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Lab-on-a-paper-based devices are promising alternatives to the existing arduous techniques for point-of-need monitoring. The present work reports an instant and facile method to produce a microfluidic paper-based analytical device (μPAD). The fabricated μPAD has been used to detect hypochlorite (OCl−) by incorporating newly synthesized chromo-fluorogenic ratiometric probes 1 and 2 into the sample reception zone. The probes showed high selectivity and fast response (<10 s) toward OCl− with an excellent linear relationship in the concentration range of 0–100 μM. The concentration-dependent fluorometric change driven by the reaction of 1@μPAD with OCl− has been monitored using gel-doc imaging systems, which is unprecedented. Digitizing the intensity of the colour solution with different mathematical models of colour has developed a straightforward method for monitoring OCl− without any interference from its competitors. 1@μPAD can detect OCl− at ∼10 times lower than the WHO recommended limit. The detection limit of 1@μPAD via a digital camera-based fluorescence technique was found to be better over digital camera-based cuvette assays. Therefore, 1@μPAD has been successfully utilized to monitor OCl− in actual environmental water samples with portability, ease of use, and sensitivity. The analytical RSD was found to be ≤3% based on fluorimetric detection using 1@μPAD. The chemodosimetric reaction between OCl− and the probe was evidenced by UV-vis and fluorescence spectroscopy, 1H NMR, and ESI-MS. The rapid response time, biocompatibility, low cytotoxicity, 100% aqueous solubility, ratiometric feature, and exclusive OCl− selectivity over other competitive ROS/RNS successfully lead to the application of the probes for bioimaging of exogenous as well as endogenous OCl− in normal cells (HEK293) and cancerous cells (HeLa). [ABSTRACT FROM AUTHOR]

A new fluorescent probe (T2) containing pyrene-hydrazone furan moieties was developed and synthesized through a two-step process and then coated onto filter paper to form a paper-based sensor for TNT detection. The T2 sensor uses photoinduced electron transfer (PET) induced fluorescence quenching to detect TNT. The sensor properties were studied using fluorescence spectra, 1H-NMR titration and density functional theory (DFT) calculations. The reaction time of the T2 paper-based sensor for TNT detection was only five minutes. A smartphone was used as an alternative instrument to detect fluorescence signals and a typical image J-processing application was employed to evaluate the grayscale values of the smartphone-captured photographs. The sensor showed a linear concentration range for TNT detection of between 30–500 μM and a detection limit of 30 μM. The T2 paper-based sensor was found to have high selectivity and sensitivity, and it can successfully detect and image TNT in actual samples. This research demonstrates that a T2 paper-based sensor is a promising alternative for TNT detection owing to its short reaction time, high selectivity, sensitivity, and easy applicability. [ABSTRACT FROM AUTHOR]

Major and trace elements in polymetallic minerals are crucial subjects of study in ore geology. However, efficient and convenient methods have yet to be developed for processing high-density and hydrophobic sulfide ores, like copper–nickel sulfide ore, which is a strategic metal resource. In this paper, a novel method for the multielement analysis of copper-nickel sulfide ore using total reflection X-ray fluorescence spectrometry (TXRF) combined with slurry sampling was developed. This approach is based on the preparation of a suspension in a liquid at a certain viscosity without sample digestion. The effects of the sample amount and particle size on the analysis results were evaluated. The method validation was achieved through these processes: comparison with inductively coupled plasma atomic emission spectrometry (ICP-AES) results; analysis of certified reference materials, including copper-nickel cobalt ore and cobalt-rich nodule. The dispersants of ethylene glycol and 1% Triton X-100 applied in sulfide ore were also evaluated. For most elements, the relative error and relative standard deviation were under 10% in ethylene glycol. By contrast, suspensions with 1% Triton X-100 showed poorer reproducibility, particluarly in samples with sulfide-rich content, requiring further enhancement. For high-specific gravity sulfide ores, a dispersant of ethylene glycol is recommended to enhance the result of accuracy and reproducibility. [ABSTRACT FROM AUTHOR]

Transmetalation plays a very important role in the study of functional MOFs, but it is rarely used in metal–organic salts (MOSs). In this paper, four kinds of MOSs were synthesized by using the tetradentate ligand N,N′-bis (pyridin-4-ylmethyl) ethane-1,2-diamine and MCl2 (M = Zn, Co, Cu), labelled as [H4L]4+·2[CoCl4]2−·2H2O (1), [H4L]4+·2[ZnCl4]2−·2H2O (2), [H4L]4+·[CuCl4]2−·2Cl− (3), and [H4L]4+·2[CuCl4(H2O)]2− (4). Salt 3 was obtained by the metal-ion exchange of salt 1, and salt 4 was successfully synthesized by liquid-assisted grinding (LAG) of salt 3 and CuCl2·2H2O, which was a stoichiometric ratio-controlled transformation that occurred with the change in the geometry of copper(II) anions from [CuCl4]2− and [CuCl4(H2O)]2−. The reaction process was monitored dynamically by atomic absorption spectroscopy (AAS), fluorescence spectroscopy, and powder X-ray diffraction (PXRD). This suggested that transmetalation combined with LAG was an alternative method to obtain MOSs for different metal ions. [ABSTRACT FROM AUTHOR]

The need for elemental analysis in quality control of food, pharmaceuticals and cosmetics, taking into account human safety, has become an essential requirement for any product destinated for commercialization and targets in particular potentially toxic elements. The main objective is to obtain reliable data on elemental content that enables end-users to make informed decisions and to address problems effectively. To align with the principles of green and sustainable analytical chemistry, recent efforts have focused on incorporating new, low-cost screening and quantitative analytical tools such as total reflection X-ray fluorescence spectrometry (TXRF). This paper provides an overview of recent TXRF applications in the elemental analysis of food, pharmaceuticals, and cosmetic samples. The state-of-the-art procedures for sample preparation with details on the sample type and amount, dilution steps, mixing agents, analysed elements, and addition of internal calibration standards are presented together with analytical parameters such as limits of detection and quantification. The current challenges for applying TXRF to each of these research fields are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis, characterization, properties and application of four new Zn(II) and Cd(II)-based luminescent metal–organic probes, {[Zn(mbhna)(bpea)]}n (1), {[Cd(mbhna)(bpea)]}n (2), {[Zn(mbhna)(bpba)]·CH3OH·H2O}n (3) and {[Cd(mbhna)(bpba)]}n (4), composed of a commercially available bis(naphthalene)-based dicarboxylate (mbhna) acting as the luminescent tag. In addition to spectroscopic and compositional characterization of 1–4 by FTIR spectroscopy, elemental analysis, and EDX and elemental mapping, their surface morphology was analysed by FESEM and TEM. Their (dispersed in water) green emission (at 548 nm for 1 and 2, 551 nm for 3, and 547 nm for 4) established by fluorescence spectroscopy on excitation at 380 nm was further explored for the effect of different solvents on their emission intensities. Taking their emissive nature into account, 1–4 were utilised for the detection of harmful amines in water. These were found to recognise the presence of 4-nitroaniline (4-NA) in water with high efficiency (as low as 97 ppb) and selectivity. The ultrafast detection as well as paper strip detection of 4-NA by 1–4 and their recyclability have confirmed that these probes can be useful for real time applications. [ABSTRACT FROM AUTHOR]

Sensing nitroaromatic explosives has gained significant attention due to both increased terrorist threats and a need for environmental protection. In this regard, a fluorescent chemosensor, 1-benzyl-3,5-di(thiophen-2-yl)pyrazin-1-ium bromide (BTPyz), was synthesized and characterized via spectroscopic methods. The photophysical properties were investigated using absorption and emission spectral analysis. As a fluorescent chemosensor, BTPyz exhibited a selective response towards 2,4,6-trinitrophenol (TNP) with a detection limit of 11.6 nM and quenching constant (KSV) of 3.8 × 104 M−1. The fluorescence quenching mechanism was attributed to ground-state charge-transfer complex formation and resonance energy transfer, as evident from Uv-visible, fluorescence and NMR spectroscopy, single-crystal XRD studies, and density functional theory calculations. BTPyz was also employed for the contact mode detection of TNP on paper strips. The detection of TNP in real water and soil samples demonstrated BTPyz to be a promising detection tool toward environmental specimens. [ABSTRACT FROM AUTHOR]

