Decrease In Gap Energy Research Articles

The impact of Sm substitution on structural and optical properties of LaFeO3: their application as a photocatalyst for the degradation of methylene blue under visible light irradiation

The objective of the present study is to enhance the photocatalytic activity of LaFeO3 by inserting Sm ions on the La site for the degradation of methylene blue. We employed citric sol–gel techniques to produce ultrafine powders of the La1-xSmxFeO3 (0.0 ≤ x ≤ 0.5) nanoperovskite samples. All samples confirmed the presence of a pure Pbnm orthorhombic phase structure. The decrease of lattice constants, crystallite sizes and cell volumes, and increase in microstrains suggest a deformation of the structure due to the addition of Sm ion on the La site of the La1-xSmxFeO3. The images of HR-TEM and FE-SEM for all samples revealed a homogeneous distribution of almost spherical nanoparticles, with decreasing average particle sizes ranging from 49.95 ± 3.12 to 34.28 ± 4.38 nm, as Sm ratios increases from 0.0 to 0.5%. The spectra of FTIR confirmed the formation of a Lax-1SmxFeO3 perovskite phase by the appearance of lower frequency bands Fe–O-Fe and La-O-La at ∼ 400 cm−1 and a higher absorption band Fe -O and La -O at ∼ 564 cm−1. The Raman spectra were employed to investigate the formation of phonon modes of La1-xSmxFeO3. Diffused reflectance spectroscopy (DRS) demonstrated the decrease of energy gap (Eg) values from 2.38 to 1.86 eV and the increase in Sm content from 0.0 to 0.5%. Since these Eg values fall within the visible light region, the photocatalytic activity of La1-xSmxFeO3 samples demonstrated a gradual increase in the degradation ratio of MB from 31.7 to 73.2% with increasing Sm content from 0.0 to 0.5%, respectively, under visible light illumination.

Comprehensive investigation of electronic structure, phonon spectrum and thermoelectric performance of LuMSb (M = Ni, Pd, Pt) half Heusler compounds from first principles.

We studied the structural, electronic, phonon spectrum and thermoelectric properties of ternary LuMSb (M = Ni, Pd, Pt) half Heusler compounds by using first principles method. The electronic properties are calculated via energy band structure and density of states by using GGA + U approximation. The calculations reveal that the replacement of Ni with Pd and Pt, energy gap decreases and LuNiSb, LuPdSb are found to have narrow indirect band gaps and exhibit semiconducting nature, while LuPtSb is found to be a gapless semiconductor. Phonon band structure calculations give only positive values of phonon frequency indicating the dynamically stability of these compounds. The thermoelectric properties have been computed using semi-classical Boltzmann transport theory. We found high Seebeck coefficient (S) and high power factor (PF) for LuNiSb and LuPdSb compounds in the whole temperature range. The ZT values of LuNiSb and LuPdSb are high in general and reach a maximum of 0.67 and 0.69 at 450 K, respectively, whereas 0.39 is the maximum ZT value for LuPtSb at the same temperature. These findings propose LuNiSb and LuPdSb compounds as promising materials for thermoelectric applications at room temperature.

[formula omitted] Mössbauer, optical and structural properties with ligand field effects of borosilicate glass doped with iron oxide

