Ultraviolet-visible Absorption Spectra Research Articles

Vapor Infiltration Synthesis of Indium Sulfide Magic Size Cluster.

The energetically favorable formation of atomically precise clusters, known as magic size clusters, in the solution phase enables a precision nanoscale synthesis with exquisite uniformity. We report the synthesis of magic size clusters via vapor infiltration of atomic layer deposition precursors directly in a polymer thin film. Sequential infiltration of trimethylindium vapor and hydrogen sulfide gas into poly(methyl methacrylate) leads to the formation of clusters with uniform properties consistent with a magic size cluster─In6S6(CH3)6. While an increase in cluster size might be expected with additional sequential infiltration cycles of the reactive In and S precursors, uniform properties consistent with magic size clusters form in multiple polymers under a range of processing conditions. Ultraviolet-visible absorption spectra of In6S6(CH3)6 are largely independent of the number of sequential infiltration cycles and exhibit air stability, both of which are attributed to an energetically favorable synthetic pathway that is evaluated with density functional theory.

Exploring the activation potential of heme for 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol

The presence of chlorophenols in water poses a significant threat to human health and the environment. In response to this issue, a study was undertaken to evaluate the catalytic capabilities of chlorinated Heme towards common chlorophenols present in water, such as 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol. The study employed the B3LYP method, a sophisticated computational technique within density functional theory, to investigate the molecular interactions and transformations involved. It scrutinized structural parameters, Wiberg Bond Indices, which offer insights into the strength and nature of chemical bonds, along with spectroscopic data including infrared vibrational spectra, ultraviolet-visible absorption spectra, and molecular fluorescence spectra. Furthermore, the research analyzed molecular binding energies and orbital energy levels before and after the formation of complexes between Heme and the targeted chlorophenols. The findings indicate that Heme displays a notable activation characteristic towards these chlorophenols. This suggests that Heme could act as an effective catalyst in the degradation of chlorophenols in water, presenting a novel approach to water purification. The theoretical insights derived from this study are invaluable, potentially guiding the development of more efficient catalytic systems for treating chlorophenol-contaminated water, thereby reducing the environmental and health risks associated with these hazardous compounds.

Porphyrin photosensitizer molecules as effective medicine candidates for photodynamic therapy: electronic structure information aided design.

Traditional photosensitizers (PS) in photodynamic therapy (PDT) have restricted tissue penetrability of light and a lack of selectivity for tumor cells, which diminishes the efficiency of PDT. Our aim is to effectively screen porphyrin-based PS medication through computational simulations of large-scale design and screening of PDT candidates via a precise description of the state of the light-stimulated PS molecule. Perylene-diimide (PDI) shows an absorption band in the near-infrared region (NIR) and a great photostability. Meanwhile, the insertion of metal can enhance tumor targeting. Therefore, on the basis of the original porphyrin PS segments, a series of metalloporphyrin combined with PDI and additional allosteric Zn-porphyrin-PDI systems were designed and investigated. Geometrical structures, frontier molecular orbitals, ultraviolet-visible (UV-vis) absorption spectra, adiabatic electron affinities (AEA), especially the triplet excited states and spin-orbit coupling matrix elements (SOCME) of these expanded D-A porphyrin were studied in detail using the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. PS candidates, conforming type I or II mechanism for PDT, have been researched carefully by molecular docking which targeted Factor-related apoptosis (Fas)/Fas ligand (Fasl) mediated signaling pathway. It was found that porphyrin-PDI, Fe2-porphyrin-PDI, Zn-porphyrin-PDI, Mg-porphyrin-PDI, Zn-porphyrin combined with PDI through single bond (compound 1), and two acetylenic bonds (compound 2) in this work would be proposed as potential PS candidates for PDT process. This study was expected to provide PS candidates for the development of novel medicines in PDT.