In this paper, Mn2+-doped Rb4CdCl6 metal halide single crystals were prepared by a hydrothermal method. The Rb4CdCl6:Mn2+ metal halide exhibits yellow emission with photoluminescence quantum yields (PLQY) as high as 88%. Due to the thermally induced electron detrapping, Rb4CdCl6:Mn2+ also displays good anti-thermal quenching (ATQ) behavior with thermal quenching resistance (131% at 220 °C). The increase in the photoionization and the detrapping of the captured electrons from the shallow trap states were appropriately attributed to this exceptional phenomenon based on thermoluminescence (TL) analysis and density functional theory (DFT) calculations. The relationship between the fluorescence intensity ratio (FIR) of the material and temperature change was further explored using the temperature-dependent fluorescence spectrum. It was used as a temperature measuring probe based on absolute sensitivity (Sa) and relative sensitivity (Sb) with the change in temperature. The phosphor-converted white light emitting diodes (pc-WLEDs) were fabricated using a 460 nm blue chip with a yellow phosphor, which has a color rendering index (CRI = 83.5) and a low correlated color temperature (CCT = 3531 K). Because of this, finding new metal halides with ATQ behavior for high-power optoelectronic applications may be made possible by our findings. [ABSTRACT FROM AUTHOR]

Obtaining accurate characteristic spectra and the net peak area is crucial in X-ray fluorescence (XRF) quantitative analysis. To improve the calculation accuracy of the net peak area of the characteristic X-ray spectrum, carrying out the baseline calibration is necessary before resolving the spectrum. First, this article proposes the use of an enhanced generative adversarial network (EGAN) depth network model for baseline calibration of XRF spectra. This method directly takes a clean spectrum after deducting the background as the optimal target for EGAN deep network training, thus eliminating the traditional cumbersome baseline fitting process. It can directly and quickly obtain the XRF spectrum after baseline calibration, and the entire process requires neither fitting the background nor knowing the background data. Further, to improve the generalization ability of the EGAN model, we introduce transfer learning in the model training process. We use the existing alloy sample spectrogram data to pretrain the EGAN model generator and then migrate the pretrained XRF-EGAN generator model to the baseline calibration task of 57 national standard soil sample spectra collected. During the model training process, a cross-validation method is used to train and test the model's effectiveness. Finally, experiments are conducted on simulated spectra and actual XRF spectra to verify the accuracy and adaptability of the proposed method. Instrument calibration curves for peak counting and element concentration are established to verify the effectiveness of baseline calibration. The coefficient of determination R2 of the calibration curves for elements Cu, Zn, Mn and Cr is increased to 0.998, 0.988, 0.922 and 0.991, respectively. The results indicate that our proposed method can effectively estimate the pure spectrum after deducting the background. In addition, this method can also be applied to the baseline correction of other similar spectral signals. [ABSTRACT FROM AUTHOR]

Three bis-benzimidazolyl bidentate ligands with phenolyl ether linkers, 1,n-bis[2-(1H-1,3-benzimidazol-1-ylmethyl)phenoxy]alkane (L1: n = 1, L2: n = 3, L3: n = 4), and their six metal complexes were synthesized by the reactions of the respective ligands with metal salts. The six metal complexes included two cobalt(II) complexes ([Co(L1)(NO3)2] (1) and [Co(L3)(LA)]n (6) (LA = maleate)), two copper(II) complexes ([Cu(L1)(SO4)]2 (4) and [Cu(L3)(SO4)]2 (5)), one zinc(II) complex ([Zn(L1)(NO3)2] (2)) and one nickel(II) complex ([Ni(L2)(NO3)2] (3)). Complexes 1 and 2 had one 16-membered macrometallocycle, and complex 3 had one 18-membered macrometallocycle. In complexes 4 and 5, two SO42- joined two macrometallocycles together (16-membered macrometallocycle for 4 and 19-membered macrometallocycle for 5). In complexes 1-5, each macrometallocycle was constructed from one ligand and one metal ion. In complex 6, 19-membered macrometallocycles were connected together by maleate groups (LA) to form a 1D polymeric chain, where each 19-membered macrometallocycle was constructed from one L3 and one Co(II) ion. In crystal packings of complexes 1-6, H-bonds, π--π interactions and C--H•••π contacts participated in the formation of 2D supramolecular layers and 3D supramolecular architectures. The conformations of complexes 1-6 were also analyzed. Additionally, the recognition performance of complex 1 as a chemosensor for HSO4- was studied through fluorescence spectra, UV/vis spectra, 1H NMR titrations, HRMS spectra and IR spectra. The large binding constant (1.81 x 104 M-1) showed that there was a strong acting force between 1 and HSO4-, and the low detection limit (1.40 x 10-7 mol L-1) indicated that the detection of 1 for HSO4- was sensitive. The experimental results showed that complex 1 can effectively differentiate HSO4- from other anions. [ABSTRACT FROM AUTHOR]

Hydrazine hydrate and hydrogen peroxide are both important raw materials for industrial production and have a wide range of applications in several fields. Owing to their damage to the human body and cellular functions by excessive exposure or ingestion, it is essential to develop an efficient and rapid assay for the detection of hydrazine hydrate and hydrogen peroxide. Fluorescence switches have been applied in many fields including for metal ion detection. However, the assembly of Prussian blue (PB) and carbon quantum dots (CDs) has never been reported for the fabrication of a fluorescence switch for the detection of hydrazine and hydrogen peroxide. In this work, a fluorescent switch PB@CD/SiO2 based on PB and CDs was constructed, which could be used as a detection platform for hydrazine hydrate and hydrogen peroxide. The surface of PB was coated with a silica layer, which contained CDs to fabricate PB@CD/SiO2 nanoparticles. The composite demonstrated reversible switching between fluorescence quenching and recovering states through the mutual conversion of PB and Prussian white (PW). The prepared composite was utilized for the detection of N2H4 and H2O2 by fluorescence spectroscopy and UV-vis absorption spectroscopy. It is worth-mentioning that the detection limit for N2H4 is calculated to be 0.15 μM (fluorescence) and the detection limit for H2O2 can reach 0.93 μM (UV). Moreover, both detection methods showed low detection limits, wide detection ranges and a short response time for N2H4 and H2O2. The proposed fluorescence switch system exhibits good performance towards the dual-spectral determination of hydrazine and hydrogen peroxide by fluorescence spectroscopy and UV-vis spectroscopy, which may be beneficial for further application in practical fields. [ABSTRACT FROM AUTHOR]

Two phenothiazine derivatives, PTCNB and PTCNTBB, were designed and synthesized to confirm whether triaryl-substituted phenothiazine has mechanofluorochromic (MFC) properties and investigate the impact of tert-butyl (t-butyl) as a steric hindrance group on the molecular response to force stimuli. It was observed that the introduction of the t-butyl moiety did not significantly alter the molecular photophysical properties in the solution state due to its minimal effect on molecular π-conjugation. However, the presence of t-butyl strongly influenced their photoluminescence behavior and force-stimulus response in the solid state. PTCNB without t-butyl exhibited orange fluorescence in its pristine solid, which transformed into red fluorescence upon grinding, accompanied by a spectral shift of 23 nm. Conversely, PTCNTBB with t-butyl displayed green fluorescence in the as-synthesized solid and subsequently emitted orange fluorescence under force stimuli, demonstrating a more pronounced color variation. The corresponding spectral shift value was measured to be 58 nm. Remarkably, both ground solids regained their original fluorescence colors after vapor fuming, indicating a reversible MFC process. XRD patterns suggested that the application of force stimuli disrupted the intermolecular ordered packing while the fuming process restored ordered stacking, leading to the recovery of fluorescence emission. Absorption spectral changes implied that the presence of t-butyl induced loose packing and weak π--π interactions in PTCNTBB's initial solid, resulting in a short-wavelength fluorescence. Under force stimuli, the intermolecular interaction between PTCNTBB molecules was significantly enhanced, leading to an obvious redshift in the fluorescence spectra. In contrast, due to the absence of bulky steric groups, intermolecular packing between PTCNB molecules was relatively dense in its pristine solid and then applying pressure did not cause significant changes in a π-packing arrangement; hence only a small spectral shift occurred. [ABSTRACT FROM AUTHOR]

