Ultra-sensitive detection of commercial vitamin B9 and B12 by graphene nanobuds through inner filter effect

Aggregation induced emission "Turn on" ultra-low detection of anti-inflammatory drug flufenamic acid in human urine samples by carbon dots derived from bamboo stem waste

Carbon dot-based fluorescence sensors have attracted research interest for the selective determination of anti-inflammatory drugs in biological fluids and environments. The overdose and accumulation of anti-inflammatory drugs in tissues can cause chronic side effects including abdominal pain, and renal damage. Herein, we report a new fluorescent probe, bamboo stem waste-derived carbon dots (BS-CDs) for highly sensitive detection of Flufenamic acid (FA), a hazardous anti-inflammatory drug. The UV-vis absorption spectra of BS-CDs show a redshifted absorption peak at 283 nm upon the addition of FA suggesting strong binding interaction between BS-CDs and FA molecule. The BS-CDs showed a fluorescence enhancement (∼2-fold) detection for FA (400 μM) in the linear concentration range (0.40 → 0.65 μM) with a limit of detection (LoD; 17 nM) and binding constant (Ka = 1.33 × 10-3 M-1). The time-resolved fluorescence decay analysis showed that the average lifetime of BS-CDs has slightly changed (4.42 → 4.67 ns) by the interaction with FA through the aggregation-induced emission (AIE) process. The interference, pH, and effect of time results suggest that BS-CDs are highly selective probes for FA detection and do not show any interference involvement during FA detection. The confirmation of the structure and morphology changes of BS-CDs after interaction with FA was carried out by XRD, FESEM, HRTEM, FTIR, and Raman spectroscopy. The practicability of the BS-CDs probe was proved by the detection of FA in human urine samples with recovery of 103-109 %. This suggests that the proposed BS-CDs-based 'turn-on' sensor could be used to determine the FA in biological fluids.

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.

Deep-Learning-Assisted Discriminative Detection of Vitamin B12 and Vitamin B9 by Fluorescent MoSe2 Quantum Dots

A facile and environmentally mindful approach for the synthesis of MoSe2 QDs was developed via the hydrothermal method from bulk MoSe2. In this, the exfoliation of MoSe2 was enhanced with the aid of an intercalation agent (KOH), which could reduce the exfoliation time and increase the exfoliation efficiency to form MoSe2 QDs. We found that MoSe2 QDs display blue emission that is suitable for different applications. This fluorescence property of MoSe2 QDs was harnessed to fabricate a dual-modal sensor for the detection of both vitamin B12 (VB12) and vitamin B9 (VB9), employing fluorescence quenching. We performed a detailed study on the fluorescence quenching mechanism of both analytes. The predominant quenching mechanism for VB12 is via Förster resonance energy transfer. In contrast, the recognition of VB9 primarily relies on the inner filter effect. We applied an emerging and captivating approach to pattern recognition, the deep-learning method, which enables machines to "learn" patterns through training, eliminating the need for explicit programming of recognition methods. This attribute endows deep-learning with immense potential in the realm of sensing data analysis. Here, analyzing the array-based sensing data, the deep-learning technique, "convolution neural networks", has achieved 93% accuracy in determining the contribution of VB12 and VB9.

Terbium(iii)-based coordination polymer with millimeter-size single crystals and high selectivity and sensitivity for folic acid

Terbium(iii)-based coordination polymer with millimeter-size single crystals and high selectivity and sensitivity for folic acid.

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.

In situ growth of novel carbon nanobuds and nanoballs on graphene nanosheets by the electrochemical method

Novel carbon nanostructures, carbon nanobuds and nanoballs in situ grown on graphene, have been synthesized by the electrochemical method in this study. Pristine graphene (GR) sheets were potentiostatic treated with sulfuric acid and were oxidized at 1.4–2.0 V constant potentials to obtain numerous nanobuds and peeled nanoballs. Scanning electron microscopy was used to determine the morphology of electrochemically treated GR nanosheets. Fourier transform infrared, X-ray diffraction analysis, and Raman spectroscopy were used to characterize the structure of samples. The above results indicate that amounts of nanobuds were in situ grown on the surface of GR sheets at a constant potential of 1.4 V was added to the GR electrode. With the constant potential increasing, the nanobuds grew into the nanoballs, exfoliating from the surface of graphene sheets, whereas the peroxidation of graphene sheets occurred at a higher potential of 2.0 V, leading to the formation of a large amount of graphene oxide fragments. Therefore, the optimal processing parameter of the formation of carbon nanoballs was under the constant potential of 1.8 V for 500 s.

Novel carbon nanostructures, carbon nanobuds and nanoballs in situ grown on graphene, have been synthesized by the electrochemical method in this study.

Excitation-independent and fluorescence-reversible N-GQD for picomolar detection of inhibitory neurotransmitter in milk samples ‒ an alleyway for possible neuromorphic computing application

N‒GQDs with an average size of ca. 20-30 nm are utilized for the picomolar detection of inhibitory neurotransmitters, glycine (Gly), in pH ca. 7.0. The crystalline nature, morphology, elemental composition, and chemical state of N-GQDs are investigated by XRD, FE-SEM, HR-TEM, XPS, and FT-IR techniques. The addition of Gly (100 × 10^-9 M; 0 → 1.0 mL) steadily quenches the fluorescence intensity of N-GQD (1 × 10^-6 M) at 432 nm (λ_ex 333 nm) due to inner filter effect (IFE) through the formation of ground-state complex, N-GQD•Gly. The excitation-independent N‒GQDs showed an outstanding selectivity and sensitivity towards Gly with binding constant (K_a = 8.97 × 10^-3 M^-1) and LoD (21.04 pM; S/N = 3). Time-correlated single-photon counting experiment confirms the static quenching of N-GQD (8.77 → 8.85 ns) in the presence of Gly. The interference of other amino acids on the strong binding of the N-GQD•Gly complex in H₂O is examined. Combinatorial Ex-OR and NOT gate logic circuits that could be useful in neuromorphic computing are developed based on the reversible fluorescence intensity changes of N-GQD upon the addition of Gly (Ф_F 0.54 → 0.39). The real-time application of N-GQD was investigated using commercially available relevant milk samples. Remarkably, not less than 99% cytotoxic reactivity of N-GQDs is attained against HeLa cells.

