Ultraviolet-visible Absorption Spectra Research Articles

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.

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.

Force/Acid-Activated and Radical-Regulated photochromic luminescence in a binuclear Zero-Dimensional complex for multi-level anti-counterfeiting

Traditional static optical anti-counterfeiting technology can only output a single emission signal, which is easy to replicate and difficult to meet the needs in current high-tech fields. Multi-level stimuli-responsive luminescent materials with internal logical relationship can improve the degree of anti-counterfeiting and resist against the flood of counterfeiting. In this work, we propose to use force and acid dual stimuli to restrict the dissipation path of photogenerated free radicals, which further lead to the radical-actuated photochromic luminescence (PCL) performance. Based on this strategy, a zero-dimensional (0D) dinuclear zinc complex Zn2(9-AC)4(IM)2 (1) with blue luminescent properties (450 nm) was designed and synthesized. The interaction between 9-AC and IM (as 9-AC/IM exciplex) can be cut off by force-induced rearrangement of structural units in the spatial dimensions or acid-induced protonation of 9-AC, achieving the luminescent transformation from 9-AC/IM exciplex (447 nm) to 9-AC/9-AC excimer (480 nm) or 9-HAC (485 nm). At the same time, the PCL performance was activated and the emission intensity quenching rate increased from 4.77 % to 93.86 % or 44.93 % under UV light irradiation, respectively. The solid-state ultraviolet–visible absorption spectra, electron paramagnetic resonance spectra and theoretical calculation confirmed that the activation of PCL performance is due to the fact that the 9-AC• radicals are more difficult to dissipate upon force- or acid-induced stimuli. Combining mechanochromic luminescence (MCL) and PCL, a dynamic anti-counterfeiting quick response (QR) code with multi-level and fast-responsive logic sequence have been designed, which are promising for the application in time-resolved information encryption. This work provides an effective strategy to construct multi-level stimuli-responsive luminescence as novel anti-counterfeiting materials by changing the photogenerated free radical dissipation pathway to activate PCL properties.

Electronic and Nonlinear Optical Properties of B(III)-Submonoazaporphyrin-π-Diimide Compounds: A Density Functional Theory Study.

Three hypothetical complexes were designed using diimides (PMDI, NTCDI, and PTCDI) as the acceptor unit and B(III)-submonoazaporphyrin (1) as the donor unit. These complexes have smaller HOMO-LUMO energy gaps (3.39-3.96 eV) than pristine 1 (6.61 eV). Further, the energy gap can be tuned by changing the number of benzene rings of these diimides. Remarkably, these proposed complexes possess considerable first hyperpolarizabilities (β0) (4865-6921 a.u.), and the regularity of the β0 values remained the same in the gas phase and toluene solvent conditions. There is an inverse relationship between the energy gap and the polarizability/first hyperpolarizability. In addition, absorption spectra, frontier molecular orbitals, and hole electron distributions were obtained using time-dependent density functional theory calculations to emphasize the relationship between structure and properties. Ultraviolet-Visible absorption spectra reveals that all complexes show satisfying IR working regions. Further analysis of the first hyperpolarizability density reveals the nature of the excellent NLO properties of the studied systems. This study can provide valuable insights for the development of potential high-performance NLO molecules.

Introducing hafnium to atomically small- and medium-sized tin clusters (HfSnn0/-/2- (n = 4–17)): A computational investigation of geometrical and growth behavior, spectral properties, electronic configuration and thermochemistry