MoS2@MIL-53 (Ni) nanocomposite for water splitting and water remediation through real time effluent treatment

A novel molybdenum disulfide@ materials institute of Lavoisier (MoS2@MIL-53 (Ni)) hetero-structure material has been designed to act as a hydrogen/oxygen generator and as a water remediation agent. Two-dimensional layered MoS2@MIL-53 (Ni) nanocomposites were prepared through the hydrothermal method. Flower and layered morphology were observed for MoS2, and MIL-53 (Ni), respectively in the field emission scanning electron microscopy (FESEM) images. The MoS2@MIL-53 (Ni) nanocomposite demonstrated a high dye degradation efficiency of ∼98 % and ∼96 % for Rhodamine B (RhB) and bodactive blue (BAB) within 80 minutes of time duration, respectively. In the case of untreated textile industrial effluent (TIE), the nanocomposite achieved an efficiency of around 86 % over a period of 9 hours. The ultraviolet-visible absorption spectra of RhB, BAB, and TIE displayed peaks at ∼565 nm, 665 nm, and 530 nm, respectively. Additionally, the nanocomposite exhibited excellent stability over five cycles when tested against RhB. During hydrogen evolution reaction (HER), MoS2@MIL-53 (Ni) nanocomposite showed a Tafel slope of 105 mV/decade and overpotential of −0.073 V vs. RHE. Similarly, oxygen evolution reaction (OER) studies exhibited a reduced over potential at 0.49 V vs. RHE @ 10 mA/cm2 and the Tafel slope was calculated to be 42 mV/decade. Further, the chronoamperometry analysis of MoS2@MIL-53 (Ni) confirmed that the sample exhibited relatively good stability with respect to both HER and OER analysis for 24 hours. This is indicative of MoS2@MIL-53 (Ni)’s structural stability and its strong electrocatalytic activity.

Scorpion-Shaped Hybrid Double Helicenes via Orthogonal Alkyne Annulation Reactions.

Scorpion-shaped hybrid double helicenes, consisting of a [5] or [6] carbohelicene and an aza[4]helicene, have been successfully constructed by orthogonal alkyne annulations via an aryl C-I bond and amido N-H bond from polyaromatic ring-fused iodoisocoumarins. In spite of the unexpected instability upon aerobic oxidation upon ambient visible light irradiation over several days, both ultraviolet-visible absorption and photoluminescence spectra along with density functional theory calculations of these helicenes have been studied, which rely heavily on the bent polyaromatic ring-fused quinolizinone conjugate skeleton. In addition, the Stokes shifts of hybrid double helicenes are generally larger than those of the structurally similar mono-carbohelicenes.

A Dual Emission Fluorescence Probe Based on Silicon Nanoparticles and Rhodamine B for Ratiometric Detection of Kaempferol.

In this paper, blue fluorescent silicon nanoparticles (SiNPs) with outstanding optical properties and robust stability were synthesized by a simple one-step hydrothermal method. By introducing red emissive rhodamine B (RhB) into SiNPs solution, a dual emission nanoprobe (SiNPs@RhB) was constructed, which showed excellent pH stability, salt resistance and photobleaching resistance. The SiNPs@RhB probe could emit two peaks at 444nm and 583nm under 365nm excitation. It was found that the fluorescence intensity of the two emission peaks decreased in different degrees with the addition of different concentrations of kaempferol (Kae). According to this phenomenon, a novel ratiometric fluorescence method was established for the detection of Kae via utilizing SiNPs@RhB as nanoprobe. The detection range and limit of detection (LOD) were 0.5 ~ 150 µM and 0.24 µM, respectively. The ratiometric fluorescence method exhibited the superiority of rapid detection, excellent stability, wide linear range and high sensitivity. The detection mechanism was studied by ultraviolet visible absorption spectra, fluorescence spectra and fluorescence lifetime. Furthermore, the method was applied to the detection of Kae in real samples (kaempferia powder, sea buckthorn granules and sea buckthorn dry emulsion).

