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Aggregation-induced emission (AIE) is an effective strategy for improving the photoluminescence (PL) performance of metal nanoclusters (MNCs). However, the origin of AIE in MNCs is still not fully understood, which is pivotal for the design of AIE luminogens (AIEgens). Here, water soluble silver nanoclusters (Ag NCs) with AIE properties were synthesized. These as-synthesized non-luminescent Ag NCs will become photoluminescent when transferred from water to ethanol, and the emission peak was redshifted from ∼560 to ∼600 nm and largely intensified with the addition of Cu2+. The addition of Cu2+ makes a big difference in the PL properties of Ag NCs. That is, the PL will be enhanced if Cu2+ is added with the sequence "Ag NCs + Cu2++EtOH." In contrast, the PL will be quenched if Cu2+ is added with the sequence "Ag NCs + EtOH + Cu2+." The PL was from the supramolecular clusters formed by the assembly of capping ligands on the confined surface of individual silver clusters through weak interactions. The addition of Cu2+ could regulate the assembly structure and further affect the energy lever (p-band) through space electron interactions. These results provide new insights into the AIE process in metal nanoclusters. [ABSTRACT FROM AUTHOR]

Nontraditional intrinsic luminescence (NTIL) which always accompanied with aggregation‐induced emission (AIE) features has received considerable attention due to their importance in the understanding of basic luminescence principle and potential practical applications. However, the rational modulation of the NTIL of nonconventional luminophores remains difficult, on account of the limited understanding of emission mechanisms. Herein, the emission color of nonconjugated poly(methyl vinyl ether‐alt‐maleic anhydride) (PMVEMA) can be readily regulated from blue to red by controlling the alkalinity during the hydrolysis process. The nontraditional photoluminescence with AIE property is from the new formed p‐band state, resulting from the strong overlapping of p orbitals of the clustered O atoms through space interactions. Hydrated hydroxide complexes embedded in the entangled polymer chain make big difference on the clustering of O atoms which dominates the AIE property of nonconjugated PMVEMA. These new insights into the photoluminescence mechanism of NTIL should stimulate additional experimental and theoretical studies and can benefit the molecular‐level design of nontraditional chromophores for optoelectronics and other applications. [ABSTRACT FROM AUTHOR]

Amaranth red is usually used as a food colorant in carbonated drinks, but long-term excess consumption of amaranth red in carbonated drinks may lead to the loss of zinc in the human body, thus causing kidney dysfunction. In this study, we developed a simple method to combine cysteamine (Cys) and silver nanoparticles (AgNPs), the surface of AgNPs was modified with Cys at room temperature, and then the amino-functionalized SERS substrate was obtained, which was applied to the determination of amaranth red in carbonated drinks. The characteristic peak in Raman spectra of amaranth red showed obvious SERS enhancement at 1570 cm−1, whose intensity had a good linear relationship with the concentration of amaranth red in carbonated drinks. The limits of detection (LOD) in water and carbonated drinks were calculated to be 1.49 μg/L and 4.13 μg/L, and the adjusted correlation coefficients (R2) were 0.992 and 0.990, respectively. In addition, the average recovery rate of amaranth red in carbonated drinks was 95.11–105.48%, and the relative standard deviation (RSD) was 4.37–8.09%. This work provides a simple and fast method for detecting amaranth red in carbonated drinks. [ABSTRACT FROM AUTHOR]

Nitrogen, boron co-doped carbon quantum dots (gCQDs), and a coloration probe (PPD-NPs) with response to cobalt ions (Co2+) were prepared by using 4-hydroxyphenylboric acid as the common precursor, with ethylenediamine and p-phenylenediamine (PPD) adopted as nitrogen-doped reagents, respectively. A noticeable brown-to-purple color change can be observed with the addition of Co2+, and a broad absorption band emerges at 535 nm. At the same time, gCQDs, which is introduced as the fluorescence signal source, will be significantly quenched due to the enhanced inner filtration effect, induced by the overlap between the emission spectrum of gCQDs and the emerging absorption band. Therefore, a colorimetric/fluorescent dual-mode sensing probe for Co2+ is constructed by combining the recognition unit PPD-NPs and the fluorescent gCQDs into PPD-NP/gCQD. Under the optimized experimental conditions, the calculated limits of detection are 1.51 × 10−7 M and 3.75 × 10−7 M for the colorimetric mode and the fluorescence mode, respectively, well qualified for the determination of Co2+ maximum permitted level in drinking water. The feasibility of the proposed method has been verified in tap water, lake water, and black tea samples. [ABSTRACT FROM AUTHOR]

