Blue-green Fluorescence Research Articles

A handheld fluorescent platform integrated with a Sm(III)-CdTe quantum dot-based ratiometric nanoprobe for point-of-use determination of phosphate.

Phosphate (Pi) is crucial for various physiological processes and aquatic environments, which emphasizes the need for a simple, on-site sensor to promptly detect Pi for human health and environmental conservation. In this study, we propose a dual-emission ratiometric fluorescence sensor for highly sensitive and visual Pi detection. The sensor employs samarium ions (Sm3+) as a core component, with cadmium telluride quantum dots (CdTe QDs) and ofloxacin (OFL) serving as signal carriers. The CdTe-Sm(III)-OFL nanoprobe emits a purple fluorescence resulting from the red fluorescence of CdTe QDs and the blue-green fluorescence of OFL. The fluorescence of OFL is quenched by Sm3+ through fluorescence resonance energy transfer (FRET). Upon Pi interaction, the FRET process is disrupted due to the competitive Pi-Sm3+ binding, which leads to the fluorescence recovery of OFL while the red fluorescence of CdTe remains steady. This enables the construction of a ratiometric fluorescent sensor for Pi detection, manifesting as a color change from purple to blue. The sensor demonstrated a linear response for Pi detection within the range of 0.1-75 μM, with a low detection limit of 17.0 nM. By utilizing the distinct fluorescence responses of various physiological phosphates and employing chemometrics, this innovative dual-emission sensor accurately distinguishes among different physiological phosphates. Furthermore, a portable lab-on-paper device based on CdTe-Sm(III)-OFL, coupled with a smartphone-integrated mini-device, is developed for swift Pi detection using an ordinary smartphone. Analytical performance validated on environmental and biological samples demonstrates the sensor's excellent robustness and adaptability. This study introduces a pioneering approach to fabricate ratiometric fluorescence sensors and customize portable, cost-effective mini-devices for precise target detection, thus opening avenues for advanced sensing strategies in various applications.

Reactive Fluorescent and Colorimetric Probe for Highly Selective and Sensitive Detection of Hg2+ in Real Water Samples.

Construction of efficient chemosensors for highly specific and sensitive detection of mercury ions remains a great challenge. In this work a highly selective and sensitive probe CY was designed and synthesized by using coumarin fluorophore as the matrix and thioacetal moiety as the reactive recognition site for Hg2+. By virtue of the thiophilicity of Hg2+, probe CL could be hydrolyzed to deprotect and the thioacetal was transformed to the acyl group after the addition of Hg2+, the blue-green fluorescence was quenched and meanwhile the solution changed from light green to yellow. The detection limit of probe CY for Hg2+ was as low as 6.8 nM, and it could completely react with Hg2+ within 3min. Moreover, probe CY exhibited good resistance against interference from competitive metal ions and biothiols, high stability in pH 1-11 and applicability for fluorogenic and chromogenic dual-modal detection of Hg2+ in real water samples over a broad range of pH 5-10.

Blue light excitable fluorescent green security ink for anticounterfeit application

AbstractFluorescent security printing inks on flexible substrates is an arena that demands consistent developments to prevent the ever increasing menace of document/product counterfeiting. Visible light is a much more accessible and safer excitation source than the commonly used ultraviolet (UV) light. In this context, a simple Schiff base 4-pyridyl-benzylidene 2,4-difluoro aniline (PBDFA) is synthesized as a colorant with significant solid-state fluorescence for preparing security ink formulation. A huge challenge lies in preparing a security ink that does not fluoresce under UV light but produces a green fluorescence when irradiated with a blue light source. Such prints would be hard to forge as compared to the existing UV luminescent security inks. The screen prints obtained on a UV dull paper substrate using the solvent-based PBDFA ink revealed good blue light excitable green fluorescence, photostability, and colorimetric, densitometric, and rub resistance characteristics.