Here, an investigation of borosilicate glass doped with iron oxide and prepared by classical melt-quenching method. The internal macrostructure, optical absorbance, ligand field parameters, and Mössbauer spectra were studied. The density increased with increasing SiO2 content, while Fourier-transform infrared (FTIR) analysis reported that BO4 and SiO4 content increase with a decrease in NBO content. Optical electronic transitions through wavelength (402–948 nm) confirmed the existence of Fe3+ state, while the Fe2+ is not observed in optical absorbance because of its inane electronic transition at 2222 nm. The electronic transitions at (402, 452, 513, 602, and 701 nm) are assigned to Fe3+ in tetrahedral coordination (FeO4), while the electronic transitions at (795 and 948 nm) are related to Fe3+ in octahedral coordination (FeO6). Astonishingly, the ligand field parameters of Fe ions were studied. The crystal field splitting exhibits increasing values, while Racah parameters exhibit decreasing values. Moreover, nephelauxetic parameters reflect the propensity of the bonding nature between the Fe cations and their ligands towards a higher covalent nature with SiO2 additives. Further, a scant decrease in the optical band gap was explained based on the mixed former effect. Moreover, non-linear refractive indices augment with SiO2 addition. The decrease in the optical gap energy justified such a trend. Bewitchingly, Mössbauer spectra reported the existence ofFe3+ ions with isomer shift (0.285–0.314) mm s−1 in tetrahedral sites, while Fe3+ ions with isomer shift (0.339–0.425) mm s−1 in octahedral sites, agreeing with optical data. Surprisingly, Fe2+ ions with isomer shift at about 0.905 mm s−1 in tetrahedral sites was observed. The observed decrease in isomer shift of all phases is due to the decrease in electronegativity of formers. Furthermore, the decrease in quadrable splitting is attributed to the decline in the polarization power of the glass former cations with SiO2 addition.

Designing Efficient Metal-Free Dye-Sensitized Solar Cells: A Detailed Computational Study.

The modulation of molecular characteristics in metal-free organic dyes holds significant importance in dye-sensitized solar cells (DSSCs). The D-π-A molecular design, based on the furan moiety (π) in the conjugated spacer between the arylamine (D) and the 2-cyanoacrylic acid (A), was developed and theoretically evaluated for its potential application in DSSCs. Utilizing linear response time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional, different donor and acceptor groups were characterized in terms of the electronic absorption properties of these dyes. All the studied dye sensitizers demonstrate the ability to inject electrons into the semiconductor's conduction band (TiO2) and undergo regeneration through the redox potential triiodide/iodide (I3-/I-) electrode. TDDFT results indicate that the dyes with CSSH anchoring groups exhibit improved optoelectronic properties compared to other dyes. Further, the photophysical properties of all dyes absorbed on a Ti(OH)4 model were explored and reported. The observed results indicate that bidentate chemisorption occurs between dyes and TiO4H5. Furthermore, the HOMO-LUMO energy gaps for almost all dye complexes are significantly smaller than those of the free dyes. This decrease of the HOMO-LUMO energy gaps in the dye complexes facilitates electron excitation, and thus more photons can be adsorbed, guaranteeing larger values of efficiency and short-circuit current density.

Multiple phases of yttrium-doped molybdenum trioxide nanorods as efficient dye degrader and bactericidal agents with molecular docking analysis

Contaminants removal is usually becoming an exciting subject of research from water considering their environmental and ecological effects. This work provides pathways to remove organic pollutants from water via nanomaterials and is used as an antibiotic against bacteria like Escherichia coli (E. coli). In this study, molybdenum trioxide (MoO3) and yttrium (Y) doped (2 and 4%) MoO3 nanorods were synthesized by co-precipitation method. Advanced characterization techniques have been introduced to study textural structures, morphological developments, and optical characteristics of produced products. X-ray diffraction studied multiple crystalline structures of prepared samples as hexagonal, orthorhombic, and monoclinic of pure MoO3 with decrease in crystallinity and crystallite size upon Y doping. UV–visible spectroscopy unveiled a redshift (bathochromic effect) in absorption pattern attributed to band gap energy (Eg) decreases. Photoluminescence spectra examined the recombination rate of electrons (e−) and holes (h+) as charge carriers. A sufficient catalytic activity (CA) was observed against methylene blue (MB) dye in an acidic medium (99.74%) and efficient bactericidal action was studied against (E. coli) with zone of inhibition (5.20 mm) for 4% Y-doped MoO3. In addition, in silico docking demonstrated potential inhibitory effect of produced nanomaterials on FabH and FabI enzymes of fatty acid biosynthesis.