Investigating the role of Ag-doped ZnO thin films in UV photodetectors produced via laser assisted chemical bath growth technique

This study introduces the innovative fabrication of Ag-doped ZnO thin films (AgxZnO(100−x) TFs) with varying silver (Ag) concentrations (x) of 0.5, 1.0, 1.5, and 2.0 at% on glass substrates using a simple and cost-effective method known as laser-assisted chemical bath growth (LACBG). This process aims to create metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors. A continuous wave semiconductor laser with a 444.5 nm wavelength, 5 W power, and 6 min irradiation time was employed to synthesize high-quality Ag-doped ZnO TFs on the glass substrate. Ag electrodes were utilized as Schottky contacts to form MSM UV photodetectors. Structural and morphological analyses conducted using XRD and SEM revealed vertically aligned nanorods and nanoflowers with a high c-axis orientation and hexagonal wurtzite facets, while EDX confirmed Ag incorporation into the ZnO lattice. The UV–Visible absorbance spectra indicated a decrease in bandgap from 3.28 to 2.84 eV with increased Ag content. The current-voltage (I–V) characteristics of the Ag-doped ZnO TFs UV photodetector showed significantly enhanced conductivity at a 2.0 at% concentration level, achieving a responsivity of 10.78 A/W, an external quantum efficiency of 34.67 % at −3 V bias voltage. Finally, the modified device exhibited a sensitivity of 14661.9 %, a gain of 147.62, and a detectivity of 2.25 ×107 Jones, demonstrating its suitability for optoelectronic applications.

Catalytic Activity of an Asymmetric Uranyl‐Salophen on 2,4‐Dichlorophenol, 2,4,6‐Trichlorophenol, and Pentachlorophenol

ABSTRACTThis study employs density functional theory to investigate whether asymmetric uranyl‐Salophen catalyzes the activation of 2,4‐dichlorophenol, 2,4,6‐trichlorophenol, and pentachlorophenol. Changes in various important parameters such as bond lengths, Wiberg bond indices, infrared vibrational absorption spectra, natural charge distributions, ultraviolet–visible absorption spectra, and 13C NMR chemical shifts of the aromatic rings of chlorophenols before and after forming complexes with asymmetric uranyl‐Salophen are analyzed. This means that asymmetric uranyl‐Salophen indeed activates 2,4‐dichlorophenol, 2,4, 6‐trichlorophenol, and pentachlorophenol, significantly lengthening the aromatic ring bonds of the three chlorophenols and increasing the electrophilicity of the carbon atoms in the aromatic ring. This suggests that the conjugated system of the aromatic ring is also partially disrupted, indicating that these three chlorophenols are indeed catalytically activated. Furthermore, this implies that this asymmetric uranyl‐Salophen may be used to degrade chlorophenols in water.

Synthesis and application of a novel turn-on fluorescent probe for the determination of sulfur ions in real samples

A novel and highly selective reactive sulfur ions (S2-) probe, 4′-(benzo[d]thiazol-2-yl)-3′-((7-nitrobenzo[c][1,2,5] oxadiazol-4-yl) oxy)-N, N-diphenyl-[1,1′-biphenyl]-4-amine (DBA), has been synthesized through covalent bonding of a 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl) unit with 4-(benzo[d]thiazol-2-yl)-4′-(diphenylamino)-3-phenylphenol (BO-OH). The structure was meticulously characterized using a combination of IR, NMR, HRMS, and LC-MS techniques. Notably, upon the addition of S2-, the fluorescence of the probe DBA solution underwent a marked enhancement, transitioning from nearly colorless to brilliant yellow-green luminescence. The Ultraviolet–visible absorption spectrum and fluorescence emission were utilized to assess the probe DBA efficacy in detecting and identifying S2-. It exhibited a substantial fluorescence amplification, enabling quantitative detection within a concentration range of 0 to 17.1 μM, and possessed a low detection limit of 66.89 nM. Moreover, this method boasts a high recovery rate, excellent accuracy, and usefulness for analysis when tracking S2- in real samples.

