HOMO States Research Articles

Harnessing Cu2O-Doped 4-tert-Butylpyridine in Spiro-OMeTAD: Study on Improved Performance and Longevity of Perovskite Solar Cells.

Recently, spiro-OMeTAD has gained prominence as a hole-transporting material (HTM) in high-performance perovskite solar cells (PSCs) due to its superior properties, cutting-edge HOMO state of energy, and solution processability. To promote hole mobility and conductivity, hygroscopic dopants and additives such as lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and 4-tert-butylpyridine (TBP) are typically incorporated. However, these components can lead to aggregation and hydrolysis in ambient conditions, forming pinholes and voids in the films. In this study, we introduce Cu2O as a spiro-OMeTAD additive to reduce voids and improve the quality of films. Incorporating Cu2O alleviates TBP evaporation and provides a more consistent dispersion of Li-TFSI, decreasing the formation of pinholes and bubbles. As a result, additional anions are added to spiro-OMeTAD+ during the oxidation process, promoting the conductivity and hole mobility of the hole-transporting layer and thus boosting PSC performance. Thus, the power conversion efficiency (PCE) percentage of the Cu2O-modified HTM reaches 14.17%, surpassing that of the control HTM at 12.25%. Furthermore, the introduction of Cu2O protects the perovskite layer from water-induced deterioration, ensuring the stability of the PSCs. Our findings offer a promising approach to enhancing both the performance and stability of HTMs and PSCs.

Comparative bioengineering and optoelectronic properties of metoprolol by DFT, molecular docking, and molecular dynamic approaches

The biophysical properties of metoprolol are investigated by the full potential-linearized augmented plane wave method and molecular docking and molecular dynamic approaches. The exchange–correlation potentials are calculated by the Perdew–Burke–Ernzerhof generalized gradient approximation as implemented in the WIEN2k package. The electronic results show the insulator nature of metoprolol with the indirect bandgap of 3.74 eV between HOMO and LUMO states. In the density of state spectra, the p state of O, C, and N elements confirm the stability of metoprolol. Metoprolol exhibits a metallic behavior in the z direction, while it has a dielectric behavior in the x and y directions. The static refractive indices are obtained 1.49, 1.53, and 1.63 in the x, y, and z directions, respectively. It was found that the maximum reflectivity occurs at the ultraviolet region in the z-direction. The calculated absorption spectra also confirm the other’s experimental results. The obtained results of molecular docking indicate the formation of hydrogen bonds between metoprolol and the beta-2 adrenergic receptors, and molecular dynamics showed a human beta-2 adrenoceptor either in its free state or in complex with a metoprolol molecule. The calculated binding energies of elements by molecular docking and the other biological properties of metoprolol by molecular dynamic are in close agreement with obtained Density Functional Theory (DFT) results for Pharmacia applications.

Enhanced Electrochemiluminescence of Rod‐Shape 25‐Atom AuAg Nanoclusters through Ligand Engineering

AbstractThe pursuit of highly emissive electrochemiluminescence (ECL) luminophores has long been a goal for both understanding mechanism and advancing detection applications. In this study, we employ ligand engineering to boost the ECL performance of bimetallic Au12Ag13 nanoclusters, substituting the PPh3 ligand with P(Ph‐OMe)3. The results demonstrate a 3.6‐fold enhancement in ECL efficiency following ligand exchange when compared to Au12Ag13‐PPh3, particularly in the presence of 1 mM tri‐n‐propylamine (TPrA) as a coreactant – surpassing the performance of the conventional Ru(bpy)32+ luminophore. Voltammetric analysis reveals the presence of both oxidative and reductive ECL signals under sweeping potentials, with corresponding ECL spectra collected. Proposed ECL mechanisms are rooted in the anodic and cathodic activities of Au12Ag13‐P(Ph‐OMe)3 nanoclusters. Notably, this work captures extremely high and transient ECL signals, sequentially activating LUMO and HOMO states, reminiscent of the behavior observed in Au12Ag13‐PPh3. Our findings present a promising strategy to enhance the ECL of metal nanoclusters, holding potential for further applications in sensing and detection.