A sensitive voltammetric and density functional theory calculations analysis for the direct interaction of sulfide ion with the multiwalled carbon nanotube

A sensitive and simple cyclic voltametric method was investigated for the direct electrochemical determination of sulfide using multiwalled carbon nanotube paste electrode (MWCNTPE). The sulfide exhibited a distinct and remarkable direct oxidation peak at about 0.56 V in a solution containing sodium chloride as a suitable supporting electrolyte. The effect of voltametric behavior of sulfide was also studied in various supporting electrolyte. Among this sodium chloride containing solution showed a well-defined oxidation peak current as compared to the other supporting electrolyte. The direct oxidation behavior of sulfide in sodium chloride solution was mainly attributed to the less hindrance effect of the electrolyte anions on the surface of electrode. Under optimized condition the oxidation peak current values were found to increase in a linear way with increasing sulfide concentration in the range from 1 × 10−7 to 3 × 10−5 M (R2 = 0.9985). The detection limit (DL) was calculated to be 4 × 10−8 M for the sulfide concentrations. The developed method showed excellent selectivity towards the voltametric determination of sulfide as compared to other competing ions like Br−, NO3−, F−, PO43−, NO2−, I−, CH3COO− present in the solution. Moreover, the method demonstrated good and reproducible results with relative standard deviation (RSD) of 3.8% after 40 successive measurements. The method was successfully applied for determination of sulfide in local tap water samples without any matrix effect. Meanwhile to support the voltametric behavior of sulfide, density functional theory (DFT) calculations were performed at ωB97XD/6-31G(d,p) level of theory to get deep insight into the electronic properties of MWCNT and adsorbed analytes (sulfide) using Gaussian 09 package. The highest interaction energy and the decrease in energy gap of multiwall carbon nanotube with sulfide (MWCNT-S2-) complex are consistent with the highest sensing behavior of MWCNT towards sulfide ion in experimental results.

Multinuclear Pd(II) oligomeric nanohoop complexes with 2,2′‐bipyridyl‐embedded cycloparaphenylenes ligands exhibiting ultrahigh third‐order nonlinear optical performance

AbstractUnlike traditionally available linear frameworks, cyclic transition‐metal architectures with cycloparaphenylenes (CPPs) ligands provide new access to develop modern nonlinear optical (NLO) materials. In this work, a sequence of “staircase” Pd(II) oligomeric nanohoop complexes with the 2,2′‐bipyridyl‐embedded CPPs ligand unit through “series connection” mode and “Ω‐type” Pd(II) trimeric isomer have been systematically designed and investigated via density functional theory. Herein, we first report the dependence of third‐order NLO responses on the number of bipyridine CPP building ligands in a quantitative way. Impressively, the Pd(II) trimeric complexes possess ultrahigh third‐order NLO responses, which are ascribed to the large orbital delocalization and decreased energy gap. To our delight, the enlargement of the nanohoop size is beneficial to improving third‐order NLO responses for Pd(II) oligomeric nanohoop complexes, and the maximum absorption spikes show the blue shift tendency. The effect of size on the third‐order NLO responses becomes much larger with the addition of bipyridine CPPs ligand. Overall, we hope the current work will deliver a new quantitative structure–property relationship toward the design and synthesis of Pd(II) oligomeric nanohoop complexes with high third‐order NLO responses.

Diagonal and Vertical B ← N Lewis Pair Functionalized Perylenes.

Two novel multiple B ← N Lewis pair functionalized perylenes are reported. While OBN-Pery shows a centrosymmetric and planar architecture, PBN-Pery displays an axisymmetric and twist structure. B ← N functionalization in both of them results in a large decrease in the HOMO-LUMO energy gap. PBN-Pery in particular has a low LUMO energy level (-3.00 eV) and red emission at the NIR I region with high fluorescence quantum yield.