Cesium lead halide-based perovskite (CsPbX 3 , X = Cl, Br, I) nanoparticles (NPs) have received considerable attention for their outstanding photophysical properties and promising applications in optoelectronic devices. However, the optoelectronic performance of CsPbX 3 NPs synthesized by most of present strategies are susceptible to external factors when exposed in atmosphere. Herein, benefiting from the unique open 3D porous architecture of dendritic mesoporous silica nanospheres (DMSNs) with cage-like spherical nanopores, highly dispersed and pure cubic CsPbX 3 NPs were successfully immobilized onto the mesoporous networks. A strategy of combining chemical anchoring and spatial isolation is designed for the one-pot synthesis of CsPbX 3 NPs. These as-fabricated CsPbX 3 @HA-DMSNs exhibit excellent luminescence property (tunable emission color and high quantum yield (QY reached a maximum of 55%)) and enhanced stability (especially for the water resistance capacity). The photoluminescence (PL) was sustained without any distinct change after 100 d storage under ambient conditions, even 90% PL intensity was maintained after continuous UV irradiation for 45 h and no obvious PL reduction was observed when soaked in water for 7 h. Most importantly, the resulting CsPbX 3 @HA-DMSNs could be easily purified by filtration without aggregation and easy to scale up production compared with the conventional solution-phase mediated synthesis, which provides an alternative for the effective fabrication of perovskite-based devices, for example, here, the white light emitting devices (LEDs). Spatial and Chemical Confined Ultra-small CsPbBr 3 Perovskites NPs in Dendritic Mesoporous Silica Nanospheres with tuning emission colors and super water-resistant stability. Image 1 • Mesoporous silica with cage-like spherical pores were used as matrices. • CsPbBr 3 perovskite nanoparticles grew in the confined nanosapce by one-pot method. • Spatial and Chemical Confined CsPbBr 3 have ultra-small size and pure cubic phase. • The nanocomposites have enhanced stability resisting moisture and irradiation. [ABSTRACT FROM AUTHOR]

The availability of a range of excited states has endowed low dimensional quantum nanostructures with interesting luminescence properties. However, the origin of photoluminescence emission is still not fully understood, which has limited its practical application. Here we judiciously manipulate the delicate surface ligand interactions at the nanoscale interface of a single metal nanocluster, the superlattice, and mesoporous materials. The resulting interplay of various noncovalent interactions leads to a precise modulation of emission colors and quantum yield. A new p-band state, resulting from the strong overlapping of p orbitals of the heteroatoms (O, N, and S) bearing on the targeting ligands though space interactions, is identified as a dark state to activate the triplet state of the surface aggregated chromophores. The UV-Visible spectra calculated by time-dependent density functional theory (TD-DFT) are in quantitative agreement with the experimental adsorption spectra. The energy level of the p-band center is very sensitive to the local proximity ligand chromophores at heterogeneous interfaces. The basic principles behind the optoelectronic properties of metal nanoclusters are still not fully understood. Here the authors manipulate the surface ligand interactions on single metal nanoclusters, within self-assembled superlattices, and in confined nanopores to achieve precise modulation of emission colors and quantum yields. [ABSTRACT FROM AUTHOR]

Stevioside is an important natural sweetener in food and beverages. There are concerns about its safety, but few methods for its determination. Silver nanoparticles (Ag NPs) functionalized with 4-mercaptophenylboronic acid (4-MPBA) were successfully used to determine stevioside in beverages based upon surface-enhanced Raman spectroscopy (SERS). The Ag NPs self-assemble with 4-MPBA through the covalent interaction of their sulfhydryl groups with the metal particles. Boronic acid groups bonded to 1,2-/1,3-diol groups form cyclic boronic esters with strong affinity and significant specificity for stevioside. The combination of the two leads to an alteration of the 4-MPBA vibrational mode. The change in the orientation of the moiety and the charge transfer resulted in a significant increase of the SERS signal. The substrates showed strong specificity and sensitivity to stevioside in the presence of other sweeteners. Also, the substrate modification conditions were optimized, including the time, ratio, and concentration. The limit of detection (LOD) for stevioside in beverages was 0.210 μmol/L, and the recovery was from 98.4% to 109.4%. In summary, the presented SERS method provides high sensitivity for stevioside. [ABSTRACT FROM AUTHOR]

With the expansion of human activities, the consequent influx of mercury (Hg) into the food chain and the environment is seriously threatening human life. Herein, nitrogen and sulfur co-doped fluorescent carbon quantum dots (yCQDs) were prepared via a hydrothermal method using o-phenylenediamine (OPD) and taurine as precursors. The morphological characteristics as well as spectral features of yCQDs indicated that the photoluminescence mechanism should be the molecular state fluorophores of 2, 3-diaminophenothiazine (oxOPD), which is the oxide of OPD. The as-synthesized yCQDs exhibited sensitive recognition of Hg2+. According to the investigation in combination of UV-Vis absorption spectra, time-resolved fluorescence spectra and quantum chemical calculations, the abundant functional groups on the surface of yCQDs allowed Hg2+ to bind with yCQDs through various interactions, and the formed complexes significantly inhibited the absorption of excitation light, resulting in the static fluorescence quenching of yCQDs. The proposed yCQDs was utilized for Hg2+ sensing with the limit of detection calculated to be 4.50 × 10− 8 M. Furthermore, the recognition ability of yCQDs for Hg2+ was estimated in tap water, lake water and bottled water, and the results indicated that yCQDs have potential applications in monitoring Hg2+. [ABSTRACT FROM AUTHOR]

