Boron Nitride Quantum Dots Research Articles

Controllable preparation of boron nitride quantum dots with small size and strong blue photoluminescence

As a new type of quantum dots (QDs), boron nitride QDs (BNQDs), show promising potentials in disease diagnosis, fluorescence imaging and bio-sensing due to its good biocompatibility, low cytotoxicity and excellent photoluminescence performance. However, there are still challenges in preparing BNQDs with uniform and small size. In this paper, the BNQDs with uniform and small size have been prepared through a hydrothermal process with the exfoliated hexagonal boron nitride nanosheets (h-BNNSs) as precursor. The as-prepared BNQDs were characterized by transmission electron microscope (TEM), high-resolution TEM, fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-vis and photoluminescence spectra (PL) for morphology, surface functional groups, element composition and optical properties. The as-prepared BNQDs have uniform particle size distribution with an average lateral size of 1.65 nm, and a PL quantum yield of 2.49 %. In addition, the as-prepared BNQDs exhibit strong blue fluorescence under UV-vis (365 nm) irradiation and nanosecond luminescent decay. Furthermore, the effect of preparation parameters on the fluorescence performance of BNQDs was investigated which provides an optimal condition for the preparation of BNQDs with excellent fluorescence performance. Together with other advantages, such as excellent physical/chemical properties, good biocompatibility and low cytotoxicity, the as-prepared BNQDs have great potentials in medical diagnosis, biosensing, photoelectric devices and other fields in the future.

Catalytical feature of optical nanoprobes of boron nitride quantum dots in the presence of Cu2+ for the determination of dopamine.

Monitoring the concentration of dopamine (DA) is vital for preventing and diagnosing DA related diseases. In contrast to the traditional sensing methods for DA, in which direct or indirect effects on the optical probes are often recorded, a novel sensing concept is disclosed based on as a result of the in situ formation of polydopamine (PDA) originating from the synergetic effect between boron nitride quantum dots (BNQDs) and Cu2+. In the co-presence of BNQDs and Cu2+, DA was catalytically oxidized to PDA, accompanied by an obvious color change from colorless to brown. In contrast to previous reports, in which BNQDs have been employed as an optical probe, herein, the BNQDs not only acted as the optical energy donor, but also as the catalysts for the formation of PDA. The quenching efficiency resulting from the inner filter effect and the electron transfer between the BNQDs and PDA was directly proportional to the concentration of DA, ranging linearly from 2 to 80 μM with a limit of detection of 0.49 μM. The present system exhibited an outstanding selectivity for DA among other interfering coexisting biomolecules. Furthermore, the practical application of the proposed platform was verified by assaying DA in human plasma samples, and satisfactory recoveries ranging from 101.24% to 111.98% were obtained. With the satisfactory reliability, repeatability and stability, the proposed simple sensor showed significant potential for use in DA detection in other biomedical applications.

White graphene quantum dots as electrochemical sensing platform for ferritin

The use of hexagonal boron nitride quantum dots (hBN QDs) as an electrochemical sensor for ferritin is reported for the first time. These QDs were synthesized using a simple liquid exfoliation method. The synthesized material was characterized using analytical techniques such as UV-visible, Fourier transform infrared (FTIR) and Raman spectroscopy, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM) to study different aspects of the QDs. These QDs were explored for their plausible application as a platform for the electrochemical detection of ferritin. For this, electrochemical impedance spectroscopy was used as a sensing technique and disposable hBN QD functionalized screen printed electrodes were used as a sensing platform. The developed immunosensor had a dynamic linear range from 10-2000 ng mL-1 of ferritin concentration with a limit of detection of 1.306 ng mL-1. The immunosensor was highly selective, did not deviate in the presence of interfering agents and was also highly reproducible.