Synthesis of CaCO3/Cu2O/GO Nanocomposite Catalysts for Hydrogen Production from NaBH4 Methanolysis

The synthesis of CaCO3/Cu2O/GO nanocomposites was developed by sol-gel auto-combustion method. The analysis of structure was completed on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and environmental scanning electron microscopy (ESEM). The XRD spectra of the nanocomposites matched the crystal structure of CaCO3/Cu2O. The average crystal size was 20 nm for Cu2O and 25 nm for CaCO3 nanoparticles. FTIR data showed the absorption bands of Cu2O and GO. Raman spectroscopy data confirmed the formation of GO sheets. ESEM micrographs displayed spherical nanoparticles dispersed in GO sheets. X-ray photoelectron spectroscopy showed the peaks of Cu 2p, O 1s, C 1s, Cu 3s, and Ca 2p. The spectra of optical absorption revealed an absorption band of around 450 nm. The calcium content increase led to a decrease in the optical energy gap from 2.14 to 1.5 eV. The production of hydrogen from NaBH4 across the methanolysis reaction was accelerated by the CaCO3/Cu2O/GO nanocomposites. Therefore, these nanocomposites are superior in catalytic hydrogen production systems.

Synthesis and Characterization of (PVA-CoO-ZrO2) Nanostructures for Nanooptoelectronic Fields

Nanocomposites have a wide range of applications, including optical integrated circuits, sensors, coatings, and medical devices. As a result, the purpose of this paper is to prepare a new type of nanocomposites made of polyvinyl alcohol (PVA) with different concentrations (0, 1, 2 and 3) wt% of cobalt oxide and zirconium dioxide (CoO-ZrO2) nanoparticles by using casting method. Microscopic photographs demonstrate the fact that the additive distribution amount of NPs in the polymer was uniform, and (CoO-ZrO2) NPs formed a continuous network within the polymer when the concentration reached 3wt.%. The outcomes of optical properties indicate that the absorbance of nanocomposites improves as the concentrations of cobalt oxide and zirconium dioxide nanoparticles increase while transmittance and the optical energy gap decrease. On the other hand, optical constants of nanocomposites (refractive index, absorption coefficient, extinction coefficient, real and imaginary the dielectric constants) and optical conductivity are increase with increases in the weight percentages of (CoO-ZrO2) nanoparticles. These outcomes demonstrate the (PVA-CoO -ZrO2) NCs use for various optical devices.

Ag doping effect on electronic and thermoelectric properties of SrTiO3 (0 0 1) surface

The search for sustainable energy sources has been a global demand in recent decades. In this context, thermoelectric materials (TE) have been an interesting alternative for this purpose and constitute a relevant research topic for increasing the efficiency of sustainable energy production. In this sense, computational simulation of the functionalization of SrTiO3 is proposed via Ag-doping on the (001) surface. The results show the emergence of a midgap trap state, leading to a band gap energy decrease, an increase in dielectric constants and the effective mass electron. The Ag-doping generates a decrease in electrical conductivity and an increase in the figure of merit, which are associated with a significant reduction in thermal conductivity (∼5 times), indicating that the material can be used with TE at high temperatures. The Ag-SrTiO3 (001) surface is promising for developing new thermoelectric devices.

End-capped modeling of dithienopicenocarbazole based derivatives for high-performance photovoltaic cells with optoelectronic response over 900 nm

Dithienopicenocarbazole (DTPC), as the inner core in the A-D-A configuration, has been recognized for its exceptionally small energy loss, narrow energy gap, and excellent power conversion efficiency. In this work, a series of six novel dithienopicenocarbazole-based molecules with wide absorption and remarkable opto-electrical properties, were designed as the new electron-donating materials for organic photovoltaic devices. (DI1-DI6) were derived by substituting end-capped moieties attached to the middle core (DTPC) with highly conjugated and electro withdrawing groups and insertion of π spacer between the donor part and the newly attached acceptor part. The findings demonstrated that the modified molecules had smaller excitation energies (Ex), a decreased energy gap (Eg), and have higher absorption (λmax) values in comparison to the DIR (reference structure). The greatest λmax (980 nm), smallest Ex (1.21 eV), and shortest Eg (1.63 eV) were all displayed by the DI4 molecule. In addition, due to its lowest RE value for the electron, DI4 might have best electron carrier ability among all. Furthermore, upon coupling each examined molecule with a PC61BM acceptor, the value of open circuit voltage (VOC) was computed. DI4 displayed the most suitable outcomes for the VOC (1.45 V), FF (0.91178) and normalized VOC (56.14). Therefore, all the altered structures, with special reference DI4, are strongly recommended to synthesize organic photovoltaic cells with exceptional optoelectronic and photovoltaic applications.