Interaction of carbon nanotube with anti-cancer drugs Busulfan and Mercaptopurine: A DFT study

In this research, the interactions of busulfan and mercaptopurine with single-walled carbon nanotubes (CNT) are investigated. The interaction of the drugs busulfan and mercaptopurine with carbon nanotube has been studied by DFT method. The chosen drugs, CNT(6,6–6), CNT/drug complexes, and their electronic properties are studied using the B3LYP/6-31G(d,p) method in the gas phase. The electronic transition is also calculated with the use of TD-DFT method. NMR Chemical shift, NBO, FMO calculations are implemented. DOS plotsand MEPare obtained for every complex. Natural bond orbital (NBO) study indicates charge transfer have occurredbetween drug molecules and CNT(6,6–6). TD-DFT results revealed the HOMO and LUMO states energy gaps of busulfan and mercaptopurine are 8.94 eV and 5.27 eV respectively, but after interaction with carbon-nanotube they are reduced to 1.63 eV and 1.74 eV. These results revealed that both complexes are favorable. Busulfan strongly interacts with carbon nanotube compare to mercaptopurine.

Density Function Theory Study of the Physicochemical Characteristics of 2-nitrophenol

2-Nitrophenol (2-NP) is utilized in the production of bio-refractory organic compounds, and petrochemicals, and in the synthesis of many drugs and weed killers. The chemical structure of 2-NP is C6H5NO3. The structure of 2-NP is important as the nitro group (NO2. In this present investigation, the Gaussian 5.0 program was used to compute the difference in energy level that exists between the HOMO and LUMO states of the BGs.This information was then used to optimize the shape of the 2-NP structures using DFT methods. The 3-21G/B3LYP base set has a minimum value for the BG energy of 3.48 eV. This is the minimum value that can be achieved. The DOS for 2-NP was measured to have its maximum possible value of 2.23 ev/atom. According to the results of the IR, and Raman spectrum, the C-H stretching vibration peak for 2-NP was found to be between 3208.96 cm-1 and 3243.76 cm-1. The maximum excitation energy was analyzed at a wavelength of 382.1 nm, and the oscillator strength was determined at 0.0537 UV Spectroscopy. In the potential energy map (PE), the colors are changed from blue to red in the range of -4.442e-2 to 4.442e-2.

An Impedance Study of the Density of States Distribution in Blends of PM6:Y6 in Relation to Barrierless Dissociation of CT States

AbstractIn an endeavor to understand why the dissociation of charge‐transfer (CT) states in a PM6:Y6 solar‐cell is not a thermally activated process, measurements of energy‐resolved impedance as well as of intrinsic photoconduction are employed. This study determines the density of states distributions of the pertinent HOMO and LUMO states and obtains a Coulomb binding energy (Eb,CT) of ≈150 meV. This is 250 meV lower than the value expected for a pair of localized charges with 1 nm separation. The reason is that the hole is delocalized in the polymer and the electron is shared among Y6 molecules forming a J‐like aggregate. There are two key reasons why this binding energy of the CT state is not reflected in the temperature dependence of the photocurrent of PM6:Y6‐diode: i) The e–h dissociation in a disordered system is a multi‐step process whose activation energy is principally different from the binding energy of the CT state and can be substantially less than Eb,CT, and ii) since dissociation of the CT state competes with its intrinsic decay, the dissociation yield saturates once the rate of dissociation grossly exceeds the rate of intrinsic decay. This study argues that these conditions are met in a PM6:Y6‐solar cell.

