A multifunctional sensor for selective and sensitive detection of vitamin B12 and tartrazine by Förster resonance energy transfer

Advances in Fluorescent Nanosensors for Detection of Vitamin B12

Vitamin B12 plays a significant role in maintaining human health. Deficiency or excess intake of vitamin B12 may cause some diseases. Therefore, it is significant to fabricate sensors for sensitive assay of vitamin B12. In the past few years, a variety of nanomaterials have been developed for the fluorescence detection of vitamin B12 in tablets, injection, human serum and food. In the review, the assay mechanisms of fluorescent nanomaterials for sensing vitamin B12 were first briefly discussed. And the progress of various nanomaterials for fluorescence detection of vitamin B12 were systematically summarized. Furthermore, the sensing performance of fluorescent nanosensors was compared with fluorescent probes. Lastly, the challenges and perspectives about the topic were presented.

A comprehensive exploration of tartrazine detection in food products: Leveraging fluorescence nanomaterials and electrochemical sensors: Recent progress and future trends

Azo dyes are widely used as food coloring agents because of their affordability and stability. Examples include brilliant blue, carmoisine, sunset yellow, allura red, and tartrazine (Tar), etc. Notably, Tar is often utilized in hazardous food goods. They are frequently flavoured and combined with food items, raising the likelihood and danger of exposure. Therefore, detecting Tar in food is crucial to prevent health risks. Fluorescence nanomaterials and electrochemical sensors, known for their high sensitivity, affordability, simplicity, and speed, have been widely adopted by researchers for Tar detection. This comprehensive paper delves into the detection of Tar in food products. It extensively covers the utilization of advanced carbon-based nanomaterials, including CDs, doped CDs, and functionalized CDs, for sensitive Tar detection. Additionally, the paper explores the application of electrochemical sensors. The paper concludes by addressing current challenges and prospects, emphasizing efforts to enhance sensitivity, and selectivity for improved food safety.

Silicon Doped Carbon Dots as an New Ratiometric Fluorescence Probe for Proanthocyanidins Assay Based on the Redox Reaction Between Cr(VI) and Proanthocyanidins

In the study, silicon doped carbon quantum dots (Si-CQDs) was prepared by one-pot hydrothermal method with (3-aminopropyl) triethoxysilane (APTES) and o-phenylenediamine (OPD) as raw materials. Then a new ratiometric fluorescent probe (RF-probe) was successfully established for sensitively and selectively monitoring proanthocyanidins (PAs) with a linear range of 10-500 nM and limit of detection (LOD) of 5.6 nM. that is, the fluorescence (FL) intensity of Si-CQDs at 570 nm was used as the built-in reference, while dopamine (DA) reacting with 4-hexylresorcinol (4-HR) could produce a new fluorescent substance (named as azamonardine, AZMON), and its FL intensity at 480 nm was reduced because Cr(VI) could oxidize DA to generate quinone without fluorescence. In the presence of PAs, Cr(VI) was reduced to Cr(III), which caused that the amount of DA reacting with 4-HR was increased, thus the FL intensity of AZMON was recovered. Furthermore, the RF-probe was successfully used for the determination of PAs in black goji berry from two different areas and PAs capsule with satisfactory results compared to the standard HPLC method.

Facile hydrothermal synthesis and purification of fluorescent carbon dots for food colorant tartrazine detection based on a dual-mode nanosensor

Colorant tartrazine is widely used in the food industry, but its long-term and excessive consumption is harmful to human health. Therefore, it is necessary to establish a sensitive detection method for tartrazine. Blue fluorescent carbon dots with L-arginine and o-phenylenediamine as precursors, namely L-Arg/oPD-CDs, were prepared via the hydrothermal method. Then, L-Arg/oPD-CDs were further purified by dialysis, thin layer chromatography and column chromatography. A dual-mode nanosensor based on fluorescent and UV absorption was successfully developed. Excellent linear ranges of 0-5 μM and 10-50 μM were obtained with a low detection limit of 42.3 nM based on fluorescence. A good linear range of 0-50 μM was obtained with a low detection limit of 130.15 nM based on UV absorption. The quenching mechanism of tartrazine towards L-Arg/oPD-CDs fluorescence was the inner filter effect. In addition, a dual-mode nanosensor was used for tartrazine determination in millet, maize flour, carbonated drink, and sugar samples. This study provides new insight into the detection of tartrazine by applying a dual-mode nanosensor.

