Visible Absorption Peak Research Articles

Colorimetric determination of hydrogen peroxide based on the robust peroxidase-like activities of flower-like YVO4 microstructures

In this study, yttrium vanadate (YVO4) flower-like microstructures assembled by quadrangular prisms (YVFPs) were prepared through a facile hydrothermal method, which were developed as a novel nanoenzyme to determine hydrogen peroxide (H2O2) for the first time. In the presence of H2O2, YVFPs exhibited a highly efficient peroxidase-like activity in catalyzing the oxidation the typical peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB). Colorless TMB would be turned into oxidized TMB with a visible blue color and UV–visible absorption peak at 652 nm. The catalytic reaction mechanism was proposed according to the kinetics experiments and active species capture tests, indicating that·O2- radicals played a key role in the peroxidase mimetic reaction. Besides, YVFPs showed a superior affinity to TMB compared with the natural enzyme horse radish peroxidase with a lower Km value. Taking advantage of the strong peroxidase-like activity of YVFPs, a simple, rapid, sensitive, and visual platform was successfully established for colorimetric detection of H2O2. The YVFPs-based colorimetric system possessed good selectivity, stability and reusability with a wider linear range from 0.5 μM to 50 μM and a lower detection limit as low as 0.126 μM towards H2O2 determination. Moreover, the feasibility of this convenient method was further validated by assaying residual H2O2 in milk and contact lens solutions. This work not only provides a novel artificial biomimetic catalyst with efficient catalytic abilities, but also opens up a new potential application field of YVO4 materials in clinical diagnosis, food safety and biomedicine.

Electronic, magnetism and optical properties of transition metals adsorbed puckered arsenene

The optical, magnetism and electronic characteristics of 16 types of transition metals adsorbed puckered arsenene (TM-arsenene) were investigated by the first principles calculations. The results illustrate that adsorption energy of all TM-arsenene systems is negative, indicating that all TM-arsenene systems possess good stability, whereas the most stable position of TM-arsenene systems is distinct. The observed Mg-, Ni-, Pb-, Pd-, Pt- and Zn-arsenene systems remain nonmagnetic semiconductors, while the Al-, Cu-, Li-, and Na-arsenene systems exhibit the metal behavior. Interestingly, the Co- and V-arsenene systems appear magnetic metal behavior, whereas the Au-, Cr-, Mn-, and Ti-arsenene systems emerge magnetic semiconductor . Moreover, the charge transfer occurs between the puckered arsenene and TM. The work function of the Al-, Au-, Cr-, Cu-, Li-, Mg-, Mn-, Na-, Ni-, Pb-, Ti- and V-arsenene systems is lower than that of pristine puckered arsenene. In particular, the work function of Ti-arsenene systems is as low as 3.26 eV, which is 24.2% lower than that of pristine puckered arsenene. Importantly, the absorption spectrum of puckered arsenene system has two puissant visible absorption peaks which located at 432.3 nm and 645.8 nm, and the absorption intensity in the visible light range is enhanced after the adsorption of transition metal. Therefore, these results reveal that TM-arsenene systems can be effectively used to design for field emission, spin electronics and photocatalysis nanodevices . • The TM-arsenene systems possess good stability, whereas the most stable position of TM-arsenene systems is distinct. • The Co- and V-arsenene systems appear magnetic metal behavior, whereas the Au-, Cr-, Mn-, and Ti-arsenene systems emerge magnetic semiconductor. • The work function of the Al-, Au-, Cr-, Cu-, Li-, Mg-, Mn-, Na-, Ni-, Pb-, Ti- and V-arsenene systems is lower than that of pristine puckered arsenene. • The absorption spectrum of puckered arsenene system has two puissant visible absorption peaks, which is enhanced after the adsorption of transition metal.