BISPHOSPHONATES-PDA: CORRELATION BETWEEN STRUCTURE AND PHYSICOCHEMICAL PROPERTIES

Bisphosphonates are used to treat a number of bone related diseases such as osteosarcoma, malignant hypercalcemia, osteomyelitis. Developing novel drug delivery systems may overcome the adverse reactions caused by traditional administration. This study uses a combination of molecular docking studies and correlation techniques between structure – physical and chemical properties to assess how different bisphosphonates (alendronate, risedronate, pamidronate, zoledronate) interact with polydopamine in order to later design new formulations. The structure of polydopamine is still under discussion therefore, its bisphosphonate binding properties have not been completely established. Polydopamine was modeled by repeated docking of tetrameric subunits combined in two ways which led to simple and mixed oligomers. Fingerprint descriptors, namely electronegativity of the OMO-UMO quantum molecular states, were used for the correlation studies. The correlation coefficients suggest that several atom species such as nitrogen and carbon have increased contributions to the formation of both HOMO and LUMO molecular states. The results showed that the most stable complex was obtained with risedronate for both simple and mixed dopamine oligomers (-186.00 kJ/mol and -184.92 kJ/mol).

An experimental approach to ensure energy quenching and fluorescence resonance energy transfer of excitons from P3HT to CuInSe2

This letter reports the paramount fluorescence resonance energy transfer mechanism for photo induced charge transfer from P3HT to solvothermally derived CuInSe2. The HOMO (-4.85 eV) and LUMO (-3.38 eV) energy states of CuInSe2 (electrical conductivity = 1.1x 10-7 Scm−1) are determined from cyclic voltammetry and optical study. This HOMO-LUMO position agrees to select P3HT polymer as possible donor of excitons. Steady-state luminescence study of composite (P3HT:CuInSe2) demonstrates possibility of successful charge transfer. Stern–Volmer analysis of absorption and emission spectroscopy ensures static energy quenching phenomena. The Förster distance (R0) of critical energy transfer is estimated as 3.61 nm. The average distance between donor–acceptor (ravg = 4.71 nm) is<8 nm and within the range 0.5R0 < r < 1.5R0 (1.81 nm < r < 5.42 nm), which ensures energy transfer from P3HT to CuInSe2.

Efficient boron-based electrolytes constructed by anionic and interfacial co-regulation for rechargeable magnesium batteries

Rechargeable magnesium batteries (RMBs) based on two-electron transfer chemistry offer great opportunities for realizing high energy density storage technology. However, the lack of magnesium-compatible electrolytes is still the biggest research and development challenge. Boron-based electrolytes, as a viable solution, have always been plagued by complex synthesis processes and high costs. In this work, an efficient boron-based electrolyte was present by a facile one-step mixed reaction of MgCl2, triphenyl borate [B(OPh)3], and tris(pentafluorophenyl)boron (TPFPB) in tetrahydrofuran (THF). By adjusting the composition and ratio of boron-based salts in the electrolyte, a modified anion structure with lower HOMO states was obtained. Besides, the as-prepared electrolyte also contributes to the formation of MgF2-rich solid electrolyte interphase (SEI) layer, which significantly inhibits the electrolyte decomposition, enhance the cycling stability of Mg anodes. Eventually, the electrolyte exhibits a wide electrochemical window (>3 V vs Mg/Mg2+), low polarization voltage (150 mV) and an average Coulombic efficiency above 98 %. Finally, the successful assembly of the Mg/CuS and Mg/Mo6S8 full batteries confirms the practicability of this electrolyte in RMBs. More importantly, the dual regulation strategy of anions and interfaces offers a novel idea for designing efficient electrolytes in RMBs.

Electric field engineering and modulation of CuBr: a potential material for optoelectronic device applications.

