Visible Absorption Band Research Articles

Dual-wavelength UV-visible metalens for multispectral photoacoustic microscopy: A simulation study

Photoacoustic microscopy is advancing with research on utilizing ultraviolet and visible light. Dual-wavelength approaches are sought for observing DNA/RNA- and vascular-related disorders. However, the availability of high numerical aperture lenses covering both ultraviolet and visible wavelengths is severely limited due to challenges such as chromatic aberration in the optics. Herein, we present a groundbreaking proposal as a pioneering simulation study for incorporating multilayer metalenses into ultraviolet-visible photoacoustic microscopy. The proposed metalens has a thickness of 1.4 µm and high numerical aperture of 0.8. By arranging cylindrical hafnium oxide nanopillars, we design an achromatic transmissive lens for 266 and 532 nm wavelengths. The metalens achieves a diffraction-limited focal spot, surpassing commercially available objective lenses. Through three-dimensional photoacoustic simulation, we demonstrate high-resolution imaging with superior endogenous contrast of targets with ultraviolet and visible optical absorption bands. This metalens will open new possibilities for downsized multispectral photoacoustic microscopy in clinical and preclinical applications.

Experimental characterization of ZnO properties and the impact of doping and DFT methods

This study focuses on zinc oxide by both computational and experimental methods. Pure and In-doped ZnO thin films were produced by spray pyrolysis at 300∘C onto glass substrate. X-ray patterns reveal the polycrystalline structure according to wurtzite along the (002) direction recording a smaller grain size in nanometric scale. This aspect is confirmed by AFM scanned pictures. High transparency of thin film is observed in spite of the indium insertion into ZnO lattice which decreases it slightly. A wide bandgap exceeds 3[Formula: see text]eV of such as-grown films were recorded. Blue and orange emissions were detected as confirmed by photoluminescence analysis. Computational result analysis is used to demonstrate the ideal geometries in the ground states of pure and doped ZnO. The UV–visible absorption band shifts from 360[Formula: see text]nm to 448[Formula: see text]nm as a result of In-doping. The HUMO and LUMO diagrams demonstrate a drop in energy E as a result of doping, and the DOS profiles validate and confirm this detail. Also, the effect of indium on the linear and nonlinear optical parameters of zinc oxide was discussed.

A structural, morphological, optical and magnetic study of nickel-substituted zinc (Ni–Zn) ferrite nanoparticles synthesized via glycine assisted gel autocombustion synthesis route

The spinel NixZn(1-x)Fe2O4(x = 0.00, 0.25, 0.50)) ferrite nanoparticles were successfully synthesized by an innovative glycine assisted gel autocombustion synthesis route. The impact of substitution Ni2+cations on the structural, morphological, optical, and magnetic study of NixZn(1-x)Fe2O4nanostructures was studied. A single-phased cubic spinel type structure was confirmed by XRD with crystallite size ranging from 28 nm to 46 nm. The two absorption bands, ν1 and ν2 below 1000 frequency in FTIR spectra corresponding to the tetrahedral and octahedral sites respectively, demonstrated the signature of the spinel lattice of the prepared nanosamples. SEM micrographs revealed agglomerated hexagonal and nearly spherical nanoparticles of size less than 60 nm. TEM micrographs showed a cluster of single crystalline agglomerated nanoparticles and the average particle size estimated from TEM is in accordance with SEM results. SAED patterns confirmed the construct of spinel nanoferrite which proportionate with the XRD pattern. Furthermore, UV-DRS absorption spectroscopy was employed to investigate the optical characteristics of NixZn(1-x)Fe2O4 ferrite nanoparticles at room temperature. UV-DRS absorption spectra of all the samples displayed an exceptional visible light absorption band in the wavelength less than 600 nm. At room temperature M − H plots indicated that NixZn(1-x)Fe2O4 spinel ferrite exhibits paramagnetic (for x = 0%) and soft ferrimagnetic (for x = 25%, 50%) behaviour depending on the Ni2+ substitution ratio. Saturation magnetization and coercivity increase with increasing Ni2+ content. These results indicates that the synthesized Ni–Zn spinel ferrite nanoparticles could be used in photocatalytic and high-frequency applications with optimum Ni2+ substitution for Zn2+cations.