Enhanced peroxidase-like activity of boron nitride quantum dots anchored porous CeO2 nanorods by aptamer for highly sensitive colorimetric detection of kanamycin

Kanamycin (KAN) residue in the environment and food have a huge risk to human health, therefore, designing simple and sensitive determination methods for KAN is in high demand. Here, a simple and low-cost colorimetric analysis was established for highly sensitive determination of KAN through integrating boron nitride quantum dots anchored porous CeO2 nanorods (BNQDs/CeO2) and aptamer. The BNQDs/CeO2 as nanozyme showed prominent peroxidase-like activity, which could effectively catalyze 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation by H2O2 because of large surface area and synergetic interaction between BNQDs and CeO2. Moreover, it presented an obviously enhanced catalytic activity after combing with KAN-specific aptamer, resulting from the increased dispersibility and substrate affinity of BNQDs/CeO2 nanozyme. While KAN could restrain such a catalytic enhancement through aptamer-target recognition event. On the basis of aptamer-regulated mimic enzyme activity, the proposed colorimetric method realized quantitative KAN determination ranging from 0.01 nM to 100 nM with an ultralow detection limit of 4.6 pM. This analysis method is facile in design and can be applied to other biomolecular recognition processes, promising as a universal detection platform for environmental monitoring and food safety.

FABRICATION OF PLATINUM NANOPARTICLE/BORON NITRIDE QUANTUM DOTS/6-METHYL-2-(3-HYDROXY-4-METHOXYBENZYLIDENAMINO)-BENZOTHIAZOLE (ILS) NANOCOMPOSITE FOR ELECTROCATALYTIC OXIDATION OF METHANOL

Since worldwide energy demand is growing, conventional fuel reserves are getting low and pollution is increasing, fuel cell applications are becoming more widespread day by day. In this study, preparation of Platinum nanoparticle (PtNPs)/boron nitride quantum dots (BNQDs)/6-methyl-2-(3-hydroxy-4-methoxybenzylidenamino)-benzothiazole (ILs) nanocomposite (PtNPs/BNQDs/ILs) has been made. Afterwards, using various equipment and methods, characterization has been carried out. These equipment and methods are as follows: Transmission Electron Microscope, Scanning Electron Microscope, X-Ray Photo Electron Spectroscopy, Energy-Dispersive X-Ray Spectroscopy and X-Ray Diffraction Method. The catalyst developed on PtNPs/BNQDs/ILs has proven to be cost-effective. Moreover, the PtNPs/BNQDs/ILs nanocomposite has achieved a higher peak for the current oxidation of methanol, when compared to BNQDs/ILs and ILs. Therefore, this catalyst has a better catalytic activity.

Bisphenol S-doped g-C3N4 nanosheets modified by boron nitride quantum dots as efficient visible-light-driven photocatalysts for degradation of sulfamethazine

Antibiotics may pose a great risk to ecosystem and human health. Photocatalysis, as a low-cost and environmentally friendly technology is widely used for the removal of antibiotics from wastewater. Graphitic carbon nitride (g-C3N4) has shown promising prospects in visible light photocatalysis, while its photocatalytic performance is greatly limited because of the sluggish charge separation and transfer. In this work, metal-free boron nitride quantum dots (BNQDs) modified bisphenol S (BPS)-doped g-C3N4 nanosheets (BNQDs/BPS-CN) heterojunction was synthesized to overcome these defects and applied in photodegradation of sulfamethazine (SMZ, a typical antibiotic) under the visible light. Multifarious characterization methods were used to explore the structure, porosity, elemental composition, optical performances, photo-electrochemical properties and photocatalytic performances of as-prepared BNQDs/BPS-CN composites. The degradation efficiency of SMZ with BNQDs/BPS-CN-4 composite reaches 100% within 60 min, and the rate constant is 13.7 times higher than that of pure g-C3N4. This phenomenon is because of the shrinking band gap width and the introduction of electronegative BNQDs, which is conducive to the absorption of visible light and high-efficiency separation of photoexcited charge carriers. Meanwhile, the results of free radical trapping experiments and electron spin resonance characterization prove that the photogenerated holes and superoxide radicals play predominant roles in the photodegradation of SMZ. This study proposes an effective mechanism for the construction of novel visible-light-driven photocatalysts using metal-free two-dimensional materials and quantum dots, which can be applied in the treatment of organic contaminants.

An electrochemiluminescence biosensor based on boron nitride quantum dots as novel coreactant for quantitative determination of concanavalin A.

