Polaronic state of conducting oligomer as a new approach to design non-lieaner optical materials: A case study of oligofurans

The geometric, electronic and nonlinear optical properties of neutral and polaron based oligofurans are studied comparatively. We have reported the role of polaron to trigger the nonlinear optical response of oligofurans (nFu). The polaron based oligomers show excellent opto-electronic properties. The effect of polaron on nFu* chains is measured by electronic properties i.e (ionization energy, electron affinity, band gap) and global reactivity descriptors like softness, hardness and chemical potential than their neutral counterpart. An interesting trends of reactivity descriptors have been observed. Lower band gaps (EH-L = 4.66 and 4.41 eV) are observed for polaronic systems as compared to their neutral counterpart. On the other hand, the TD-DFT study further demonstrated that, as the size of chain increases, the absorption maxima (λmax) also increases with significant reduction in excitation energies (ΔE). Furthermore, the nonlinear optical response is confirmed through the linear polarizability (αo), static first order hyperpolarizability (βo) and dynamic (frequency denepndent) hyperpolarizability. Electric filed induced second harmonic generation (EFISHG) and electro-optic pockle effect (EOPE) at 532 nm and 1064 nm, commonly used lasers frequencies have also been employed. Our results showed that the maximum hyperpolarizabilities are observed for polaron based 7Fu* and 9Fu* i.e 1.3 × 104, and 3.1 × 104 au. This study concluded that these polaron based organic polymers (nFu*) are useful as an efficient NLO material with vast applications in different fields.

DFT analysis on the adsorption of melamine in Ga12-N12/P12 nanocages: solvent effects, SERS analysis, reactivity properties

Due to its negative effects on people, melamine contamination in food products are detected and filtered. Amongst several sensory schemes for the screening of melamine poisoning, one of the most promising techniques is the use of nanomaterial based sensing for real time applicability in industries. In the current work, we have looked into the way melamine binds to Ga12-N12/P12 nanocages. Surface-enhanced Raman scattering (SERS), a successful spectroscopic technique is used to monitor melamine. Density functional theoretical (DFT) computations were used to study the sensing properties of melamine (Me) with Ga12-N12/P12 nanocages. Reactivity and Mulliken charge analyses show charge transfer from melamine to nanocage. Me-Ga12-N12 and Me-Ga12P12 clusters have adsorption energies of -47.54 and -33.12 kcal/mol, respectively. All nanocage-Me systems have a significant increase in polarizability. The electron densities revealed non-covalent interactions in the adsorbed systems. All adsorption energies in aqueous media are negative, indicating an attractive and exothermic reaction, with maximum value in water for Me-Ga12N12 and in acetone for Me-Ga12P12. Evidence of SERS is observed due to the enhancement of different vibrational modes.Communicated by Ramaswamy H. Sarma.

Giant NLO response and deep ultraviolet transparency of dual (alkali/alkaline earth) metals doped C6O6Li6 electrides

The designing of new materials having outstanding nonlinear optical (NLO) response is much needed for use in latest optics. Herein, the geometric, electronic and NLO properties of alkali and alkaline earth metals doped C6O6Li6 (alk-C6O6Li6-alkearth, alkearth = Ca, Mg, Be and alk = K, Na, Li) electrides is studied via quantum chemical approach. The interaction energies (Eint) are examined to illustrate their thermodynamic stability. The strong interaction energy of -39.99 kcal mol-1 is observed for Ca-C6O6Li6-Li electride in comparison to others. Frontier molecular orbitals (FMOs) energy gap of considered complexes is changed due to the electronic density shifting between metals and C6O6Li6 surface, which notifies the semi conducting properties of these electrides. The FMOs isodensities and natural bond orbital (NBO) charge analysis are performed to justify charge transfer between dopants and complexant. UV-Visible study also confirmed the application of these electrides as deep ultra-violet laser devices. NLO response is studied through calculation of first hyperpolarizability (βo). The highest βo value of 1.68 × 105 au is calculated for Mg-C6O6Li6-K electride. NLO response is further rationalized by three- and two-level models approach.