The correlation of alkyl chain modulation and the efficiency of Y-series non-fullerene acceptor: A DFT approach

Y6, a highly efficient non-fullerene acceptor, could present distinctly different power conversion efficiency in organic solar cells when its alkyl side chains are replaced by others. However, the underlying mechanism is still unclear. To dissect this point, ten kinds of Y-series acceptors with variant side chains are studied. The density functional theory is used to calculate their ground geometry, frontier molecular orbital, ultraviolet–visible absorption spectra, the free energy of solvation, intramolecular electron transfer, and electronic structures on the excited state in chloroform. Results reveal that the presence of the branched R1 could reduce the dihedral angle and balance the planarity of molecular skeletons. The free energy of solvation is less than −1.5 eV and R2 has a greater impact on it than R1. Acceptors with longer R2 have better light absorption between 400 nm and 600 nm. Molecular dynamics simulation is also applied to the blending films with these acceptors and PM6. Molecules that possess branched R1 and longer R2 have a better morphology and are found to be promising candidates for highly efficient acceptors.

Solvent Effect for the Structural Control of Molecular Architectures Consisting of Trinuclear Ruthenium Clusters and Ligands at the HOPG Surface.

The molecular architecture of a triruthenium complex and 1,4-di(4-pyridyl)benzene on highly oriented pyrolytic graphite was investigated by drop-casting mixed tetrahydrofuran and methanol solutions. Atomic force microscopy revealed the formation of one-dimensional molecular wires on highly oriented pyrolytic graphite after heating the mixed tetrahydrofuran solution, whereas large ring structures were formed in the methanolic solution. It was found that the molecular architectures composed of triruthenium complexes and 1,4-di(4-pyridyl)benzene strongly depend not only on the temperature of the solution but also on the organic solvents. The formation of the molecular architecture was supported by the ultraviolet-visible absorption spectra of the mixed solution and the electrochemical responses of the deposited film.

Hybrid Amino Acid Ligand-Regulated Excited Dynamics of Highly Luminescent Perovskite Quantum Dots for Bright White Light-Emitting Diodes.

Organic-inorganic hybrid perovskite quantum dots (QDs) have garnered significant research interest owing to their unique structure and optoelectronic properties. However, their poor optical performance in ambient air remains a significant limitation, hindering their advancement and practical applications. Herein, three amino acids (valine, threonine and cysteine) were chosen as surface ligands to successfully prepare highly luminescent CH3NH3PbBr3 (MAPbBr3) QDs. The morphology and XRD results suggest that the inclusion of the amino acid ligands enhances the octahedral structure of the QD solutions. Moreover, the observed blue-shifted phenomenon in the photoluminescence (PL) aligns closely with the blue-shifted phenomenon observed in the ultraviolet-visible (UV-Vis) absorption spectra, attributed to the quantum confinement effect. The time-resolved spectra indicated that the introduction of the amino acid ligands successfully suppressed non-radiative recombination, consequently extending the fluorescence lifetime of the MAPbBr3 QDs. The photoluminescence quantum yields (PLQYs) of the amino acid-treated MAPbBr3 QDs are increased by 94.8%. The color rendering index (CRI) of the produced white light-emitting diode (WLED) is 85.3, with a correlated color temperature (CCT) of 5453 K. Our study presents a novel approach to enhancing the performance of perovskite QDs by employing specially designed surface ligands for surface passivation.

Incorporating ReS2 Nanosheet into ZnIn2S4 Nanoflower as Synergistic Z-Scheme Photocatalyst for Highly Effective and Stable Visible-Light-Driven Photocatalytic Hydrogen Evolution and Degradation.