Daylight-driven photosensitive antibacterial melt-blown membranes for medical use

The application of long-lasting antibacterial microorganism materials has presented enormous challenges, especially when infection by pathogenic bacteria triggers global public health and safety issues. In this study, PPCL@PDA-TAEG melt-blown membranes with rechargeable, storable, and antibacterial property are constructed by grafting bisbenzophenone-structured 4,4, -terephthaloyl diphthalic anhydride photosensitizer and epigallocatechin gallate antibacterial agent on the PPCL melt-blown membranes. Result shows that after chemical grafting, the synergistic effects of rechargeable and antibacterial performance on the melt-blown membrane are achieved under ordinary daylight irradiation. Moreover, the resultant melt-blown membranes show enhanced chemical stability, and the UV–vis absorption peak intensity remains above 80% after 1 month of storage under dark conditions. The sterilization rate of Staphylococcus aureus and Escherichia coli can reach 99.9% and 95%, respectively. The air permeability and moisture permeability of PPCL@PDA-TAEG melt-blown membranes are 22.3% and 43.7% higher, respectively, than those of PPCL melt-blown membranes. This facile and low-cost method for preparing PPCL@PDA-TAEG melt-blown membranes provides a new strategic direction for designing biomedical medical materials with long-lasting antibacterial efficacy.

UV-irradiated hydrothermal synthesis of reduced graphene quantum dots for electrochemical applications

This paper reports the structural and electrochemical properties of graphene quantum dots (GQDs) and reduced graphene quantum dots (rGQDs). The synthesis of GQDs by glucose and obtained the rGQDs by 365 nm UV-source irradiated glucose precursor used in microwave assisted hydrothermal reaction. The modification in chemical interaction was studied by Fourier Transforms Infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) confirms the structural change due to UV-irradiation effects. The Raman spectra confirms change in the intensity ratio of G and D band, and UV–Visible absorption peak of GQDs observed at 243, 245, 248 and 262 nm for 24, 48, and 72 h UV-irradiated modified rGQDs. Transmission electron microscopy (TEM) images shows reduced the size with increasing UV-irradiation time which confirms the rGQDs. Atomic force microscopy (AFM) employed to know topological surface study. The electrochemical performance of Cyclic Voltammetry from a typical rectangular shape of the integral area suggesting it is exhibits strong electrochemical activity and specific capacity behaviour by redox reaction at different scan rate from 100 to 500 mV/s for GQDs and rGQDs. The current-voltage plot exhibited a gradual increase in current with applied voltage as well as irradiation at different hours.

Electronic and optical properties of Te-doped GaN monolayer before and after adsorption of dimethylmercury - DFT+U/TDDFT & DFT-D2 methods

Electronic, magnetic and optical properties of Te doped g-GaN monolayer, before and after adsorbing the dimethylmercury molecule, (CH3)2Hg, were studied by DFT approach. Our calculations show that, unlike pure g-GaN monolayer, the g-GaN + Te is n-type, in which the previous gap (2.16 eV) changes to the spin gaps of 1.53 and 1.65 eV. This monolayer is a III-V ferromagnetic, that it can be used in the spin field effect transistors (FET). We showed that the adsorption of (CH3)2Hg by g-GaN + Te monolayer is possible. The g-GaN + Te+(CH3)2Hg layer is n-type, and its band gap is 2.23 eV. Both g-GaN + Te and g-GaN + Te+(CH3)2Hg layers, beside the g-GaN monolayer, can be used in the GaN-based p-n junction betavoltaic cells and GaN p-i-n diodes. Also, in the g-GaN + Te+(CH3)2Hg case there are two terahertz gaps with values of 0.02 and 0.11 eV. After calculating the optical properties of both g-GaN + Te and g-GaN + Te+(CH3)2Hg layers by TDDFT, we found that the refractive index has values of 1.15 and 1.25, respectively. Also, the g-GaN + Te and g-GaN + Te+(CH3)2Hg layers, each have one visible absorption peak at 2.89 and 1.83 eV, respectively.