Synthesis of dragonfruit-based silicon nanoparticles at room temperature and their application in the real-time fiber-optic detection of doxorubicin

Doxorubicin (DOX) has been extensively used in cancer chemotherapy as an antibiotic drug, but when DOX concentration exceeds the threshold value, irreversible liver toxicity and cardiotoxicity can be triggered. Therefore, it is a significant theme to detect DOX concentration of patient blood and metabolites for the optimization of drug dosage. Linear correlation between fluorescence quenching of silicon nanoparticles (SiNPs) and DOX concentration enables SiNPs to present good prospect to address this tricky issue. Inspired by these aspects, we put forward a novel method to synthesize dragonfruit-based SiNPs (DSiNPs) at room temperature, and leverage them in the fiber-optic sensing of urine DOX. Firstly, we investigate a simple and green synthesis method of DSiNPs emitting blue-green fluorescence through a one-step redox reaction at room temperature with organosilane as silicon source and fresh dragonfruit juice as reducing agent. Secondly, depending on optical characterization, we demonstrate mechanism of DSiNPs in the detection of DOX. Thirdly, a fiber-optic sensor is used to measure the fluorescence intensity of DSiNPs under diverse salt concentrations, pH values, and illumination time to explore the tolerance of DSiNPs. Fourthly, based on optimization of parameters and validation of specificity, we acquire linear response range of this method to DOX from 0 to 50 μM with detection limit of 3 μM. Finally, this method is leveraged in the detection of urine DOX, and obtained the recovery rates of 92.30 % and 107.30 %. This method holds excellent potential in the clinical analysis of anti-tumor drugs for the advantages of environmental friendliness and simple operation.

Self-ratiometric fluorescence approach based on room-temperature instantaneously synthesized carbon dots from Folin's reagent and ethanolamine for determination of nitroxinil in water, milk, and food samples

BackgroundNitroxinil has been used extensively to treat parasitic worms, mainly Fasciola, in food-producing cattle and sheep. The reported methods for nitroxinil analysis included expensive instrumentation, the need for skilled operators, and tedious procedures. Fluorimetry is one of the fastest and simplest methods widely used; hence, we aimed to develop a simple, cost-effective, and convenient fluorometric approach for the estimation of nitroxinil in various matrices. Compared with other detection methods, self-ratiometric fluorescent probes are considered a promising approach for the detection of analytes as their detection accuracy overcomes traditional fluorescence sensing probe in that it is not affected by the probe concentration, solution polarity, instrument parameters, and other factors. In this research, room temperature instantaneously synthesized carbon dots were used as a sensitive and selective self-ratiometric probe for the determination of the veterinary medicine nitroxinil in various matrices. ResultsA room-temperature synthesized quinone-ethanolamine carbon dots (RTQECDs) was fabricated using the instantaneous reaction of sodium 1,2-naphthoquinone-4-sulfonate (Folin's) with ethanolamine, without any energy/catalyzing reagents, for the first time. The prepared carbon dots show green-blue fluorescence at 450 nm upon exposure to UV light at 365 nm with a quantum yield of 26.6 %. Upon interaction with nitroxinil, the fluorescence intensity of RTQECDs at 450 nm is quenched and shifted to a longer wavelength at 475 nm. Meanwhile, the fluorescence of RTQECDs at 400 nm (absorbance maxima of nitroxinil) was more extremely quenched under the same conditions. Taking this in hand, a new RTQECDs self-ratiometric probe was developed for the determination of nitroxinil using the decrease in peaks at 450 nm and 400 nm and the shift of the fluorescence maxima to 475 nm as built-in reference peaks. The probe showed a quantitative increase in signal output of F475/F400 in the range of 0.10–30.0 μg/mL nitroxinil with a limit of detection of 30.0 ppb. The nitroxinil-sensing mechanism using RTQECDs is mainly ascribed to the partial secondary blue-type inner filter effect (IFE). The designed study was applied for the estimation of nitroxinil in veterinary dosage forms (recoveries; 99.78 %–100.35 %), river water (recoveries; 98.55 %–101.53 %), and food products, including meat, liver, kidney, and milk (recoveries; 97.60 %–104.25 %). SignificanceThe novelty of our work includes the immediate synthesis of the sensing probe at room temperature, as well as its use as a self-ratiometric fluorescence probe for the determination of nitroxinil in veterinary samples, river water, and food products with excellent sensitivity down to 30.0 ppb. RTQECDs own the highest response and selectivity to nitroxinil compared with cations, anions, as well as other co-administered drugs, including cefotaxime and ivermectin.

Application of Ultraviolet-Enhanced Fluorescence Dermoscopy in Basal Cell Carcinoma.