All-inorganic CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) are widely recognized as promising materials for optoelectronic devices. This is due to their ability to exhibit a variable band gap, narrow emission properties, and high photoluminescence quantum yield (PLQY). However, the use of traditional ligands like alkyl acid and amine could not anchor NCs tightly. Consequently, this has led to inefficient passivation of surface defects and poor stability of CsPbX3 NCs. In this study, we present the preparation of CsPbBr3 nanocrystals using the room temperature saturation recrystallization method with urea as a co-ligand. Urea, a small molecule ligand with bifunctional groups, acts as a zwitterionic ligand and effectively modifies the surface state of CsPbBr3 nanocrystals through its C=O and N–H functional groups. The as-prepared CsPbBr3 nanocrystals, with a photoluminescence quantum yield (PLQY) of up to 80%, exhibit improved water stability compared to pristine CsPbBr3 nanocrystals. X-ray diffraction and photoluminescence (PL) results demonstrate that the addition of urea as a co-ligand promotes crystallization and enhances the emission intensity of CsPbBr3. Meanwhile, the photoluminescence mechanism of CsPbBr3 NCs was investigated using ultrafast transient absorption and time-resolved photoluminescence spectroscopy. This study presents a straightforward ligand-assisted method for preparing stable CsPbBr3 NCs with high PLQY, while also enhancing the understanding of the interaction between ligands and the PL properties of CsPbBr3 NCs. [ABSTRACT FROM AUTHOR]

In this study, we report a straightforward strategy for Hg2+ ion detection. Fluorescent Au nanoparticles (NPs) were one-pot synthesized using a polymer (polyvinyl pyrrolidone [PVP]) as both capping and fluorescence agent. The as-synthesized PVP-Au NPs showed a remarkably rapid response selectively for Hg2+ ions compared to 14 other metal ions. The detection limit of Hg2+ was estimated at 100 nM. We discuss the emission and quenching mechanism of the PVP-Au NPs, the former being attributed to metal enhanced fluorescence and the latter being related to static quenching by Hg2+. The fluorescence of PVP-Au NPs offers an efficient and reliable strategy for Hg2+ ions detection. They therefore have a great potential for applications in health and environmental monitoring. [ABSTRACT FROM AUTHOR]

Double perovskite Cs 2 AgInCl 6 is a new direct band gap semiconductor material. Compared with traditional perovskite CsPbX 3 (X = Cl, Br, I), double perovskite Cs 2 AgInCl 6 has good stability and wide fluorescence half peak width. This study reports the mechanochemical synthesis, characterization and application of a lead-free double perovskite Cs 2 AgInCl 6 doped with Na and Bi ions. It was found that through a facile room temperature mechanical ball milling process, the double perovskite structure can be obtained within 30 min. Then, Na and Bi ions were used to dope to optimize its luminescence properties. By this synthesis method, the sample with the best doping ratio obtained in the experiment is Cs 2 Ag 0.7 Na 0.3 In 0.9 Bi 0.1 Cl 6 with the photoluminescence quantum yield (PLQY) of 32.7%. The X-ray diffraction (XRD) and photoluminescence (PL) results show that Na and Bi ions can promote the crystallization and optimize the luminescence properties of Cs 2 AgInCl 6. The theoretical calculation results show that both conduction band minimum (CBM) and valance band maximum (VBM) of Cs 2 Ag 0.7 Na 0.3 In 0.9 Bi 0.1 Cl 6 are flat, which is favorable for the generation of self-trapped excitons. Packaging Cs 2 Ag 0.7 Na 0.3 In 0.9 Bi 0.1 Cl 6 sample on an ultraviolet (UV) LED chip, and a warm white LED with good performance can be obtained, which shows a bright potential application in the field of white LED. [Display omitted] • By ball milling, the doped Cs 2 AgInCl 6 can be synthesized quickily without pollution. • The doped perovskite has unique optical properties, and the mechanism is explored. • The products can be used as the effective warm white-light emitting phosphors. [ABSTRACT FROM AUTHOR]