Formation and Evaluation of Au/ZnO Particles by a Spray Pyrolysis Method

ZnO/Au is expected to exhibit catalytic properties by absorbing ultraviolet and visible light because ZnO and Au nanoparticles can absorb ultraviolet and visible light, respectively. Doping studies on Au nanoparticles on ZnO (ZnO/Au) have been conducted to expand the absorption wavelength range. This study generates ZnO/Au particles by an ultrasonic spray pyrolysis method (USP). To prevent particle aggregation, Triton X-100, a non-ionic surfactant, is added, and its effects are examined. The generated ZnO/Au particles are characterized using different methods. SEM reveals the particle size is several micrometers, while XRD analysis indicates that ZnO and a metallic Au crystalline are present. The TEM images of the particles show that the Au crystals are well dispersed in the inner and outer portions of ZnO. UV-Vis spectroscopy confirms that the smaller the Au particle size, the higher the visible absorption peak near 400 nm. Adding Triton X-100 shifts the absorption peak toward the longer wavelength side but improves the aggregation of Au particles.

Pure-Blue Fluorescence Molecule for Nondoped Electroluminescence with External Quantum Efficiency Approaching 13%

A pure-blue light-emitting material is one of the key components in the preparation of organic light-emitting diode (OLED) displays. Although high-efficiency blue OLEDs have been realized in therma...

Cascade synthesis and optoelectronic applications of intermediate bandgap Cu3VSe4 nanosheets

Two-dimensional (2D) ternary materials recently generated interest in optoelectronics and energy-related applications, alongside their binary counterparts. To date, only a few naturally occurring layered 2D ternary materials have been explored. The plethora of benefits owed to reduced dimensionality prompted exploration of expanding non-layered ternary chalcogenides into the 2D realm. This work presents a templating method that uses 2D transition metal dichalcogenides as initiators to be converted into the corresponding ternary chalcogenide upon addition of copper, via a solution-phase synthesis, conducted in high boiling point solvents. The process starts with preparation of VSe2 nanosheets, which are next converted into Cu3VSe4 sulvanite nanosheets (NSs) which retain the 2D geometry while presenting an X-ray diffraction pattern identical with the one for the bulk Cu3VSe4. Both the scanning electron microscopy and transmission microscopy electron microscopy show the presence of quasi-2D morphology. Recent studies of the sulfur-containing sulvanite Cu3VS4 highlight the presence of an intermediate bandgap, associated with enhanced photovoltaic (PV) performance. The Cu3VSe4 nanosheets reported herein exhibit multiple UV–Vis absorption peaks, related to the intermediate bandgaps similar to Cu3VS4 and Cu3VSe4 nanocrystals. To test the potential of Cu3VSe4 NSs as an absorber for solar photovoltaic devices, Cu3VSe4 NSs thin-films deposited on FTO were subjected to photoelectrochemical testing, showing p-type behavior and stable photocurrents of up to ~ 0.036 mA/cm2. The photocurrent shows a ninefold increase in comparison to reported performance of Cu3VSe4 nanocrystals. This proves that quasi-2D sulvanite nanosheets are amenable to thin-film deposition and could show superior PV performance in comparison to nanocrystal thin-films. The obtained electrical impedance spectroscopy signal of the Cu3VSe4 NSs-FTO based electrochemical cell fits an equivalent circuit with the circuit elements of solution resistance (Rs), charge-transfer resistance (Rct), double-layer capacitance (Cdl), and Warburg impedance (W). The estimated charge transfer resistance value of 300 Ω cm2 obtained from the Nyquist plot provides an insight into the rate of charge transfer on the electrode/electrolyte interface.