Basal cell carcinoma (BCC) is the most common non-melanoma skin cancer. The aim of the current study was to analyze the ultraviolet-enhanced fluorescence dermoscopy (UVFD) characteristics of BCCs. BCCs were evaluated under polarized dermoscopy (PD) and UVFD. The findings in PD were described using predefined parameters for dermoscopic evaluation in dermato-oncology. UVFD characteristics were determined based on personal observations, and included interrupted follicle pattern, absence of pink-orange or blue-green fluorescence, well-demarcated borders, and dark silhouettes. In total, 163 BCCs were analyzed. Under UVFD, the interrupted follicle pattern (p < 0.001), absence of pink-orange fluorescence (p = 0.005) and well-demarcated borders (p = 0.031) were more frequently noted in BCCs < 5 mm than in bigger tumors. Lesions on the face showed clearly defined borders (p = 0.031) and interrupted follicle pattern (p < 0.001) more frequently than tumors located beyond the face. Nodular BCCs displayed interrupted follicle pattern (p = 0.001) and absence of pink-orange fluorescence (p < 0.001) more commonly than superficial subtypes. Non-pigmented BCCs more frequently showed lack of blue-green fluorescence (p = 0.007) and interrupted follicle pattern (p = 0.018) compared to pigmented variants. UVFD may be a valuable, complementary to PD, tool in the diagnosis of BCC, particularly in small tumors, lesions located on the face and nodular or non-pigmented subtypes.

Direct lithography of CsPbCl3, CsPbBrxCl3−x and CsCdxPb1−xBr3 perovskite nanocrystals in organic media

The in-situ generation of perovskite nanocrystals within organic media using a femtosecond laser can greatly simplify the sample preparation process and save pulse energy. In this work, three perovskite nanocrystals (PNCs), CsPbCl3, CsPbBrxCl3−x, and CsCdxPb1−xBr3, were generated in situ within organic media using a femtosecond laser. These three perovskite nanocrystals emitted pure blue or blue-green fluorescence under ultraviolet (UV) irradiation. It was also found that by controlling the laser pulse energy, the CsCdxPb1-xBr3 nanocrystals transitioned from green to blue-green fluorescence. Furthermore, we have successfully realized the patterning of these three perovskite nanocrystals in organic media.

A chlorinated benzimidazole fluorescent probe for sensitive and rapid detection of iron and ferrous ions

A ‘off-on’ benzimidazole-based fluorescent probe ((E)-2-((4-(5-chloro-1H-benzo[d]imidazole-2-yl)benzylidene)amino)phenol) probe CBAP for the detection of Fe3+/2+ (probe CBAP) was developed. It didn't exhibit fluoresce at 450 nm in EtOH: H2O (v:v = 9:1), which was mainly attributed to the isomerization and rotation of the CN bond. The dihedral angle rotation hindered the charge transfer between benzimidazole and o-aminophenol. However, the CN in probe CBAP was cleaved to form compound 3 upon adding Fe3+/2+. Its electrons were transferred from the benzimidazole ring to the benzaldehyde portion upon excitation and showed blue-green fluorescence. Probe CBAP had high selectivity and sensitivity, with a detection limit as low as 1.12 nM, and didn't interfere with other analytes. In addition, the optimized structure and orbital energy levels of probe CBAP and compound 3 were calculated using time-varying density functional theory (TD-DFT) and PBE0 function. Moreover, the application of probe CBAP on mobile phones for rapid detection of Fe3+/2+ content in wine and confirmation of whether it exceeded the standard was explored.

A highly efficient molecularly imprinted fluorescence sensor for selective and sensitive detection of tetracycline antibiotic residues in pork

Tetracyclines (TCs) residues in animal-based foods may cause consumer poisoning or allergic reactions, as well as resistance of pathogenic microorganisms. Therefore, a method to accurately monitor TCs is urgently needed. Here, a sensitive and greenificated molecularly imprinted fluorescent sensor (CDs@MIP) for detecting TCs residues using non-covalent imprinting binding method has been synthesized in a simple and safe manner. The sensor was demonstrated to contain specific adsorption sites and high adsorption capacity by static adsorption test results and Freundlich and Langmuir model analyses, and the maximum adsorption capacity was 45.8 mg/g. Moreover, the sensor exhibited intense blue-green fluorescence under UV light, and the fluorescence was gradually quenched as TCs was adsorbed to achieve the detection. The fluorescent spectrum experiment demonstrated that the prepared sensor has good recognition and detection performance for TCs with a linear range of 0.02–50 mg/L and a detection limit of 0.18 μg/L. Furthermore, This sensor is recyclable and can be used to determine TCs content in pork with a recovery rate of 98 %–108 %. Therefore, the constructed sensor provides a new convenient strategy for detecting TCs residues.