Inspired by natural photosynthesis, the visible-light-driven Z-scheme system is very effective and promising for boosting photocatalytic hydrogen production and pollutant degradation. Here, a synergistic Z-scheme photocatalyst is constructed by coupling ReS2 nanosheet and ZnIn2S4 nanoflower and the experimental evidence for this direct Z-scheme heterostructure is provided by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and electron paramagnetic resonance. Consequently, such a unique nanostructure makes this Z-scheme heterostructure exhibit 23.7 times higher photocatalytic hydrogen production than that of ZnIn2S4 nanoflower. Moreover, the ZnIn2S4/ReS2 photocatalyst is also very stable for photocatalytic hydrogen evolution, almost without activity decay even storing for two weeks. Besides, this Z-scheme heterostructure also exhibits superior photocatalytic degradation rates of methylene blue (1.7 × 10-2 min-1) and mitoxantrone (4.2 × 10-3 min-1) than that of ZnIn2S4 photocatalyst. The ultraviolet-visible absorption spectra, transient photocurrent spectra, open-circuit potential measurement, and electrochemical impedance spectroscopy reveal that the superior photocatalytic performance of ZnIn2S4/ReS2 heterostructure is mostly attributed to its broad and strong visible-light absorption, effective separation of charge carrier, and improved redox ability. This work provides a promising nanostructure design of a visible-light-driven Z-scheme heterostructure to simultaneously promote photocatalytic reduction and oxidation activity.

Bio-coloration and Antibacterial Function of Wool grafted with pomegranate peel polyphenols catalyzed by laccase

With the deterioration of environmental problems and world energy consumption, the improvement of textile dyeing has been paid more and more attention by researchers. The application of natural dyes in the dyeing of wool fabrics had become a research hotspot. However, the main drawback of the application of natural dyes lies in the poor color stability on wool fabrics. Therefore, research on environmentally and economically friendly dyeing processes has gained crucial importance. In this paper, the effect of pomegranate pigment on the functional dyeing of wool fabric under the catalysis of laccase was discussed. The dyeing effect of different methods on wool fabric was compared and the laccase catalytic dyeing process was optimized. Firstly, the properties of pomegranate peel pigment were analyzed by Ultraviolet-visible absorption spectrum (UV-Vis) and Fourier infrared spectroscopy (FTIR). Then the surface morphology and properties of wool fabric were observed by scanning electron microscope (SEM), microscope and FTIR. Lastly the function and stability of dyed wool fabric were tested by color characteristic value, UV resistance, antibacterial property, color fastness and tensile strength. The results showed that better dyeing effect of wool fabric were obtained by dyeing firstly with pomegranate peel and then catalysis with laccase. The optimum process of laccase catalysis was as follows: catalysis time 8 h, laccase dosage 3.3 U, temperature 50℃, pH 5. The results of SEM, FTIR and microscope tests showed that the phenolic compounds in the pigment of pomegranate peel was catalyzed by laccase to form the deepened coloration polymers and the phenolic polymers were finally combined with the wool fabric. Laccase-catalyzed dyed wool fabric showed good performance stability, such as color fastness to rubbing and soap-washing, strong antibacterial property, great enhancement of UV resistance and excellent tensile strength. The application of laccase in the natural dyeing process of textiles can provide a better way to improve the dyeing properties.

Visual fluorescence detection kit for Cr (VI) based on biological matrix-derived carbon dots and assisted for AA