Do amino acid functionalization stratagems on carbonaceous quantum dots imply multiple applications? A comprehensive review

Amino acids are the noteworthy entity among biological molecules with diverse properties such as zwitterionic and amphoteric. Functionalizing carbon-based quantum dots using amino acids might be used for the extreme enhancement of electronic and optical properties of quantum dots and improve the performance of the resultant amino acid-functionalized quantum dots. The amino acid-functionalized quantum dots are highly soluble, sustainable, and biocompatible with virtuous optical and electrical performance, which makes them potential and suitable candidates for fabricating optoelectronic devices. The tenacity of using amino acids as functional groups to functionalize quantum dots and their novel properties are conferred to attain their multiple applications. The goal of this review is to provide the choices of amino acids based on the desired applications and a variety of functionalization techniques to make them a noteworthy material for future applications. The method of one-step and two-step functionalization strategies along with the properties of the resultant functionalized quantum dots and their plausible applications and future scope of the material are highlighted. Amidation is the basic principle behind the functionalization of quantum dots with amino acids. This review would be an exciting prospect to explore the pathways of the possible applications in different domains, in which the amino acid-functionalized quantum dots have not yet been explored. Further, this review article helps in pitching a variety of prominent applications right from sensors to energy storage systems either using the optical property or electronic property of amino acid-functionalized quantum dots.

Recent progress on graphene quantum dots-based fluorescence sensors for food safety and quality assessment applications

The versatile photophysicalproperties, high surface-to-volume ratio, superior photostability, higher biocompatibility, and availability of active sites make graphene quantum dots (GQDs) an ideal candidate for applications in sensing, bioimaging, photocatalysis, energy storage, and flexible electronics. GQDs-based sensors involve luminescence sensors, electrochemical sensors, optical biosensors, electrochemical biosensors, and photoelectrochemical biosensors. Although plenty of sensing strategies have been developed using GQDs for biosensing and environmental applications, the use of GQDs-based fluorescence techniques remains unexplored or underutilized in the field of food science and technology. To the best of our knowledge, comprehensive review of the GQDs-based fluorescence sensing applications concerning food quality analysis has not yet been done. This review article focuses on the recent progress on the synthesis strategies, electronic properties, and fluorescence mechanisms of GQDs. The various GQDs-based fluorescence detection strategies involving Förster resonance energy transfer- or inner filter effect-driven fluorescence turn-on and turn-off response mechanisms toward trace-level detection of toxic metal ions, toxic adulterants, and banned chemical substances in foodstuffs are summarized. The challenges associated with the pretreatment steps of complex food matrices and prospects and challenges associated with the GQDs-based fluorescent probes are discussed. This review could serve as a precedent for further advancement in interdisciplinary research involving the development of versatile GQDs-based fluorescent probes toward food science and technology applications.

Surface and morphology analyses, and voltammetry studies for electrochemical determination of cerium(iii) using a graphene nanobud-modified-carbon felt electrode in acidic buffer solution (pH 4.0 ± 0.05)

Trace determination of radioactive waste, especially Ce3+, by electrochemical methods has rarely been attempted. Ce3+ is (i) a fluorescence quencher, (ii) an antiferromagnet, and (iii) a superconductor, and it has been incorporated into fast scintillators, LED phosphors, and fluorescent lamps. Although Ce3+ has been utilized in many industries due to its specific properties, it causes severe health problems to human beings because of its toxicity. Nanomaterials with fascinating electrical properties can play a vital role in the fabrication of a sensor device to detect the analyte of interest. In the present study, surfactant-free 1,8-diaminonaphthalene (DAN)-functionalized graphene quantum dots (DAN-GQDs) with nanobud (NB) morphology were utilized for the determination of Ce3+ through electrochemical studies. The working electrode, graphene nanobud (GNB)-modified-carbon felt (CF), was developed by a simple drop-coating method for the sensitive detection of Ce3+ in acetate buffer solution (ABS, pH 4.0 ± 0.05) at a scan rate of 50 mV s-1 using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. CV and DPV studies validated the existence of distinctive peaks at approximately +0.20 and +0.93 V (vs. SCE), respectively, with a limit of detection of approximately 2.60 μM. Furthermore, electrochemical studies revealed that the GNB-modified-CF electrode was (i) stable even after fifteen cycles, (ii) reproducible, (iii) selective towards Ce3+, (iv) strongly pH-dependent, and (v) favored Ce3+ sensing only at pH 4.0 ± 0.05. Impedance spectroscopy results indicated that the GNB-modified-CF electrode was more conductive (1.38 × 10-4 S m-1) and exhibited more rapid electron transfer than bare CF, which agrees with the attained Randles equivalent circuit. Microscopy (AFM, FE-SEM, and HR-TEM), spectroscopy (XPS and Raman), XRD, and energy-dispersive X-ray (EDX) analyses of the GNB-modified-CF electrode confirmed the adsorption of Ce3+ onto the electrode surface and the size of the electrode material. Ce3+ nanobuds increased from 35-40 to 50-55 nm without changing their morphology. The obtained results provide an insight into the determination of Ce3+ to develop an electrochemical device with low sensitivity.