I-VII semiconductors, well-known for their strong luminescence in the visible region of the spectrum, have become promising for solid-state optoelectronics because inefficient light emission may be engineered/tailored by manipulating electronic bandgaps. Herein, we conclusively reveal electric-field-induced controlled engineering/modulation of structural, electronic and optical properties of CuBr via plane-wave basis set and pseudopotentials (pp) using generalized gradient approximation (GGA). We observed that the electric field (E) on CuBr causes enhancement (0.58 at 0.0 V Å-1, 1.58 at 0.05 V Å-1, 1.27 at -0.05 V Å-1, to 1.63 at 0.1 V Å-1 and -0.1 V Å-1, 280% increase) and triggers modulation (0.78 at 0.5 V Å-1) in the electronic bandgap, leading to a shift in behavior from semiconduction to conduction. Partial density of states (PDOS), charge density and electron localization function (ELF) reveal that electric field (E) causes a major shift and leads to Cu-1d, Br-2p, Cu-2s, Cu-3p, and Br-1s orbital contributions in valence and Cu-3p, Cu-2s and Br-2p, Cu-1d and Br-1s conduction bands. We observe the control/shift in chemical reactivity and electronic stability by tuning/tailoring the energy gap between the HOMO and LUMO states, such as an increase in the electric field from 0.0 V Å-1 → 0.05 V Å-1 → 0.1 V Å-1 causes an increase in energy gap (0.78 eV, 0.93 and 0.96 eV), leading to electronic stability and less chemical reactivity and vice versa for further increase in the electric field. Optical reflectivity, refractive index, extinction coefficient, and real and imaginary parts of dielectric and dielectric constants under the applied electric field confirm the controlled optoelectronic modulation. This study offers valuable insights into the fascinating photophysical properties of CuBr via an applied electric field and provides prospects for broad-ranging applications.

Adsorption of cytosine on Si and Ge doped graphene: A DFT study

This study describes how the cytosine adsorption on Si and Ge-doped Graphene uses density functional theory (DFT) calculations. The adsorption energies of cytosine on Si and Ge-doped Graphene are computed. The method used a hybrid B3LYP approach with 6-31G (d,p) and LANL2DZ basis sets to determine the Highest Occupied Molecular Orbital -Lowest Unoccupied Molecular Orbital HOMO and LUMO states and descriptors; and charge distribution potential. According to charge distributions, both Ge-doped and Si-doped graphene structures are sensitive to the cytosine base. The DNA base cytosine plays a crucial role as an adsorbent. When cytosine was adsorbed on Ge- and Si-doped graphene structures, the Highest Occupied Molecular Orbital -Lowest Unoccupied Molecular Orbital (HOMO-LUMO) gap decreased. This finding implies that the electrical conductivity of both systems has increased. The result shows that the Ge- and Si-doped graphene structures might be introduced as strong adsorbents for biosensor applications in various fields.

Nanodiamond islands confined between two graphene sheets as perspective 2D quantum materials

Based on direct space DFT PBE0/6-31G* electronic structure calculations, the structure and properties of nanodiamond islands confined between two finite graphene fragments (NDI-c2G) was proposed and theoretically explored. DFT simulations revealed that fusion of planar aromatic molecules with two parent graphene fragments may form either cubic or hexagonal allotropes of NDI-c2Gs lattices accompanied with formation of local corrugated sp3 sites with substituted dangling bonds embedded into graphene sublattices. It was shown that at the DFT level of theory, low distortion energies of NDI-c2Gs lattices are comparable or smaller than the energy of van-der-Waals interactions, which allows the NDI-c2G lattices to be stabilized by a support and finally synthesized. The Nuclear Independent Chemical Shift calculations, shows that in the vicinity of NDI regions, graphene lattices are estimated to be either low-, or anti-aromatic. Furthermore, the formation of NDI-c2Gs leads to localization of HOMO and LUMO states at different sites of the NDI-c2Gs lattices. The NDI-c2G regions with confined frontier orbitals can be considered as arrays of quantum dots isolated from each other by NDI scattering centres of 3.82 Å dimension. The results demonstrates that NDI-c2G should be considered as strongly-correlated entangled hybrid quantum dots which may form extended quantum ensembles with great potential for advanced quantum applications.