Sn-alloying of BaZrS3 chalcogenide perovskite as eco-friendly material for photovoltaics: First principle insight

This paper focuses mainly on investigating the effects of partial substitution of Zr cations by Sn cations on the structural, opto-electronic and photovoltaic properties of the chalcogenide perovskite BaZr1−xSnxS3 (x ≤ 0.25). For this purpose, we have used first-principles calculations. Through this approach, we show that the lattice constants and the gap energy (Eg) decrease as the Sn content (x) increases. Furthermore, the Eg values obtained decrease from 1.55 to 0.96 eV. our calculated decomposition energies suggest that it will be difficult to synthesize BaZr1−xSnxS3 alloys for higher Sn contents under thermal equilibrium conditions. Also, the calculated dielectric functions and absorption coefficient show a red shift for higher Sn content. Besides, our theoretical approach, indicate that, the compound BaZr0.815Sn0.125S3 presents a maximum photovoltaic efficiency η of 32.5% for a thickness L = 500 nm, which is close to the Shockley–Queisser limit (33.7%), which makes it a promising candidate for the production of high power conversion efficiency solar cells with ultra-thin absorption layers. sulfide alloys for lead-free perovskite solar cells.

Gamma irradiation induced surface modification of (PVC/HDPE)/ZnO nanocomposite for enhancing the oil removal and conductivity using COMSOL multiphysics

Blend nanocomposite film was prepared by loadings of irradiated ZnO in ratios of (5 wt%) inside the PVC/HDPE matrix using a hot-melt extruder technique. The physical and chemical properties of the irradiated and unirradiated ZnO samples are compared. The Vis–UV spectrum of ZnO shows an absorption peak at a wavelength of 373 nm that was slightly red-shifted to 375 nm for an irradiated sample of ZnO at a dose of 25 kGy due to the defect of crystal structure by the oxygen vacancy during gamma irradiations. This growth of the defect site leads to a decrease in energy gaps from 3.8 to 2.08 eV. AC conductivity of ZnO sample increased after the gamma irradiation process (25 kGy). The (PVC/HDPE)/ZnO nanocomposites were re-irradiated with γ rays at 25 kGy in the presence of four different media (silicon oil, sodium silicate, paraffin wax and water). FTIR and XRD were performed to monitor the changes in chemical composition. The new peak at 1723 cm−1 attributed to C=O groups was observed in irradiated (PVC/HDPE)ZnO samples at only sodium silicate and water media. This process induced new function groups on the surface of the (PVC/HDPE)/ZnO blend sample. This work aims to develop (PVC/HDPE)ZnO for oil/water separation. The highest oil adsorption capability was observed in samples functionalized by C=O groups based on the different tested oils. The results suggest that the surface characterization of the (PVC/HDPE)/ZnO can be modified to enhance the oil adsorption potential. Further, the gamma irradiation dose significantly enhanced the AC conductivity compared to the unirradiated sample. According to COMSOL Multiphysics, the irradiated sample (PVC/HDPE)ZnO in water shows perfect uniform electric field distribution in medium voltage cables (22.000 V).

Microwave-assisted hydrothermal synthesis of type II ZnSe/ZnO heterostructures as photocatalysts for wastewater treatment

The ZnSe/ZnO heterostructures were synthesized with the microwave-assisted hydrothermal method, using zinc acetate and zinc nitrate as a source of Zn2+ ions. Materials were characterized by X-ray diffraction (XRD), X-ray photoemitted electron spectroscopy (XPS), Raman spectroscopy, and scanning electron microscopy (SEM). The incorporation of ZnSe into the ZnO matrix produced changes both in the size of the ZnO crystallites and in the lattice parameters. Optical and texture analyses revealed that ZnSe particles cause a decrease in gap energy and a greater than 90% increase in the specific surface area of ZnSe/ZnO heterostructures compared to bare ZnO particles. ZnSe/ZnO heterostructures synthesized using zinc acetate as a Zn ion source exhibited better photocatalytic performance in visible light compared to pure ZnO.

