. Optical absorption and radio-luminescence measurements affirm the direct bandgap nature of the crystals. Impedance spectroscopy measurements with various applied AC voltages within the 20 Hz–10 MHz frequency range depict the influence of ionic motions on electrical transport across crystal planes. We have extracted electrical transport parameters in CH3NH3PbBr3 crystals from the Nyquist plots, which we found to be distinctly varied wherein two different AC voltage amplitude regimes, broadly for 10–50 mV and 100–500 mV AC voltage range.

Throughout a few years, carrier transport studies across HaP single crystals have gained enormous importance for current generation photovoltaic and photodetector research with their superior optoelectronic properties compared to commercially available polycrystalline materials. Utilizing the room-temperature solution-grown method, we synthesized MAPbBr3crystals and examined their electrical transport properties. Although the X-ray diffraction reveals the cubical nature of the crystals, we have observed anisotropy in the electrical transport behavior and variation in dielectric constant across the three opposite faces of the crystals of mm dimensions. The face with a higher dielectric constant depicts improved parameters from electrical characteristics such as lower trap densities and higher mobility values. We further explore the origin of its anisotropic nature by performing X-ray diffraction on three opposite faces of crystals. Our studies define the specific faces of cuboid-shaped MAPbBr3crystals for efficient electrical contact in the fabrication of optoelectronic devices.

The charge transport across a molecular junction formed by sandwiching molecules between two electrodes in testbed architectures depends not only on the work function of the metal electrodes and energy gap of the molecules but also on the efficacy of the molecule–electrode electronic coupling. Insights into such molecule–electrode coupling would help to understand the relation between the coupling strength and electron transport processes. With this aim, the optoelectronic modulation across bacteriorhodopsin-based molecular junctions has been studied using experimental current–voltage traces obtained by conducting-probe atomic force microscopy under various illuminations. The energy barrier (ε) , molecule–electrode coupling (Γg), and other transport parameters were determined utilizing the Landauer model with a single-Lorentzian transmission function, transition voltage spectroscopy, and the law of corresponding states in the universal tunneling model approach. The findings reveal that the optoelectronic modulation of bacteriorhodopsin molecular junctions originate from alteration of the molecule–electrode coupling, which could originate from modulation of electronic states and the electrostatic environment of retinal chromophores made of the protein under dark and green or green–blue illumination conditions.

Thermochromic material coating on windows or thermochromic paints on building reflects the solar radiation, especially the infrared regime and transmit visible radiation regime. This enables to use thermochromic material for smart window/building applications. This chapter introduces the physics of organic and inorganic thermochromic materials, their developments and applications for maintaining building temperature naturally, with reducing electricity usage. We have reviewed different methods utilized recently to develop thermochromic paints or thin films on plastic or glass windows. Thermochromic smart coating on glass or plastic substrates are designed as an intelligent system that can actively adjust transmission/reflection of sun light by coordinating its phase transition with building's lighting and temperature in order to maintain the environment desired by a building occupant while minimizing energy loss.