In this study, a novel green donkey-hide gelatin carbon dots (D-CDs) were synthesized by hydrothermal method and a portable detector based on Cr (VI) fluorescent test strips was prepared. The synthesized D-CDs exhibited bright blue fluorescence which was used for the detection of Cr (VI) and ascorbic acid (AA). It still exhibited high sensitivity and acceptable selectivity under high concentration of other interfering ions. The morphology and elemental characteristics of D-CDs were characterized. Meanwhile, the “on-off” quenching mechanism of Cr (VI) on D-CDs was studied by ultraviolet-visible absorption spectra, fourier transform infrared spectroscopy and fluorescence spectra. Then a D-CDs/Cr (VI) fluorescence sensing platform was constructed, and reopened by AA, thus eliciting an “on-off-on” fluorescence reaction. Under the optimal conditions, the fluorescence intensity was quenched significantly with the increase of Cr (VI) concentration and restored by the good reducibility of ascorbic acid (AA), with the linear ranges of 0.5–400 μM and 1–400 μM, respectively. The detection limits of Cr (VI) and AA can be as low as 0.08 μM and 0.14 μM. Consequently, it has low toxicity and can be successfully used as a fluorescent probe to determine Cr (VI) in river water and AA in fruits with satisfactory results. It not only lays a foundation for the development of fluorescence sensor in the field of environment and food, but also provides a good application prospect for its detection of heavy metal ions and AA.

Individual quantification of ozone and reactive nitrogen species in mixtures by broadband UV–visible absorption spectra deconvolution

Ozone (O3), nitrogen oxides (NO x ), and reactive nitrogen species (RNS) play critical roles in atmospheric-pressure plasma applications. Although it is crucial to individually quantify these species to understand atmospheric-pressure plasmas and increase their effectiveness, the lack of reliable and cost-effective diagnostics makes this difficult for many researchers. To address this problem, we introduce a new deconvolution method of broadband ultraviolet–visible absorption spectra for the simultaneous measurement of eight species—O3, NO, NO2, NO3, N2O4, N2O5, HONO, and HNO3. Processing of broadband spectra enables deconvolution of similar cross-section profiles and measurement of high densities exceeding the instrumental limit. Novel correction processes enable accurate analysis despite incomplete cross-section data and utilize a priori chemical knowledge to ensure theoretically reasonable results. Two case studies test the efficacy of the method: NO2 and N2O4 equilibria, and reactive species produced by a surface dielectric barrier discharge. With an analysis time of 15–20 ms per spectrum, the measured densities agree well with other theoretical and experimental results, and detection limits on the order of ppmv were achieved with a short path length of 15 cm. This spectral analysis method will facilitate the real-time monitoring of O3, NO x , and RNS in many scientific research and industrial applications of atmospheric pressure plasmas.

A Highly Sensitive and Selective Fluorescent Sensor for Folic Acid Detection Based on D-penicillamine Stabilized Ag/Cu Alloy Nanoclusters.

In this work, a highly sensitive and selective method for detecting folic acid (FA) was developed using D-penicillamine (DPA) stabilized Ag/Cu alloy nanoclusters (DPA@Ag/Cu NCs). The yellow emission of DPA@Ag/Cu NCs was found to be quenched upon the addition of FA to the system. The fluorescence intensity quenching value demonstrated a linear relationship with FA concentrations ranging from 0.01 to 1200 μM, with a limit of detection (LOD) of 5.3 nM. Furthermore, the detection mechanism was investigated through various characterization analyses, including high resolution transmission electron microscopy, fluorescence spectra, ultraviolet-visible absorption spectra, and fluorescence lifetime. The results indicated that the fluorescence quenching induced by FA was a result of electron transfer from FA to the ligands of DPA@Ag/Cu NCs. The selectivity of the FA sensor was also evaluated, showing that common amino acids and inorganic ions had minimal impact on the detection of FA. Moreover, the standard addition method was successfully applied to detect FA in human serum, chewable tablets and FA tablets with promising results. The use of DPA@Ag/Cu NCs demonstrates significant potential for detecting FA in complex biological samples.