Synergistic effects of combinatorial chitosan and polyphenol biomolecules on enhanced antibacterial activity of biofunctionalized silver nanoparticles

The present study reports the synergistic antibacterial activity of biosynthesized silver nanoparticles (AgNPs) with the aid of a combination of chitosan and seaweed-derived polyphenols as a green synthetic route. Under optimum synthesis conditions, the rapid color change from yellowish to dark brown and UV–visible absorption peak at 425 confirmed the initial formation of AgNPs. DLS, TEM, XRD, and EDX analyses revealed the spherical shape of pure biogenic AgNPs with a mean diameter size of 12 nm ± 1.5 nm, and a face-centered cubic crystal structure, respectively. FTIR and TGA results indicated the significant contribution of chitosan and polyphenol components into silver ions bioreduction and thermal stability of freshly formed AgNPs. Long-term colloidal stability of AgNPs was obtained after 6-month storage at room temperature. The bio-prepared AgNPs possessed a negative surface charge with a zeta potential value of − 27 mV. In contrast to naked chemical silver nanoparticles, the green Ag nanosamples demonstrated the distinct synergistic antibacterial in vitro toward all selected human pathogens presumably due to the presence of high content of biomolecules on their surface. The results show that synergy between chitosan and polyphenol results in the enhancement of bactericidal properties of biogenic AgNPs. We also highlighted the underlying mechanism involved in AgNPs formation based on nucleophile–electrophile interaction.

Synthesis and characterization of ultrasmall Cu2O nanoparticles on silica nanoparticles surface

The hybrid structure of SiO2-Cu2O nanocomposite was prepared by synthesizing ultrasmall cuprous oxide nanoparticles on the surface of silica nanoparticles. The spherical shaped silica nanoparticles were acted as seeds for the continuous deposition of Cu2O NPs on the surface of SiO2. First, the well-known ammonia catalyzed Stober method was utilized for the synthesis of SiO2 NPs. Then the SiO2-Cu2O nanocomposite was synthesized by reacting SiO2 NPs with copper sulfate solution in the presence of NH4OH and hydrazine monohydrate. The structural, morphological, and elemental analyses have been carried out using XRD, FTIR, FESEM, UV–Vis Spectrometer, and XPS. The UV–Visible absorption peak was observed around 465 nm. XRD data revealed the formation of the FCC phase of Cu2O NPs on silica nanoparticles. The binding energies correspond to Cu2p3/2 and Cu2p1/2 were in good agreement with the reported data.

Fabrication of nano-bismuth colloids in deionized water using an electrical discharge machine

Bismuth (Bi) is used to treat certain diseases, however the Bi powder or colloids used in medicine must be nonpolluting and safe. The use of electrical discharge machines (EDMs) to produce nano-Bi powder is a green process. A nonpolluting and safe nano-Bi colloid can be produced swiftly and easily in deionized water using the electrical spark discharge method, adjusting the discharge pulse width Ton, Toff and the discharge current IP of the EDM. Transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy, the Zetasizer technique, ultraviolet–visible spectroscopy (UV–Vis), and other techniques were used to analyze a nano-Bi colloid prepared under various discharge parameters to optimize the preparation of Bi nanoparticles (Bi-NPs) using EDMs. The results of this study indicated that Bi-NP colloids were successfully prepared using EDM. TEM images revealed that the NPs were smaller than 50 nm with only the Bi element in the colloid. Furthermore, the zeta potential of the nano-Bi colloid exceeded 30 mV, which indicated that the suspension of the colloid was excellent. A UV–Vis absorption peak was observed at approximately 234–237 nm.

Exploring multidimensional applications of natural bioactive molecule isodihydrocadambine-4-oxide: DFT approach