In this paper, we proposed an efficient method for mercury(II) and glutathione detection using a fluorescent nanoprobe as a sensor. Carbon dots were synthesized from polyethyleneimine and ammonium citrate via a one-step hydrothermal method. The fluorescence of carbon dots was quenched since electron transfer occurred due to the interaction between mercury(II) and functional groups on the surface of carbon dots. Adding glutathione to the carbon dots-mercury(II) system, the fluorescence was recovered due to the stronger binding ability of glutathione to mercury(II). Based on the above-mentioned principle, this "off-on" fluorescent sensor can easily achieve the detection of mercury(II) and glutathione, which provided limits of detection of 22.45 nM and 61.89 nM, respectively. In this paper, the proposed method has been applied to detect mercury(II) and glutathione in real lake water and serum, respectively, and a logic gate for sensing glutathione was presented. The developed "off-on" fluorescent sensor with high sensitivity and selectivity has shown great potential for mercury(II) and glutathione detection in environmental and biosensing fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon nanodots (CNDs) were synthesized through a facile microwave method. • The fluorescence of CNDs was selectively quenched by gold nanoparticles (AuNPs). • Once introduced, thiourea triggered the reversion of quenched fluorescence. • Effective applications in environmental water and compound fruit-vegetable juice. Illegal abuse results in the presence of thiourea (TU) in soil, wastewater, and even fruits, which is harmful for the environment and human health. It has urgent practical significance to design an efficient and reliable probe for TU detection. Herein, a sensitive fluorescent probe with off–on response for harmful TU was reported. The probe was designed with fluorescent carbon nanodots (CNDs) and gold nanoparticles (AuNPs) based on fluorescence resonance energy transfer (FRET) effect. Firstly, the CNDs were pre-combined with AuNPs and the fluorescence of CNDs was quenched due to the FRET effect. Upon addition of TU, the fluorescence of CNDs recovered due to the unbinding of CNDs and AuNPs, since the coordination interaction between TU and AuNPs is stronger than the electrostatic interaction among CNDs and AuNPs. Under the optimum parameters, a linear relationship was found between the relative fluorescence intensity of the probe and the concentration of TU in the range of 5.00 × 10-8-1.00 × 10-6 M (R2 = 0.9958), with the limit of detection (LOD) calculated to be 3.62 × 10-8 M. This proposed method is easy to operate and has excellent selectivity and sensitivity for TU, which can be effectively applied in environmental water and compound fruit-vegetable juice. [ABSTRACT FROM AUTHOR]

[Display omitted] • The β-CD-AgNPs substrate can selectively combine with NFX. And the proposed method can be applied in the detection of real milk samples. • The "host–guest" interaction of NFX and β-CD-AgNPs was verified by the UV–Vis absorption spectroscopy, fluorescence spectroscopy, Zeta potential and DLS. • This developed SERS method is simple and sensitive, the LOD of NFX was 3.214 pmol/L in standard solution and 5.327 nmol/L in milk. The norfloxacin (NFX) residue in milk will increase human resistance to drugs and pose a threat to public health. In this work, a highly sensitive method for detection of NFX was developed based on surface enhanced Raman spectroscopy (SERS) using β-cyclodextrin functionalized silver nanoparticles (β-CD-AgNPs) as substrate. The unique spatial size and hydrophilicity of β-CD on the surface of AgNPs could selectively capture the target molecule (NFX) through some weak interactions, including hydrogen-bond interaction, electrostatic interaction, etc. The interactions were characterized by the UV–Vis absorption spectroscopy, fluorescence spectroscopy, Zeta potential and DLS. The Raman signal of NFX is largely enhanced when anchored by β-CD on the surface of AgNPs due to SERS effect. Through a series of experiments and analysis, the limit of detection (LOD) in standard solution and spiked milk were calculated to be 3.214 pmol/L and 5.327 nmol/L. The correlation coefficients (R2) were 0.986 and 0.984, respectively. For milk sample determination of NFX, the recovery was 101.29% to 104.00% with the relative standard deviation (RSD) from 2.986% to 9.136%. To sum up, this developed SERS strategy is sensitive and specific to detect NFX in milk, it has practical application value and prospects. [ABSTRACT FROM AUTHOR]