The global and local minimum configurations of single Hf atom doped Sn clusters are conducted via density function theory (DFT) combined with artificial bee colony algorithm (ABCluster). Furthermore, DFT method is also used to systematically investigate on their structural growth evolution, spectral and electronic information, thermochemical properties following the size of tin clusters doped Hf atom. Structurally, the ground-state geometries of neutral, anion and di-anion are discovered that, from n = 4, the number of Sn atoms in cluster, HfSnn0/-/2- adsorb additional Sn atom on the prior architecture one by one until forming n = 17 for HfSnn-10/-, as well as forming n = 16 for HfSnn-12-. And for the HfSn110/- and HfSn102- as beginning the species veritably develop sealed architectures. The strongest vibrational modes of sealed nanoclusters are stretching modes of Hf atom with infrared actives and breathing modes of the Sn cage framework with Raman actives, respectively. The natural population analysis (NPA) elucidates the stronger relationship between the Hf atoms and the tin frameworks in sealed clusters than that in unsealed clusters. The results of thermochemical properties, molecular orbital shell (MOs), adaptive natural density partitioning (AdNDP) and ultraviolet visible absorption spectrum (UV–Vis) indicate that, the HfSn16 with high symmetry of Td exhibits thermochemical stability and optoelectronic properties, which is utilized potentially as zero-dimensional unit of self-assembling fluorescent nanomaterials.

Enhanced visible light photocatalytic degradation of styrene by g-C3N4 quantum dots/P25 nanocomposites

The enhancement of the visible light response of P25 is of significant importance for the photocatalytic degradation of volatile organic compounds (VOCs). Graphitic carbon nitride quantum dots (CNQD) are nano-sized counterparts of g-C3N4, exhibiting excellent optical properties. Using a simplified hydrothermal one-step approach, CNQD-loaded P25 (CNQD/P25) was obtained in this work. Under visible light, CNQD/P25 achieved styrene degradation rate of 95 % within 240 minutes, surpassing the 60 % degradation rate of pure P25 under identical conditions. This indicates that the presence of CNQDs greatly enhances the photocatalytic performance of P25 in the visible light region. Further investigations revealed that CNQD/P25 exhibited noticeable enhancement in the ultraviolet-visible absorption spectrum, demonstrating increased visible light absorption. CNQD/P25 demonstrated higher photocurrent response, lower photoresistance, and weaker fluorescence response compared to P25 at similar conditions. Therefore, the presence of CNQDs can enhance visible light absorption of P25, increases the number of photo-generated electrons, optimizes charge separation efficiency, and simultaneously reduces the recombination rate of electrons and holes.

Non-enzymatic Detection of Uric Acid in Serum and Urine by Fluorescent and Visual Dual-Mode Sensor Based on 3-aminophenylboric Acid Functionalized Carbon Dots.

Herein, we developed a sophisticated dual-mode sensor that utilized 3-aminophenylboric acid functionalized carbon dots (APBA-CDs) to accurately detect uric acid (UA). Our innovative process involved synthesizing APBA-CDs that emitted at 369nm using a one-step hydrothermal method with 3-aminophenylboric acid and L-glutamine as precursors, ethanol and deionized water as solvents. Once UA was introduced to the APBA-CDs, the fluorescence of the system became visibly quenched. The results of Zeta potential, Fourier transformed infrared (FTIR) spectra, fluorescence lifetime, and other characteristics were analyzed to determine that the reaction mechanism was static quenching. This meant that after UA was mixed with APBA-CDs, it combined with the boric acid function on the surface to form complexes, resulting in a decrease in fluorescence intensity and a blue shift in the absorption peak at about 295nm in the Ultraviolet-visible (UV-vis) absorption spectra. We were pleased to report that we have successfully used the dual-reading platform to accurately detect UA in serum and human urine. It provided a superior quantitative and visual analysis of UA without the involvement of enzymes. We firmly believe that our innovative dual-mode sensor has immense potential in the fields of biosensing and health monitoring.

Stable MOF-In2S3/ZnFe layered dioxide heterostructures for improving photocatalytic degradation: Degradation pathways, kinetics, and charge migration