Optical and Photocatalytic Properties of Cobalt-Doped LuFeO3 Powders Prepared by Oxalic Acid Assistance

B-site cobalt (Co)-doped rare-earth orthoferrites ReFeO3 have shown considerable enhancement in physical properties compared to their parent counterparts, and Co-doped LuFeO3 has rarely been reported. In this work, LuFe1-xCoxO3 (x = 0, 0.05, 0.1, 0.15) powders have been successfully prepared by a mechanochemical activation-assisted solid-state reaction (MAS) method at 1100 °C for 2 h. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies demonstrated that a shrinkage in lattice parameters emerges when B-site Fe ions are substituted by Co ions. The morphology and elemental distribution were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The UV-visible absorbance spectra show that LuFe0.85Co0.15O3 powders have a narrower bandgap (1.75 eV) and higher absorbance than those of LuFeO3 (2.06 eV), obviously improving the light utilization efficiency. Additionally, LuFe0.85Co0.15O3 powders represent a higher photocatalytic capacity than LuFeO3 powders and can almost completely degrade MO in 5.5 h with the assistance of oxalic acid under visible irradiation. We believe that the present study will promote the application of orthorhombic LuFeO3 in photocatalysis.

Rational Design, Stabilities and Nonlinear Optical Properties of Non-Conventional Transition Metalides; New Entry into Nonlinear Optical Materials

Electronic and nonlinear optical properties of endohedral metallofullerenes are presented. The endohedral metallofullerenes contain transition metal encapsulated in inorganic fullerenes X₁₂Y₁₂ (X = B, Al & Y = N, P). The endohedral metallofullerenes (endo-TM@X₁₂Y₁₂) possess quite interesting geometric and electronic properties, which are the function of the nature of the atom and the size of fullerene. NBO charge and frontier molecular orbital analyses reveal that the transition metal encapsulated Al₁₂N₁₂ fullerenes (endo-TM@Al₁₂N₁₂) are true metalides when the transition metals are Ni, Cu and Zn. Endo-Cr@Al₁₂N₁₂ and endo-Co@Al₁₂N₁₂ are at the borderline between metalides and electrides with predominantly electride characteristics. The other members of the series are excess electron systems, which offer interesting electronic and nonlinear optical properties. The diversity of nature possessed by endo-TM@Al₁₂N₁₂ is not prevalent for other fullerenes. Endo-TM@Al₁₂P₁₂ are true metalides when the transition metals are (Cr-Zn). HOMO-LUMO gaps (E_H-L) are reduced significantly for these endohedral metallofullerenes, with a maximum percent decrease in E_H-L of up to 70%. Many complexes show odd-even oscillating behavior for E_H-L and dipole moments. Odd electron species contain large dipole moments and small E_H-L, whereas even electron systems have the opposite behavior. Despite the decrease in E_H-L, these systems show high kinetic and thermodynamic stabilities. The encapsulation of transition metals is a highly exergonic process. These endo-TM@X₁₂Y₁₂ possess remarkable nonlinear optical response in which the first hyperpolarizability reaches up to 2.79 × 10⁵ au for endo-V@Al₁₂N₁₂. This study helps in the comparative analysis of the potential nonlinear optical responses of electrides, metalides and other excess electron systems. In general, the potential nonlinear optical response of electrides is higher than metalides but lower than those of simple excess electron compounds. The higher non-linear optical response and interesting electronic characteristics of endo-TM@Al₁₂N₁₂ complexes may be promising contenders for potential NLO applications.

Anthracene-bridged sensitizers for environmentally compatible dye-sensitized solar cells: In silico modelling and prediction