Fe-MFI zeolite-encapsulated copper oxide with excellent re-usability for efficient tetracycline degradation

Impregnation handlement can load highly dispersed CuO nanoparticles on the Fe-MFI zeolite and effectively enhances its catalytic activity in the tetracycline degradation reactions, but encounters serious re-usability problems. In this work, Fe-MFI zeolite-encapsulated copper oxide CuO@Fe-MFI was prepared via one-step hydrothermal synthesis and utilized as heterogeneous catalyst for the removal of tetracycline. The obtained 2CuO@1Fe-MFI zeolite presented a external surface area of 270 m2/g, which was almost 5.5 folds of 2CuO/1Fe-MFI zeolite obtained by impregnation handlement. In addition, there may be a near-neighbor effect between encapsulated CuO and framework iron evidenced by the shifts of UV–Vis absorption bands as well as binding energies for Fe 2p and Cu 2p. At pH = 7.0, 2CuO@1Fe-MFI zeolite attained the largest tetracycline removal rate of 99.6% within 20 min at experimental conditions: [TCE] = 50 mg/L, [Catalyst] = 0.5 g/L, [PMS] = 1.0 g/L, 323 K, and the biggest degradation rate constant of 2.42 min−1, which was almost 11.1 folds of that for 2CuO/1Fe-MFI zeolite. The large external surface area and near-neighbor effect together gave rise to the excellent tetracycline degradation performance for 2CuO@1Fe-MFI zeolite. On the same time, the obtained 2CuO@1Fe-MFI zeolite can be reused for more than five times. Quenching experiments and EPR characterizations demonstrated the reactive species for tetracycline removal over 2CuO@1Fe-MFI zeolite were •OH, SO4•−, •O2− and 1O2 species, and moreover 1O2 served as the major active species. Furthermore, possible tetracycline degradation pathways over 2CuO@1Fe-MFI zeolite were proposed.

Historically Inspired Strategy to Achieve Sustainable and Effective Coloration of Bioplastics

The use of historical organic pigments is an interesting strategy to provide color nuances to biopolymers while achieving good solid optical effects. In this work, aqueous extracts of logwood (LW) are tested as a natural source of color for the sustainable production of an organic purple pigment (LWP) taking advantage of the historical lake approach. Different amounts of LWP (0.01–2% wt) are used for the effective coloration of polycaprolactone (PCL), polybutylene succinate (PBS), and polylactide (PLA). The full characterization of LWP and LWP-treated biopolymer samples enables the spectral and color properties of the composites to be defined where the exceptional color efficiency of LWP is demonstrated by the very low amount (0.5% wt) necessary to reach the saturation. The evolution of spectra and color coordinates under accelerated aging conditions is monitored for LWP-polymer samples. A 10–12% decrease of the visible absorption band is detected after prolonged irradiation, resulting in a moderate color fading for PBS compared to PCL samples, while negligible changes are observed for PLA samples. The results demonstrate that LWP constitutes an efficient and sustainable source of color for the analyzed polymers without causing significant changes in the tensile and thermal properties of the polymeric matrix.