In this paper, MOF-In2S3 were modified by ZnFe-layered dioxides (LDO) with strong stability to obtain high catalytic performance composite. The successful preparation of ZnFe-LDO/MOF-In2S3 not only retains the advantages of large specific surface area of MOF-In2S3 and the stability of ZnFe-LDO, but also improves its charge separation efficiency and the light absorption region through the construction of heterojunctions. As expected, the experimental results show that ZnFe-LDO/MOF-In2S3 has superior photo-electrocatalytic properties. The photocatalytic degradation efficiency of ZnFe-LDO/MOF-In2S3 for TCH and OTC reach 92.92% and 80%, respectively, within 25 min. And the corresponding degradation rate constants are up to 1.41332 and 0.45451 L·mg−1·min−1, respectively, which are accord with the pseudo-second-order kinetic constants. The intermediate of 0.6LDO/M-I degradation of TCH was proposed by liquid mass spectrometry (LC-MS). Notably, a special transient surface photovoltage (TPV) technique was used for discussing the charge transfer kinetics and the lifetime of photogenerated carriers. Based on Mott-Schottky (M-S), Ultraviolet-visible absorption spectrum (UV), X-ray Photoelectron Spectroscopy (XPS) results, electron paramagnetic resonance (EPR) results, and active substance capture experiment results, a Z-scheme heterojunction system was proposed. The above research work proposed a new approach to enhance the stability of catalytic materials by using the aid of layered dioxides. In addition, the characterization of surface photovoltage provides a new way to study charge transfer.

Chicken Meat and Beef Identification in UV-Vis Absorbance Spectrum by Applying Savitzky-Golay Method

Spectroscopy is one of the techniques suitable for validation of the quality, safety, and hygiene of meat due to some advantages, such as rapid detection capability, ease of use, and non-destructive measurement. Utilizing an ultraviolet-visible (UV-Vis) spectrometer, with a wavelength range of 200 nm to 1100 nm, this paper proposes a method for processing spectrum data profiling of chicken meat and beef. A 360-time reflectance spectrum was acquired from each chicken breast and beef loin at the optimum integration time of 60 ms. Subsequently, the spectrum was converted into an absorbance spectrum, and the apparent noise was excluded by applying the Savitzky-Golay (SG) method. The result shows the difference in spectrum between chicken meat and beef in which the chicken meat has two peaks at the wavelength of 284.79 nm and 422.69 nm, meanwhile, the beef shows three peaks at wavelengths of 282.46 nm, 419.03 nm, and 577.97 nm. It was found that the SG method enhanced the absorbance spectrum, showing the difference in spectrum behaviors in the wavelength range of 450∼600 nm. Consequently, to shorten the computational time, building a light, cheap, and compact prototype reading device within this specific wavelength range will be the next target in the near future.

Effect of SbCl5 Doping on the Electrical and Optical Properties of Polyamide Nylon 6 Films

Polyamide nylon 6 (PA6) films were fabricated using a solution casting method and the films were doped with SbCl5. The electrical conductivity increased with the dopant concentration due to the increase in formation of radical cations through the charge transfer from the isolated double bonds (–C=O–) in the polymer chains. The DC electrical conductivity reached a maximum of 0.01 S/cm for 0.5 ml SbCl5 doped films. Structural and optical characteristics of the pure and doped films were examined using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Diffraction (XRD), and Ultraviolet-Visible (UV-Vis) absorption spectra. The doped films exhibited discernible shifts in the optical band gap energy. The direct band gap values of PA6 films were reduced from 4.5 eV to 1.7 eV when doped with 0.5 ml SbCl5. ATR-FTIR spectral studies, and optical studies indicated the formation of charge transfer complexes with the amide group of nylon 6, resulting in the electrical conduction. The XRD studies disclosed the reduction in the crystallinity of the doped films. The thermal stability was studied using differential scanning calorimetry (DSC) and thermogravimetric analysis-derivative thermogravimetric (TGA-DTG) studies. The melting and crystallization temperatures were recorded from the DSC thermograms. The peak melting temperature of PA6 reduced from 217 °C to 186 °C for 0.5 ml SbCl5 doped films. The peak of crystallization observed at 182 °C for pure films was absent, for the doped samples. The peak degradation temperatures for both pure and doped samples were above 400 °C, revealing the thermal stability of both materials. The thermally stable, semi-crystalline and semiconducting polymer films, we suggest, would be suitable for optoelectronic applications.