The calculations of spectroscopic characteristics, non-linear optical properties, HOMO-LUMO energy band gap, molecular electrostatic potential surface, chemical reactivity descriptors and thermodynamic parameters of Isodihydrocadambine-4-Oxide using density functional theory as well as its protein-ligand interactions using molecular docking approach have been discussed in the present study. The theoretical 1H and 13C NMR chemical shifts have been found in good conformity with the corresponding experimental values. The maximum peak in IR spectrum has been calculated to be occurred at 1048 cm−1 vibrational frequency. The UV–visible absorption peak has been observed to be occurred at 712 nm resulting from electronic transitions HOMO + 1 → LUMO + 6, HOMO + 1 → LUMO + 8. The calculated value of dipole moment of the title compound is found to be 3.14 Debye which is 2.29 times greater than that of urea. The first order hyper polarizability has been calculated to be 6405.41 × 10−33esu which is 18.66 times greater than that of Urea indicates that it is non-linear optically active. The HOMO- LUMO energy band gap has been calculated to be practically small ≈0.12 a.u. and MESP surface to be suited for the recognition of receptor molecule required for the drug activity. The zero-point energy of this molecule has been obtained to be 387.75Kcal/Mol. The binding with 1HSG, 1GCN, 2NMO and 3I40 protein receptors of this bio molecule has been obtained through the virtual screening to project the title molecule to be multifunctional natural drug agent. It is, therefore, concluded that the said bioactive natural molecule may be explored as a multifunctional material for variety of applications and the present study may form a theoretical basis for the study of biologically active naturally occurring macromolecules.

Density functional theory calculations of spectral, NLO, reactivity, NBO properties and docking study of Vincosamide-N-Oxide active against lung cancer cell lines H1299

The present paper reports the density functional theory calculations of IR, NMR and UV–Visible, nonlinear optical (NLO) properties, highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy band gap as measure of reactivity, molecular electrostatic potential surface (MESP), thermodynamic parameters and natural bond orbital (NBO) properties of the title molecule as well as its possible protein–ligand interactions using molecular docking approach. Theoretical NMR chemical shifts (1H and 13C) as well as the characteristics regions in IR active vibrations are in fair agreement with their experimental counterparts. UV–Visible absorption peak resulting from electronic transitions HOMO-5 → LUMO, HOMO-4 → LUMO observed at 324.27 nm is also in good agreement with its experimental value. The first order hyper polarizability of this molecule has been calculated to be 3182.124 × 10–33 esu which is 9.26 times to that of Urea indicating its suitability for nonlinear optical applications. The HOMO–LUMO energy band gap has been found to be reasonably small ≈ − 0.14596 a.u and MESP surface to be a chemically reactive site suited for drug activity. It is observed that the C11-atom of ring is more prone to the electrophilic attack. NBO analysis reveals that donor (O23) π → π *(C18-N22) acceptor interaction corresponds to the highest second order perturbation energy E(2) = 29.12 kcal/mole associated with electron delocalization. This biomolecule binds with 1GCN, 1HSG, 1X2J, 2NMO, 3I40 and 5C5S protein receptors showing that this molecule possesses multifunctional biological activity. Nonlinear optical and multifunctional biological activity reported in our study may be exploited for the novel applications of the heading molecule.

Incorporation of silver ion on structural and optical characteristics of CeO2 nanoparticles: White LED applications

CeO2 and Ag incorporated CeO2 nanoparticles were prepared by the chemical co-precipitation method. The samples were analyzed by XRD, HRTEM, FESEM, EDX, UV–vis, Photoluminescence, FTIR, and Photocatalytic studies. XRD results showed that Ag incorporation did not alter the structure and phase of pure CeO2 lattice. Crystallite size was reduced due to Ag ions substitution and these are good agreement with HR-TEM results. Particle size was measured as ∼5−7 nm. EDX and FTIR spectra confirmed the existence of elements as per the targeted stoichiometry. FESEM showed the surface morphology of samples and they possessed a spherical structure with surface smoothening as a function of Ag initial addition. UV–vis absorption peak intensity was increased for every increase of Ag concentration. Better optical transmittance was received for the Ag composition of 6 %. Blueshift was taken place for the incorporation of Ag ions in CeO2 host and the reason was discussed in terms of size effect and electron transition from band to band. Two peaks were received from Photoluminescence study that is one weak emission from the UV region strong emission from the red region. Red peaks were shifted to a higher wavelength side against the addition of Ag. A fast degradation response was observed for Ag-doped CeO2 nanoparticles through photocatalytic study.