Advancement in solar cells has gained the attention of researchers due to increasing demand and renewable energy sources. Modeling of electron absorbers and donors has been performed extensively for the development of efficient solar cells. In this regard, efforts are being made for designing effective units for the active layer of solar cells. In this study, CXC22 was utilized as a reference in which acetylenic anthracene acted as a π bridge and infrastructure was D-π-A. We theoretically designed four novel dye-sensitized solar cells JU1-JU4 by utilizing reference molecules to improve the photovoltaic and optoelectronic properties. All designed molecules differ from R by donor moiety modifications. Different approaches were done to R and all molecules to explore different analyses like binding energies, excitation energies, dipole moment, TDM (transition density matrix), PDOS (partial density of states), absorption maxima, and charge transfer analysis. For the evaluation of results, we used the DFT technique and the findings demonstrated that the JU3 molecule showed a better redshift absorption value (761 nm) as compared to all other molecules due to the presence of anthracene in the donor moiety which lengthens the conjugation. JU3 was proven to be the best candidate among all due to improved excitation energy (1.69), low energy band gap (1.93), higher λ_max value, and improved electron and hole energy values leading toward higher power conversion efficiency. All the other theoretically formed molecules exhibited comparable outcomes as compared to a reference. As a result, this work revealed the potential of organic dyes with anthracene bridges for indoor optoelectronic applications. These unique systems are effective contributors to the development of high-performance solar cells. Thus, we provided efficient systems to the experimentalists for the future development of solar cells.

Geometric, Electronic, and Optoelectronic Properties of Carbon-Based Polynuclear C3O[C(CN)2]2M3 (where M = Li, Na, and K) Clusters: A DFT Study

Carbon-based polynuclear clusters are designed and investigated for geometric, electronic, and nonlinear optical (NLO) properties at the CAM-B3LYP/6-311++G(d,p) level of theory. Significant binding energies per atom (ranging from -162.4 to -160.0 kcal mol^-1) indicate excellent thermodynamic stabilities of these polynuclear clusters. The frontier molecular orbital (FMOs) analysis indicates excess electron nature of the clusters with low ionization potential, suggesting that they are alkali-like. The decreased energy gaps (E_H-L) with increased alkali metals size revael the improved electrical conductivity (σ). The total density of state (TDOS) study reveals the alkali metals' size-dependent electronic and conductive properties. The significant first and second hyperpolarizabilities are observed up to 5.78 × 10³ and 5.55 × 10⁶ au, respectively. The β_o response shows dependence on the size of alkali metals. Furthermore, the absorption study shows transparency of these clusters in the deep-UV, and absorptions are observed at longer wavelengths (redshifted). The optical gaps from TD-DFT are considerably smaller than those of HOMO-LUMO gaps. The significant scattering hyperpolarizability (β_HRS) value (1.62 × 10⁴) is calculated for the C3 cluster, where octupolar contribution to β_HRS is 92%. The dynamic first hyperpolarizability β(ω) is more pronounced for the EOPE effect at 532 nm, whereas SHG has notable values for second hyperpolarizability γ(ω).

Quantum design of transition metals decorated on boron phosphide inorganic nanocluster for Favipiravir adsorption: a possible treatment for COVID-19

Herein, a quantum drug delivery design of transition metals decorated on boron phosphide (B12P12) inorganic nanocage for favipiravir adsorption has been presented. Thus, these systems may facilitate us as COVID-19 therapy.

Oxacarbon superalkali C3X3Y3 (X = O, S and Y = Li, Na, K) clusters as excess electron compounds for remarkable static and dynamic NLO response

An intriguing class of excess electron oxacarbon superalkali clusters is explored for nonlinear optical response through density functional theory (DFT) methods at CAM-B3LYP/6-311++G(d,p). These superalkali clusters shows noticeable binding energies per atom (E_b) which reveals their thermodynamic stabilities (-86.45 ∼ -119.44 kcal mol^-1). The obtained significant VIPs values also suggest the electronic stability of these clusters. The VIP values range from 2.06 eV to 3.42 eV. These clusters show remarkable electronic properties and their HOMO-LUMO gaps (E_H-L) are significantly reduced. The lowest H-L gap of 0.96 eV is obtained for C₃O₃K₃ while the highest H-L gap of 2.07 eV is calculated for C₃S₃Li₃. The obtained PDOS spectra further provide evidence for the superior electronic properties of these clusters. The clusters show excellent nonlinear optical properties as revealed from remarkable values (1.6 × 10⁶ au) of static first hyperpolarizability. The controlling factors for hyperpolarizability are also explored by using conventional two-level model. The calculated values of β_o are correlated nicely with β_tl. The crucial excitation energy is the key factor in controlling the first hyperpolarizability. In these excess electron clusters, the second hyperpolarizability (γ_o) response increases up to 4.3 × 10⁹ au. Moreover, the calculated scattering hyperpolarizability (β_HRS) values are quite significant in these clusters and the highest value of 1.3 × 10⁶ au is calculated for C₃S₃K₃. Additionally, these clusters also possess larger dynamic nonlinearities. The dynamic second hyperpolarizability with dc-Kerr effect increases up to 1.0 × 10¹¹ au. The remarkable values for refractive index (n₂) also suggest the excellent nonlinearity of these superalkali clusters.