Transient chemical and structural changes in graphene oxide during ripening

Graphene oxide (GO)—the oxidized form of graphene—is actively studied in various fields, such as energy, electronic devices, separation of water, materials engineering, and medical technologies, owing to its fascinating physicochemical properties. One major drawback of GO is its instability, which leads to the difficulties in product management. A physicochemical understanding of the ever-changing nature of GO can remove the barrier for its growing applications. Here, we evidencde the presence of intrinsic, metastable and transient GO states upon ripening. The three GO states are identified using a π−π*\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi -{\\pi }^{*}$$\\end{document} transition peak of ultraviolet–visible absorption spectra and exhibit inherent magnetic and electrical properties. The presence of three states of GO is supported by the compositional changes of oxygen functional groups detected via X-ray photoelectron spectroscopy and structural information from X-ray diffraction analysis and transmission electron microscopy. Although intrinsic GO having a π−π*\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi -{\\pi }^{*}$$\\end{document} transition at 230.5 ± 0.5 nm is stable only for 5 days at 298 K, the intrinsic state can be stabilized by either storing GO dispersions below 255 K or by adding ammonium peroxydisulfate.

Influence of Dilution Upon the Ultraviolet-Visible Peak Absorbance and Optical Bandgap Estimation of Tin (IV) Oxide and Tin(IV) Oxde-Molybdenum(IV) Sulfide Solutions

The study investigated the constraints associated with the dilution technique in determining the optical bandgap of nanoparticle dispersion and modified nanocomposites, utilizing ultraviolet-visible absorbance spectra and Tauc plot analysis. A case study involving SnO2 dispersion and SnO2-MoS2 nanocomposite solutions, prepared through the direct solution mixing method, was conducted to assess the implications of dilution upon the absorbance spectra and bandgap estimation. The results emphasize the considerable impact of the dilution technique on the measured optical bandgap, demonstrating that higher dilution factors lead to shift in bandgap values. Furthermore, the study highlights that dilution can induce variations in the average nanoparticle sizes due to agglomeration, thereby influencing bandgap estimation. In the context of nanocomposites, the interaction between SnO2 nanoparticles and exfoliated MoS2 nanosheets diminishes with increasing dilution, leading to the estimated optical bandgap being primarily attributable to SnO2 nanoparticles alone. These observations underscore the necessity for caution when employing the dilution technique for bandgap estimation in nanoparticles dispersion and nanocomposites, offering valuable insights for researchers and practitioners in the field.

Screening, Identification, and Pigment Characteristics of Actinomycin D-Producing Actinomycetes from Purple Soil in the Sichuan Basin

Background: Natural pigments from microbial sources are a class of compounds with various structures and a wide range of uses, which have become an important source of antibiotic production. Objectives: This study aimed to screen and identify a new type of pigment-producing microorganism from purple soil in the Sichuan Basin. At the same time, this study aimed to purify and identify the produced pigment, preliminarily optimize its fermentation conditions, and characterize its antibacterial activity. Methods: Through morphology, physiology, biochemistry, and molecular sequencing, the strain LS-2 was identified. The pigment was purified by column chromatography, and its antibacterial activity was characterized by a disc diffusion assay. Through the analysis of the ultraviolet-visible (UV-vis) absorption spectrum, infrared (IR) absorption spectrum, and liquid chromatography-mass spectrometry (LC-MS), the yellow pigment was identified. Results: An actinomycin D-producing Streptomyces parvulus was isolated from the purple soil in the Sichuan Basin. Its optimal fermentation conditions were culture at 34°C on Gause’s synthetic medium with pH 6.5, and the yield reached 540 mg/L after 48 hours. The actinomycin D produced by the strain has excellent antibacterial activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli). Conclusions: A new actinomycin D-producing strain of Streptomyces parvulus LS-2 was isolated and identified. The strain has a high production of actinomycin D, which has excellent antibacterial activity.