Mannoside-Modified Branched Gold Nanoparticles for Photothermal Therapy to MDA-MB-231 Cells.

Recently, gold nanoparticles (Au NPs) have been used to study the treatment of malignant tumors due to their higher biocompatibility and lesser toxicity. In addition, they can be excited through a specific wavelength to produce oscillating plasmonic photothermal therapy (PPTT) on the basis of the localized surface plasma resonance (LSPR) effect. Au NPs can be heated to kill cancer cells in specific parts of the body in a noninvasive manner. In this study, branched gold nanoparticles (BAu NPs) were prepared by mixing HAuCl4 in a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution in a molar ratio of 1:2000. The UV–vis absorption peak was detected in the range of 700–1000 nm. Subsequently, BAu NPs were chemically linked to a thiol-modified mannoside molecule via a stable sulfur–Au covalent bond (Man@BAu NPs). Due to the presence of abundant mannose receptors on human-breast-cancer cells, MDA-MB-231, Man@BAu NPs were found to be abundant inside cancer cells. After irradiating the Man@BAu NP-laden MDA-MB231 switch with a near-infrared (NIR) laser at 808 nm wavelength, the photothermal-conversion effect raised the surface temperature of Man@BAu NPs, thus inducing cell death. Our experiment results demonstrated the advantages of applying Man@BAu NPs in inducing cell death in MDA-MB-231.

A trilayered organic-inorganic hybrid perovskite material with low bandgap

A lead(II) organic-inorganic hybrid perovskite material [(TMA)2(MA)2Pb3I10] (1) has been synthesized by reactions of 2-thienylmethylamine (TMA) and methylamine (MA) with PbI2 in HI/H3PO2 aqueous solution. The crystallographic diffraction indicated the inorganic moiety in 1 is a trilayered perovskite structure constructed with [PbI6] octahedra, and the two organic amines are located between the inorganic layers, or embedded in the octahedral cavity of inorganic layers. The solid UV–vis absorption peak of compound 1 is located at 600 nm, and the bandgap calculated by DFT is 1.60 eV, both indicating it is a semiconductor and has potential application in organic-inorganic hybrid solar cell.

Electro-Optical Properties of Monolayer and Bilayer Pentagonal BN: First Principles Study.

Two-dimensional hexagonal boron nitride (hBN) is an insulator with polar covalent B-N bonds. Monolayer and bilayer pentagonal BN emerge as an optoelectronic material, which can be used in photo-based devices such as photodetectors and photocatalysis. Herein, we implement spin polarized electron density calculations to extract electronic/optical properties of mono- and bilayer pentagonal BN structures, labeled as , , and . Unlike the insulating hBN, the pentagonal BN exhibits metallic or semiconducting behavior, depending on the detailed pentagonal structures. The origin of the metallicity is attributed to the delocalized boron (B) 2p electrons, which has been verified by electron localized function and electronic band structure as well as density of states. Interestingly, all 3D networks of different bilayer pentagonal BN are dynamically stable unlike 2D structures, whose monolayer is unstable. These 3D materials retain their metallic and semiconductor nature. Our findings of the optical properties indicate that pentagonal BN has a visible absorption peak that is suitable for photovoltaic application. Metallic behavior of pentagonal BN has a particular potential for thin-film based devices and nanomaterial engineering.