A novel algorithm to extrapolate ultraviolet absorption of chromophoric dissolved organic matter from remote sensing ocean color

Accurate estimation of the absorption of chromophoric dissolved organic matter (CDOM) in ultraviolet (UV) wavelength range is crucial for understanding photochemical and biochemical processes in the global ocean. Here, we propose a novel UV absorption extrapolation (UVAE) algorithm. It extrapolates the absorption coefficients (ag(λ) where λ is the wavelength in nm) of CDOM in the UV wavelength range from ocean color data in the visible wavelength range observed by satellite remote sensing. The extrapolation is based on the assumption that three characteristic Gaussian bands describe the CDOM UV–visible absorption spectra (275–443 nm). The UVAE algorithm retrieves the ag(275), ag(295), ag(330), and ag(380) using the characteristics of the spectral slope (S) of the absorbance spectra of CDOM at specific wavelength intervals, namely 275–295, 295–330, 330–380, and 380–443 nm. With the UVAE algorithm, the spatial variability of CDOM spectral features can be captured on a global scale using data from the Moderate-resolution Imaging Spectroradiometer (MODIS) Aqua mission. The retrieved ag(275), ag(295), ag(330), and ag(380) values match well with in-situ observed values, with mean absolute percent differences (MAPDs) of 19.2 %, 26.1 %, 36.9 %, and 46.6 %, respectively. The performance of the UVAE algorithm demonstrates a significant improvement compared to that of existing algorithms, especially for ag(λ) at lower wavelengths.

Engineered K-doped ZnO/borneol based hydrogel composite material for led-based photocatalytic degradation of methylene blue and evaluation of antimicrobial activity

The significant improvement of decolorization and disinfection technologies has been a hotspot in wastewater reutilization. In this study, we realized a novel construction of K-doped nano-ZnO and borneol based hydrogel composite material (K-ZnO/B-hydrogel) by low-temperature in situ sol–gel growth. The techniques such as fourier transform infrared (FTIR), X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS) were applied to recognize the synthesized hydrogel. The results revealed that K-doped ZnO nanoparticles had been uniformly decorated onto the B-hydrogel. Ultraviolet-visible (UV–vis) absorption spectra showed that impurity doping of potassium element into ZnO could reduce the band gap, improving the visible light absorption efficiency. Under LED illumination, the photodegrading rate of K-ZnO/B-hydrogel was approximately 2.3 times greater than that of K-ZnO/B-hydrogel on methylene blue (MB) removal. Remarkably, aside from CO2 and H2O, no by-products were generated during the photodegradation process. In addition, the antimicrobial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) of K-ZnO/B-hydrogel achieved up to 99.9%, which were at least 1.5 times higher than K-ZnO/B-hydrogel. This composite will push ahead with a closed-loop wastewater treatment system for dye and pathogenic microorganism disposal, which combines the excellent adsorption ability of hydrogel and the outstanding photocatalytic ability of ZnO nanoparticles with easy sample handling and separation, and help to eliminate secondary pollution.

Preparation and characterization of chiral carbon dots with red emission

Methods for the synthesis of chiral carbon dots (CDs) possessing bright long-wavelength emission are highly desirable. Here, we develop red-emissive chiral CDs from hydrothermal treatment of L-/D-lysine and o-phenylenediamine (OPD). Pure chiral CDs are obtained by filtration and dialysis. Ultraviolet-visible (UV–vis) absorption spectra, photoluminescence (PL) spectra, PL quantum yield (QY), and PL decay of the chiral CDs are thoroughly studied. The chiral CDs exhibit bright red fluorescence with PL QY in the range of 26.6%–42.2% in different solvents. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) indicate that the chiral CDs have a mean particle size of 2.7 nm, and consist of graphite-like carbons and abundant functional groups at their surfaces. Circular dichroism spectroscopy shows new Cotton bands at about 300 and 610 nm for chiral CDs differed from those of L-/D-lysine, revealing the generation of optical chirality for CDs. Then transparent optical resins made of CDs/epoxy resin composites are prepared, possessing red fluorescence and circular dichroism, broadening potential applications of solid materials with chiroptical properties. Finally, we discuss the possible origins of chirality and fluorescence of the CDs. The exploitation of highly red-emissive chiral CDs may promote the development and application of chiral CDs.