Selective adsorption analysis of BAPTA depressants on the surface of carbonate minerals: Insights into flotation behavior and adsorption mechanism

Flotation separation of magnesite and calcite, two carbonate minerals, poses a significant challenge due to their intrinsic surface similarities. In this study, 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) was employed as a depressant to selectively regulate the mineral surface property in magnesite-calcite flotation. Micro-flotation experiments demonstrated that successful separation of magnesite-calcite mixtures could be achieved with 40 mg/L BAPTA and 100 mg/L sodium oleate (NaOL). Contact angle measurements and Ultraviolet-Visible absorption spectrum analysis revealed that pre-adsorption of BAPTA selectively hindered the adsorption of sodium oleate onto calcite surface, effectively eliminating the surface hydrophobicity of calcite induced by sodium oleate. The Extended-Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory further indicated a reduced attractive interaction energy between magnesite and calcite particles in the presence of BAPTA. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) simulation elucidated the stronger binding affinity of BAPTA towards calcium ions. Finally, a model was established for the selective formation of cage-like chelating structures on the calcite surface by BAPTA.

Biological Synthesis and Characterization of Silver-Doped Nanocomposites: Antibacterial and Mechanistic Studies

The development of antimicrobial resistance has increased the prevalence of infectious diseases, causing a global health problem that accounts for over 4.95 million deaths worldwide annually. The side effects associated with current antibiotics prompt a crucial need to search for effective and safe antimicrobial agents. In this study, silver nanoparticles (AgNPs) were prepared by chemical reduction method using silver nitrates as a metallic precursor and Croton macrostachyus bark aqueous extract as a reducing and capping agent. The nanoparticles were further functionalized using C. macrostachyus-based activated carbon (CAC) to generate nanocomposites (CAC-AgNPs). The nanomaterials were characterized by ultraviolet-visible (UV–vis) absorption spectra and Fourier transform infrared (FTIR) spectra. The antibacterial activity of the as-prepared nanomaterials was evaluated against an array of bacterial strains by microdilution method, whereas their cytotoxicity profile was evaluated using Vero cells (human mammalian cells). Antibacterial mechanistic studies of active nanomaterials were carried out through bacterial growth kinetics, nucleic acid leakage tests, and catalase inhibition assays. As a result, the as-prepared nanomaterials exhibited antibacterial activity against an array of bacterial strains (minimum inhibitory concentration (MIC) range: 62.5 to 500 µg/mL), the most susceptible being Escherichia coli and Staphylococcus aureus. Cytotoxicity studies of the nanomaterials on Vero cells revealed that the nanocomposite (median cytotoxic concentration (CC50): 213.6 µg/mL) was less toxic than its nanoparticle (CC50 value: 164.75 µg/mL) counterpart. Antibacterial mechanistic studies revealed that the nanomaterials induced (i) bacteriostatic activity vis à vis E. coli and S. aureus and (ii) inhibition of catalase in these bacteria. This novel contribution regarding the antibacterial mechanisms of action of silver nanocomposites from C. macrostachyus-based activated carbon may contribute to our understanding of the antibacterial action of these biomaterials. Nevertheless, more chemistry and in vivo experiments as well as in depth antibacterial mechanistic studies are warranted for the successful utilization of these antibacterial biomaterials.

Reduction of graphene oxide (GO) to reduced graphene oxide (rGO) at different hydrothermal temperatures and enhanced photodegradation of zinc oxide/rGO composites

Scholars are shifting their attention to the development of environmentally friendly materials with a high degradability of environmental pollutants. Among various photocatalytic materials, zinc oxide (ZnO)/reduced graphene oxide (rGO) nanomaterials can meet these requirements. In this study, ZnO/rGO nanomaterials with different hydrothermal temperatures were fabricated through a hydrothermal method. We determined the hydrothermal temperature variations to create different structures and identify the morphologies and sizes of the ZnO/rGO material. The average crystal size of ZnO/rGO nanomaterials decreased from 32.25 nm to 30.30 nm when the hydrothermal temperature was increased from 100 °C to 180 °C. The detailed x-ray diffraction (XRD) study showed that the diffraction peak position of ZnO decreased, the lattice constant increased, and the unit cell volume increased with the increase in hydrothermal temperature. rGO-related diffraction peaks were also observed in the XRD patterns of ZnO/rGO samples, which indicates the formation of a ZnO/rGO crystalline structure. Fourier transform infrared spectra revealed the chemical bonding of ZnO and rGO materials. The photoluminescence (PL) spectra of ZnO/rGO nanocomposites presented two characteristic emission peaks at 383 and 558 nm. The Raman scattering spectra of ZnO/rGO nanomaterials exhibited ZnO-related peaks at 329, 436, and 1123 cm−1 and rGO-related peaks at 1352, 1579, 2706, and 2936 cm−1. The ultraviolet-visible (Vis) absorption spectra of ZnO/rGO nanomaterials manifested the characteristic absorption peaks of ZnO and rGO at 381 and 291 nm, respectively. The photocatalytic properties of ZnO/rGO nanomaterials were studied through the decomposition of methylene blue (MB) under Vis light. The effect of hydrothermal temperature on the properties of ZnO/rGO materials and the photodecomposition mechanism of MB were investigated in detail.