A new amphiphilic boron-dipyrromethene (BODIPY) dye bearing a hydrophobic 2,3,4-tris(n-dodecyloxy) phenyl group at the meso-position and two hydrophilic cationic moieties at the boron was synthesized. This dye exhibited kinetically controlled and thermodynamically controlled aggregation pathways in aqueous solution, leading to the formation of two types of J-aggregates, i.e., the metastable Agg. I and thermodynamically more stable Agg. II. Further kinetic analysis of the spontaneous transformation from Agg. I to Agg. II indicated that Agg. I was an off-pathway aggregate species. Moreover, both Agg. I and Agg. II displayed J-aggregate characteristics with enhanced fluorescence quantum yields and shortened fluorescence lifetime with respect to that of the monomeric dye. In particular, Agg. II exhibited a narrowed and intense J-band, reflecting the strong excitonic coherence in the aggregate. Morphological studies revealed that Agg. I consisted of spherical nanoparticles, while Agg. II had a multilamellar vesicular structure. In addition, in the fluorescence spectra of Agg. I and Agg. II, an unexpected broad band at longer wavelength than that of the J-aggregate emission was observed, which could be ascribed to the possible formation of excimers in these J-aggregates in aqueous solution. [ABSTRACT FROM AUTHOR]

Red fluorescent materials have important application value in the background light and LED lighting fields of displays. In this work, a novel type of rare earth free deep-red phosphor LiMg4SbO7:Mn4+ was prepared successfully, and its crystal structure, microstructure, fluorescence spectrum, quantum yield, thermal stability, fluorescence lifetime, color coordinates and color purity were studied in detail. The excitation spectra of LiMg4SbO7:Mn4+ phosphors are located at 200–600 nm, which can be matched with ultraviolet, near-ultraviolet, and blue-light chips. The exciting result is that the LiMg4SbO7:0.002Mn4+ phosphor exhibits astonishing quantum efficiency, thermal stability and color purity. Finally, the developed LiMg4SbO7:Mn4+ and the yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce3+) were mixed and coated on a blue light chip (460 nm) to produce a w-LED, which exhibited warm white luminescence with color coordinates of (0.3575, 0.3809), correlated colour temperature (CCT) of 4687 K, and color rendering index (CRI) of 83.6. It is reasonable to consider that LiMg4SbO7:Mn4+ phosphors with excellent photoluminescence performance have great application value in LED lighting fields. [ABSTRACT FROM AUTHOR]

Nitrogen and sulfur-doped carbon quantum dots (N,S-CQDs) were successfully synthesized utilizing Aegle Marmelos as an environmentally friendly precursor via an innovative method. Various spectroscopic and microscopic techniques, including fluorescence spectroscopy, XPS and HR-TEM, were employed to analyse the N,S-CQDs. The material demonstrates excitation-dependent emission behaviour, emitting a blue light under UV lamp illumination. Notably, the emission remains pH-independent. The synthesized N,S-CQDs exhibit a high quantum yield of 31.42%. The resulting blue-emitting N,S-CQDs were utilized for both quantitative and qualitative determination of brilliant green (BG) dye and Cu2+ ions in aqueous environmental samples, with drinking water and treated wastewater as representative real samples, demonstrating a robust recovery of BG dye of 99.6–101.06% for drinking water and 102.4–105.8% for treated wastewater samples and favourable recovery for Cu2+ ions of 99.2–104% for drinking water and 100.8–107.4% for treated wastewater samples. The fluorescence of N,S-CQDs was influenced by BG dye/Cu2+ ions through the PET mechanism, causing fluorescence quenching/enhancement. Fluorescence lifetime decay analysis confirmed dynamic quenching with BG dye and aggregation-induced high fluorescence emission with Cu2+ ions. [ABSTRACT FROM AUTHOR]

Enzyme-instructed self-assembly (EISA) has been explored for many applications in the life sciences including imaging and therapeutics. To date, use of the strategy is limited by the relatively high concentration – often in the mM regime – required for assembly. Here, a porphyrin–peptide conjugate (1) was designed as a water-soluble, EISA substrate. Compound 1 is built around a trans-AB porphyrin chassis that is equipped with a monodisperse 1 kDa polyethylene glycol (PEG) linker (a surrogate for a potential targeting agent) and an enzymatically triggerable self-assembly motif. The latter is comprised of two identical self-assembly peptides (also known as hydrogelators) attached to the 2,6-positions of an aryl group. The peptides have sequence GffY and in protected form contain tyrosine as an O-phosphoester GffY(p). Treatment of 1 with alkaline phosphatase (ALP) gave rise to the self-assembly (or aggregation) process as characterized by absorption spectroscopy. A control compound without the phosphoester trigger was synthesized and examined for the self-assembly process using fluorescence and absorption spectroscopy. A concentration-dependent study showed that at 10 nM approximately 50% of porphyrin–peptide conjugate was in the aggregated form. The nanomolar assembly suggests possible applications of EISA substrates in chemotherapy, although a further decrease in concentration to the picomolar regime may be required for use in targeted molecular radiotherapy, where very low mass dosing is typical. [ABSTRACT FROM AUTHOR]

Scattering interference (SI) is the possible scattering of intense radiation from the source, which is superimposed directly onto the resonance fluorescence signal of interest. It will lead to sham high results when using a non-dispersive optical system for As detection. To solve the SI of As, in this paper, a real-time suppression method named the non-fluorescent line ratios (NFLR) method was proposed after detailed analysis using dispersive atomic fluorescence spectrometry based on an ultraviolet digital micromirror device spectrometer (UV-DMD-AFS). Specifically, according to the characteristic of fast wavelength selection of UV-DMD-AFS, the source of SI and the effect of external factors on SI were analyzed, the non-fluorescent lines of As and the ratios of non-fluorescent lines to fluorescent lines (simplified as "Ratios") were determined, and the stability of the Ratios was studied under different parameters. The NFLR method suppressed the SI of As effectively, whose suppression proportion was 98.50–102.43%. Compared with the non-dispersive AFS, the NFLR method had a higher long-term accuracy (>99.20%) validated with certified reference materials (CRMs) of water quality samples. [ABSTRACT FROM AUTHOR]

In this paper, a novel Schiff base ligand NaHL (NaHL = sodium (S,E)-2-((4-chloro-2-hydroxybenzylidene) amino) propanoate) was designed and synthesized, and three novel complexes with Zn(II) were obtained by a solvent evaporation technique. Single crystal X-ray diffraction indicated that [Zn(L)(H2O)]n1 and [Zn(L)(H2O)]n2 were one-dimensional coordination polymers (CPs) with a helix structure, while [Zn2(L)2(bipy)] 3 was a two-dimensional CP with the participation of an auxiliary ligand. Fluorescence spectra exhibited that 1 and 2 had good fluorescence properties in both solution and solid states, but 3 was basically quenched due to the addition of ancillary ligands in the solid state. Density functional theory (DFT) calculations have been performed to further reveal the intrinsic fluorescence properties and mechanisms of 1 and 2, which demonstrated the chelate fluorescence enhancement effect (CHEF). Moreover, 1 and 2 show selective recognition of NH4+ and HPO42− accompanied by an efficient fluorescence "turn off" phenomenon, and a series of related experiments demonstrate that 1 and 2 were fully quenched through the removal of Zn2+ from the complex and the protonation of the ligand. [ABSTRACT FROM AUTHOR]

Polychromatic emission can be achieved by controlling the distribution of the rare earth activator in multi-cation lattices, which can be used in the fields of white light LED and fluorescence temperature sensing. However, it is still a challenge to control their distribution and location of the target site in a given host material because the distribution of the rare earth activator is uncertain. In this paper, we have chosen Li4SrCa(SiO4)2 as the multi-cation site host and induced the distribution of Eu2+ ions between different cation sites through anion substitution, for the first time, to regulate the luminescence characteristics of a series of Li4SrCaSi2O8-yN2y/3:Eu2+ phosphors. In Li4SrCa(SiO4)2:Eu2+ phosphors, the substitution of O2- by N3- triggered a distinct ordered to disordered structure transition of the SiO4 tetrahedron and induced the remote distribution of the Eu2+ activator, which was verified through the analysis of the XRD, EPR, FT-IR and fluorescence spectra. Due to the location of Eu2+ ions in different cation sites (Eu2+ Sr and Eu2+ Ca), two distinguishable emission peaks with tunable color emissions and different responses to temperature were realized. The white LED that utilized blue-orange-emitting Li4SrCaSi2O4N8/3:Eu2+ and green-emitting BaSi2O2N2:Eu2+ (500 nm) displayed an outstanding color rendering index (Ra) of 85.1. Based on the fluorescence intensity ratio (FIR) technique, an optical temperature measurement mechanism was hypothesized and studied in the temperature range of 293-473 K. The highest Sa of the material was 0.086 K-1, and Sr was 1.76% K-1 based on the FIR detection technology, revealing obviously better than most inorganic optical temperature-measuring materials reported before. Our work indicates that Li4SrCaSi2O8-2yN4y/3:Eu2+ is a promising material for application in White LEDs and optical thermometers. [ABSTRACT FROM AUTHOR]