A Novel Ratio Probe Based on Mixing of Thiocyanuric Acid- Enhanced Silver Nanoclusters with N, S Co-Doped Carbon Quantum Dots for Detecting Sodium 2,3-Dimercapto Propanesulfonic Acid

Background

The ratio fluorescent probe (RF-probe) has the characteristics of self-calibration and eliminating the influence of experimental factors (such as probe concentration, excitation intensity stability, and solution environment) in quantitative assays based on the linear relationship between the intensity ratio of two emission peaks and the concentration of analyte, especially in a complex biological matrix.

Objective

High-luminescent Ag nanoclusters (AgNCs) were prepared at room temperature due to aggregation-induced emission (AIE) through the incorporation of trithiocyanuric acid (TA). Subsequently, a new RF-probe based on mixing of AgNCs-TA with nitrogen and sulfur co-doped carbon quantum dots (N, S-CQDs) was prepared for sensitively and selectively assaying sodium 2, 3-dimercaptopropane-1-sulfonate (DMPS).

Methods

The fluorescence of N, S-CQDs was quenched in the presence of the AgNCs-TA mainly deriving from the inner filter effect (IFE), and its fluorescence intensities at 440 and 650 nm could recover and drop upon the addition of DMPS (λex = 370 nm).

Results

The RF-probe enables DMPS to be detected by fluorometry with a linear response in the 0.67–30.0 μmol/L concentration range and a 54.7 nmol/L detection limit (at 3σ/slope). At the same time, we also used the labeled recovery method to confirm the reliability of the method. The recoveries were 97.93–106.33%, and the corresponding standard deviations (RSD) were less than 1.87%.

Conclusion

The N, S-CQDs/AgNCs-TA RF-probe can also semi-quantitatively monitor DMPS by naked eyes.

Highlights

The mechanism of fluorescence enhancement of the AgNCs by TA also were investigated by the N, S-CQDs/AgNCs-TA-DMPS system. What’s more, the RF-probe of N, S-CQDs/AgNCs-TA was successfully utilized to monitor DMPS in real samples.

N,P-codoped carbon quantum dots-decorated TiO2 nanowires as nanosized heterojunction photocatalyst with improved photocatalytic performance for methyl blue degradation

N,P-doped carbon quantum dots (N,P-CQDs) are deemed as a promising candidate to environmentally friendly materials owing to the inexpensive, biocompatible nature. TiO₂ nanowire is a prospective photocatalyst because of its efficient migration of photoexcited carriers in wastewater treatment. However, the N,P-CQDs-decorated TiO₂ nanowire (N,P-CQDs/NW-TiO₂) photocatalysts have been rarely reported. In this study, we build N,P-CQDs on the surface of TiO₂ nanowires via a simple deposition process. Our investigations demonstrate that N,P-CQDs/NW-TiO₂ has a great photocatalytic degradation for methyl blue (MB) under irradiation. The degradation rate of can reach 93.6% within 120 min under proper conditions. The excellent degradation performance of N,P-CQDs/NW-TiO₂ is ascribed to the mesoporous structure and high separation rate of photoexcited carriers. In addition, the N,P-CQDs/NW-TiO₂ have outstanding recycled photocatalytic capability. After being recycled four times, the N,P-CQDs/NW-TiO₂ still maintain 59.9% photocatalytic activity. The fabricated nanosized photocatalyst can be widely utilized in the field of photocatalysis for wastewater treatment.

Nicotinamide-Functionalized Carbon Quantum Dot as New Sensing Platform for Portable Quantification of Vitamin B12 in Fluorescence, UV-Vis and Smartphone Triple Mode