Comparison of characterization and composition of melanoidins from three different dried apple slices

The composition of melanoidins in dried apple that affects quality remains unclear. The composition and structure of melanoidins in dried apple slices by hot air drying (HAAM), instant controlled pressure drop drying (DICAM), and vacuum freeze-drying (FDAM) were investigated. It showed that the melanoidins were highly heterogeneous mixtures with a light-yellow color and blue-green fluorescence, belonging to polysaccharide-type melanoidins. Specifically, HAAM had a large molecular weight (929.5 g/mol) and wide molecular weight distribution, with more double-bond conjugated systems. DICAM (610.9 g/mol), possessing the strongest fluorescence intensity, was mainly composed of compounds with fewer π-conjugated structures and more electron-donating groups. As a control, the low level of Maillard reaction in FDAM resulted in the formation of the smallest molecular weight (458.6 g/mol) with weak fluorescence intensity. Moreover, 10 compounds were tentatively identified in apple melanoidins. This study provides the foundation for the future functional preparation of apple melanoidins.

A new novel series of vanillin-based hexaimine-Schiff bases: Synthesis, characterization and investigation of chromic and fluorescence properties

Here, new symmetrical diimines D1 and D2 were prepared by the condensation reaction of o-vanillin with 2-nitro-p-phenylenediamine or 4-nitro-o-phenylenediamine, respectively. Diimines were reduced selectively to their amino derivatives, and reacted with terephthaldehyde to obtain of a novel symmetrical hexaimines (H1 and H2). Their structures were identified on the basis of microanalyses, IR, 1H/13C NMR, HRMS and UV–vis spectroscopy. The enol–keto tautomeric equilibrium in these Schiff bases were elucidated by chromically and fluorescence spectra with respect to the influence of solvent, acid–base and light. They acted non-emissive in the solid state (λexc = 365 nm). Diimines displayed a weak green, bluish-green/blue emission in basic DMSO and DMF solution (v/v, 1:1), but they were non-fluorescent in other media. In contrast to this, hexaimines emitted a strong greenish-blue fluorescence in pure, bluish-green/greenish-blue fluorescence in acidic, and purplish-blue/blue fluorescence in basic aqueous DMSO and DMF media.Mass spectrum of Schiff bases exhibited the ion peaks as following positions: (D1): m/z (RI%) = 447.1329 (100 %), 424.1517 (60 %), 322.1454 (20 %), 288.0988 (30 %), 102.1277 (55 %) (Fig. S7). (D2): m/z (RI%) = 422.1361 (20 %), 288.0996 (100 %) (Fig. 6). (H1): m/z (RI%) = 883.4259 (10 %), 528.2244 (100 %), 510.2038 (20 %), 392.1605 (10 %), 102.1276 (10 %) (Fig. S8). (H2): m/z (RI%) = 882.3320 (10 %) [M + 2H]+, 434.1278 (40 %), 392.1710 (50 %), 374.1588 (100 %), 322.1523 (10 %), 256.1142 (15 %), 102.1297 (15 %) (Fig. S9). Mass spectral pattern of D1 displayed [M + 3H]+ ion peak at m/z 424.1517. The base peak was observed at m/z 447.1329, which may be due to [M + 3H+Na]+ ion. And the following fragment ion appeared at m/z 288.0988, which may be due to [C14H14N3O4]+ ion (4-((2‑hydroxy-3-methoxybenzylidene)amino)-3-nitrobenzenaminium)). D2 showed [M + H]+ molecular ion at m/z 422.1361. The similar fragmentation was observed at m/z 288.0996. This base peak may be due to fragment [C14H14N3O4]+ ion (2-((2‑hydroxy-3-methoxybenzylidene)amino)-4-nitrobenzenaminium)). H1 exhibited [M + 3H]+ molecular ion at m/z 883.4259. The base peak was observed at m/z 528.2244, which may be due to [C35H24N6]+ ion (3,3′-(((2-((4-(((2-amino-5-(methyleneamino)phenyl)imino)methyl)benzylidene)amino)-1,4-phenylene) bis(azanylylidene))bis(methanylylidene))bis(benzene-1,2-diylium)). In the case of H2, [M + 2H]+ ion peak was seen at m/z 882.3320. The following fragmentation was observed at m/z 434.1278, which may be belonged to fragment [C30H18N4]+ ion (3,3′-(((4-((4-((vinylimino)methyl)benzylidene)amino)1,2phenylene)bis(azanylylidene))bis(methanylylidene))bis(benzene-1,2-diylium)). The base peak was recorded at m/z 374.1588, which may be due to fragment [C26H208N3]+ ion (3,3′-(((4-((2-vinylbut-2-en-1-ylidene)amino)-1,2-phenylene)bis(azanylylidene))bis(methanylylidene))bis(benzene-1-ylium)).

