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Tuning Photoinduced Electron Transfer Efficiency of Fluorogenic BODIPY- <i>α</i> -Tocopherol Analogues
摘要： Fluorogenic analogues of α-tocopherol developed by our group have been instrumental in monitoring reactive oxygen species (ROS) within lipid membranes. Prepared as two-segment trap-reporter (chromanol-BODIPY) probes, photoinduced electron transfer (PeT) was utilized to provide these probes with an off/on switch mechanism warranting the necessary sensitivity. Herein we rationalize within the context of Marcus theory of electron transfer how substituents on the BODIPY core and linker length joining the trap and reporter segments, tune PeT efficiency. DFT and electrochemical studies were used to estimate the thermodynamic driving force of PeT in our constructs. By tuning the redox potential over a 400 mV range, we observed over an order of magnitude increase in PeT efficiency. Increasing the linker length between the chromanol and BODIPY by 2.8 angstroms in turn decreased PeT efficiency 2.7-fold. Our results illustrate how substituent and linker choice enable “darkening” the off state of fluorogenic probes based on BODIPY fluorophores, by favoring PeT over radiative emission from the singlet excited state manifold. Ultimately, our work brings light to the sensitivity ceiling one may achieve in developing fluorogenic antioxidants analogues of α-tocopherol. The work provides general guidelines applicable to those developing fluorogenic probes based on PeT.
关键词： electrochemical studies,α-tocopherol,lipid membranes,reactive oxygen species,redox potential,photoinduced electron transfer,Marcus theory,DFT,Fluorogenic analogues,BODIPY
更新于2025-09-09 09:28:46
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Defected graphene as ammonia sensor: Theoretical Insight
摘要： Defects are often symbolised as deformity in material that deteriorate its performance. However in nanoscale regime, defects lead to generate a useful and novel material for device applications. In the present report, the vacancy defects i.e. single vacancy and double vacancy defects (with different symmetry) on graphene sheet have been analysed to understand the electronic as well as transport properties using density functional theory and NEGF approach. Conductance, current-voltage and sensitivity analysis, these defected graphene sheet have been examined for gas sensing application particularly for ammonia gas. The study observes that a single vacancy defected graphene is a good candidate for ammonia molecule sensing, in comparison to double vacancy.
关键词： DFT,Sensitivity,Ammonia,Graphene,Defects,Conductance
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Advanced Algorithms for Ab-initio Device Simulations
摘要： Numerical algorithms dedicated to large-scale quantum transport problems from first-principles are presented in this paper. They can be decomposed into three main categories: (i) the calculation of the open boundary conditions that connect the simulation domain and its environment, (ii) the solution of the resulting Schr?dinger equation in the ballistic limit of transport, and (iii) the extension of this case to situations involving scattering, e.g. electron-phonon interactions. It will be shown that ab-initio device simulations require algorithms specifically developed for that purpose and that graphics processing units (GPUs) can bring significant speed ups as compared to solvers based on CPUs only. As an illustration, the computational times coming from the investigation of a realistic conductive bridging random access memory cell will be reported.
关键词： DFT,algorithms,NEGF,quantum transport
更新于2025-09-09 09:28:46
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Electronic, Structural and Vibrational Properties of GaP Diamondoids and Nanocrystals: A Density Functional Theory Study
摘要： The electronic, structural and vibrational properties of gallium phosphide diamondoids and nanocrystals were investigated using density functional theory at PBE/6-31(d) level, which included polarization functions. The energy gap obeyed the quantum confinement size effect with shape fluctuations. The gap converged towards its bulk limit at 2.26 eV. The Ga-P bond lengths of higher diamondoids were found to be distributed around the bulk experimental value at 2.36 Angstrom. Tetrahedral angles were found around the ideal bulk zincblende value at 109.47, degrees while dihedral angles were distributed around the ideal bulk zincblende values at ±60 and ±180 degree. These findings illustrate that diamondoids are a good representative of bulk structure. An analysis of vibrational modes, in terms of reduced masses, force constants and IR intensity, was then performed. The size-related change of certain vibrational frequencies of GaP diamondoids was compared with the experimental bulk. Radial breathing mode frequency began from 187 cm-1 for the smallest molecule GaPH6 and decreased with fluctuations, heading to 0 cm-1 as its bulk limit. Longitudinal optical mode began from 187 cm-1 for the smallest molecule and increased with fluctuations, heading to 376.9 cm-1 (11.3 THz) as its bulk limit. Hydrogen-related vibrations were relatively constant and can therefore be used to identify GaP diamondoids because of their high IR and Raman intensity peaks.