An electrochemiluminescence (ECL) analytical platform is constructed based on boron nitride quantum dots (BNQDs) as a novel coreactant of luminol for quantitative assay of concanavalin A (Con A). Different from previous research that mainly focuses on its superior optical properties, BNQDs are used for the first timeas a coreactant for boosting ECL intensity of luminol, which has a 10-fold enhancement compared with individual poly(luminol/aniline) nanorods loaded on reduced graphene oxide (PLA-rGO) using GCE. On the basis that BNQDs contain an abundance of active amino, a possible mechanism of amino oxidation facilitating ECL emission is proposed. Firstly, luminol as light spices are oxidized to luminol•- and BNQDs generate an abundance of BNQDs-NH+• via electrochemical oxidization, producing reductive intermediates BNQDs-N• in alkaline conditions. Finally, BNQDs-N• react with luminol•- to obtain the excited species AP2-*, returning to ground state and emitting light. Due to the hindrance effect of Con A, the ECL intensity decreases gradually as various concentrations of Con A are modifying the electrodesurface. Therefore, a sensitive ECL biosensor for detecting Con A is constructed exhibiting awide linear range of1.0pg·mL-1 to 1.0μg·mL-1 and a low detection limit of 0.15pg·mL-1. Graphical abstract Schematic representation of an electrochemiluminescence (ECL) biosensor based on boron nitride quantum dots (BNQDs) as an efficient coreactant of reduced graphene oxide functionalized poly(luminol/aniline) (PLA-rGO) for quantitative assay of concanavalin A (Con A).

Amino Acids as the Nitrogen Source to Synthesize Boron Nitride Quantum Dots for Fluorescence Turn‐off‐on Detection of Ascorbic Acid

AbstractThe BNQDs are synthesized by simple one‐step hydrothermal method, using amino acids as nitrogen source and boric acid as boron source. The BNQDs prepared by different amino acids emit strong blue fluorescence with the excitation wavelength from 280 to 400 nm. An “on‐off‐on” BNQDs fluorescent sensor is designed to detect ascorbic acid with Fe3+ as medium, extending the application in sensing. The fluorescence of BNQDs is quenched by Fe3+ on basis of the inner filter effect. With increasing of ascorbic acid, the fluorescence of BNQDs is recovered due to the oxidation‐reduction between Fe3+ and ascorbic acid. The assay is capable of recognizing ascorbic acid in the concentration range of 1–100 μM with a detection limit of 0.0833 μM. In addition, the method has the potential to determine Fe3+ and ascorbic acid in real water samples and human serum.

Boron nitride quantum dots as electrochemiluminescence coreactants of rGO@Au@Ru–SiO2 for label-free detection of AFP in human serum

A label-free electrochemiluminescence (ECL) immunosensor is developed to detect alpha-fetoprotein (AFP). Ru (bpy)32+-doped silica nanoparticles (Ru–SiO2) and gold nanoparticle-modified reduced graphene oxide (rGO@Au) are integrated to form an rGO@Au@Ru–SiO2 composite. The composite is employed as a carrier for immobilizing the target antibody, and a label-free ECL immunosensor is constructed via antigen–antibody interaction. Owing to the numerous Ru (bpy)32+ molecules in the Ru–SiO2, a high ECL signal is acquired. With excellent conductivity and a large surface area, the rGO@Au composite not only accelerates electron transfer but also improved the ECL signal and captures antibodies, thus enhancing ECL response and sensitivity. Moreover, boron nitride quantum dots (BNQDs) are used as rGO@Au@Ru–SiO2 coreactants, achieving high ECL intensity. The proposed ECL system exhibits significant potential in bioanalysis, which is attributed to the excellent biocompatibility and good stability of BNQDs. Under optimal experimental conditions, the sensor has a linear range of 0.0001 ng mL−1 to 100 ng mL−1 and a limit of detection equal to 0.03 pg mL−1 (S/N = 3). The proposed technique is successfully applied in the susceptible detection of AFP in human serum. The recovery ranges from 99% to 100%, and the RSD is less than 2.8%. The constructed ECL immunosensor exhibits acceptable performance during actual application.

Interaction of hydrated metals with chemically modified hexagonal boron nitride quantum dots: wastewater treatment and water splitting.