Magnetically separable and reusable Fe3O4/chitosan nanocomposites green synthesized utilizing Moringa oleifera extract for rapid photocatalytic degradation of methylene blue

This study focused on the green synthesis of Fe3O4/Chitosan (Cs) nanocomposites using Moringa oleifera leaf extract, which showed good photocatalytic activity when exposed to ultraviolet (UV) irradiation. X-ray diffraction spectrum of Fe3O4/Cs informs the cubic inverse spinel and has crystallite size in the 10.1 – 11.7 nm range. The crystallite size also increased with the increase of Cs mass. The morphology of Fe3O4 and Fe3O4/Cs was nearly spherical. The transmission electron microscope showed the most uniform size of nanocomposites at around 17.1 nm. The Fourier transform infrared spectrophotometer result identified Fe-O in the 576–583 cm−1 range, indicating that Fe3O4 successfully bonded to Cs. Other functional groups, including O–H, C–H, C–O, C–O–C, and NH2, were also found, indicating that the formation of Cs was effective. The element composition of Fe3O4 is Fe (70.9 %) and O (29.1 %). Meanwhile, Fe3O4/Cs (4:4) is 47.9 %, 36.4 %, 11.3 %, and 4.4 % for Fe, O, C and N, respectively. The hysteresis curve indicated that Fe3O4 and Fe3O4/Cs nanocomposites have soft ferromagnetic properties. Meanwhile, the saturation magnetization of Fe3O4 and Fe3O4/Cs (4:2) nanocomposites are 54.0 and 42.3 emu/g, respectively. Peaks are seen in the UV–visible absorption spectrum of Fe3O4 and Fe3O4/Cs nanocomposites between wavelengths 365–377 nm. The optical band gap energy (Eg) of Fe3O4 and Fe3O4/Cs (4:2) are 3.4 and 3.0 eV, respectively. As the mass of Cs increases, the band gap energy decreases. Under UV light irradiation, 50 mg of Fe3O4 and Fe3O4/Cs were analyzed on 7 ppm of methylene blue, pH = 4. The maximum photocatalytic activity Fe3O4/Cs (4:3), achieved an impressive degradation rate of 94.7 % after 120 min of irradiation. The magnetically separable capability means nanocomposites can be recycled and reused five times with high degradation. Furthermore, Fe3O4/Cs has the potential to be a low-cost and environmentally friendly reusable photocatalyst for rapid wastewater degradation.

Anthracene and tetraphenylsilane based conjugated porous polymer nanoparticles for sensitive detection of nitroaromatics in water