关键词： DFT,Diamondoids,Nanocrystals
更新于2025-09-09 09:28:46
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Oxidative Addition to Palladium(0) Made Easy through Photoexcited-State Metal Catalysis: Experiment and Computation
摘要： Visible-light induced, palladium catalyzed alkylations of α,β-unsaturated acids with unactivated alkyl bromides are described. A variety of primary, secondary, and tertiary alkyl bromides are activated by the photoexcited palladium metal catalyst to provide a series of olefins at room temperature under mild reaction conditions. Mechanistic investigations and density functional theory (DFT) studies suggest that a photoinduced inner-sphere mechanism is operative in which a barrierless, single electron oxidative addition of the alkyl halide to Pd(0) is key for the efficient transformation.
关键词： Excited-state,Palladium,Alkyl halide,Decarboxylation,Barrierless,DFT
更新于2025-09-09 09:28:46
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Adsorption mechanism of typical oxygen, sulfur, and chlorine containing VOCs on TiO2 (0?0?1) surface: First principle calculations
摘要： The photocatalytic degradation of volatile organic compounds has been gaining much interest in recent years to solve the long-standing problem of indoor air pollution. For this purpose, anatase TiO2 and its derivatives are regarded as potential photocatalyst materials. Thus, we study the adsorption mechanism of selected volatile organic compounds such as formaldehyde, methyl chloride, and carbon disulfide on TiO2 (0 0 1) surface using first principle calculations to comprehend their surface interaction and catalytic degradation in depth. The study suggests that formaldehyde interacts with TiO2 (0 0 1) surface through chemical bonds that form a saddle-like structure exhibiting a high adsorption energy value (0.543 eV). It can be inferred that the fivefold coordinated Ti5c and twofold coordinated O2c atoms are the only adsorption sites on TiO2 (0 0 1) surface. However, significant variations are observed for chloride and sulfur containing groups. For instance, the methyl chloride and carbon disulfide physisorbed on the surface of TiO2 (0 0 1) without any chemical bond formation exhibits low adsorption energy values. The results are further confirmed by calculating the corresponding density of states, and electron density differences in all cases. This study provides a detailed investigation of various VOCs on the surface of TiO2 (0 0 1), which provides further insight into the construction of photocatalytic materials for the photodegradation of VOCs.
关键词： Methyl chloride,TiO2 (0 0 1) surface,Formaldehyde,VOCs,DFT
更新于2025-09-09 09:28:46
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Investigation of half-metallic ferromagnetism in hafnium and tantallum doped NiO for spintronic applications: A DFT study
摘要： Full Potential Linearised Augmented Plane Wave (FP-LAPW) method was used to investigate the electronic and magnetic properties of NiO doped with Hf and Ta within the frame work of density functional theory(DFT). NiO is found to be stable in rock salt structure. NiO shows metallic character for the lattice constant of 4.155?. Doping Hf and Ta in the metallic super cell of NiO separately in the doping concentration of 12.5%, the compounds Hf0.125Ni0.875O and Ta0.125Ni0.875O are formed. These compounds of Hf0.125Ni0.875O and Ta0.125Ni0.875O are found to be stable in the ferromagnetic phase. The density of states and band structure plots predict that these compounds exhibit half metallic character with formation of energy gap in one of the spins at the Fermi level. The total spin magnetic moments found in these compounds are 12.00689 μB and 10.97628 μ B.