Ligand Engineering toward the Trade‐Off between Stability and Activity in Cluster Catalysis

AbstractWe report the structures, stability and catalysis properties of two Ag21 nanoclusters, namely [Ag21(H2BTCA)3(O2PPh2)6]SbF6 (1) and [Ag21(C≡CC6H3‐3,5‐R2)6(O2PPh2)10]SbF6 (2) (H4BTCA=p‐tert‐butylthiacalix[4]arene, R=OMe). Both Ag21 structures possess an identical icosahedral kernel that is surrounded by eight peripheral Ag atoms. Single‐crystal structural analysis and ESI‐MS revealed that 1 is an 8‐electron cluster and 2 has four free electrons. Theoretical results show that the P‐symmetry orbitals are found as HOMO‐1 and HOMO states in 1, and the frontier unoccupied molecular orbitals (LUMO, LUMO+1 and LUMO+2) show D‐character, indicating 1 is a superatomic cluster with an electronically closed shell 1S21P6, while 2 has an incomplete shell configuration 1S21P2. These two Ag21 clusters show superior stability under ambient conditions, and 1 is robust even at 90 °C in toluene and under oxidative conditions (30 % H2O2). Significantly, 2 exhibits much higher activity than 1 as catalyst in the reduction of 4‐nitrophenol. This work demonstrates that ligands can influence the electronic structures of silver clusters, and further affect their stability and catalytic performance.

Ligand Engineering toward the Trade-Off between Stability and Activity in Cluster Catalysis.

We report the structures, stability and catalysis properties of two Ag21 nanoclusters, namely [Ag21 (H2 BTCA)3 (O2 PPh2 )6 ]SbF6 (1) and [Ag21 (C≡CC6 H3 -3,5-R2 )6 (O2 PPh2 )10 ]SbF6 (2) (H4 BTCA=p-tert-butylthiacalix[4]arene, R=OMe). Both Ag21 structures possess an identical icosahedral kernel that is surrounded by eight peripheral Ag atoms. Single-crystal structural analysis and ESI-MS revealed that 1 is an 8-electron cluster and 2 has four free electrons. Theoretical results show that the P-symmetry orbitals are found as HOMO-1 and HOMO states in 1, and the frontier unoccupied molecular orbitals (LUMO, LUMO+1 and LUMO+2) show D-character, indicating 1 is a superatomic cluster with an electronically closed shell 1S2 1P6 , while 2 has an incomplete shell configuration 1S2 1P2 . These two Ag21 clusters show superior stability under ambient conditions, and 1 is robust even at 90 °C in toluene and under oxidative conditions (30 % H2 O2 ). Significantly, 2 exhibits much higher activity than 1 as catalyst in the reduction of 4-nitrophenol. This work demonstrates that ligands can influence the electronic structures of silver clusters, and further affect their stability and catalytic performance.

Comparison of traditional and fullerene-based adsorbents for extraction of 1,4‑dioxane and 2‑methyl-1,3‑dioxolane from milk

Using density functional methods, the results of the analysis of traditional adsorbents and adsorbents based on nanosized particles capable of trapping 1,4‑dioxane and 2‑methyl-1,3‑dioxolane molecules in milk are presented. We considered the following interacting compounds: 1,4‑dioxane — primary amine, 1,4‑dioxane — secondary amine, 1,4‑dioxane — fullerene C20, 1,4‑dioxane — a fragment of the structure of activated carbon, 2‑methyl-1,3‑dioxolane — primary amine, 2‑methyl-1,3‑dioxolane — secondary amine, 2‑methyl-1,3‑dioxolane — fullerene C20, 2‑methyl-1,3‑dioxolane — a fragment of the structure of activated carbon. We determined the optimal configurations of the corresponding interacting structures, estimated their binding energies and chemical potentials. The highest binding energy was obtained for 1,4‑dioxane adsorbed on C20 fullerene. At the same time, the energy gaps between the occupied HOMO and unoccupied LUMO molecular states were calculated, which makes it possible to characterize the reactivity and stability of molecules. Compounds of 1,4‑dioxane and 2‑methyl-1,3‑dioxolane with amines have rather large gaps HOMO-LUMO. Using the concept of the electronic localization function, we found that a covalent bond is formed between 1,4‑dioxane and C20 fullerene with a sufficiently high degree of electron localization in the bond region. In other cases, the value of the localization function indicates the absence of a chemical bond between the compounds. The proposed study gives recommendations on the adsorption of 1,4‑dioxane and 2‑methyl-1,3‑dioxolane for further solid-phase microextraction, which will allow them to be found in milk by gas chromatography using a flame ionization detector.