Nitrite ion is one of the materials widely used in human life, and the accurate, sensitive and stable detection of nitrite ions is of great significance to people’s healthy life. In this study, nitrogen-doped fluorescent carbon dots (N-CDs) for detecting nitrite salt solutions were prepared using citric acid monohydrate and Chrysoidin as precursors through a one-pot hydrothermal method. Under the condition of pH = 3, a noticeable quenching phenomenon occurred in the carbon dot solution with the increase in nitrite ion concentration. This quenching effect might be attributed to the diazonium effect. N-CDs have been successfully used as fluorescence probes for NO2− detection. NO2− can effectively quench the fluorescence intensity of N-CDs, providing a linear response to fluorescence quenching efficiency with respect to NO2− concentration within the range of 0–10µM and 10–30µM, and a detection limit of 52nM, showing high sensitivity. In addition, the probe was applied to the determination of NO2− in ham sausage samples with a detection limit of 0.67µM and recoveries in the range of 99.5-102.3%, the fluorescent probe showed satisfactory reliability.Schematic illustration for detecting nitrite ion in ham sausage using N-CDsSchematic illustration for detecting nitrite ion in ham sausage using N-CDsGraphical Abstract: Nitrite ion is one of the materials widely used in human life, and the accurate, sensitive and stable detection of nitrite ions is of great significance to people’s healthy life. In this study, nitrogen-doped fluorescent carbon dots (N-CDs) for detecting nitrite salt solutions were prepared using citric acid monohydrate and Chrysoidin as precursors through a one-pot hydrothermal method. Under the condition of pH = 3, a noticeable quenching phenomenon occurred in the carbon dot solution with the increase in nitrite ion concentration. This quenching effect might be attributed to the diazonium effect. N-CDs have been successfully used as fluorescence probes for NO2− detection. NO2− can effectively quench the fluorescence intensity of N-CDs, providing a linear response to fluorescence quenching efficiency with respect to NO2− concentration within the range of 0–10µM and 10–30µM, and a detection limit of 52nM, showing high sensitivity. In addition, the probe was applied to the determination of NO2− in ham sausage samples with a detection limit of 0.67µM and recoveries in the range of 99.5-102.3%, the fluorescent probe showed satisfactory reliability.Schematic illustration for detecting nitrite ion in ham sausage using N-CDsSchematic illustration for detecting nitrite ion in ham sausage using N-CDs [ABSTRACT FROM AUTHOR]

[Display omitted] • In this study, a stable, uniform, and sensitive SERS substrate was successfully synthesized by combining COFs and AgNPs. • We conducted a detailed analysis of the specific role of COFs in the substrate through their characterization and DFT simulation. • The detection limits achieved in amoxicillin aqueous solution, lake water, and honey were found to be satisfactory. Specifically, the detection limits were 0.279 μg/L in the aqueous solution, 8.246 μg/L in lake water, and 2.47 ng/g in honey. This study presents the design of a Surface-enhanced Raman scattering (SERS) substrate, COF@Ag, for the sensitive detection of Amoxicillin (AMX) in lake water and honey. Furthermore, the study investigates the role of covalent organic frameworks (COFs) in SERS detection. The characterization results demonstrate the capability of COFs to efficiently enrich Ag nanoparticles (AgNPs), resulting in a more concentrated distribution of hotspots and an enhanced electromagnetic field on the substrate. By employing density functional theory (DFT) simulation, the frontier electronic orbitals of COFs and AMX were analyzed, and the chemical bonds and weak interactions in the system were examined using the Interaction Region Indicator (IRI) method to propose potential enhancement mechanisms. In aqueous solutions, the linear range is 1 μg/L-30 μg/L, with a limit of detection (LOD) 0.279 μg/L. In lake water, the linear range span from 100 μg/L to 500 μg/L, with a detection limit of 8.244 μg/L. For honey, the linear range extend from 20 ng/g to 100 ng/g, with a detection limit of 2.917 ng/g. This method holds key significance in facilitating the rapid detection of amoxicillin and advancing the application of COFs in SERS. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is the first time that carbon dots have been synthesized using ammonium citrate and glutamic acid as precursors. • The fluorescence stability of carbon dots is fully explored, facilitating their use in real-world environments. • This method achieves high selectivity and sensitivity in the trace detection range. • Monitoring Cd2+ ions in tap water and lake water. In this study, fluorescent carbon dots were synthesized for the first time using ammonium citrate and glutamic acid as precursors via a one-pot hydrothermal method. The synthesized carbon dots emit blue fluorescence at 436 nm (excited at 320 nm) and demonstrate excellent photobleaching resistance and fluorescence stability in high salt environments. Within the range of 1–25 μM, the fluorescence of CDs gradually increases with the increasing concentration of Cd2+, reaching a limit of detection as low as 13 nM. This phenomenon could be ascribed to the chelation-enhanced fluorescence, a result of Cd2+ forming complexes with the abundant surface functional groups such as CN–, –COOH, –OH, –NH 2 in CDs. Furthermore, this turn-on fluorescent probe has been successfully used for the detection of Cd2+ in tap water and lake water, providing an efficient and sensitive method for the analysis of environmental metals. [ABSTRACT FROM AUTHOR]

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 369 nm 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 295 nm 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. [ABSTRACT FROM AUTHOR]