Aggregation-induced emission enhancement (AIEE) active bispyrene-based fluorescent probe: “turn-off” fluorescence for the detection of nitroaromatics

The detection of nitroaromatic explosives in real samples is essential for environmental monitoring because of their strongly powerful nature and wide applications in industries. Aggregation-induced emission enhancement (AIEE) active fluorescent probe has been widely employed to detect nitroaromatic explosives. Hereby, a simple V-shaped bispyrene-based fluorescent probe (called py-o) with AIEE properties was designed and synthesized, which was fully charactered by 1D NMR, ESI, FTIR, and 2D NOESY spectra. The py-o displayed bright blue-green fluorescence excimer emission at 480 nm in DMF/H2O (v/v 1:1). It is observed that the fluorescence excimer emission of py-o at 480 nm was quenched by PA in solution with a quenching constant of 5.45 × 104 M–1, and the limit of detection was approximately 0.139 μM. The details of the sensing mechanism were explained using 1H NMR titrations, Job’s plot and Bensi-Hildebrand methods, which revealed a 1:1 binding ratio via the π-π interactions between PA and py-o. Meanwhile, it exhibited outstanding anti-interference ability in the detection of PA when interfering analytes were added under the same conditions. Furthermore, low-cost thin-layer chromatography (TLC) plates coated with py-o were developed as fluorescent tools for naked-eye detection of PA in the solid state. Therefore, this work provides a new method for constructing an AIEE fluorescent probe for the detection of nitroaromatic explosives to utilize in environmental monitoring.

Hexagonal 2D magnesium sulfide nanosheets biosensor for fluorescence detection of ferritin in serum sample: 2D alkaline earth metal sulfide (2D-AEMS) as an effective fluorescent biosensor

We have developed a highly sensitive and selective ferritin biosensor using the two dimensional (2D) fluorescent Magnesium Sulfide (MgS) nanosheets (NS) using ultra-sonication probe method. Ferritin (Fe3+) is spherical iron containing blood protein which acts as a storage house for iron. This Fe3+ protein is an important biomarker for the detection of iron deficiency (anemia) such as, oxidative stress and cancer. Ultrasonication probe with one pot stirring method to synthesizethe 2D MgS NS was physicochemical, morphological, and analytical studied. The greenish-blue fluorescence of synthesized 2D MgS NS was optimized with maximum intensity at the excitation wavelength of 370 nm and emission wavelength of 435 nm. The quantum yield was 52.6 % found for fluorescent 2D MgS NS. The key role of 1-methylimidazole revealed 2D hexagonal nanosheets with high stability of fluorescence. Besides, the greenish-blue fluorescence of the proposed material was well quenched with the addition of Fe3+, resulting in a linear upward trend in the Stern-Volmer plot owing to static quenching. Further, the selectivity analysis of novel MgS NS shows an excellent selectivity for Fe3+ in the presence of other analytes showing 77 % quenching efficiency and LOD 9 nM with a wide linear range of 10 to 200 nM for Fe3+ detection. The proposed biosensor was successfully employed to detect Fe3+ in blood serum samples with excellent linearity and applicability in clinical diagnosis.