Inorganic electrides of alkali metal doped Zn12O12 nanocage with excellent nonlinear optical response

Finding new materials with exceptionally large nonlinear optical response is an interesting and challenging avenue for scientific research. Here, we report the alkali metal doped Zn₁₂O₁₂ nanocages as inorganic electrides with excellent nonlinear optical response. Density functional theory calculations have been performed for geometric, electronic and nonlinear optical response of exo- and endohedrally alkali metal doped Zn₁₂O₁₂ nanoclusters. For exohedral doping, all different possible doping sites are considered for decoration of alkali metal on the nanocage. The electride nature of the complexes is highly dependent on the position of alkali metal doping. All exohedral complexes except for alkali metal doping on six membered ring (r₆) are electride in nature, as revealed from frontier molecular orbital analysis. Interaction energies reveal that all doped nanoclusters except endo-K@Zn₁₂O₁₂ are thermodynamically stable. The exothermic encapsulation of alkali metals in Zn₁₂O₁₂ nanocages is in marked contradiction with other inorganic fullerenes where encapsulation is an endothermic process. The barriers for boundary crossing are also evaluated in order study the interconversion of exo- and endohedral complexes. Doping of alkali metal significantly influences the properties of nanocages. HOMO-LUMO (H-L) gap is reduced significantly whereas hyperpolarizability is increased several orders of magnitude. The NLO response of exohedrally doped complexes is higher than the corresponding endohedral complexes, which is in mark contradiction with the behavior of phosphide or nitride nanocages. The highest first hyperpolarizability of 1.0 × 10⁵ au is calculated for K@r₆-Zn₁₂O₁₂ complex. Third order NLO response of these complexes is calculated and compared with the best systems reported in the literature at the same level of theory.

DFT studies of single and multiple alkali metals doped C24 fullerene for electronics and nonlinear optical applications

The geometric, electronic and nonlinear properties of exohedral and endohedral single and multiple alkali metal (Li, Na and K) atom doped C₂₄ fullerene are studied. First, the most stable orientations at the most stable spin state are evaluated. Complexes with odd metal atoms are stable at doublet spin state and complexes with even number of metal atoms are stable at singlet spin state. Thermodynamic analysis shows that Li₄C₂₄ among all complexes with highest thermodynamic stability has interaction energy of -190.78 kcal mol^-1. The energy gaps (G_H-L) are fairly reduced in single and multi-doped cages, and the lowest energy gap is observed for K₄C₂₄ complex. NBO analysis is performed to validate the charge transfer from alkali metal toward C₂₄. The largest amount of charge (0.95 |e|) transfer is monitored in exohedral K₂C₂₄ complex where the highest charge transfer is for potassium (K) metal. Total density of states (TDOS) spectra of doped complexes justify the involvement of alkali metals and nanocage in new HOMO formation for the excess electrons. First hyperpolarizability is descriptor of NLO properties of single and multi-doped complexes are calculated. It is observed that doping of alkali metal atoms (Li, Na and K) greatly enhances the first hyperpolarizability. Among all the complexes of C₂₄, Na₃C₂₄ shows the highest hyperpolarizability value of 2.74 × 10⁵ au. The results of this study are a guideline for the computational designing of highly efficient and thermodynamically stable complexes for the optical and optoelectronic technologies.