Synthesis of 3‐arylated chlorophyll‐a derivatives via Diels–Alder reaction and their atropisomerism

AbstractMethyl pyropheophorbides‐a possessing an o/m‐(methoxycarbonyl)phenyl group at the 3‐position were prepared by Diels–Alder reaction of 3‐(trans‐1,3‐butadienyl)chlorin with methyl propiolate and successive didehydrogenation of the resulting 1,4‐cyclohexadienes. The 3‐arylated chlorin bearing the sterically demanding o‐COOMe group as the major product was a 1:1 mixture of high‐performance liquid chromatography‐separable rotational isomers around the C3–C31 bond, while the minor product with the m‐COOMe was less sterically hindered to exhibit rapid atropisomerization at room temperature. The 3‐aryl group of the major product was nearly perpendicular to the chlorin π‐system and less conjugated with the chlorin moiety than that of the minor product wherein more π‐conjugation occurred to give slightly red‐shifted Qy bands. Although both the atropisomers of the o‐substitute in dichloromethane showed similar visible absorption bands and fluorescence emission data, their circular dichroism bands in the ultraviolet‐C light region were dependent on the stereochemistry.

Green synthesis of silver nanoparticles using hydroalcoholic root extract of Potentilla fulgens and evaluation of its cutaneous wound healing potential

The present study focuses on the green synthesis of silver nanoparticles (AgNPs) using hydro-alcoholic root extract of Potentilla fulgens and evaluation of its wound healing properties in the rat model. The dried roots of PF were refluxed in alcohol: water mixture (70:30) for 24 h and the extract were evaporated to dryness using a rotary evaporator. For the synthesis of AgNP-PF, different concentrations of the extract (1–5 mg) were allowed to react with different concentrations of silver nitrate (1–5 mM). The completion of the reaction was noted through color change from colorless to brown and this can be further confirmed using UV–visible spectroscopy. The optimized formulation was further characterized using DLS, TEM, EDX, FTIR, and XRD. The biosynthesized AgNP-PF were loaded into a topical carbopol gel and finally investigated for wound healing potential in experimental rats. Results revealed that the ratio of different concentrations of AgNO3 to plant extract significantly affected the particle size, shape, yield and stability of the AgNP-PF. A UV–visible absorption band of 410–440 nm indicated the synthesis of AgNP-PF. TEM data with a size range of 10–20 nm showed that the AgNP-PF were spherical in shape. FTIR revealed the presence of -OH group responsible for the reduction and stabilization, while XRD confirmed the crystallinity of the AgNP-PF. Topical AgNP-PF gel showed promising wound healing property with significant wound contraction in experimental rats. In conclusion, stable silver nanoparticles were successfully formulated by green synthesis and loaded efficiently for efficient wound healing.

Light and Solvent Effect on Isomerization and Excimer Formation of Pyrene—Schiff Base Conjugate Sensing Aromatic Analytes

AbstractPyrene is a fluorescent polycyclic aromatic compound and it will be fascinating whether its excimer complex can be used for sensing of aromatic analytes. So, (E)‐3,4,5‐tris(dodecyloxy)‐N'‐(pyren‐1‐ylmethylene) benzohydrazide (P@M) is synthesized. The E (trans)‐isomer of P@M exhibits bright fluorescence for excimer formation in non‐aromatic solvents for closeness of pyrene moieties of E‐P@M. Upon photo‐irradiation with λ = 254 nm E‐P@M changes to Z‐P@M (cis ‐isomer) at 10−4 M concentration in methyl cyclohexane (MCH) yielding diminished PL‐intensity. Interestingly, upon photo irradiation with λ = 365 nm, the Z‐isomer of P@M reverts to E‐isomer indicating that, E‐Z isomerization of P@M is reversible in nature. The UV–vis absorption band at 370 nm of E‐P@M in MCH at 10−4 M shifts to 344 nm for its Z‐isomer formation. The thick supramolecular aggregated morphology of E‐P@M changes to flowery needle like morphology after photo irradiation with λ = 254 nm. The fluorescent emission of E‐P@M in MCH is quickly quenched on addition of different aromatic analytes through both static and dynamic path way. In solid state E‐P@M also sense aromatic vapors efficiently via fluorescence quenching.