The electronic and adsorption properties of chemically modified square hexagonal boron nitride quantum dots are investigated using density functional theory calculations. The free energy and frequency calculations show that all the boron nitride flakes are stable before/after modification and metal adsorption. Edge modification significantly enhances the stability and interactivity of the flake. For instance, the free energy of binding decreases from -6.5 eV in the hydrogenated flake to -7.1 eV in the pristine one and the dipole moment increases from 4.5 D to 53.7 D, respectively. A wide spectrum of band gaps can also be achieved, where the band gap can be smoothly varied from ∼6 eV in edge fluorinated flakes to 0.2 in sulfurated ones. Six hydrated metals, Cd, Co, Cr, Cu, Fe, and Zn, are considered for adsorption by the flakes. The transition metals are highly selected by the flakes while heavy metals are weakly adsorbed. All hydrated metals are physically adsorbed by the edge and surface of hydrogenated flakes except Cu, which is chemically adsorbed. Chemical groups or elements attached to the flake strongly enhance the adsorption strength; the adsorption energy of hydrated Cr on the surface increases from 0.6 eV to 8.6 eV after attaching two COOH groups to the surface. Hydrogen evolution has also been observed through the adsorption process. The calculated low overpotential for the oxygen evolution reaction (0.52 V) and hydrogen adsorption strength (0.11 eV) for the hydrogen evolution reaction indicate that boron nitride quantum dots are not only potential candidates for the removal of different metals from wastewater but also for efficient water splitting.

White-Light-Emitting Diodes from Directional Heat-Conducting Hexagonal Boron Nitride Quantum Dots

In quantum-dots-converted white-light-emitting diodes (QDs-WLEDs), red-emitting quantum dots are usually mixed with yellow-emitting phosphors in luminescent polymer layer to achieve a high color re...

Mo2C combined with carbon material nanosphere as an electrochemiluminescence super-enhancer and antibody label for ultrasensitive detection of cardiac troponin I

To sensitively detect cardiac troponin I (cTnI), a novel electrochemiluminescence (ECL) immunosensor was constructed on the basis of the core-shell Mo2C combined with carbon material (Mo2C@C) nanosphere as an ECL super-enhancer and a label of secondary antibody (Ab2). Mo2C@C nanosphere with excellent conductivity and high chemical stability could increase the ECL intensity of the tris-(2,2′-bipyridine)ruthenium (Ru(bpy)32+). Mo2C@C/polyethylenimine (Mo2C@C/PEI) firmly anchored Ab2 by covalent bonding. Otherwise, amino-modified multiwall carbon nanotubes@nafion (MWCNTs-NH2@N) composite film, as substrate material, could connect with the Ru(bpy)32+ by ion exchange and immobilize primary antibodies (Ab1) by amide bond. In addition, the boron nitride quantum dots (BNQDs) were utilized as the co-reactant, which were synthesized by using low-cost material melamine as a nitrogen source. Under optimal experimental conditions, the proposed ECL immunosensor possessed a low detection limit of 0.03 pg/mL (S/N = 3) and a wide linear range from 0.1 pg/mL to 50 ng/mL. The ultrasensitive ECL immunosensor had excellent stability, outstanding specificity and great reproducibility. It was also used to detect cTnI in human serum with satisfactory results.

Modulating water oxidation kinetics utilizing h-BN quantum dots as an efficient hole extractor on fluorine doped hematite photoanode

The sluggish water oxidation kinetics in hematite photoanode is dominated by unfavorable recombination of photogenerated holes which restrict the efficiency of photoelectrochemical (PEC) water splitting. Herein, we demonstrate a superior photoelectrochemical performance using boron nitride quantum dots (BNQDs), which is incorporated over fluorine doped hematite (F–Fe2O3) photoanode. An impressive carrier density of 2.08 × 1020 cm−3 is achieved, which is two orders of magnitude higher than that of the bare α-Fe2O3 photo anode, resulting in a photocurrent density of 2.24 mA cm−2 at 1.23 V vs reversible hydrogen electrode (RHE) for F–Fe2O3-BNQDs, which is six-fold higher than bare hematite. It is found that BNQD acts as an efficient hole extractor, which enhances the carrier separation on hematite surface and decreases the hole trapping probability. Present work emphasizes on two important parameters, i.e. (i) Enhancement in carrier density via fluorine doping directly onto the substrate using soluble precursor, organic Selectflour (ii) Modification with BNQDs to provide a simple, novel and effective strategy for the design and development of more efficient PEC water splitting systems.