Herein, a fluorescent “on-off-on” nanosensor based on N,S-CDs was developed for highly precise and sensitive recognition of Hg2+ and ampicillin (AMP). Nitrogen and sulfur co-doped carbon dots with blue fluorescence were synthesized by one-pot hydrothermal method using ammonium citrate and DL-methionine as precursors. N,S-CDs exhibited a surface abundant in -OH, -COOH, and -NH2 groups, aiding in creating non-fluorescent ground state complexes when combined with Hg2+, leading to the suppression of N,S-CDs’ fluorescence. Subsequent to additional AMP application, the mixed system’s fluorescence was restored. Based on this N,S-CDs sensing system, the thresholds for detection for AMP and Hg2+ were discovered to be 0.121 µM and 0.493 µM, respectively. Furthermore, this methodology proved effective in identifying AMP in real samples of tap and lake water, yielding satisfactory results. Consequently, in the area of bioanalysis in intricate environmental sample work, the sensing system showed tremendous promise. [ABSTRACT FROM AUTHOR]

In this paper, fluorescent carbon dots were prepared by hydrothermal method using 3,5-dihydroxybenzoic acid and l -Arginine as precursors. The synthesized CDs have excitation-dependent emission with emission peaks at 354 nm and 460 nm, corresponding to the optimal excitation wavelengths of 295 nm and 330 nm, respectively. CDs have good dispersion and resistance to photobleaching in aqueous solution, and can maintain stable fluorescence in highly concentrated salt environment. Based on the inner filter effect, Cr(VI) with strong absorption can shield the excitation light of CDs at 295 nm and absorb the emission fluorescence at 354 nm simultaneously. Due to the intermolecular electrostatic interaction, Hg(II) can coordinate with CDs surface groups and cause static quenching, which significantly reduces the fluorescence intensity of CDs emitted at 460 nm. The linear ranges were 0.1–2 μM and 0.4–5 μM for Cr(VI) and Hg(II) detection, respectively, and limits of detection were 0.024 μM and 0.084 μM. Additionally, the probe was successfully applied to tap water and lake water samples. With high sensitivity and spectral selectivity, this sensing strategy realized the detection of two heavy metal ions by a single fluorescent probe, demonstrating its great potential in the field of environmental metal analysis. [Display omitted] • First synthesis of carbon dots with spectral selectivity using 3,5-dihydroxybenzoic acid and l -arginine as precursors. • Separate detection of Cr(VI) and Hg(II) ions using the same carbon dots under different excitations. • This method achieves high selectivity and sensitivity in the trace detection range. • Monitoring Cr(VI) and Hg(II) ions in tap water and lake water. [ABSTRACT FROM AUTHOR]

In this paper, we obtained nitrogen and phosphorus co-doped carbon dots through a hydrothermal method using o-phenylenediamine and citric acid in a 40% phosphoric acid environment. The carbon dots emitted fluorescence at 476 nm under excitation at 408 nm and exhibited good selectivity and high sensitivity towards mercury ions. These carbon dots showed excellent dispersibility in water and maintained stable fluorescence even in high concentration salt environments. The interaction between mercury ions and functional groups on the carbon dots surface through electrostatic interaction resulted in static quenching. Simultaneously, by detecting the lifetime and transient absorption spectra of the carbon dots, we observed that the coordination of mercury ions with the carbon dots broadened the band structure of the carbon dots, and the existing photoinduced electron transfer process increased the non-radiative transition channel. The combined effect of dynamic quenching and static quenching significantly reduced the fluorescence intensity of the carbon dots at 476 nm. The carbon dots exhibited linear detection of mercury ions in the range of 0.01-1 µM, with a detection limit as low as 0.0245 µM. In terms of practical water environmental detection applications, these carbon dots were able to effectively detect mercury ions in tap water and lake water, demonstrating their broad application prospects in the field of environmental metal analysis. [ABSTRACT FROM AUTHOR]

As a dihydrochalcone natural sweetener extracted from Lithocarpus litseifolius , trilobatin is an emerging functional sweetener in the international arena in recent years and is gaining attention in the food industry. The detection of trilobatin has also gradually received the attention of researchers, however, the detection means for trilobatin still remain in the traditional high performance liquid chromatography (HPLC) and other traditional methods, which are costly and have a large detection range. In this work, a method based on the principle of surface-enhanced Raman (SERS) using a composite substrate of silver nanoparticles (Ag NPs) and covalent organic frameworks (COFs) materials is proposed for the detection of trilobatin in tea beverages. After Gaussian simulation and a series of spectral analysis methods for validation, the functionalized SERS substrates contain abundant hydroxyl groups on the surface, which can be combined with trilobatin through hydrogen bonding and greatly enhance the Raman signal of trilobatin. The specific detection of trilobatin in tea beverages has been realized and the problem of weak SERS signal of trilobatin in liquid environment has been solved. The limit of detection (LOD) of trilobatin in tea beverage was 2.8 nM, and the correlation coefficient (R2) was 0.995. The recoveries were in the range of 100.6∼106.0% with the RSD of 1.756∼4.921%. In conclusion, the experimental method is highly sensitive and specific, and can realize the nondestructive detection of trilobatin in samples with high practical value. [Display omitted] • First SERS-based method for the detection of trilobatin in beverages using Ag@COF substrates. • This method can be applied in the detection of real drink samples without pretreatment procedures. • The detection time of the substrate to the sample is short and the recovery rate is high. [ABSTRACT FROM AUTHOR]