Adsorption of gas molecules on group III atoms adsorbed g-C3N4: A first-principles study

The first-principles based on density functional theory are used to calculate the adsorption of gas (CO, NO) molecules on group III (B, Al, Ga, In) atoms adsorbed g-C3N4. It is revealed that the B, Al, Ga, and In-g-C3N4 adsorption systems exhibit magnetic semiconducting behavior, while pristine g-C3N4 is a non-magnetic semiconductor. Next, adsorption of the gas molecules on g-C3N4 was investigated. The results show that the charge transfer amount of NO/g-C3N4 is larger than that of CO/g-C3N4. The CO/g-C3N4 system exhibits non-magnetic semiconductor. However, the NO/g-C3N4 system exhibits magnetic semiconductor behavior. Lastly, adsorption of the gas molecules on III-g-C3N4 was also investigated. It is revealed that all gas molecule adsorbed III-g-C3N4 exhibit a magnetic semiconductor. Interestingly, all the gas/III-g-C3N4, except NO/Al-g-C3N4, NO/Ga-g-C3N4, and NO/In-g-C3N4 systems, can promote the charge (electron) transfer from gas molecule to the III-g-C3N4 system, which is conducive to gas sensing. The absorption spectrums of gas molecules adsorbed III-g-C3N4 systems have many strong visible light absorption peaks. Especially, the absorption peak intensity of NO adsorbed In-g-C3N4 system at 436 nm reached 1.19 × 105 cm−1. Thus, above results indicate that the gas molecules adsorption systems will facilitate design of spintronics, gas sensing and high efficiency photocatalytic device.

Improved photocurrent generation of three hybrid films made of [BW11Co(H2O)O39]7- and hemicyanines with alkyl linkers of varying length

A series of electrostatically self-assembled films consisting of a Keggin-type cobalt-substituted tungstoborate anion [BW11Co(H2O)O39]7- (BW11Co) and three hemicyanine cations with two chromophores linked by varying lengths of alkyl chains, (E)-1,1'-(propane-1,3-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) cation (H3), (E)-1,1'-(hexane-1,6-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) cation (H6), and (E)-1,1'-(decane-1,10-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) cation (H10), were successfully prepared by layer-by-layer self-assembly technique. UV–visible spectra showed that BW11Co and Ha (a = 3, 6, 10) components were uniformly deposited in each dipping cycle. The visible absorption peaks of (BW11Co/Ha)n films are obviously red shifted as compared with those of corresponding Ha solution, which is beneficial for improving photoelectric conversion. As irradiated with white light, the (BW11Co/Ha)n films generated stable, large cathodic photocurrents that increasing with increasing negative applied bias potentials, increasing of electron acceptor concentrations and decreasing electron donor concentrations in the electrolyte solution. The photocurrents were also found to be strongly depending on layer number of the films, and alkyl chain length in the hemicyanine dyes of Ha (a = 3, 6, 10). The maximum photocurrent densities generated by (BW11Co/H3)4, (BW11Co/H6)5, and (BW11Co/H10)4 films were found to be 18.05, 16.6 and 15.8 μA/cm2, respectively. The photocurrent generation performance of (BW11Co/Ha)n films is superior to that of POM-free hemicyanine dye films. POM components can significantly improve the photocurrent generation properties of hemicyanine dyes by efficient electron transference between the ITO electrode and the hemicyanine, and retardation of recombination reaction in photoelectrochemical cells. This study would guide molecular design for more efficient photoelectrocatalytic, and energy conversion and storage devices.

Biosynthesis of silver nanoparticles using upland cress: purification, characterisation, and antimicrobial activity

Silver nanoparticles have traditionally been synthesised using physical and chemical methods, often requiring expensive equipment and reagents that pose risks to the environment. This work provides a green method for the biosynthesis of silver nanoparticles using leaf extracts from upland cress: Barbarea verna. Natural reducing agents within the leaf extracts of upland cress reduce silver ions from silver nitrates, resulting in the formation of silver nanoparticles. The silver nanoparticles were purified using centrifugation and extraction using Triton X-114. The resulting nanoparticles were characterised using UV–Vis spectroscopy, dynamic light scattering, atomic force microscopy, and scanning electron microscopy. Silver nanoparticles were shown to have a diameter of 30–40 nm with a characteristic UV–Vis absorption peak at 420 nm. Antimicrobial properties of the synthesised silver nanoparticles were also confirmed using S. epidermis and E. coli bacteria.