Chloroplast-inspired microenvironment engineering of inverse opal structured IO-TiO2/Chl/IL for highly efficient CO2 photolytic reduction to CH4

Low CO2 capture and sunlight utilization, rapid recombination of photocarriers restrict application of TiO2 photocatalyst in CO2 photoreduction. Herein, inverse opal structured IO-TiO2/Chl/IL with chloroplast-inspired microenvironment was constructed to achieve the synergistic effect of CO2 capture and light-reaction system for efficient photoreduction CO2 to CH4. Ionic liquid ([BMIM][BF4]) coated on Chl(Cu)/TiO2 surface through Ti-F bond resembled the CO2 capture function of stroma in chloroplast, while TiO2 combined with Chl(Cu) to mimic the light-reaction system of thylakoid in chloroplast, these two parts imitating chloroplast microenvironment. The photonic band tuning of IO-TiO2/Chl/IL to overlap Chl(Cu) visible absorption band, enhancing light utilization of IO-TiO2/Chl/IL by slow photon effect. [BMIM][BF4] and Chl(Cu) coordinated with TiO2 significantly promoted electron transfer ability, redox ability and photogenerated carriers separation of IO-TiO2/Chl/IL. IO-TiO2/Chl/IL exhibited excellent photocatalytic performance (44.9 μmol·g−1·h−1) with high CH4 selectivity (93%), providing a biomimetic chloroplast microenvironment strategy with high efficiency photocatalytic CO2 reduction.

A comparative analysis of UV–vis transitions in hetaryl and ferrocenyl thioketones

Electronic transitions in a series of symmetrical and nonsymmetrical hetaryl- and/or ferrocenyl-functionalized thioketones have been studied using quantum chemistry methods. An in-depth theoretical characterization was carried out for low-energy electronic transitions. The effects of hetaryl and ferrocenyl groups on the energy of these transitions were recognized and elucidated in terms of atomic and molecular orbital contributions involved in the transitions. A comparison was drawn between the low-energy transitions in the thioketones and in their carbonyl counterparts. The effect of solvents on the position of UV–vis absorption bands, in particular, on those originating in the low-energy transitions, is discussed. The theoretical calculations indicate that the introduction of ferrocenyl group into the hetaryl-functionalized thioketones changes the character of their first two electronic transitions from n → π* and π → π* into dominant d → π*. The most intense band of all studied thioketones appears in the near-UV region and undergoes a redshift upon solvation.

Phase behaviour and adsorption of deoxyribonucleic acid onto an azobenzene liquid crystalline ligand at the interfaces

Azobenzene liquid crystalline (ALC) ligand contains a cholesteryl group linked to an azobenzene moiety through a carbonyl dioxy spacer (C7) and terminated with an amine group as a polar head. The phase behaviour of the C7 ALC ligand at the air-water (A-W) interface is investigated employing surface manometry. The surface pressure-area per molecule isotherm shows that C7 ALC ligand exhibit two different phases following the phase sequence viz., liquid expanded (LE1 and LE2) and then collapse to three-dimensional crystallites. Further, our investigations under different pH conditions and in the presence of DNA reveal the following. Compared to the bulk, the acid dissociation constant (pKa) of an individual amine reduces to 5 at the interfaces. For pH (3.5) < pKa, the protonation of amine groups of C7 ALC ligand facilitates the condensation of the film and enhances the stability. For pH values > pKa, the phase behaviour of the ligand remains the same due to the partial dissociation of the amine groups. The presence of DNA in the sub-phase result in the expansion of isotherm to the higher area per molecule and the compressional modulus extracted reveals the phase sequence; liquid expanded, liquid condensed, followed by a collapse. Further, the kinetics of adsorption of DNA to the amine groups of the ligand is investigated, suggesting the interactions are influenced by surface pressure corresponding to different phases and pH of the sub-phase. Brewster angle microscope studies are carried out at different surface densities of the ligand as well as in the presence of DNA also supports this inference. Atomic force microscope is employed to acquire the surface topography and height profile of C7 ALC ligand (1 layer) after transferring on onto a silicon substrate using Langmuir Blodgett deposition. The difference in the surface topography and thickness of the film indicates the adsorption of DNA onto the amine groups of the ligand. The characteristic UV–visible absorption bands of the ligand films (10 layers) at the air-solid interface are tracked and the hypsochromic shift of these bands is also attributed to these DNA interactions.