Conjugated porous polymers (CPPs) are a kind of promising sensing materials for the detection of nitroaromatic compounds, but their sensing applications in aqueous media are limited because of their poor dispersity or solubility in water. In this study, we prepared anthracene and tetraphenylsilane based CPPs named PSiAn by conventional Suzuki coupling and Suzuki-miniemulsion polymerization, respectively. The structure, morphology and porosity of the CPPs were characterized by Fourier Transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR), transmission electron microscope (TEM) and N2 sorption isotherm, respectively. Both of the CPPs have porous structure which is beneficial for the adsorption and diffusion of the analytes within them. The particle size of PSiAn nanoparticles prepared by Suzuki-miniemulsion polymerization is 10–40 nm from the TEM image, which facilitates the dispersion in the aqueous phase. Combined with the porosity and nanoparticle morphology, PSiAn nanoparticles realized the efficient photoluminescence (PL) sensing of nitroaromatic explosives in aqueous phase. The limit of detection (LOD) and limit of quantitation (LOQ) of PSiAn nanoparticles for 2,4,6-trinitrophenol (TNP) detection in the pure aqueous phase are 0.33 μM and 1.11 μM, respectively. Meanwhile, the good selectivity and anti-interference in presence of other nitro-compounds were observed. Furthermore, the spike/recovery test for the TNP detection in real water samples by PL sensing based on PSiAn nanoparticles indicates the quantitative recovery of TNP from 100.74 % to 101.00 %. The electrochemical test, ultraviolet–visible absorption spectra, excitation and emission spectra, and time-resolved PL spectra were investigated to explore the PL sensing mechanism. As a result, it is found that the fluorescence inner filter effect might be the predominant quenching mechanism during the detection of nitrophenolic compounds such as TNP and 4-nitrophenol (4-NP).

Nitrogen-Doped Graphene Quantum Dot-Passivated δ-Phase CsPbI3: A Water-Stable Photocatalytic Adjuvant to Degrade Rhodamine B.

Inorganic halide perovskite CsPbI3 is highly promising in the photocatalytic field for its strong absorption of UV and visible light. Among the crystal phases of CsPbI3, the δ-phase as the most aqueous stability; however, directly using it in water is still not applicable, thus limiting its dye photodegradation applications in aqueous solutions. Via adopting nitrogen-doped graphene quantum dots (NGQDs) as surfactants to prepare δ-phase CsPbI3 nanocrystals, we obtained a water-stable material, NGQDs-CsPbI3. Such a material can be well dispersed in water for a month without obvious deterioration. High-resolution transmission electron microscopy and X-ray diffractometer characterizations showed that NGQDs-CsPbI3 is also a δ-phase CsPbI3 after NGQD coating. The ultraviolet-visible absorption spectra indicated that compared to δ-CsPbI3, NGQDs-CsPbI3 has an obvious absorption enhancement of visible light, especially near the wavelength around 521 nm. The good dispersity and improved visible-light absorption of NGQDs-CsPbI3 benefit their aqueous photocatalytic applications. NGQDs-CsPbI3 alone can photodegrade 67% rhodamine B (RhB) in water, while after compositing with TiO2, NGQDs-CsPbI3/TiO2 exhibits excellent visible-light photocatalytic ability, namely, it photodegraded 96% RhB in 4 h. The strong absorption of NGQDs-CsPbI3 in the visible region and effective transfer of photogenerated carriers from NGQDs-CsPbI3 to TiO2 play the key roles in dye photodegradation. We highlight NGQDs-CsPbI3 as a water-stable halide perovskite material and effective photocatalytic adjuvant.

Insights into the β‐phase of polyfluorene: characterization, regulation, and mechanism

AbstractDue to the unique blue‐light properties, wide excited emission interval and so on, polyfluorenes (PFs) are among the most promising blue‐light polymers that are widely used in organic lasers and organic light‐emitting diodes. Usually, PFs exhibit two different phases: α‐phase and β‐phase, and the β‐phase has higher photoluminescence efficiency and carrier mobility than the one of α‐phase. Hence, improving the content of β‐phase is very important to enhance the device performance. In this paper, we introduce the methods for characterizing the β‐phase in PFs and summarize the recent research progress in regulating the β‐phase content. Firstly, the differences between the α‐phase and the β‐phase of PFs in terms of structure, aggregation behavior, and optoelectronic properties are summarized. Then, the characterization for the β‐phase, including ultraviolet–visible absorption spectrum (UV–vis), photoluminescence spectrum (PL), and Raman spectrum, transmission electron microscope (TEM), and X‐ray diffraction (XRD) are introduced, and the calculating rules for the content of β‐phase is also introduced. Furthermore, the methods to increase the content of β‐phase are reviewed. Finally, a brief outlook on the challenges and future development prospects of β‐phase in PFs are discussed.