Cobalt isatin-Schiff-base derivative of MOF as a heterogeneous multifunctional bio-photocatalyst for sunlight-induced tandem air oxidation condensation process

A sunlight-induced tandem air oxidation-condensation of alcohols with ortho-substituted anilines or malononitrile for the efficient synthesis of benz-imidazoles/-oxazoles/-thiazoles, or benzylidene malononitrile catalyzed by Co-isatin-Schiff-base-MIL-101(Fe) as a heterogeneous multifunctional bio-photocatalyst is reported. In these reactions, Co-isatin-Schiff-base-MIL-101(Fe) acts both as a photocatalyst, and a Lewis acid to catalyze the reaction of the in-situ formed aldehydes with o-substituted anilines or malononitrile. A significant decrease in the band gap energy and an increase in the characteristic emission of MIL-101(Fe) after functionalization with cobalt Schiff-base according to the DRS analysis and fluorescence spectrophotometry, respectively, indicate that the photocatalytic effectiveness of the catalyst is associated primarily to the synergetic influence of Fe–O cluster and Co-Schiff-base. EPR results obviously pointed out that Co-isatin-Schiff-base-MIL-101(Fe) is capable of creating 1O2 and O2⋅− as active oxygen species under visible light irradiation. Using an inexpensive catalyst, sunlight irradiation, air as a cost-effective and abundant oxidant, and a low amount of the catalyst with recoverability and durability in ethanol as a green solvent, make this methodology as an environmentally friendly process with energy-saving organic synthetic strategies. Furthermore, Co-isatin-Schiff-base-MIL-101(Fe) displays excellent photocatalytic antibacterial activity under sunlight irradiation against E. coli, S. aureus and S. pyogenes. Based on our knowledge, this is the first report of using a bio-photocatalyst for the synthesis of the target molecules.

Simple fabrication of PVA/PEG blend doped with methyl blue dye with superior optical limiting performance: Enhanced luminescence property, structural, and dielectric properties

Using the casting technique, films of 90 wt% PVA/ 10 wt% PEG blend doped with numerous concentrations of methyl blue dye (MYB) were prepared. The effect of methyl blue dye on the unique functional groups of PVA and PEG was detected using a Fourier Transform infrared (FT-IR) spectrometer. The PVA/PEG blend's semi-crystalline characteristic was discovered via the X-ray diffraction pattern. With a rise in MYB doping concentration, the crystallinity of the doped blends degrades. The optical characteristics of the PVA/PEG mixture and the PVA/PEG mixture doped with various concentrations of (MYB)have been measured, including the absorption, transmission, reflection spectra, optical energy gap, optical absorption coefficient, and extinction coefficient. As the MYB dye's weight percentage increases, the composites show a decreasing energy gap and an increasing refractive index. As MYB doping rose, Urbach's energy surged from 8.5 meV to 28.88 meV. (PVA-PEG)/MYB composites demonstrated acceptable optical limiting characteristics. The emission peaks in terms of photoluminescence characteristics shiftto red with rising MYB content in (PVA-PEG)/MYB MYB composite sample films, with the peak emission occurring at wavelength λem = 600 nm. According to research done in the frequency range of 100 Hz to 1 MHz, the MYB contents impact the dielectric characteristics and AC electrical conductivity. All of the aforementioned characteristics point to the (PVA-PEG)/MYB polymer composite as a promising choice for laser filters, solar cell technology, electric energy storage, and different optoelectronic applications.