Atomically Precise Ni Nanoclusters for Improving Hydrogen Evolution Reaction Performance

The generation of green hydrogen via electrocatalytic water splitting is an emerging strategy in the prospect of developing future energy devices. Herein, we designed water-soluble atomically precise Ni nanoclusters (NCs) on MoSe2 nanosheets (NSs) to enhance the hydrogen evolution reaction (HER) performance. The strong UV–vis absorption band and matrix-assisted laser deposition ionization (MALDI) time-of-flight mass spectra confirm the formation of Ni7 NCs. The energy-dispersive X-ray spectroscopy mapping confirms the homogeneous distribution of Ni, Mo, and Se throughout the surface of the ultrathin NS. X-ray photoelectron spectroscopy study reveals the strong interfacial interaction between Ni NCs and MoSe2 in the nanocomposite by substantial electron density transferring from Ni NCs to the MoSe2 NSs. It is seen that the 5 wt % Ni/MoSe2 composite structure exhibits the most notable HER efficiency with an overpotential of 170 mV vs reversible hydrogen electrode @ 10 mA/cm2 which is significantly lower than that of bare MoSe2 NSs (350 mV). The significantly lower Tafel slope of the Ni/MoSe2 nanocomposite indicates that the HER kinetics of MoSe2 is accelerated in the presence of Ni NCs. The charge-transfer resistance of the nanocomposite is significantly low compared to pristine MoSe2, confirming the enhanced interfacial charge transfer. This work opens up further opportunities to design efficient and low-cost electrocatalysts for improving the HER performance by incorporating the advantages of both non-precious atomically precise metal NCs and transition-metal dichalcogenides in one system.

Synthesis and Characterization of Novel Triphenylamine-Containing Electrochromic Polyimides with Benzimidazole Substituents.

Two novel electrochromic aromatic polyimides (named as TPA-BIA-PI and TPA-BIB-PI, respectively) with pendent benzimidazole group were synthesized from 1,2-Diphenyl-N,N'-di-4-aminophenyl-5-amino-benzimidazole and 4-Amino-4'-aminophenyl-4″-1-phenyl-benzimidazolyl-phenyl-aniline with 4,4'-(hexafluoroisopropane) phthalic anhydride (6FDA) via two-step polymerization process, respectively. Then, polyimide films were prepared on ITO-conductive glass by electrostatic spraying, and their electrochromic properties were studied. The results showed that due to the π-π* transitions, the maximum UV-Vis absorption bands of TPA-BIA-PI and TPA-BIB-PI films were located at about 314 nm and 346 nm, respectively. A pair of reversible redox peaks of TPA-BIA-PI and TPA-BIB-PI films that were associated with noticeable color changed from original yellow to dark blue and green were observed in the cyclic voltammetry (CV) test. With increasing voltage, new absorption peaks of TPA-BIA-PI and TPA-BIB-PI films emerged at 755 nm and 762 nm, respectively. The switching/bleaching times of TPA-BIA-PI and TPA-BIB-PI films were 13 s/16 s and 13.9 s/9.5 s, respectively, showing that these polyimides can be used as novel electrochromic materials.

