Unique Fluorescence Properties Research Articles

A Review on Graphene Quantum Dots for Electrochemical Detection of Emerging Pollutants.

Graphene quantum dots which are known as zero-dimensional materials are gaining increasing attention from researchers all over the world. This is predicated upon their relatively unique chemiluminescent, fluorescent, electrochemiluminescent, and electronic properties. The precise mechanism of electrochemiluminescence continues to be a subject of debate in the research world, and this is important in identifying synthetic pathways for graphene quantum dots. Heavy metals and other emerging pollutants are global health and environmental concerns. Several studies have reported the sensitivity and limit of detection of graphene quantum dots up to the nano-, pico-, and femto- levels when used as sensors. This review seeks to bridge information gaps on the reported electrochemiluminescence chemosensors for emerging pollutants using graphene quantum dots under the sub-headings, synthesis, characterization, electrochemiluminescence chemosensor detection, and comparison with other detection methods.

Water-Soluble Single-Benzene Chromophores: Excited State Dynamics and Fluorescence Detection.

Two water-soluble single-benzene-based chromophores, 2,5-di(azetidine-1-yl)-tereph- thalic acid (DAPA) and its disodium carboxylate (DAP-Na), were conveniently obtained. Both chromophores preserved moderate quantum yields in a wide range of polar and protonic solvents. Spectroscopic studies demonstrated that DAPA exhibited red luminescence as well as large Stokes shift (>200 nm) in aqueous solutions. Femtosecond transient absorption spectra illustrated quadrupolar DAPA usually involved the formation of an intramolecular charge transfer state. Its Frank–Condon state could be rapidly relaxed to a slight symmetry-breaking state upon light excitation following the solvent relaxation, then the slight charge separation may occur and the charge localization became partially asymmetrical in polar environments. Density functional theory (DFT) calculation results were supported well with the experimental measurements. Unique pH-dependent fluorescent properties endows the two chromophores with rapid, highly selective, and sensitive responses to the amino acids in aqueous media. In detail, DAPA served as a fluorescence turn-on probe with a detection limit (DL) of 0.50 μM for Arg and with that of 0.41 μM for Lys. In contrast, DAP-Na featured bright green luminescence and showed fluorescence turn-off responses to Asp and Glu with the DLs of 0.12 μM and 0.16 μM, respectively. Meanwhile, these two simple-structure probes exhibited strong anti-interference ability towards other natural amino acids and realized visual identification of specific analytes. The present work helps to understand the photophysic–structure relationship of these kinds of compounds and render their fluorescent detection applications.

Sterically Stabilized Carbon Dots as Solid-State Phosphors for White-Light-Emitting Diodes

Solid-state photoluminescence (PL) is highly important for practical optoelectronic applications. However, conventional carbon dots often suffer from fluorescence quenching induced by aggregation in a solid state, limiting their potential applications. In this report, sterically stabilized polymeric carbon dots (PCDs) (<2 nm) are prepared to achieve effective PL emission even in the solid-sate composite using a simple one-step hydrothermal treatment. These PCDs show unique fluorescence properties of tunable PL color change with the concentration covering the visible spectrum range from blue to orange in aqueous solution and the wavelength-dependent broad PL with maximum excitation at around 480 nm in solid-state epoxy composite. Practically applicable “single phosphor on a chip” in white-light-emitting diodes (WLEDs) application is successfully demonstrated by combining our PCDs/epoxy composite with a 460 nm blue-based LED chip, which is longer than most studies on the performance of CD-related white LEDs using UV or deep-blue LED chips as the excitation source. These results suggest that this type of PCDs may not only effectively suppress the aggregation-caused quenching effect in solid matrices but also show enhanced PL properties as a solid-state phosphor for practical white light emission applications.