Target-Induced 3D DNA Network Structure as a Novel Signal Amplifier for Ultrasensitive Electrochemiluminescence Detection of MicroRNAs.

Here, a target-induced three-dimensional DNA network structure (T-3D Net) produced by catalytic hairpin assembly (CHA) was proposed as a novel signal amplifier to fabricate an ultrasensitive electrochemiluminescence (ECL) biosensor for microRNAs detection. Usually, conventional CHA can produce only one output DNA in each target cycle, while the proposed strategy could produce multiple output DNA by using DNA-functionalized magnetic beads (MBs) and gold nanoparticles (AuNPs) to form T-3D Net. Then, the T-3D Net with high loading capacity could be completely collapsed by dissolving AuNPs to efficiently convert trace microRNA-21 into a large amount of output DNA. Furthermore, the nanocomposite containing Ru(bpy)32+ as luminophore and boron nitride quantum dots (BNQDs) as coreactant provided a strong initial ECL response owing to the short electron transfer distance between luminophore and coreactant (signal-on). Next, the DNA duplex probes labeled withN-(4-aminobutyl)-N-ethylisoluminol (ABEI) and dopamine (DA) (S1-ABEI/S2-DA) were further immobilized on the nanocomposite to reduce the background signal due to the double quenching effect of DA for both ABEI and Ru(bpy)32+ (signal-off). In the presence of the output DNA with enzyme-assisted self-recycling, S2-DA was displaced and detached from the electrode surface to achieve ECL signal recovery. Simultaneously, S1-ABEI restored a stable hairpin structure, making ABEI close to the electrode surface for more effective resonance energy transfer (RET) between ABEI and Ru(bpy)32+, which greatly improved the final ECL response (signal-super on). Thus, the ECL biosensor demonstrated superior performance for ultrasensitive detection of microRNA-21 with low detection limit (0.33 aM) and was successfully applied to monitor the expression of microRNA-21 in human cancer cell lysates. This strategy provided an ultrasensitive way for the detection of biomolecules and revealed an effective avenue for diseasesdiagnosis.

Hexagonal Boron Nitride Quantum Dots as a Superior Hole Extractor for Efficient Charge Separation in WO3-Based Photoelectrochemical Water Oxidation

Photoelectrochemical (PEC) water splitting is one of the most desirable techniques to harvest clean chemical energy from abundant solar energy. However, the anodic half reaction, i.e., water oxidat...

BN quantum dots decorated ZnO nanoplates sensor for enhanced detection of BTEX gases

Benzene, toluene, ethyl benzene and xylene (BTEX) used in petroleum and industrial products, are highly toxic in nature and threaten human health. It is necessary to develop efficient ppm-level detection by a cost effective and available online technique. An economically viable gas sensor based on boron nitride quantum dots (BNQDs) decorated ZnO nanoplates has been fabricated for sensing BTEX vapors. Pure ZnO nanoplates, BNQDs and ZnO-BNQDs were synthesized by solvothermal method and characterized using XRD, HRTEM, SEM and EDAX. The sensing response of ZnO-BNQDs towards BTEX gases was markedly enhanced compared with that of pure ZnO, especially to xylene displaying more than 3.5 times sensitivity. ZnO-BNQDs sensor showed almost unbated response over a period of 50 days. Also, the response to changed humidity was studied. The results investigated by XPS and BET show that BNQDs decoration can generate active sites and more oxygen vacancies on ZnO substrate surface for catalytic oxidation of BTEX gas molecules.

A novel electrochemiluminescence sensor based on resonance energy transfer system between nitrogen doped graphene quantum dots and boron nitride quantum dots for sensitive detection of folic acid

Electrochemiluminescence resonance energy transfer (ECL-RET) between quantum dots (QDs) was firstly proposed. In this work, boron nitride quantum dots (BNQDs) as the donor and nitrogen doped graphene quantum dots (NGQDs) as the acceptor were confirmed by the absorption spectrum, the emission spectrum and fluorescence spectrum. Based on the reaction between FA and the SO4•− in the ECL system of NGQDs/BNQDs/K2S2O8, the ECL sensing platform for FA was successfully constructed. Surprisingly, a stable and strong ECL signal was obtained based on the RET, which was used for signal-off detection of FA in the presence of coreactant K2S2O8. Notably, about 10-fold enhancement was observed compared with the absence of BNQDs. The proposed sensor showed wide linear ranges of 1.0 × 10−11 M to 1.0 × 10−4 M and a low detection limit of 5.13 × 10−12 M. Simultaneously, the sensor was successfully applied to detection of FA in human serum samples with excellent recoveries. Therefore, the NGQDs/BNQDs system provided a new perspective for development of novel ECL-RET sensors.