In this paper, BaAl2O4:Eu2+–Al2O3 ceramics were successfully prepared by spark plasma sintering (SPS). The optical properties of the multiphase ceramics doped with different concentrations of alumina were studied. Under excitation with 365 nm ultraviolet light, the luminescent color of the samples can be adjusted by changing the sintering temperature and the contents of alumina addition. The temperature dependent fluorescence spectra in the temperature range of 4 K–434 K were measured, and the temperature dependent fluorescence intensity ratio (FIR) was calculated. The FIR monotonically increased with the increase of temperature, indicating that the material could be used for temperature sensing. The absolute sensitivity Sa of the temperature sensing fluorescent material is larger than 0.005 K−1 at 334 K–434 K, and the relative sensitivity Sr is larger than 0.75% K−1 at 304 K–434 K. The results show that the BaAl2O4:Eu2+–Al2O3 ceramic is a promising non-contact temperature sensing material. [ABSTRACT FROM AUTHOR]

The combination of photothermal therapy (PTT) and chemotherapy has been extensively investigated as a promising anticancer strategy, which can maximize therapeutic effects, reverse multidrug resistance, and reduce side effects. However, a conventional nanodrug delivery system incorporating a photothermal agent and chemotherapeutic drug together shows some disadvantages, including lower drug loading content, complex preparation process, and unpredictable safety risks of the carrier. Herein, a perylene diimide (PDI) derivative, PDI0, was synthesized as a photothermal agent, which could co-assemble with the chemotherapeutic drug DOX to develop novel multifunctional supramolecular nanodrugs. The prepared nanodrugs DP1, DP2, and DP3 with ultra-high drug loading capacity were carefully characterized by UV-vis absorption spectroscopy, fluorescence spectroscopy, DLS, and TEM. Notably, DP2 showed an appropriate average size of ∼73.4 nm. DP2 was sensitive to the stimuli of external light and internal lysosome acidic pH, and the photothermal conversion efficiency (η) was ∼54.34%. The photothermal and photoacoustic (PA) dual-mode imaging and anticancer effect were further evaluated by in vitro and in vivo investigations. Therefore, our prepared carrier-free nanodrug DP2 may have potential applications for dual-mode imaging guided synergistic PTT-chemotherapy. [ABSTRACT FROM AUTHOR]

Er3+/Yb3+ codoped glass ceramics containing BaF2 crystals were obtained through a melt quenching process; the precipitation of BaF2 nanocrystals was confirmed by structural characterization. The effects of crystal quantity and size on the transmittance and upconversion fluorescence of the samples were analyzed. The precipitation of nanocrystals leads to a significant increase in upconversion luminescence intensity. The fluorescence spectra at different pump powers were measured. Er3+ and Yb3+ energy level diagrams and possible energy transfer routes during upconversion luminescence were explored. Furthermore, the functional relationship between temperature and the upconversion fluorescence intensity ratio of the samples was analyzed. When the temperature is 293 K, the relative sensitivity reaches the maximum of 1.38% K−1. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis, crystal structure, and antibacterial activity of a new Ni(II) complex derived from the N, O donor (E)-2,4-dibromo-6-(2-(1-phenylethylimino) ethyl) phenol ligand. Both the ligand and the complex were characterized by employing FT-IR, UV-Visible, and fluorescence spectroscopy as well as single-crystal X-ray diffraction studies. The crystallographic results reveal that the complex crystalizes in the monoclinic unit cell with the space group C2, and the coordination environment around the Ni centre consists of NiN2O2 donor sites exhibiting a highly distorted tetrahedral geometry. The oxidative assay of DPPH (α,α-diphenyl-β-picrylhydrazyl) was used for evaluating the radical scavenging activity or antioxidant properties of the complex in terms of IC50 values (50% inhibition); it was observed that the complex showed reasonable antioxidant activities with ascorbic acid (AA) as the standard. Detailed interaction studies with calf thymus (CT) DNA and bovine serum albumin (BSA) were performed through various spectroscopic and theoretical approaches and indicated that the complex has promising binding capability with both the systems. Comprehensive biological studies were performed and showed that the complex exhibits notable antibacterial activity against Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) by interfering with its cell wall integrity. Microscopic imaging confirmed cellular abnormalities, such as alterations in the cell shape, size, and quantity. Molecular docking analyses also provided insights into the activities of the complex. In contrast, the complex displayed minimal growth inhibition properties against Gram-negative Klebsiella pneumoniae (KP) even at higher complex concentration, indicating that the specific inhibition activity of the complex is only against Gram-positive MRSA. Moreover, based on optical density readings, the results demonstrated that the complex exhibited effective antibacterial activity against MRSA with an MIC value between 34 and 36 μg ml−1, whereas the MIC value of standard cefoxitin is >70 μg ml−1. Thus, our complex demonstrated better antibacterial activity than the conventional antibiotic. [ABSTRACT FROM AUTHOR]

The four new ligands, dialkyl esters of (S,S)-propylenediamine-N,N′-di-(2,2′-di-(4-hydroxy-benzil))acetic acid (R2-S,S-pddtyr·2HCl) (R = ethyl (L1), propyl (L2), butyl (L3), and pentyl (L4)) and corresponding palladium(II) complexes have been synthesized and characterized by microanalysis, infrared, 1H NMR and 13C NMR spectroscopy. In vitro cytotoxicity was evaluated using the MTT assay on four tumor cell lines, including mouse mammary (4T1) and colon (CT26), and human mammary (MDA-MD-468) and colon (HCT116), as well as non-tumor mouse mesenchymal stem cells. Using fluorescence spectroscopy were investigated the interactions of new palladium(II) complexes [PdCl2(R2-S,S-pddtyr)]; (R = ethyl (C1), propyl (C2), butyl (C3), and pentyl (C4)) with calf thymus human serum albumin (HSA) and DNA (CT-DNA). The high values of the binding constants, Kb, and the Stern–Volmer quenching constant, KSV, show the good binding of all complexes for HSA and CT-DNA. The mentioned ligands and complexes were also tested on in vitro antimicrobial activity against 11 microorganisms. Testing was performed by the microdilution method, where the minimum inhibitory concentration (MMC) and the minimum microbicidal concentration (MMC) were determined. [ABSTRACT FROM AUTHOR]

Protein phase separation plays a very important role in many biological processes and is closely related to the occurrence and development of some serious diseases. So far, the fluorescence imaging method and fluorescence correlation spectroscopy (FCS) have been frequently used to study the phase separation behavior of proteins. Due to the wide size distribution of protein condensates in phase separation from nano-scale to micro-scale in solution and living cells, it is difficult for the fluorescence imaging method and conventional FCS to fully reflect the real state of protein phase separation in the solution due to the low spatio-temporal resolution of the conventional fluorescence imaging method and the limited detection area of FCS. Here, we proposed a novel method for studying the protein phase separation process by objective scanning-based fluorescence cross-correlation spectroscopy (Scan-FCCS). In this study, CRDBP proteins were used as a model and respectively fused with fluorescent proteins (EGFP and mCherry). We first compared conventional FCS and Scan-FCS methods for characterizing the CRDBP protein phase separation behaviors and found that the reproducibility of Scan-FCS is significantly improved by the scanning mode. We studied the self-fusion process of mCherry-CRDBP and EGFP-CRDBP and observed that the phase change concentration of CRDBP was 25 nM and the fusion of mCherry-CRDBP and EGFP-CRDBP at 500 nM was completed within 70 min. We studied the effects of salt concentration and molecular crowding agents on the phase separation of CRDBP and found that salt can prevent the self-fusion of CRDBP and molecular crowding agents can improve the self-fusion of CRDBP. Furthermore, we found the recruitment behavior of CRDBP to β-catenin proteins and studied their recruitment dynamics. Compared to conventional FCS, Scan-FCCS can significantly improve the reproducibility of measurements due to the dramatic increase of detection zone, and more importantly, this method can provide information about self-fusion and recruitment dynamics in protein phase separation. [ABSTRACT FROM AUTHOR]