Development of an efficient, portable and simple nanosensor-based systems with reliable analytical performance for on-site monitoring of vitamin B12 (VB12) are still major problems and a challenging work for quality control of manufacturers. Herein, a new fluorescence, UV-Vis and smartphone triple mode nanosensors were designed for the simultaneous detection of VB12 with high sensitivity and accuracy. A novel nanosensor was synthesized through nicotinamide-functionalizing of carbon quantum dot (NA-CQDs) by an one-step microwave-assisted method with green approach. The NA-CQDs sensor showed excellent fluorescence properties and wide linear ranges from 0.1-60 µM with the detection limits of 31.7 nM. Moreover, color changes of NA-CQDs induced by the VB12 could also be detected by UV-Vis spectrophotometer and inhouse-developed application installed on smartphone as a signal reader, simultanusly. The Red, Green and Blue (RGB) intensities of the colorimetric images of NA-CQDs/VB12 system which taken by smartphone's camera converted into quantitative values by the application. A smartphone-integrated with NA-CQDs as colorimetric sensing platform displays good linear ranges (4.16 to 66.6 μM) for on-site determination of VB12 with detection limit of 1.40 μM. The method was successfully applied in the determination of VB12 in complex pharmaceutical supplement formulations without any sample pre-treatment and matrix interfering effects. The recovery results (96.52% to 105.10%) which were in agreement with the reference methods, demonstrating the capability of the smartphone-assisted colorimetric sensing platform in many on-site practical applications of quality controls.

A ratiometric fluorescent sensing of proanthocyanidins by MnO2 nanosheets simultaneously tuning the photoluminescence of Au/AgNCs and thiamine

By simultaneously regulating the photoluminescence of alloy Au/Ag nanoclusters (NCs) and thiamine (VB1) through MnO₂ nanosheets (MnO₂ NS), a novel ratiometric fluorescent probe (RF-probe) was established for sensitively and selectively monitoring proanthocyanidins (PAs). The introduction of Ag (I) ions could enhance significantly the quantum yields (QYs, 11.1%) of AuNCs based on the synthetic method of UVI (UV irradiation) combined with MWH (microwave heating). MnO₂ NS could quench the fluorescence (FL) of Au/AgNCs mainly coming from Förster resonance energy transfer (FRET), while it could act as a nanozyme catalyst for directly catalyzing the oxidation of VB1 to produce highly fluorescent oxVB1. In the presence of PAs, MnO₂ was reduced to Mn²⁺, which caused that its quenching capacity and oxidase-like activity were vanished, thus the FL of oxVB1 and Au/AgNCs was reduced and recovered. The concentration of PAs could be monitored by the RF-probe with a linear range of 0.27-22.4 μmol L^-1 and corresponding limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 75.9 and 250.5 nmol L^-1. Furthermore, the RF-probe was successfully used for the determination of PAs in mineral water, PAs additive and PAs capsule with satisfactory results compared to the standard HPLC method.

Synthesis and Characterization of a Novel Heterocyclic Schiff Base and Development of a Fluorescent Sensor for Vitamin B12

A heterocyclic Schiff base (MPDPI)was synthesized by the condensation reaction of 1-phenylisatin with 4,5-dimethylphenylene diamine. It was characterized by using spectroscopic methods including UV visible, Infrared, ¹H-NMR, ¹³C-NMR and mass spectrometry. It acts as the fluorescent probe for the detection of Vitamin B12 (Vit.B12) which shows high selectivity over other species via dynamic quenching mechanism. It is also highly sensitive towards Vit.B12 with a detection limit of [Formula: see text]M and showed a linear concentration ranging from [Formula: see text] to [Formula: see text]. Effect of other coexisting species was also studied. The satisfactory results were also obtained in real samples.Since, there are only few reports on Vit.B12, development of selective fluorescent probes for Vit.B12 would be worthwhile.

Development of a highly sensitive fluorescence method for tartrazine determination in food matrices based on carbon dots

In this work, an ultrasensitive sensing system based on fluorescent carbon dots (CDs) was developed for the tartrazine (Tar) determination. The CDs were prepared via a simple one-pot hydrothermal method with m-phenylenediamine as the only precursor. The physical and chemical properties were in detail characterized by transmission electron microscopy (TEM), MALDI-TOF MS, UV-vis absorption and photoluminescence (PL) spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy (FTIR). Upon exposure to Tar, the fluorescence of CDs was efficiently quenched via the dynamic interaction between CDs and Tar as well as the inner filter effect (IFE). With this information, the CDs were proposed as a fluorescence probe for Tar detection. It was found that CDs had high sensitivity and selectivity for Tar sensing, and the linear relationship was observed in the range of 0.01-25.0 μM with the corresponding detection limit (3σ/k) of 12.4 nM, which is much more sensitive than any of the existed CD-based sensing platform. The investigated sensing system was finally utilized for Tar sensing in various food matrices with a high degree of accuracy. The spiked recoveries were in a range of 96.4-105.2%, and the relative standard deviations (RSDs) were lower than 4.13%. This work highlights the great application prospects of CDs for Tar sensing in a rapid, simple, and sensitive way.