Investigations of adsorption behavior and anti-inflammatory activity of glycine functionalized Al12N12 and Al12ON11 fullerene-like cages

The adsorption behavior of the amino acid, glycine (Gly), via the carboxyl, hydroxyl, and amino groups onto the surfaces of Al₁₂N₁₂ and Al₁₆N₁₆ fullerene-like cages were computationally evaluated by the combination of density functional theory (DFT) and molecular docking studies. It was found that Gly can chemically bond with the Al₁₂N₁₂ and Al₁₆N₁₆ fullerene-like cages as its amino group being more favorable to interact with the aluminum atoms of the adsorbents compared to carboxyl and hydroxyl groups. Oxygen and carbon doping were reported to reduce steric hindrance for Glycine interaction at Al site of Al₁₂ON₁₁/Gly and Al₁₂CN₁₁/Gly complexes. Interaction was further enhanced by oxygen doping due to its greater electron withdrawing effect. Herein, the Al₁₂ON₁₁/Gly complex where two carbonyl groups of Gly are bonded to the aluminum atoms of the Al₁₂N₁₂ fullerene-like cage is the most stable interaction configuration showing ∆_adsH and ∆_adsG values of -81.74 kcal/mol and -66.21 kcal/mol, respectively. Computational studies also revealed the frequency shifts that occurred due to the interaction process. Molecular docking analysis revealed that the Al₁₂N₁₂/Gly (-11.7 kcal/mol) and the Al₁₂ON₁₁/Gly (-9.2 kcal/mol) complexes have a good binding affinity with protein tumor necrosis factor alpha (TNF-α). TNF-α was implicated as a key cytokine in various diseases, and it has been a validated therapeutic target for the treatment of rheumatoid arthritis. These results suggest that the Al₁₂N₁₂/Gly complex in comparison with the Al₁₆N₁₆/Gly, Al₁₂ON₁₁/Gly, and the Al₁₂CN₁₁/Gly complexes could be efficient inhibitors of TNF-α.

Endohedral metallofullerene electrides of Ca12O12 with remarkable nonlinear optical response

Herein, the structural, electronic, thermodynamic, linear and nonlinear optical properties of inorganic electrides, generated by alkali metal doping in group II–VI Ca₁₂O₁₂ fullerene, are studied. Endohedral doping of alkali metal leads to the formation of electrides whereas no such phenomenon is seen for exohedral doping. The electride nature of the endohedral fullerenes is confirmed through the analysis of frontier molecular orbitals. The results show that doping of alkali metal atoms leads to a reduction of the HOMO–LUMO gap and increase of the dipole moment, polarizability and hyperpolarizability of nanocages. Doping causes shifting of electrons from alkali metal atoms towards the Ca₁₂O₁₂ nanocage, which serve as excess electrons. Furthermore, the participation of excess electrons for enhancing the NLO response of these nanocages has been confirmed through the calculation of hyperpolarizability (β_o). For exploring the controlling factors of hyperpolarizability, a two level model has been employed and the direct relation of hyperpolarizability with Δμ & f_o, while an inverse relation of hyperpolarizability with ΔE has been studied. The electrides possess remarkable nonlinear response where the highest hyperpolarizability can reach up to 1.0 × 10⁶ a.u. for endo-K@Ca₁₂O₁₂. This electride has the lowest ΔE of 0.63 eV among all compounds studied here. These intriguing results will be expedient for promoting the potential applications of the Ca₁₂O₁₂-based nano systems in high-performance nonlinear optical (NLO) materials.

Electride formation by alkali metal doping with a drastic increase in hyperpolarizability

Designing Novel Zn-Decorated Inorganic B12P12 Nanoclusters with Promising Electronic Properties: A Step Forward toward Efficient CO2 Sensing Materials

Gas sensing materials have been widely explored recently owing to their versatile environmental and agriculture monitoring applications. The present study advocates the electronic response of Zn-decorated inorganic B12P12 nanoclusters to CO2 gas. Herein, a series of systems CO2-Zn-B12P12 (E1-E4) are designed by adsorption of CO2 on Zn-decorated B12P12 nanoclusters, and their electronic properties are explored by density functional theory. Initially, placement of Zn on B12P12 delivers four geometries named as D1-D4, with adsorption energy values of -57.12, -22.94, -21.03, and -14.07 kJ/mol, respectively, and CO2 adsorption on a pure B12P12 nanocage delivers one geometry with an adsorption energy of -4.88 kJ/mol. However, the interaction of CO2 with D1-D4 systems confers four geometries named as E1 (E ad = -75.12 kJ/mol), E2 (E ad = -25.89 kJ/mol), E3 (E ad = -42.43 kJ/mol), and E4 (E ad = -28.73 kJ/mol). Various electronic parameters such as dipole moment, molecular electrostatic potential analysis, frontier molecular orbital analysis, Q NBO, global descriptor of reactivity, and density of states are also estimated in order to understand the unique interaction mechanism. The results of these analyses suggested that Zn decoration on B12P12 significantly favors CO2 gas adsorption, and a maximum charge separation is also noted when CO2 is adsorbed on the Zn-B12P12 nanocages. Therefore, the Zn-decorated B12P12 nanocages are considered as potential candidates for application in CO2 sensors.