An efficient electron transport properties of fullerene functionalized with tricyanovinyldihydrofuran (TCF)

The charge mobility is an important property of organic optoelectronic materials. Fullerene (C60) derivatives have been extensively used as electron acceptor materials in optoelectronics. However, the effect of structural modification of fullerene with furan moieties on its charge transport characteristics has rarely been studies. Herein, we synthesized (E)-2-(3-cyano-5,5-dimethyl-4-styrylfuran-2(5H)-ylidene)malononitrile (S1), phenyl functionalized C60 (S2) and furan functionalized C60 (S3) using S2 as a reactant. These compounds have been fully characterized by means of FTIR, 1H NMR, 13C NMR spectroscopy and MALDI-TOF spectrometry for their structure. The photophysical and electrochemical characteristics of S1, S2 and S3 were studied to understand the effect of structural architecture change of C60over redox and optical properties. The electron mobility inS1, S2 and S3 was studied using space-charge limiting current (SCLC) model where, S3 shows 18x higher mobility than the most used acceptor PB61BM. After thermal treatment at 70 °C, S1, S2 and S3 displayed a maximum electron mobility (μe) of (1.39 ± 0.30) × 10−3, (1.3 ± 0.24) × 10−4 and (1.84 ± 0.26) × 10−3 cm2/V.s respectively. Further, computational method was employed to model the S1, S2 and S3electronic structure and frontier electron transitions. Both HOMO and LUMO states drop by exactly the same amount upon structural change from S2 to S3 to give equal Eg when calculated using B3LYP. This suggests that conjoint molecular architecture of TCF and fullerene exhibits interesting photophysical and electrochemical an efficient charge transport properties.

Investigation of structural, spectral, optical and nonlinear optical properties of nanocrystal CdS: Electrodeposition and quantum mechanical studies

Nanocrystalline CdS semiconductor was synthesized by electrodeposition technique, and characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and FTIR spectroscopic methods. XRD analysis result showed that it is a hexagonal crystal structure. SEM micrographs showed that the CdS nanocrystal is homogeneously distributed on the surface. The roughness of the CdS thin films was measured by AFM. The presence of band in the FTIR spectrum at 558 cm−1 corresponds to the stretching of CdS. CdS nanocrystals were modeled separately and calculated in the Gaussian program. Structural, spectroscopic, and nonlinear optical (NLO) properties were investigated using the DFT/Lanl2dz and semi-empirical/pm6 level. Besides, by making energy calculations, Homo, Lumo, band gap, and total state density (TDOS) were calculated. The experimental band gap was measured at 2.40 eV, while this calculated for hexagonal and cubic structure as 2.21 and 2.01 eV with semiemprical/pm6 model, 2.44 and 2.25 eV with DFT/lanl2dz level.These results support that CdS nanostructures are crystallized in hexagonal structure. With this study, the obtaining of nano structured CdS films by electrodeposition method, their structural, optical and surface properties were experimentally examined, supported by theoretical calculations, and additionally NLO properties were investigated. It has been determined that the nanocrystals obtained are suitable material for optoelectronic applications.