Anti-adhesion multifunctional poly(lactic-co-glycolic acid)/polydimethylsiloxane wound dressing for bacterial infection monitoring and photodynamic antimicrobial therapy

Wound infection and adhesion are important factors affecting wound healing. Early detection of pathogen infection and reduction of wound-to-dressing adhesion are critical for improving wound healing. Herein, Ester-J, which can rapidly respond to lipase secreted by bacteria, was designed and synthesized. Then, Ester-J was co-spun with poly(lactic-co-glycolic acid) (PLGA) and polydimethylsiloxane (PDMS) to prepare a PP-EsJ hydrophobic anti-adhesion dressing with a contact angle of 140.7°. When the PP-EsJ membrane came into contact with the bacteria, the loaded Ester-J was hydrolyzed to Tph-TSF-OH, releasing bright cyan-blue fluorescence, thus providing a fluorescence switch for an early warning of infection. The detection limits of PP-EsJ for Pseudomonas aeruginosa and Staphylococcus aureus were 1.0 × 105 and 1.0 × 106 CFU/mL, respectively. Subsequently, Tph-TSF-OH released 1O2 through light irradiation, which rapidly killed P. aeruginosa and S. aureus, and accelerated wound healing. Compared with the control group, enhanced wound closure (up to 99.80 ± 1.10 %) was observed in mice treated with the PP-EsJ membrane. The PP-EsJ membrane not only effectively reduced the risk of external infection but also reduced adhesions to the skin during dressing changes. These characteristics make PP-EsJ membranes potentially useful for clinical treatment.

Bacterial cellulose/gelatin-based pH-responsive functional film for food freshness monitoring

Food safety is related to public health and environmental safety. Therefore, it is necessary to develop accurate and effective detection methods to assess food quality and safety. In this study, a pH-responsive functional film (BC/GA/FITC/PCA) was generated for the real-time and visual monitoring of shrimp freshness. Bacterial cellulose /Gelatin (BC/GA) was used as a film-forming matrix, and fluorescein isothiocyanate (FITC) and red cabbage (PCA) were used as the response signals. The addition of FITC and PCA increased the shading capacity (< 30 %) and antioxidant properties (22.8 %) of the films. WCA (82.73 ± 0.95°), WVP (1.48 × 10−11 g·cm/cm2·s·Pa) and OTR (2.42 × 10−15 cm3·cm/cm2·s·Pa) indicated that the film possessed water resistance and oxygen barrier properties. When exposed to daylight, the film underwent a color transition from purple to green as the ammonia concentration increased. In addition, the blue-green fluorescence of the films gradually increased and the detection limit was low (170 ppb). In particular, the change in film color caused by shrimp spoilage corresponded to the TVBN value. This study work provides a new strategy for controlling and monitoring food safety and has a wide range of applications in the fields of food-active packaging and smart packaging.

Two-dimensional oxygen-deficient ZnO1-x nanosheet as a highly selective and sensitive fluorescence probe for ferritin detection: the electron transfer biosensor (ETBS).

Iron proteins are of great scientific interest due to their importance as an excellent biomarker for human diseases. Ferritin (Fe3+), being an iron-rich blood protein, is related to various diseases like anemia and cancer. For the first time, we have developed a highly sensitive and selective ferritin biosensor based on fluorescent oxygen-deficient zinc oxide nanosheets through hydrothermal and probe-ultrasonication combined methods. The fluorescence study showed an intense bluish-green fluorescence at λex = 370 nm, after optimization at different excitation wavelengths. In addition, the fluorescence of ZnO1-x nanosheets can be efficiently quenched due to electron transfer reactions in order to achieve quantification analysis. The limit of detection (LOD) was calculated to be 0.015 nM (7.2 ng mL-1) with high linearity (R2 = 0.9930). In addition, the real-world application of the proposed biosensor has been performed on human blood serum samples in the presence of various interfering analytes showing high selectivity and sensitivity with a regression value R2 = 0.9980 indicating the current approach is an excellent biosensor platform.

Rational design of niobium carbide MXene quantum dots decorated with arginine for the fluorescence sensing of superoxide anion in Saccharomyces cerevisiae cells

In this work, arginine functionalized niobium carbide MXene quantum dots (arginine-Nb2C MQDs) were synthesized using Nb2AlC, NaOH and arginine as reagents. The as-synthesized probe showed bluish-green fluorescence under UV light at 365 nm. The structural and morphological changes of as-synthesized arginine-Nb2C MQDs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy and high-resolution transmittance electron microscopy (HR-TEM). The synthesized fluorescent arginine-Nb2C MQDs were stable, with an average size of 1.92 ± 0.52 nm. As-synthesized arginine-Nb2C MQDs act as a sensor for detecting superoxide anion (O2•−) via a fluorescence “turn-off” mechanism with the detection limit of 31.89 nM. The fluorescence of arginine-Nb2C MQDs is quenched by O2•− via dynamic fluorescence quenching mechanism. Fascinatingly, the synthesized arginine-Nb2C MQDs showed negligible cytotoxicity on HeLa cells and acted as promising candidates for sensing of O2•− in Saccharomyces cerevisiae cells.