Lanthanide ion-doped up-conversion (UC) luminescent materials are highly coveted for their utility in diverse applications such as anti-counterfeiting, fluorescence labeling, and temperature sensing. Here, we attempt to adopt SrY2S4 as a novel host lattice for UC luminescence and high-sensitive optical thermometry under near-infrared irradiation. The results show that the single Er3+-doped SrY2S4 samples present their main emissions in green and red regions under 1550 and 980 nm excitations, which correspond to the H11/2/4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions, respectively. The green to red intensity ratio increases with the Er3+ concentration under both 980 and 1550 nm excitations. The mechanisms of UC luminescence and energy transfer are further systematically investigated by UC spectra and fluorescence decay dynamics. Furthermore, the non-contact temperature sensing performance of the SrY2S4:10%Er3+ sample is explored via employing fluorescence intensity ratio (FIR) technology. At an excitation of 980 nm, the maximum absolute sensitivity (SA) reaches 7.5 × 10−3 K−1 at 480 K. By utilizing a much safer excitation laser of 1550 nm, the maximum SA achieves 8.4 × 10−3 K−1 at 450 K, with a high and stable SA of more than 7.9 × 10−3 K−1 over a broad temperature range of 360–570 K. The relative sensitivity is 1.06% and 1.01% K−1 under 980 and 1550 nm excitations, respectively. These results indicate that the ternary sulfide SrY2S4 can be adopted as a novel host to achieve promising UC luminescence and thermal sensing performance. [ABSTRACT FROM AUTHOR]

Coffee, one of the top ten most globally traded commodities, can be grown in different agricultural regions presenting peculiar characteristics. Thus, the determination of inorganic nutrients in ground-roasted coffee has nutritional relevance and allows authentication as well as tracking of the origin of the product. Analytical methods routinely used to determine inorganic nutrients in food are based on time-consuming steps that involve acid digestion followed by elemental quantification. In this study, analytical strategies for the direct determination of inorganic macronutrients (P, K, Ca, and Mg) in commercial samples of ground-roasted coffee were evaluated by portable X-ray fluorescence spectrometry (pXRF) using two commercial spectrometers. Two calibration approaches were tested: (i) using plant-based certified reference materials (CRMs); (ii) matrix-matched calibration, using samples of ground-roasted coffee as well as the corresponding solid residues resulting from infusion, the spent coffee grounds (SCG). The analyte mass fractions in these samples were determined by the reference method (decomposition using HNO3 and H2O2 followed by ICP OES measurements). In the latter method, calibration models were built using reference values and analytical signals obtained by pXRF. Pressed pellets from the samples (CRMs, ground-roasted coffee, and SCG) were prepared. The samples were irradiated for 50 s using both spectrometers under two experimental conditions: X-ray tube voltage of 15 kV and 50 kV. Calibration models with excellent linearity were obtained (r ≥ 0.90) for all analytes. The proposed matrix-matched calibration method was considered the most accurate approach for elemental determination (mainly P and K) in samples of ground-roasted coffee as well as in the spent coffee grounds, an alternative agricultural fertilizer. [ABSTRACT FROM AUTHOR]

Carbazole derivatives are widely used to make highly efficient optoelectronic materials. In this context, we developed a method for synthesizing conjugated carbazole derivatives using bimetallic Pd–Cu nanoparticles (NPs) immobilized on reduced graphene oxide (rGO) sheets. Pd–Cu NPs were synthesised in a one-pot wet chemical process with ascorbic acid as the reducing agent. The Pd–Cu NPs have an average diameter of 3.8 ± 1.2 nm. X-ray diffraction, SEM, TEM, EDS, and cyclic voltammetry were used to characterise the structure and morphology of the Pd–Cu@rGO NPs. N-Protected-3-aryl/heteroaryl carbazoles were efficiently synthesized using the Pd–Cu@rGO catalyst, which enabled the Suzuki–Miyaura (SM) cross-coupling reaction between N-protected-3-bromo-carbazoles and a range of aryl/heteroaryl boronic acids. The prepared compounds were characterized by NMR (1H & 13C) and HRMS spectra. For the SM reaction, the catalytic performance of the monometallic Pd@rGO and bimetallic Pd–Ni@rGO and Pd–Cu@rGO catalysts were studied with various metal loadings. In comparison to the monometallic Pd@rGO and bimetallic Pd–Ni@rGO catalysts, the bimetallic Pd–Cu@rGO heterogeneous catalyst (L3) demonstrated improved catalytic performance with yields of up to 98%. The material exhibits excellent recyclability and can be reused up to five times without experiencing any decline in its effectiveness. The electronic structure modification offered by the Pd–Cu ensemble on rGO may be responsible for its higher catalytic efficiency. UV and fluorescence spectra were used to investigate the optoelectronic properties of the produced carbazole compounds. Among the compounds studied, 5f, 5n, and 5h exhibited superior UV absorption and fluorescence emission due to the presence of auxochromes and extended conjugation. This study explores the efficacies of the reduced graphene oxide-supported Pd–Cu bimetallic system with different weight% for milder SM reactions. [ABSTRACT FROM AUTHOR]

By reacting a series of 2,6-diacetylpyridine bis-hydrazones containing pyrimidine (H2L1), benzimidazole (H2L2) and phthalazine (H2L3) heterocyclic fragments with copper(II) chloride and bromide, a variety of pentacoordinated complexes of the composition [Cu(H2L1)X]X, [Cu(HL2)X] and [Cu(HL3)X], where X = Cl−, Br−, are formed. The properties and structure of the compounds were studied by means of NMR, IR, UV-vis, ESR, and X-ray absorption spectroscopy, cyclic voltammetry and X-Ray single crystal diffraction methods. It was shown that complexes of the cationic type [Cu(H2L1)X]X have an asymmetric structure with a distorted square-pyramidal geometry of the coordination unit. The coordination polyhedron of metal chelates [Cu(HL2)X] and [Cu(HL3)X] is an almost ideal square pyramid. Investigations of the cytotoxic activity of the obtained compounds in vitro on human hepatocellular carcinoma (HepG2) and non-tumor human lung fibroblast (MRC-5) cell lines demonstrated that complexes show higher activity compared with the well-known anticancer agent cisplatin. In addition, metal chelates [Cu(H2L1)Cl]Cl, [Cu(HL2)Cl], [Cu(HL2)Br] and [Cu(HL3)Cl] were less toxic to non-tumor cells MRC-5. A study of the binding of complexes to bovine serum albumin (BSA) protein using fluorescence spectroscopy showed that copper complexes are strongly bound to BSA. To study the mechanism of interaction of the complexes with the DNA of cancer cells, molecular dynamics simulation of the compound [Cu(HL3)Cl] was carried out. It was shown that the complex enters into π-stacking interactions predominantly with adenine and thymine bases. [ABSTRACT FROM AUTHOR]

A long afterglow material CaAl2O4:Eu2+,Pr3+ emitting blue light has been synthesized by a high-temperature solid-phase method. The effect of a series of preparation conditions on CaAl2O4:Eu2+,Pr3+ was first investigated using a single-factor preference method, and the optimal synthesis conditions were then obtained through orthogonal tests. The target products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), elemental mapping, fluorescence spectroscopy, and afterglow properties. The XRD results indicate the successful synthesis of CaAl2O4:Eu2+,Pr3+ materials, which was further verified by XPS analysis. The afterglow properties of the target products were further improved by doping with Nd3+ under optimum conditions obtained from orthogonal tests. The improvement was analyzed through XRD, fluorescence, afterglow and thermoluminescence analysis. The results indicate that doping with Nd3+ in CaAl2O4:Eu2+,Pr3+ materials significantly enhanced the afterglow properties, including an initial brightness of 2318 mcd m−2 and a duration of 26.5 hours. Thanks to its excellent blue long afterglow luminescence, the material is anticipated to have applications in energy-efficient lighting systems and solar energy systems. [ABSTRACT FROM AUTHOR]