The quantum dot-FRET-based detection of vitamin B12 at a picomolar level

Herein we report the picomolar level detection of vitamin B12 (VB12) using orange-red emitting ligand-free Mn²⁺-doped ZnS quantum dots (QDs; λ _em = 587 nm) in an aqueous dispersion. Sensing was achieved following the quenching of the luminescence of the Mn²⁺-doped ZnS QDs with an increasing concentration of VB12. The Stern-Volmer constant was determined to be 5.2 × 10¹⁰ M^-1. Importantly, the Mn²⁺-doped ZnS QDs exhibited high sensitivity towards VB12, with a limit of detection as low as 1.15 ± 0.06 pM (in the linear range of 4.9-29.4 pM) and high selectivity in the presence of interfering amino acids, metal ions, and proteins. Notably, a Förster resonance energy transfer (FRET) mechanism was primarily proposed for the observed quenching of luminescence of Mn²⁺-doped ZnS QDs upon the addition of VB12. The Förster distance (R _o) and energy transfer efficiency (E) were calculated to be 2.33 nm and 79.3%, respectively. Moreover, the presented QD-FRET-based detection may bring about new avenues for future biosensing applications.

Poly(sodium-p-styrenesulfonate)-enhanced fluorescent silver nanoclusters for the assay of two food flavors and silicic acid

A water-soluble, long-term stable, poly(sodium-p-styrenesulfonate)-enhanced and d-penicillamine stabilized argentum nanoclusters (PSS-DPA-AgNCs) was synthesized by a one-step ultraviolet radiation combined with microwave heating method. The effects of different types of polyelectrolytes and energy suppliers on the AgNCs photo-luminescence performance were investigated in detail. The prepared AgNCs are exhibited to be viable fluorescent method for 2-Mercapto-3-butanol (2-M-3-B), 3-Mercapto-2-butanone (3-M-2-B) and silicate (SiO₃^2-) determinations. The fluorescence (FL) of PSS-DPA-AgNCs is quenched with the addition of 2-M-3-B/3-M-2-B/SiO₃^2- mainly originating from a static quenching process. The method can monitor 2-M-3-B/3-M-2-B by fluorometry with a linear response in the range of 0.33-90.0/0.33-80.0 μM and a 74/250 nM detection limit (at 3σ/slope). For the SiO₃^2- assay, corresponding data are 3.33-100.0 μM and 278 nM. Moreover, the proposed method was successfully used for the assays of two food flavors in the steamed bread and soda drinks, and silicate in the mineral water samples respectively.

Fluorometric assay of iron(II) lactate hydrate and ammonium ferric citrate in food and medicine based on poly(sodium-p-styrenesulfonate)-enhanced Ag nanoclusters

Poly(sodium-p-styrenesulfonate)-enhanced and D-penicillamine stabilized Ag nanoclusters (PSS-DPA-AgNCs) were prepared using one-step ultraviolet irradiation combined with microwave heating method, and the effects of the AgNCs photo-luminescence performance based on different types of polyelectrolytes and energy suppliers were studied detailedly. The as-prepared AgNCs can be used as a viable fluorescent probe for monitoring indirectly iron(II) lactate hydrate (ILH) and ammonium ferric citrate (AFC), respectively. The fluorescence (FL) quenching of PSS-DPA-AgNCs by Fe³⁺ (it is obtained from oxidized ILH/ionized AFC) mainly derives from a dynamic quenching process. Excellent linear relationships exist between the FL quenching degree of the AgNCs and the concentrations of ILH/AFC in the range of 0.17-6.00/0.067-3.33 μmol·L^-1, and corresponding limit of detection (at 3σ/slope) is 12.4/6.04 nmol·L^-1. Moreover, the AgNCs probe was extended to the assays of ILH in tablets, solid beverage or ILH additive and AFC in two kinds of edible salts or syrup with satisfactory results compared with the standard 1, 10-phenanthroline method. In addition, the AgNCs probe reveals a good temperature sensing capability.