Tetraarylimidazole-based fluorescence sensor for halosulfuron-methyl

The fluorescence sensor for various guests had been studied widely based on their merits. Fluorescent probes for pesticide detection are of great significance, but there are few reports on the aspect. In this work, the first example of fluorescent sensor for pesticide halosulfuron-methyl was described based on bis-amido tetraphenylimidazole pyridinium salts (Bis-ATPM) prepared conveniently in 76 % yield. It exhibited the obvious “turn-on” blue-green fluorescence after sensing halosulfuron-methyl with excellent sensing selectivity among various ions and pesticides in aqueous media. The detection limitation was as low as 1.8 × 10−7 M. The 1:1 sensing mechanism was confirmed as that halosulfuron-methyl was located in the cavity of Bis-ATPM, resulting in the reduction of the non-radiative energy conduction and the increase of fluorescence emission. The sensing ability of Bis-ATPM for halosulfuron-methyl was effectively applied on the analysis of paper test, agricultural products and water samples, implying the excellent application prospect for Bis-ATPM on simple, rapid, and in-situ sensing halosulfuron-methyl in real environments.

Eu3+ ion-doped strontium vanadate perovskite quantum dots-based novel fluorescent nanosensor for selective detection of creatinine in biological samples

Creatinine (CR) assay in biological fluids is an emerging clinical tool for assessing renal failure, thyroid dysfunction, and muscular injuries. As a result, a simple, quick, and effective CR determinationapproach is critical to human health. A new fluorescent nanosensor, Eu3+-doped strontium vanadate perovskite quantum dots (Eu3+:SrV PQDs), are produced in this study via a solid-state reaction of Sr(NO3)2, VCl3, and Eu(CH3CO2)3 and followed by ultrasonication treatment. The as-synthesized Eu3+:SrV PQDs showed greenish-blue fluorescence when exposed to UV light and exhibited stable fluorescence with a quantum yield of 14.36 %. The greenish-blue emitting Eu3+:SrV PQDs are used as fluorescent nanosensor for the assay of CR with good specificity and sensitivity (the lowest limit of detection was 16 nM). Furthermore, the present approach was also applied to analyze CR in biological samples.

Synthesis of 2D VO2 Nanosheets for the Dual Optical Sensor Method by Colorimetric and Fluorometric Sensing of Catecholamines.

For the first time, we report a dual optical sensor method (DOSM) using novel 2D VO2 nanosheets to act as fluorometric and colorimetric sensors to perform quantitative analysis of epinephrine (EP) and dopamine (DA). The wide color spectrum of the 2D vanadium oxidation series and specifically metastable blue 2D VO2 nanosheets were used to develop a DOSM biosensor. DA and EP are the major catecholamines in the human body that play vital roles as neurotransmitters and stress-responsive hormones of the endocrine system, respectively. Accurate and selective detection of these biomolecules can assist in the diagnosis of many neuroendocrine system-related diseases. The newly synthesized 2D VO2 nanosheet sensor showed bluish-green fluorescence as the first-ever fluorescence from 2D VO2 nanosheets. This sensor showed dual-function sensing toward EP by a dominant color change and fluorescence quenching. It is capable of individually detecting and quantifying both EP and DA with high selectivity and sensitivity by using both colorimetry and fluorometry simultaneously, with the detection limits of 1.07 and 5.54 μM for colorimetric analysis, respectively, and 48.07 and 3.98 μM for fluorescence analysis, respectively. The DOSM sensor was directly applied to real urine samples and gained satisfactory recovery above 90% by means of spiked concentrations. This study has opened a new platform using the DOSM and the vanadium oxidation spectrum in a much more effective way for biosensing. The fluorescence capabilities of this metal oxide can be further applied to many sensor applications based on both fluorescence and colorimetric detection.