EFFECT OF PHASE TRANSFORMATION ON OPTICAL PROPERTIES OF ZNTIO3 CERAMIC POWDER PREPARED BY SOL-GEL METHOD

ZnTiO3 powders were prepared by sol-gel method using ammonium hydroxide. The effects of calcination temperature (500– 1000∘ C). and the molar ratios ZnO/TiO2. The synthesis of a nano perovskite ZnTiO3 usually results in the formation of one or more of the compounds such as Zn2TiO4, and ZnTiO3 with other secondary impurity phases such as rutileTiO2 or ZnO. To obtain a phase-pure a nano perovskite ZnTiO3 at a low processing temperature is one of the challenges in materials chemistry., pure ZnTiO3 can not be synthesized under normal conditions, because it transforms into Zn2TiO4 and rutile. In the current study, the crystalline and phase transformation behaviors of sol-gel synthesized a nano perovskite ZnTiO3 has systematically been investigated with regard to various Zn:Ti precursor molar ratios. The ZnTiO3 phase can be detected by XRD in the powders calcined above 600 °C. The formation of ZnTiO3 is a slow reaction process, which leads to the development of large ZnTiO3 particles, with dimensions after calcination at 700 °C for 5 h in the range of 68–81 Nm. Calcination temperature increased considerably the crystallite size of the nano perovskite ZnTiO3 from 68 to 81 nm This treatment led also to the creation of holes in the matrix of calcinated solids which increased the mobility of charge carriers (electrons) leading to a significant decrease in the decrease in the optical energy gap reaching to (2.7 to 2 )e.v.

Chemical sensing ability of aminated graphdiyne (GDY-NH2) toward highly toxic organic volatile pollutants

The detection of common environmental pollutants through chemical sensors has received significant interest from the scientific community. Acetamide (AM), benzamide (BM), thioacetamide (TAM), and thiobenzamide (TBM) are hazardous chemicals to humans and can cause many diseases including cancer, chronic liver damage, and acute skin irritations. Recently, functionalized 2D carbon-based materials have been used extensively as chemical sensors. Functionalization of these materials introduces adsorption sites which facilitates the interactions with the analytes. In this study, the sensing capability of the recently synthesized aminated graphdiyne material (GDY-NH2) is explored towards AM, BM, TAM, and TBM via density functional theory (DFT) calculations. The results revealed that GDY-NH2 forms stable complexes with the considered analytes. The interaction energies are −10.64, −11.92, −11.19, and −13.28 kcal/mol for AM@GDY-NH2, BM@GDY-NH2, TAM@GDY-NH2, and TBM@GDY-NH2, respectively. Quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analyses revealed that the interaction between GDY-NH2 and the analytes occurs mainly via weak non-covalent van der Waals forces. A decrease in the HOMO-LUMO energy gap after interaction corresponds to a change in conductivity of the material. Furthermore, to ensure that the analytes are properly released after the detection, the turnover time has been theoretically calculated.

Strong phonon mode induced by carbon vacancy accelerating hole transfer in SiC/MoS2 heterostructure

The van der Waals SiC/MoS2 heterostructure with a type-II band alignment is promising for potential applications in photocatalytic and optoelectronic devices. By performing time-dependent nonadiabatic molecular dynamics simulations, we study the dynamics of single sulfur and carbon vacancy-mediated of photoexcited hole transfer at the interface of SiC/MoS2. The results indicate that single C-vacancy in SiC atomic layer promotes interlayer hole transfer more sufficiently in a shorter timescale of 68 fs than those of S-vacancy and pristine heterostructures. This promotion is attributed to the decreased energy gap related to intralayer hole transfer in SiC layer, resulting from the split of acceptor state, the excitation of a stronger in-plane carbon atom vibration mode at 600 cm−1, and the enhancement of electron–phonon coupling. Meanwhile, electron-hole recombination is three orders of magnitude slower than hole transfer, ensuring an effective charge separation in SiC/MoS2 with C-vacancy. This work provides theoretical insights into the dynamics of photoexcitation hole transfer in MoS2/SiC heterostructure.