Cyclic versus straight chain oligofuran as sensor: A detailed DFT study

This study presents a novel approach for exploring the sensitivity and selectivity of cyclic oligofuran (5/6/7CF) toward gaseous analytes and their comparison with straight chain analogues (5/6/7SF). The work is not only vital to understand the superior sensitivity but also for rational design of new sensors based on cyclic ring structures of oligofuran. Interaction of cyclic and straight chain oligofuran with NH₃, CO, CO₂, N₂H₄, HCN, H₂O₂, H₂S, CH₄, CH₃OH, SO₂, SO₃ and H₂O analytes is studied via DFT calculation at B3LYP-D3/6-31++G (d, p) level of theory. The sensitivity and selectivity are illustrated by the thermodynamic parameters (E_bind, SAPT0 energies, NCI analysis), electronic properties (H-L gap, percentage of average energy gap, CHELPG charge transfer, DOS spectra), and UV-Vis analysis. All these properties are simulated at B3LYP/6-31G (d) level of theory while UV-Vis is calculated at TD-DFT method. Cyclic oligofurans have high binding energies with analytes compared to 5/6/7SF which corresponds to higher sensitivity of 5/6/7CF. Furthermore, the cyclization of oligofuran significantly improves the sensitivity and selectivity of the system. Alteration in electronic properties of 5/6/7CF and 5/6/7SF is remarkably high upon complexation with SO₂ and SO₃. Further the stability of rings (5, 6 and 7 membered cyclic oligofurans) and their SO₃ complexes is also confirmed by molecular dynamics calculations. The findings of the work clearly suggest that the cyclic geometry enhances not only sensitivity but also selectivity of conducting polymers (oligofuran).

Exceptionally high NLO response and deep ultraviolet transparency of superalkali doped macrocyclic oligofuran rings

Cyclic oligofurans containing five and six furan rings (5CF & 6CF) doped with superalkalis are presented here as a new type of NLO material.

Superhalogen doping: a new and effective approach to design materials with excellent static and dynamic NLO responses

The first-ever example where superhalogen doping alone is introduced as a new and effective approach to impart large NLO responses.

Photo-tunable linear and nonlinear optical response of cyclophanediene-dihydropyrene photoswitches

Cyclophanediene (CPD)-dihydropyrene (DHP) is a negative T-type photochrome pair having a thermodynamically stable colored form, i.e., DHP. Interconversion between cyclophanediene and dihydropyrene is associated with significant changes in dipole moment, absorption wavelength and polarizability, which can impart substantial linear and nonlinear optical response. In this study, phototunable linear and nonlinear optical response of cyclophanediene-dihdyropyrene photoswitches is described. Cyclophanedienes and dihydropyrenes are functionalized at the internal position for maximum changes in volume and polarizability. The UV-Vis spectra are calculated at ɷB97XD, which was validated through a benchmark approach. An excellent correlation is observed between theoretical and experimental absorption spectra. Several CPD-DHP pairs have been recognized for clean interconversion in UV-Vis light without formation of a photostationary state. Nonlinear optical response of dihydropyrenes is remarkably higher than that of cyclophanedienes. In general, the calculated hyperpolarizability values of dihydropyrenes are about two to three orders of magnitude higher than those for cyclophanedienes. The trends in calculated hyperpolarizabilities are rationalized through two level method. The high nonlinear optical response of dihydropyrenes stems from low excitation energies. The remarkable difference in hyperpolarizabilities of these isomeric forms paves path for the design of phototunable nonlinear optical materials.

A comprehensive DFT study on the sensing abilities of cyclic oligothiophenes (nCTs)

Linear conducting polymers are extensively studied as sensors for various analytes, whereas studies on cyclic analogues are limited.