A dinuclear complex [(H2O)Zn(LH)Eu(NO3)3] containing a hexadentate Schiff-base {N2O4}-donor ligand LH2− was prepared and characterized by X-ray structural analysis and IR, electronic and fluorescence spectroscopy. DC magnetic data show that upon heating the diamagnetic complex with the ground state Eu(III)–7F0 and Zn(II)–1S switches to paramagnetic species due to the population of 7FJ (J = 1 to 6) magnetic multiplets. The magnetic susceptibility increases from zero, passes through a maximum, and then decreases upon heating. This behaviour can be explained using a spin–orbit Hamiltonian with an axial distortion term. There is an alternative interpretation of the susceptibility data based on a two-level model similar to that used in the spin crossover theory. [ABSTRACT FROM AUTHOR]

This article describes the synthesis of acetylenic-indole conjoined silane (4) and silatrane (5, 6) and their structural characterization by NMR (1H and 13C) spectroscopy, TGA and ESI-QTOF mass spectrometry. The prepared compound 5 was screened for its cationic chemosensing activity, which showed selective and sensitive recognition of Co2+ and Cu2+ ions with considerable change in the intensities of absorption and emission maxima. Furthermore, the binding constant, Stern–Volmer constant and limit of detection were calculated by plotting the BH-plot, Stern–Volmer plot and linear calibration curve, respectively. The LOD values obtained from fluorescence spectroscopy for Co2+ and Cu2+ ions were 0.3812 × 10−6 M and 0.4130 × 10−6 M, respectively, which are below the WHO allowable limits of Co2+ (1.70 μM) and Cu2+ (20 μM) ions in drinking water, suggesting that the silatrane receptor 5 may be used for biological and industrial purposes. Moreover, the molecular docking studies provide useful information about the interaction of compound 5 with the α-glucosidase enzyme (PDB ID: 3A4A). [ABSTRACT FROM AUTHOR]

Fire blight, an extremely disastrous plant disease caused by the bacterium Erwinia amylovora, has the capacity to wipe out entire orchards in just one growing season when ideal conditions are present. A recent discovery has revealed that 6-thioguanine (6TG) plays a significant role in the development of fire blight caused by the plant pathogen. Therefore, it is of utmost importance to effectively prevent and manage fire blight in order to ensure the health and productivity of these fruit trees. In this research, we have developed a novel and significant approach focusing on trapping 6TG to disrupt the spreading of fire blight among trees. We have developed carbon quantum dots (N-CQDs) that efficiently bind 6TG through a fluorescence quenching process resulting in the alleviation of the disease. The quenching mechanism and related phenomena have been extensively elucidated through the implementation of analytical tools including the Stern–Volmer plot, UV-vis spectroscopy, fluorescence titration, and fluorescence lifetime decay analysis. Furthermore, the structural attributes and size of the nitrogen-doped carbon quantum dots (N-CQDs) have been definitively established through a comprehensive array of techniques, including Fourier-transform infrared (FT-IR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDX, EM), and X-ray Photoelectron Spectroscopy (XPS). The nanodot has been successfully applied in guava saplings (Psidium guajava) to investigate the trapping of 6TG by treating them with N-CQDs. This process has been validated through the use of confocal microscopic imaging, providing visual confirmation of the 6TG trapping mechanism. [ABSTRACT FROM AUTHOR]

Presented here is the first demonstration of supervised discretization to ‘declutter’ multivariate classification data in chemical sensor applications. The performance of multivariate classification models is often limited by the non-informative chemical variance within each target class; decluttering methods seek to reduce within-class variance while retaining between-class variance. Supervised discretization is shown to declutter classes in a manner that is superior to the state-of-the-art External Parameter Orthogonalization (EPO) by constructing a more parsimonious model with fewer parameters to optimize and is, consequently, less susceptible to overfitting and information loss. The comparison of supervised discretization and EPO is performed on three classification applications: X-ray fluorescence spectra of pine ash where the pine was grown in three distinct soil types, laser induced breakdown spectroscopy of colored artisanal glasses, and laser induced breakdown spectroscopy of exotic hardwood species. [ABSTRACT FROM AUTHOR]

A new polymorf of Schiff base (N-(4′-methoxybenzylidene)-4-aminobenzoic acid) and five of its distinct salts (chloride, bromide, nitrate, hydrosulfate and dihydrophosphate) were designed and synthesized. Detailed examinations were conducted to determine the structure and spectral properties of these compounds, employing methods like X-ray diffraction, as well as IR, UV-Vis and fluorescence spectroscopy. Interestingly, all the synthesized Schiff base salts displayed fluorescence when in solid state. However, the intensity of this fluorescence was found to differ, depending on the type of anion present within the structure. This result provides evidence that a strategy similar to supramolecular complexation can effectively be used to adjust the emission wavelength and control the intensity of fluorescence in the resulting solid materials. [ABSTRACT FROM AUTHOR]

Biogenic amines are responsible for transmitting electrical impulses in biological systems and hold immense physiological significance. To detect these amines under physiological conditions, optical sensing methods are favoured due to their simplicity, affordability, and rapid response. Probes based on macrocycles or molecular capsules have proven superior for chemosensing applications due to their unconventional structures and intriguing properties. Here we report the synthesis of a BF2-containing molecular capsule with high luminescence and long lifetimes in solution and in the solid state. The cylindrical cavity in the capsule encompassing polarised Bδ+–Fδ− bonds facilitates the formation of multiple hydrogen bonds with dopamine, and the complexation is signalled through visual changes in colour and fluorescence. The mechanism of interaction was studied using fluorescence and NMR spectroscopy and further supported by molecular dynamics simulations, which revealed that multiple non-covalent interactions between the molecular capsule and dopamine are responsible for stabilizing the inclusion complex. Finally, we demonstrate the use of the molecular capsule as a simple probe by preparing a test strip using a polymer for the sensing of dopamine under various conditions. [ABSTRACT FROM AUTHOR]

Three novel carbazole–anthracene–cyanostilbene based D–A conjugates were designed and synthesized with slight structural modification of the acceptor unit (cyanostilbene; OMe is 5a; H is 5b; Cl is 5c) to understand the effect of the change of the optical properties. The photophysical characteristics of the compounds in various solvents and in the solid state, and aggregation emission behaviour were extensively examined. The fluorescence spectrum of compound 5a was completely different from those of the other two compounds (5b and 5c), which exhibited reverse solvatochromism on increasing the polarity of solvents, whereas the other two exhibited positive solvatochromism. The compounds displayed AIE characteristics in a solution of acetonitrile-H2O mixture, could be attributed to the non-planar/twisted geometry of cyanostilbene and the restriction of intramolecular motion (RIM) in aggregated states and formation of aggregates was confirmed by FE-SEM and AFM images. Remarkably, all compounds exhibited reversible mechanofluorochromic (MFC) characteristics in which the color of compound 5a changed from bluish green to green color, while the other compounds showed greenish yellow to yellow color in the solid state, which was further supported by powder XRD and solid-state emission data. The optimized ground state structures of compounds 5a–c were obtained using theoretical investigations. The current work presents an extensive evaluation of the optical, electronic, AIE, and MFC properties of carbazole–anthracene–cyanostilbene derivatives caused by structural modifications of the acceptor unit (cyanostilbene). [ABSTRACT FROM AUTHOR]

The mycotoxin patulin is a common contaminant in rotten fruits, posing severe food safety risks and threats to human health. Developing a convenient, sensitive and reliable method for patulin detection is of utmost importance but remains challenging. In this study, we have successfully designed and synthesized a small-molecule fluorescent probe, FITC–Lys, which demonstrates good sensitivity in detecting patulin. Upon contact with patulin, the terminal Lys group of the FITC–Lys probe reacts with patulin, resulting in the formation of the fluorescein dimer that subsequently quenches fluorescence. This variation of fluorescence enables the visualization and sensitive detection of patulin. The probe exhibits good sensitivity with a low LOD of 8 ng mL−1 for the fluorescence spectrum method and a LOD of 12 ng mL−1 for the fluorescence imaging method. Moreover, we have validated the probe's capability for patulin detection in apple and pear juices, achieving good recoveries ranging from 98.60% to 103.80%. Notably, the probe FITC–Lys is the first small-molecule fluorescent probe that has proven successful in visualizing patulin in juices derived from decayed apples and pears. Consequently, this probe holds great potential as a practical tool for monitoring patulin in foodstuffs, thereby contributing to enhanced food safety standards. [ABSTRACT FROM AUTHOR]