Chrysoidine, an industrial dye, is a banned chemical for use as a food additive. Studies have shown that excessive ingestion, inhalation and dermal contact with the substance can cause acute and chronic toxicological damage. Surface enhanced Raman spectroscopy (SERS) is a spectroscopic detection technique with high selectivity and sensitivity. In this study, a mixture of silver nanoparticles (AgNPs) and polyethyleneimine (PEI) was used as the SERS substrate at room temperature for the rapid and sensitive detection of Chrysoidine in mirinda soft drink, and PEI could attract Chrysoidine to the hot spot region of the AgNPs and enhance its Raman signal. The characteristic peak of the SERS spectrum of Chrysoidine showed obvious SERS enhancement at 1180 cm− 1, and there was a good linear relationship between the SERS intensity and the concentration of Chrysoidine. The limits of detection (LOD) in both water and mirinda soft drink were determined to be 1.32 µg/L and 5.11 µg/L, respectively. In addition, the average recoveries ranged from 95.65 to 102.08% with the RSDs of 3.41-5.02%. The method can be successfully used for the rapid and sensitive detection of Chrysoidine in mirinda soft drink, which provides a new idea for the detection of Chrysoidine in other different samples. [ABSTRACT FROM AUTHOR]

Herein, we presented an ingenious method for the detection of trace ascorbic acid (AA) using fluorescent sensing system, which was composed of periodate (IO 4 −) and nitrogen-boron co-doped carbon dots (N, B-CDs). Highly photoluminescent carbon dots with a quantum yield of 84.5% were synthesized by a one-step hydrothermal method using citric acid, ethylenediamine and boric acid as raw materials. The fluorescence of N, B-CDs could be statically quenched by IO 4 −, and non-fluorescent complexes were formed on the surface of carbon dots at the same time. With the pre-addition of ascorbic acid, the process of fluorescence quenching by IO 4 − was inhibited due to the preferential redox reaction between AA and IO 4 −. Based on the principle mentioned above, we designed the "inhibition" fluorescent sensor that can easily realize the detection of AA, and an extremely low limit of detection of 0.035 nM with a linear interval of 0–1600 pM was obtained. In addition, the sensing system has been applied to the detection of AA in human urine and obtained satisfactory results. The developed "inhibition" fluorescent sensor with high sensitivity and selectivity, has shown great potential and application prospects in the field of biosensing. [Display omitted] • The carbon dots (N, B-CDs) were synthesized by citric acid, ethylenediamine and boric acid. • The N, B-CDs showed a high quantum yield of 84.5% with an intense blue fluorescence. • The "inhibition" fluorescent sensor was constructed of periodate (IO 4 −) and N, B-CDs. • The sensing platform was highly sensitive with a very low detection limit of 0.035 nM. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is the first time that carbon dots were synthesized using cysteine and ethylenediamine as precursors. The synthesis method is green and simple, and the prepared N -CDs have good fluorescence stability. • The developed experimental conditions for the detection of Fe3+ using nitrogen-doped carbon dots as fluorescent probes have been fully optimized to significantly improve the sensitivity. • The method is simple, sensitive and highly feasible, with LOD as low as 0.069 μM in deionized water. And, linear models were also constructed in tap water and lake water with LOD of 0.21 μM and 0.59 μM, respectively. In this study, we synthesized stable nitrogen-doped carbon dots by a simple and economical one-step hydrothermal method using l -cysteine and anhydrous ethylenediamine as precursors. The prepared carbon dots have bright and stable blue light emission near 383 nm and can be used as fluorescent probes to detect the concentration of Fe3+ in environmental waters. It was demonstrated that due to intermolecular electrostatic interaction, a non-fluorescent complex N -CDs/Fe3+ is formed by coordination of Fe3+ with amino and carboxyl functional groups on the surface of carbon dots. Therefore, in combination with internal filtration effect, the fluorescence of carbon dots can be quenched in the presence of Fe3+, and the degree of quenching is linearly related to the concentration of Fe3+. The limit of detection in deionized water was as low as 0.069 μM with R2 of 0.998 and a linear range of 0.3 to 20 μM. In addition, satisfactory recoveries were achieved for the determination of Fe3+ in environmental water samples. The method is reliable, with highly sensitivity and selectivity, and has potential for practical applications in environmental metal analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The interaction between emodin and Zn2+ was studied by various spectroscopic techniques. • Zn2+ changed the surface electrostatic potential of emodin and enhanced its antioxidant properties. • The fluorescence lifetime of Zn(II)-Emodin increased by about 4 times compared with emodin. • The non-radiative transition rate of Zn(II)-Emodin is obviously attenuated and the radiative transition rate is