Surface/edge functionalized boron nitride quantum dots: Spectroscopic fingerprint of bandgap modification by chemical functionalization

Promising properties of boron nitride nanomaterials such as their chemical, thermal, and mechanical stability have made them suitable materials in a various range of applications. However, their low electrical conductivity and wide bandgap, particularly in the case of boron nitride quantum dots (BNQDs), have given rise to severe limitations. Efforts on bandgap engineering through doping and surface functionalization have gained little success due to their high thermodynamic stability and inertness. Herein, we present a novel approach to functionalize BNQDs by hydroxyl, methyl, and amine functional groups aiming to adjust the electronic structure. The successful exfoliation is demonstrated by transmission electron microscopy, and surface functionalization is elaborated by FTIR and XPS. Modifications of the electronic and optical properties are shown by UV–Vis and PL measurements. The formation of two absorption edges in bandgaps of BNQDs due to the delocalizing of the Px and Pz orbitals as result of edge/surface passivating groups is demonstrated. Splitting of the main transition bandgap of bulk BN from 5.9 eV to two absorption edges for hydroxyl (2.3-3.6 eV), methyl (3.2-4.2 eV), and amine (3.1-4 eV) is shown. These findings offer a bandgap engineering approach for BNQDs, which can boost their applications in quantum emitters (nanophotonics) and photovoltaic devices.

Fabrication of hexagonal boron nitride quantum dots via a facile bottom-up technique

The smaller size of the Boron nitride quantum dots (BNQDs) leads to the quantization of energy due to the confinement of electrons and holes. As a result, it behaves like an artificial atom with higher quantum yield. Unlike, previously used complex and lengthy experimental procedures, a facile bottom-up technique based on nanoscale precursors and dual roles of ammonia gas has been developed to synthesize BNQDs in 25 min growth duration at 1200 °C. Shape and morphology of the synthesized BNQDs look like beads of different sizes. Fast Fourier transform (FFT) shows a hexagonal atomic structure of the synthesized BNQDs whereas XPS, Raman, and XRD confirms the Boron and Nitrogen elemental compositions and hexagonal phase of the synthesized sample. The as-synthesized BNQDs has excellent properties for a variety of potential applications in the fields of biomedical (for bioimaging and drug delivery), microelectromechanical systems (MEMS), catalysis, sensors, and solid-state neutron detectors.

Sulfur Regulated Boron Nitride Quantum Dots Electrochemiluminescence with Amplified Surface Plasmon Coupling Strategy for BRAF Gene Detection.

Because boron nitride quantum dots (BN QDs) have a wider gap (5.0-6.0 eV) than other QDs, the edge configurations, chemical functionalities, and heteroatom dopants can decrease and regulate the band gap of BN QDs, thereby ameliorating the QDs' properties. Now, the precise control and regulation of BN QDs are still at an early stage and is a challenging task. Therefore, we used thiourea and l-cysteine as different sulfur precursors to regulate the BN QDs' optoelectronic properties in this study. It is interesting that two kinds of S-regulated BN QDs present significantly different electrochemiluminescence (ECL) properties and electro-optical activity. Furthermore, a ratiometric and enzyme-free ECL sensing mode is constructed with the amplified surface plasmon coupled-ECL (SPC-ECL) strategy. The proposed DNA sensor can quantify the BRAF gene from 1 pmol/L to 1.5 nmol/L with a limit of detection (LOD) of 0.3 pmol/L. The change of BN QDs' ECL signal was easily observed with a smartphone camera. This work for the first time provides insight into the role of sulfur regulation in enhancing ECL efficiency and the electro-optical activity of BN QDs.