关键词： DFT,Hf and Ta doping,spintronics,Half-metallic ferromagnetism,NiO
更新于2025-09-09 09:28:46
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Electronic states of dibenzo-p–dioxin. A synchrotron radiation linear dichroism Investigation
摘要： The UV absorbance bands of dibenzo-p-dioxin (dibenzo-1,4-dioxin, DD) are investigated by synchrotron radiation linear dichroism (SRLD) spectroscopy on molecular samples aligned in stretched polyethylene. The investigation covers the range 58000–30000 cm–1 (170–330 nm), thereby providing new information on the transitions of DD in the vacuum UV region. The observed polarization data enable experimental symmetry assignments of the observed transitions, leading to revision of previously published assignments by Ljubi? and Sablji? (J. Phys. Chem. A 109 (2005) 8209-8217). In general, the experimental spectra are well predicted by the results of quantum chemical calculations using time-dependent density functional theory (TD–DFT). The observed absorbance in the region 58000–55000 cm–1 (170–180 nm) in the vacuum UV is almost entirely short-axis polarized, in pleasing agreement with the predicted spectrum.
关键词： Dibenzo-p-dioxin,Near and vacuum UV,Stretched polyethylene,Polarization directions,Time-dependent density functional theory (TD-DFT),Synchrotron radiation,Linear dichroism (LD)
更新于2025-09-09 09:28:46
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Reverse saturable absorption behaviour of Disodium 8-Hydroxy-5,7-Dinitro-2-Naphthalenesulfonate Hydrate for nonlinear optical applications
摘要： Nonlinear optical properties, vibrational features, optical and electronic properties of organic dye Disodium 8-Hydroxy-5,7-Dinitro-2-Naphthalenesulfonate Hydrate have been studied. Spectral and electronic properties were studied by FT-IR, FT-Raman and UV-visible spectroscopic technique combined with density functional theory (DFT) and time dependent density functional theory (TD-DFT) methods respectively. The intramolecular charge transfer interactions leading to nonlinear optical response have been analyzed by natural bond orbital analysis. The kinetic stability, chemical reactivity and electrophilicity index were studied by frontier molecular orbital analysis. The first- and second hyperpolarizabilities were calculated at DFT level using B3LYP and CAM-B3LYP hybrid functional. The third-order nonlinear optical performance of the compound have been investigated experimentally by open and closed aperture Z-scan techniques. Z-scan measurements were performed using Q-switched Nd: YAG laser with 5 ns pulses at 532 nm with different dye concentrations and intensities. The Z-scan results confirm the sign of nonlinear absorption and refraction is positive. The optical limiting threshold and laser damage threshold were measured. The obtained results promote the title compound can be considered as a promising candidate for developing future optoelectronic and photonic devices.
关键词： RSA,Third-order NLO,Optical limiting,Z-Scan,DFT
更新于2025-09-09 09:28:46
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A 1,8 Naphthalimide anchor Rhodamine B Based FRET Probe for Ratiometric Detection of Cr3+ion in Living Cells
摘要： A 2-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)acetaldehydeanchored rhodamine B based probe, RDNAP detects Cr3+ ion by fluorescence resonance energy transfer (FRET) process in aqueous buffered acetonitrile media (7:3, v/v). Conversely, conjugation of 2-(1,3-dioxo-6-(piperidin-1-yl)-1H-benzo[de]isoquinolin-2(3H)-yl)acetaldehyde with rhodamine B provides another probe, RDNAP-PY that undergoes Cr3+assisted ratiometric fluorescence and colorimetric change in the same media. RDNAP-PY provides higher FRET efficiency and detects as low as 1.81×10?6 M Cr3+with an association constant, 15.9 × 104 M-1. Other common ions do not interfere. RDNAP-PY efficiently images intracellular Cr3+ in live Hep3B, MCF-7, HeLa, SiHa and HEK 293T cells under fluorescence microscope in a ratiometric and time dependent manner. 1H NMR titration and DFT studies strongly support experimental findings.
关键词： 1,8 Naphthalimide,Live cell imaging,Ratiometric probe,fluorescence resonance energy transfer,DFT calculation
更新于2025-09-09 09:28:46