slightly accelerated. Emodin is a natural drug for treating neurodegenerative diseases and plays a vital role in the mitigation of nerve damage. Metal ions can modify the drug properties of emodin, where Zn2+ can synergize with the emodin molecule and enhance the drug effect of emodin. Besides, complex changes can be observed in the fluorescence intensity and fluorescence lifetime of the emodin molecule as the concentration of Zn2+ increases. Herein, the synergistic effects of ligand structural in Zn(II)-Emodin complexes and the electronic effects of metal elements on the antioxidant properties of the complexes are discussed in detail based on UV–vis absorption spectroscopy, fluorescence spectroscopy, time-correlated single photon counting (TCSPC) technique and quantum chemical calculations at the B3LYP/6-31G(d) level. The experimental results confirm that Zn2+ can coordinate with the hydroxyl groups on the emodin to make the molecule structure more rigid, thus inhibiting the non-radiative processes such as high-frequency vibrations of the emodin molecule in solution. The suppression of non-radiative processes leads to an increase in the average fluorescence lifetime of the emodin molecule, and finally results in the enhanced fluorescence intensity. The chemical softness of Zn(II)-Emodin is then confirmed to be higher than that of emodin by Gaussian calculations, indicating its higher chemical reactivity and lower stability. The stronger electron donating ability of Zn(II)-Emodin compared to emodin may explain the higher antioxidant activity of Zn(II)-Emodin, which gives it a stronger pharmacological activity. The results of this study show that emodin can well complex with Zn2+ to remove excess Zn2+ in human body and the resulting complex has better antioxidant properties, which helps to understand the role of Zn2+ in drug-metal coordination and provides guidance for the design of new drugs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The AgNPs-4MPBA composite structure was first designed as SERS substrate for detection of fructose in urine. • This method achieve the LOD of fructose to be 0.535 µmol/L in urine. • This method realizes rapid fructose detection in less than 10 min. The accurate detection of fructose in human urine can help prevent and screen for diseases such as fructokinase deficiency and hereditary fructose intolerance. Surface-enhanced Raman spectroscopy (SERS) is an analytical technique with selectivity and high sensitivity, which has been widely applied to the detection of targets with complex backgrounds. In this work, 4-mercaptophenylboronic acid (4-MPBA) was modified on the surface of silver nanoparticles (AgNPs) under mild conditions to obtain a boronic acid-functionalized SERS substrate for the detection of fructose in artificial urine. The detection mechanism was based on the deboronization reaction of 4-MPBA on the surface of AgNPs, which was induced by fructose, and the Raman signal of the generated thiophenol (TP) molecules was significantly enhanced by the silver nanoparticles, with a linear increase in SERS peak intensity at 1570 cm−1. We achieved the detection limits of 0.084 µmol/L in water and 0.535 µmol/L in urine by this method. The relative standard deviation (RSD) in the recovery experiments of urine ranged from 1.01 % to 2.22 %, and the whole detection time was less than 10 min, which indicated that this method is highly reliable for fructose detection and has a good prospect in bioassay and clinical medicine. [ABSTRACT FROM AUTHOR]

The detection of glucose in drinks (especially for sugar-free drinks) is of great practical significance. The traditional method for the detection of glucose was based on an enzymatic reaction using glucose oxidase, which takes a long time. Herein, a TMB-AgNPs@COF based SERS probe was designed for the rapid detection of glucose in drinks. The SERS probe was fabricated using silver nanoparticles loaded covalent organic frameworks (COFs) as substrate, 3,3',5,5'-Tetramethylbenzidine (TMB) was introduced as a signal molecule to solve the problem of weak SERS signal of glucose. The fabricated SERS probe is denoted as TMB-AgNPs@COF. The detection mechanism was based on the competitive binding of TMB and glucose with AgNPs@COF substrate. Glucose was more likely to bond with the substrate which was verified by Gaussian theory simulation. The SERS signal of TMB gradually decreased when glucose was introduced. The interaction between the substrate and glucose can also be demonstrated by SERS spectroscopy. By applying this method, we could achieve the detection limit of 0.096 μg/mL in drinks. The relative standard deviations were 2.63 %− 4.89 % in the recovery experiments of drinks. The whole detection time was less than 5 min and the substrate had good reproducibility. Therefore, the method was confirmed with a high potential for the detection of glucose in drinks. [Display omitted] • The TMB-AgNPs@COF was first designed as SERS probe for detection of glucose in drinks. • This method can be applied in the detection of real drink samples without pretreatment procedures. • This method realizes rapid glucose detection in less than 5 min. [ABSTRACT FROM AUTHOR]