Bias-polarity dependent electroluminescence from a single platinum phthalocyanine molecule

By using scanning tunneling microscope induced luminescence (STML) technique, we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine (PtPc) molecule and the electron excitation mechanisms behind. The molecule is found to emit light at both bias polarities but with different emission energies. At negative excitation bias, only the fluorescence at 637 nm is observed, which originates from the LUMO→HOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions. Strong fluorescence in region (I) is excited by the carrier injection mechanism with holes injected into the HOMO state first; moderate fluorescence in region (II) is excited by the inelastic electron scattering mechanism; and weak fluorescence in region (III) is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spin-triplet relay state. At positive excitation bias, more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated. The sharp molecule-specific emission peak at ~911 nm is attributed to the anionic emission of PtPc− originated from the LUMO+1→LUMO transition, whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.

Electronic and optical studies of Eu3+ doped Ca6-xNa2Y2(SiO4)6F2 fluorapatite ceramic synthesized by solution combustion method

This paper reports, the electronic and optical properties of Ca6-xNa2Y2(SiO4)6F2:xEu3+ (x = 0–0.05 mol%) fluorapatite ceramic prepared by solution combustion method. The electronic properties such as energy band gap, total density of states, partial density of states, frontier molecular orbitals and mulliken population analysis were investigated with B3LYP hybrid GGA function by density functional theory (DFT). The lattice parameters value of Ca6Na2Y2(SiO4)6F2 fluorapatite ceramic calculated by DFT shows a good agreement with experimental crystallographic (XRD) analysis. The least square approach was used for computation of crystallographic parameters through Rietveld refinement analysis of XRD patterns. Fourier transform infrared (FTIR) spectra show four different symmetric stretching and bending modes due to the presence of (PO4), (CO2) and (OH) groups in Ca6-xNa2Y2(SiO4)6F2:xEu3+ fluorapatite ceramic. The band gap value calculated by DFT was 5eV whereas calculated by UV–visible spectroscopy was 4.1 eV, which shows the insulating behaviour of Ca6Na2Y2(SiO4)6F2 ceramic. From frontier molecular orbital calculations the energy band gap between HOMO and LUMO states was found to be 5.194 eV. Mulliken population analysis shows that Ca1, Na1, Si1 and F1 are main electron donors whereas Y1 and O1 are main electron acceptor atoms in Ca6Na2Y2(SiO4)6F2 ceramic. It also confirms that Y bonds are more covalent in nature than Na and Ca bonds. Photoluminescence (PL) spectroscopy of Ca6-xNa2Y2(SiO4)6F2:xEu3+fluorapatite ceramic shows three intense peaks at 600 nm, 623 nm and 698 nm perceiving 5D0 – 7F1, 5D0 – 7F2 and 5D0 – 7F4 transitions in orange and red regions under 250 nm UV excitation. The CIE chromaticity diagram shows cool emission in red and orange region with an application in optical and electronic devices.

The electronic and magnetic properties of 3d VIIB and VIII atom-substituted C20 cage

To analyze the contributions of the metal atoms to stabilize and synthesize the small cage-like carbon clusters, the configurations, electronic and magnetic characteristics of Mn-, Fe-, Co- and Ni-substituted C[Formula: see text] cage have been investigated using the PBE functional. The results demonstrate that the TM (TM[Formula: see text]=[Formula: see text]Mn, Fe, Co and Ni) substitution decreases the structural stability of the C[Formula: see text] cages, while increases the activity of the C[Formula: see text] cages. Electronic migrations between the TM atoms and C atoms are less. All the TM–C bonds of the TMC[Formula: see text] and TM2C[Formula: see text] clusters display covalent bond characters. The [Formula: see text] orbitals of TM atoms lose electrons, the [Formula: see text] and [Formula: see text] orbitals of TM atoms obtain electrons. The special distributions of the HOMO states of the TMC[Formula: see text] and TM2C[Formula: see text] clusters are mainly from the hybridization of the C [Formula: see text] orbitals and the TM [Formula: see text] orbitals. The Mn2C[Formula: see text] cages display the highest spin polarization.