Green preparation of Cu nanoparticles of the avocado seed extract as an adsorbent surface

The pollution of water with heavy metals is one of the most important health and economic problems globally. Therefore, the green preparation of Cu2+ nanoparticles from avocado seed extract can provide a method of adsorbing these heavy metals at the lowest cost and easily and safely. In addition, our research was motivated by the ability of these nanoparticles to inhibit some types of bacteria. In this study, seed extract was prepared and then reacted with copper2+ solution to obtain nanoparticles using the biosynthesis method. These nanoparticles were diagnosed by means of the FESEM, XRD, AFM, UV–vis, and FTIR techniques. FESEM images showed Cu peaks at about 1 and 9 keV of a crystal nature. The crystal size was 62.25 nm, according to the XRD results. The AFM images showed that the spherical particles had an average height of 21.289 nm. AUV–vis absorption band was observed at 530 nm, indicating copper2+ nanoparticles. The FTIR spectra showed the interaction of the seed extract with Cu2+ ions via a reduction reaction. The synthesized copper2+ nanoparticles demonstrated the inhibition of bacterial activity when used against E. coli and Staphylococcus aureus. Copper nanoparticles were used as a surface adsorbent for cadmium2+ ions of contaminated water, and the nanoparticles showed an active role.

Self-aggregation of 32-substituted bacteriochlorophyll-d analogs in aqueous micelle

As naturally occurring bacteriochlorophyll-[Formula: see text] models, zinc methyl (31R)-bacteriopheophorbides-[Formula: see text] possessing ethyl, vinyl, and ethynyl groups at the 32-position were prepared by chemically modifying chlorophyll-[Formula: see text]. The synthetic molecules self-aggregated in an aqueous Triton X-100 micelle solution similarly as in the major light-harvesting antenna of photosynthetic green bacteria to give supramolecularly ordered large oligomers with red-shifted and broadened visible absorption bands, compared with the monomeric bands. The sequential hydrogenation of the 32-ethynyl to ethyl group via the vinyl group gradually suppressed the chlorosomal self-aggregation ability. The successive elongation of the 31-alkyl chain from a methyl to propyl group via an ethyl group also diminished the [Formula: see text]-aggregation ability. These decreases in the self-aggregation were ascribable to the steric enhancement of the 32-substituents near the 31-hydroxy group requisite for the [Formula: see text]-aggregation.

Increasing the Photocatalytic Activity of BiVO4 by Naked Co(OH)2 Nanoparticle Cocatalysts

Bismuth vanadate (BiVO4 or BVO) is one of the most studied photocatalysts for water oxidation because of its excellent visible light absorption and appropriate band energy positions. However, BVO presents a low charge mobility and a high electron–hole recombination rate. To address these fundamental limitations, this study proposes the coating of previously synthesized phase-pure monoclinic scheelite BVO with different amounts of naked cobalt (further oxidized to cobalt hydroxide) nanoparticles (NPs) via a modified magnetron sputtering deposition. The resulting BVO/Co photocatalysts were investigated for methylene blue (MB) photodegradation, photocatalytic oxygen evolution, and photoelectrochemical (PEC) water oxidation. In the MB photodegradation tests, the BVO/Co sample prepared with a deposition time of 5 min (BVO/Co(5 min)) presented the highest photoactivity (k = 0.06 min−1) compared with the other sputtering investigated times (k = 0.01–0.02 min−1), as well as the pristine BVO sample (k = 0.04 min−1). A similar trend was evidenced for the PEC water oxidation, where a photocurrent density of 23 µA.cm−2 at 1.23 V (vs. RHE) was observed for the BVO/Co(5 min) sample, a value 4.6 times higher compared with pristine BVO. Finally, the BVO/Co(5 min) presented an O2 evolution more than two times higher than that of the pristine BVO. The increased photocatalytic performance was ascribed to increased visible-light absorption, lesser electron–hole recombination, and enhanced charge transfer at the liquid/solid interface. The deposition of Co(OH)2 NPs via magnetron sputtering can be considered an effective strategy to improve the photocatalytic performance of BVO for different target catalytic reactions, including oxygen evolution, water oxidation, and pollutant photodegradation.