Pyrene-substituted amphiphilic ATRP polymers (P1) were used to stabilize the pyrene-substituted gold(I) NHC complex (Au-1) within the hydrophobic compartment of micellar structures in a methanol/water mixture through non-covalent π-π stacking interactions. The stacking interactions between pyrene groups of the polymer and the catalyst were investigated by means of fluorescence spectroscopy by comparing excimer and monomer emission signals of the pyrene moiety. The supported catalyst (Au-1@P1) formed spherical micellar structures in a water/methanol mixture with an average size of 55.6 (±13.1) nm as confirmed from TEM analysis. The performance of the catalytic system was tested on alkyne hydration reactions of alkynes. When compared to the unsupported analog, the supported catalyst showed an improved performance as a result of stabilization through π-stacking interactions within the hydrophobic compartment in the micellar structure. [ABSTRACT FROM AUTHOR]

In vivo X-ray fluorescence spectrometry is a technique used to quantify trace elements in bone tissue by using an external γ-ray source to irradiate a section of the body. The current system for bone metal quantification is capable of detecting metals such as strontium in human bone by using an 125I radionuclide excitation source with photon detection using a Si(Li) detection system. The historical choice of phantom material, plaster of Paris, has introduced numerous complications in terms of its suitability for the calibration of systems of bone metal quantification. A chemically pure hydroxyapatite phantom material of known composition and stoichiometry has been developed for the purpose of calibrating systems of bone metal quantification as a replacement for plaster of Paris while also removing the required coherent conversion (correction) factor from the protocol. Hydroxyapatite, however, is not necessarily stable over time and thus this study assessed common calcium phosphate glasses prepared with metal oxides as potential candidate calibrators. Monte Carlo simulations were carried out using the bench-marked EGS5 code to evaluate if calcium phosphate glasses can be used in the same fashion as hydroxyapatite. Selected glasses were assessed for their differential cross-sections for coherent scattering as well as the implications on the correction factor. The calcium phosphate glasses did not show much agreement with hydroxyapatite when comparing the slopes of the normalized calibration curves nor when directly calculating the correction factor from the ratios of the differential coherent scattering cross-sections for bone mineral to the glass phantoms. This simulation study thus concludes that the removal of the correction factor from the calibration protocol requires the use of a hydroxyapatite phantom and that conventional calcium phosphate glasses, although desirable, cannot be used reliably as calibrators. [ABSTRACT FROM AUTHOR]

Monochromatic excitation X-ray fluorescence (ME-XRF) spectrometry is an emerging technique for elemental analysis with many potential forensic applications. In this study, a method for rapid and efficient quantification of As, Hg, Tl, and Pb in biological tissues using ME-XRF was established and applied to actual cases. The instrument's operating conditions were optimized, and the optimum method for sample preparation was determined. According to the calibration curves of each element, a new model for the detection of biological tissues was developed based on the fundamental parameter (FP) method. The LOD values of As, Hg, Tl, and Pb were 0.04, 0.04, 0.06, and 0.07 μg g−1, respectively. Through systematic evaluation and validation, the feasibility of using ME-XRF in forensic toxicology analysis was confirmed. [ABSTRACT FROM AUTHOR]

High-quality single crystals of new Nd-doped scheelite, Bi2Mo2.66W0.34O12 (Nd:BMO), with dimensions up to 80 × 57 × 35 mm3 were grown via the top-seeded solution growth (TSSG) method using a mixture of MoO3–WO3 as a flux for the first time. The polarized absorption and fluorescence spectra as well as the fluorescence decay curve of the crystal were investigated in detail at room temperature (RT). Comparisons between the radiative and fluorescence lifetimes indicate a high fluorescence quantum efficiency (close to unity) and, thereby, the nonradiative transition from the 4F3/2 multiplet can be neglected in the laser performance. Some important spectroscopic parameters, including the effective intensity parameters for different polarizations, were calculated based on the Judd–Ofelt (JO) theory. The continuous wave (CW) laser performance at 1064 nm was demonstrated with Y- and Z-cut crystals under output coupler transmissions of 2% and 5%, respectively. A maximum output power of 113 mW was achieved under the absorbed power of 650 mW, corresponding to an optical-to-optical conversion efficiency of 17.4% and a slope efficiency of 21.6%. Considering the intrinsic high cleavability of the crystal along the (010) plane and the intense Raman activity of molybdates and tungstates, it is reasonable to expect that the Nd:BMO single crystals may have potential applications in microchips and self-stimulated Raman lasers. [ABSTRACT FROM AUTHOR]

Five covalently bonded polyoxometalate (POM)-porphyrin hybrids were synthesized by reacting the Wells–Dawson type polyoxometalate [N(C4H9)4]5H4P2W15V3O62 with five tris-functionalized porphyrins containing different numbers of tris groups at different peripheral positions. These hybrids were thoroughly characterized using elemental analysis, NMR (1H, 31P, and 51V), mass spectrometry (ESI-MS, MALID-TOF-MS), FT-IR, UV-Vis, and fluorescence spectroscopies. The results proved that different quantities (one, two, and three) of the vanadium-capped Wells–Dawson type metal–oxide cluster P2W15V3O629− can be grafted onto a porphyrin moiety via covalent bonding with different orientations, depending on the number and position of peripheral functional groups on the porphyrin. Interestingly, remarkable fluorescence quenching (60% in 3Py-P@1POM, 75% in trans-2PyP@2POM, 80% in cis-2PyP@2POM, 85% in cis-2PhP@2POM, and 55% in 1Py-P@3POM, as compared to the fluorescence intensity of their corresponding porphyrin precursor) was observed under excitation (λexc = 328 nm), indicating electron transfer from the porphyrin moiety to the POM moiety through covalent linkage. [ABSTRACT FROM AUTHOR]

Soil is an important source of potentially toxic metal intake for humans through the food chain. Accurate determination of elemental concentrations in soil is of great significance to safeguard human health, thereby requiring reliable detection techniques. This work aimed to propose a new quantitative analysis method that combines pre-processing and concentration prediction. A total of 59 soil samples were collected and subjected to laboratory analyses and energy dispersive X-ray fluorescence (ED-XRF) scans. Firstly, a novel pre-processing method based on iterative adaptive window empirical wavelet transform and Gaussian convolution (IAWEWT-GC) was proposed, which can identify and remove spectral background. Secondly, the instrument calibration curves of peak counts and elemental concentrations were established and the pre-treatment effect was verified by comparison with other common methods. The instrument calibration curves' coefficient of determination (R2) was enhanced to 0.988, 0.962, and 0.980 for Cr, Mn, and Cu, respectively. Finally, to accurately detect the elemental concentration, a hierarchical deep neural network (HDNN) was designed for estimating potentially toxic metals, enabling quantitative regression of multiple elements simultaneously. The proposed method was evaluated and compared with conventional algorithms (DNN, BPNN, and PLSR). The HDNN model achieved the highest R2 of 0.943, 0.983, and 0.979 for Cr, Mn, and Cu, respectively, with the lowest RMSEP of 5.74, 84.45, and 29.17, and lowest MAE of 4.51, 78.51, and 16.35, indicating its ability to enable simple, rapid, and effective quantitative analysis of multiple elements. Overall, our proposed method provides a new option for the elemental analysis of samples rich in potentially toxic metals. [ABSTRACT FROM AUTHOR]

An in situ investigation of the influence of pretreatment lignin distribution and interaction with enzymes can provide insights into the mechanism of lignin, limiting the enzymatic efficiency of cellulose. One of the main focuses of this study is to elucidate the differences in cellulase hydrolysis caused by surface lignin after pretreatment (including pseudo-lignin deposited on biomass surface lignin and soluble lignin) compared to residual lignin in the pretreated material. Particularly, the combination of different non-destructive spectroscopies (atomic force microscopy (AFM), surface plasmon resonance (SPR), and fluorescence spectrometry (FLS)) was used to examine the nonproductive adsorption mechanisms of cellulase with differing lignin fractions from pretreated poplar. The results showed that surface lignin (SL) from pretreated poplar had almost no inhibitory effect on the Avicel hydrolysis yield. In contrast, residual lignin (RL) in pretreated poplar significantly inhibited the Avicel hydrolysis yield from 74.6% to 50.94%. The characterization results revealed that SL has lower hydrophobicity, molecular weight, and linkage content (β-O-4, β–β and β-5), which is significantly different from the structure of RL. The multi-dimensional non-destructive spectroscopy indicated that the interaction forces between SL and cellulase fractions (0.044–2.04 nN) were smaller than that of RL and cellulase fractions (0.11–3.62 nN). The SL binds to cellulase mainly through hydrogen bonds and van der Waals forces, while the RL interacts mainly through hydrophobic forces. Furthermore, SL bound to cellulase is more likely to dissociate compared with RL. This study provides a fundamental understanding of lignin-cellulase interactions for effectively converting lignocellulose into biofuels. [ABSTRACT FROM AUTHOR]