Computational Study of Some 4’-Aryl-1,2,4-triazol-1-ium-4-R2-phenacylid Derivatives in Vacuum and Dimethylformamide

Four carbanion monosubstituted 4’-aryl-1,2,4-triazol-1-ium-4-R2-phenacylids, used as precursors in obtaining new heterocyclic compounds, and their corresponding derivatives belonging to the C2v point group of symmetry were studied by computational means in dimethylformamide (DMF) solutions compared with their isolated state. The changes in the computed parameters induced by the solvent compared with those of the isolated molecules were analyzed in this paper. The charge distribution and the molecular energies in the HOMO and LUMO, the electronic states responsible for the visible absorption band of 4’-aryl-1,2,4-triazol-1-ium-4-R2-phenacylids, in their isolated state and in solutions achieved in DMF were computed and compared with the visible electronic absorption spectra. The molecular descriptors of the studied compounds were computed, and the higher reactivity of the carbanion monosubstituted 4’-aryl-1,2,4-triazol-1-ium-4-R2-phenacylids compared with symmetric derivatives was established. The obtained results can help researchers to obtain new heterocycles with applications in the drug industry.

Acidic Devinylation of Nickel Chlorophyll Derivatives

Abstract A nickel(II) complex of methyl pyropheophorbide-a bearing a vinyl group at the 3-position was treated with methanesulfonic acid in refluxing benzene to give smoothly the corresponding 3-devinylated product. The 7- and 8-vinyl groups in the related chlorophyll-a/b derivatives were readily removed under the same conditions, while the 12-vinyl group neighboring the electron-withdrawing 13-keto carbonyl moiety was hardly defunctionalized. The devinylations blue-shifted all the visible absorption bands in dichloromethane. The deethylation at the 3-position bathochromically moved the redmost Qy maximum, and the dealkylations at the 7-, 8-, and 12-positions hypsochromically moved the Qy(0,0) maxima, which were reproduced by time-dependent density functional theory calculation. Since no vinyl periphery in the free base counterparts was removed under the mild conditions, nickel 3-unsubstituted deoxophylloerythroporphyrin in geological samples would be produced via the nickel metalation of chlorophylls-a/b/c from ancient phototrophs or their derivatives followed by the acidic 3-devinylation.

Vinyl substituted triphenylamine based turn-off fluorescent probe for selective and sensitive detection of mercury (II) in water and live cells

Here, we report vinyl substituted triphenylamine (TPA-alk) fluorescent probe for the rapid and efficient detection of mercury ion (Hg2+) in water and biological environment. TPA-alk detects Hg2+ selectively over a wide range of competitive metal ions with a blue shift of 43 nm in the UV absorbance spectrum. The detection limit is found to be 0.146 µM (29.2 ppb) with high selectivity over a wide range of competitive metal ions. DFT study explains the blue shift in the UV–vis absorption band of the optical probe upon the addition of Hg2+. Cell viability assay illustrates that the probe is biocompatible and it has low cytotoxicity even at its higher concentration. Cell imaging studies demonstrate the efficiency of the TPA-alk probe for the micromolar detection of mercury (II) in live BMG1 cells.

2D solar cell with record high power conversion efficiency based on low-symmetry IV-V2 bilayer heterostructure

The structural, electronic, and optical properties of two-dimensional (2D) low-symmetry orthorhombic IV-V2 bilayer heterostructures (HSs) were investigated using first-principles calculations. Our data show that all the constructed bilayer HSs (SiAs2/GeAs2, SiAs2/SiP2 and SiP2/GeAs2) are stabilized by van der Waals interaction. The IV-V2 bilayer HSs exhibit strong visible light absorption and type-II band alignments, which are beneficial for the effective separation of photo-generated electron–hole pairs in solar cells. Notably, the 2D SiAs2/GeAs2 HS-based solar cell exhibits a record-high power conversion efficiency (23.98%) higher than those of previously-reported 2D HSs-based solar cells obtained by high-throughput computational screening, owing to its small conduction band offset (0.2 eV) and suitable bandgap (1.49 eV). Our results provide insights into the structures and electronic and photovoltaic properties of the IV-V2 bilayer HSs and may be useful for related 2D solar cell applications.