Hemoglobin serves a multitude of biological functions and its activity and stability are influenced by structural alterations. Fibrillation of this protein is one such complication that can hinder its physiological levels resulting in numerous health disorders. This study focuses on providing a comprehensive elucidation on the binding interaction of bioactive esculin and esculetin with bovine hemoglobin (BHb) and ultimately determining the anti-fibrillation properties of these compounds. UV/vis spectroscopy and fluorescence measurements verified the presence of a static form of quenching mechanism for the BHb-esculin complex and a combined quenching mechanism for the BHb–esculetin complex. The binding affinity (Kb) was determined to be higher for the BHb–esculetin complex than for the BHb-esculin complex. This could be due to the lower binding distance observed between a β2-Trp37 residue and esculetin, as observed through Förster's theory, molecular docking, and molecular dynamic (MD) simulation. The calculated thermodynamic parameters indicated the presence of hydrophobic forces and hydrogen bonding stabilizing the complexes. Synchronous, 3D fluorescence, REES, and anisotropy measurements revealed microenvironmental alterations around the Trp residue induced by esculin/esculetin binding. Secondary structural changes of BHb in the presence of esculin/esculetin were observed through UV/vis absorption, CD, and FTIR studies. BHb was subjected to fibrillation in the presence of fructose, and ThT fluorescence, fluorescence microscopy, FESEM, Soret absorption, ANS measurements, and Congo red assay provided evidence of the anti-fibrillation effects of esculin and esculetin. [ABSTRACT FROM AUTHOR]

Two novel thiosemicarbazone-based iron(III) complexes (Fe1 and Fe2) were synthesized and identified by analytical and spectroscopic methods. Their antiproliferative activity was investigated using the 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) test against HT-29, HeLa, and L929 cell lines. The interaction between the complexes and calf thymus DNA were determined using electronic spectra and fluorescence spectra analysis. Gel electrophoresis was used to examine DNA cleavage and human topoisomerase-IIα inhibitory action. The complexes were screened for xanthine oxidase (XO) inhibitory activity and their antioxidant activities were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and phosphomolybdenum methods. In silico screening was performed to evince some pharmacological characteristics such as drug-likeness, bioactivity score and probable activity spectra of compounds (PASS) analysis using Molinspiration and PASS software. The iron(III) complexes promoted the cleavage of DNA from the supercoiled form (Form I) to the nicked circular form (Form II), but did not create Form III, indicating single-stranded DNA cleavage. MTT results showed that Fe2 has more effective antiproliferative activity on HT-29 cells, Fe1 has more effective antiproliferative activity on HeLa cells, and the complexes generally moderately affect normal fibroblast L929 cells. The antiproliferation levels were consistent with the DNA interaction results. Both complexes had antioxidant activity and inhibited XO better than the standard drug allopurinol. In silico studies have shown that the iron(III) complexes can have drug-like characteristics associated with remarkable pharmacokinetic properties that make sense of the experimental data regarding DNA-targeting, antioxidant, topoisomerase-IIα and XO inhibitory abilities. [ABSTRACT FROM AUTHOR]

Autophagy is a fundamental and phylogenetically conserved self-degradation process and plays a very important role in the selective degradation of deleterious proteins, organelles, and other macromolecules. Although flow cytometry and fluorescence imaging techniques have been used to assess autophagic flux, we remain less able to in vivo monitor autophagic flux in a highly sensitive, robust, and well-quantified manner. Here, we reported a new method for real-time and quantitatively monitoring autophagosomes and assessing autophagic flux in living cells based on fluorescence correlation spectroscopy (FCS). In this study, microtubule-associated protein 1A/1B-light chain 3B (LC3B) fused with an enhanced green fluorescent protein (EGFP-LC3B) was used as a biomarker to label autophagosomes in living cells, and FCS was used to monitor EGFP-LC3B labeled autophagosomes by using the characteristic diffusion time (τD) value and brightness per particle (BPP) value. By analyzing the distribution frequency of the τD values in living cells stably expressing EGFP-LC3B, mutant EGFP-LC3B (EGFP-LC3BΔG) and enhanced green fluorescent protein (EGFP), we found that the τD value greater than 10 ms was attributed to the signal of EGFP-LC3B labeled autophagosomes. So, we proposed a parameter PAP as an indicator to assess the basal autophagic activity and induced autophagic flux. This new method was able to evaluate autophagy inducers, early-stage autophagy inhibitors, and late-stage autophagy inhibitors. Compared with current methods, our method shows high spatiotemporal resolution and very high sensitivity for autophagosomes in low EGFP-LC3B expressing cells and will become an attractive and alternative method for biological and medical studies, some drug screening, and disease treatment. [ABSTRACT FROM AUTHOR]

Using 2-(9H-fluoren-9-ylidene)hydrazinyl)thiazol-4(5H)-one and substituted benzaldehydes, a new library of fluorenone–thiazolidine-4-one scaffolds (5a–u) were synthesized and characterized using FT-IR, 1H NMR, 13C NMR and mass spectral data. Single crystals of compound 5s were developed and crystallographic data were collected. Hirshfeld surface evaluation was used to investigate the intermolecular interactions that exist within the crystals. The synthesized compounds were screened for in vitro antioxidant and anti-diabetic properties by DPPH scavenging activity and α-glucosidase inhibition, respectively. Compounds 5a–l exhibited promising DPPH scavenging activity. Compound 5l showed an IC50 value of 27.70 ± 0.8 μM, which is 4.25-fold greater as compared to that of the standard, gallic acid (an IC50 value of 117.92 ± 2.8 μM). Compound 5g exhibited good α-glucosidase inhibition with an IC50 value of 114.58 ± 1.6 μM, which is less than that of the standard inhibitor, acarbose, with an IC50 value of 115.49 ± 2.2 μM. The mechanism of binding of compound 5g with human serum albumin (HSA) and calf thymus DNA (Ct-DNA) was studied by fluorescence spectroscopy. Furthermore, the ADME properties of the designed compounds were studied using the SwissADME online tool. The molecular docking studies of the compounds were performed against acid-α-glucosidase, in complex with 1-deoxynojirimycin (PDB ID: 5NN5). [ABSTRACT FROM AUTHOR]

Polyoxometalates (POM), as inorganic polydentate oxygen donors, provide binding opportunities for oxophilic lanthanide metal centers to construct novel Ln-substituted POM materials with exciting structures and attractive properties. Herein, we have reported four arsenotungstate [α-AsW9O33]9− based lanthanide-containing polyoxometalates [CsxK36–x{Ln6(H2O)12(α-AsW9O33)6}]·yH2O (Ln = Er (1), Gd (2), Ho (3), and Tb (4)), which are synthesized in an alkaline medium. Complexes 1–3 are the dimeric structures of [Ln3(H2O)6(α-AsW9O33)3]18− polyanions, whereas complex 4 is a hexamer of the polyanion [Tb (H2O)2(α-AsW9O33)]6− as a building unit. In all the complexes, [α-AsW9O33]9− units are staggered up and down and give rise to the chair conformation, where one [α-AsW9O33]9− unit bridges two Ln(III) centers through four μ2-oxygen and two terminal oxygen atoms, resulting in the hexagonal arrangement of lanthanides. The dynamic magnetic measurement indicates that only complex 1 exhibits slow relaxation of magnetization with an applied dc field (1500 Oe). To gain insight into the slow relaxation of magnetization in complex 1, the ligand-field parameters and the splitting of the ground-state multiplet of the Er(III) ions have been estimated. The ab initio calculation results confirm that the ground state wave function of these molecules (1, 3, and 4) is mainly composed of a mixture of mJ states, and the non-axial crystal field (CF) terms are more predominant than the axial CF term. The solid-state fluorescence spectra of 1–4 reveal that the photoexcitation O → M ligand-to-metal charge-transfer (LMCT) of arsenotungstate fragments is effectively quenched due to the spatial coordination environment around the Ln(III) ion. [ABSTRACT FROM AUTHOR]