Potential Risk of Nanotechnology Radioactive Materials for Diagnostics

The manufacture of personalized, real time, specific, and sensitive diagnostic tools continue to be of importance as the need for rapid diagnosis and monitoring of disease persists. In many health conditions like cancer and Covid-19 infection timely diagnosis of diseases can affect chances of survival. The accurate and timely diagnosis of diseases is enhanced by the unique optical, fluorescent, and magnetic properties of nanoscale elements. However, ultra-fine Nano particles unintentionally released into the air through human activities like combustion have been linked to respiratory and cardiovascular diseases. This makes it important for Nano engineered devices to be assessed for safety and toxicity concerns. Toxicity studies on the bulk material of the nanoscale elements used in diagnosis does not suffice as Nano materials due to their small size have unique interactions with biological membranes. Radioactive functionalized nanoparticles have been employed in several diagnostic imaging techniques such as Positron Emission Tomography, Magnetic Resonance Imaging, Computed Tomography, and Optical Imaging. These radioactive nanoparticles provide many benefits over conventional contrast agents including their theranostic ability. Spherical gold nanoparticles used in vivo for CT imaging have shown a 3-fold higher X ray attenuation than an iodine-based contrast agent. The tremendous benefits associated with use of radioactive functionalized nanoparticles calls for study of the risks associated with them as more and more radioactive nanotechnology-based products are employed in health care. Radioactive functionalized nanoparticles should be assessed for safety in both their radionucleotide component and nanomaterial component. Recent studies of nanoparticles have shown that they can lead to DNA damage by generation of Reactive Oxygen Species (ROS). Some of the discovered factors that play a key role in the generation of ROS include size, composition, surface charge, and shape. Understanding of the method of different radio nucleotide nanoparticle toxicity, the extent to which it causes toxic effects, and factors involved in its toxicity can help manufacturers reduce or eliminate their toxic profile while maximizing their benefits.

A Highly Fluorescent σ‐Bonded Platinum(II) Diketopyrrolopyrrole Complex

AbstractA σ‐bonded platinum(II) diketopyrrolopyrrole (Pt‐DPP) complex was synthesized from a reaction of p‐pinacolatoborylphenyl‐substituted DPP with dichloro(1,5‐cyclooctadiene)platinum(II), followed by a ligand exchange reaction with triphenylphosphine. The Pt‐DPP complex is highly fluorescent not only in solution but also in the solid state. From the comparison of the emission properties with those of N‐benzyl‐DPPs bearing phenyl and p‐bromophenyl substituents, the intense emission of the Pt‐DPP complex is ascribed to the DPP‐centered fluorescence. In the solid state, aggregation‐caused quenching is mitigated by the well‐segregated molecular packing due to the bulky triphenylphosphine ligands. The facile synthesis and unique fluorescence properties of the Pt‐DPP complex are beneficial for creating DPP‐based functional chromophores.

Carbazole-siloxane based polymers for the selective detection of 4-nitrophenol and Fe3+

Silicone-containing polymers have broad application prospects in the detection of many analytes due to their unique fluorescence properties. Environmental pollutants are very complex, which have prompted researchers to explore different detection methods. In this report, two kinds of polymers were synthesized via Heck-reaction between tetramethyltetravinylcyclotetrasiloxane (D4vi) and carbazole derivatives. The polymers showed excellent fluorescent properties and exhibited high sensitivity to 4-nitrophenol (4-NP) and Fe3+ in solution. Furthermore, the polymers still showed high sensitivity for Fe3+ in living cells. We estimate that the cyclic structure of D4vi and carbazole structure will serve as responsive sites for Fe3+ and 4-NP, respectively. The frontier molecular orbitals of polymers were calculated by Materials Studio and the effect of the cyclic structure of D4vi on their responsiveness had been discussed. The design idea of the polymer sensors can provide a new direction for the synthesis of multi-response polymer fluorescent probes.

The fabrication of water-stable perovskite-europium hybrid polychromatic fluorescence nanosensor for fast visual sensing of tetracycline

The development of real-time and efficient visual tetracycline sensors is helpful to evaluate the pollution status of tetracycline antibiotics in the environment. Considering the unique fluorescence properties of perovskite and rare earth elements, an innovative water-stable perovskite-europium hybrid fluorescence sensor MAPbBr3@PbBr(OH)@SiO2-Cit-Eu was fabricated. The introduction of tetracycline resulted in the increase of the fluorescence intensity of Eu complex, while the fluorescence intensity of perovskite quantum dots decreased slowly, accompanied by visual green-red switching. The sensor had good linear response in the range of 0–25 μM, and the detection limit was 11.15 nM. With the help of color analysis software in smart phones, the real-time intelligent detection of TC was realized. In addition, the wearable glove sensor obtained by fixing the nanosensor in the gel can realize the qualitative and semi-quantitative visual sensing of TC on the surface of many foods (eggs, apples, bananas, pears and oranges). It is believed that this work will open a new avenue for perovskite-europium hybrid nanosensors in intelligent sensing fields.

Fabrication of sodium dinitrophenol derived carbon dots and its effect on seed germination of cotton

Sodium dinitrophenol, which was a cheap and common plant growth regulator, was used to fabricate novel carbon dots by a simple and green hydrothermal treatment. The sodium dinitrophenol derived CDs (SCDs) obtained were found to possess good water solubility, excellent stability, and unique fluorescence properties. Furthermore, the effect of SCDs on the seed germination of cotton was explored in dark environment. Interestingly, the SCDs could promote seed germination obviously and the optimum concentration was tested to be 0.02 mg/mL. By the analysis of the contents of free water and bound water for the sprouts, it was assumed that the phenomenon might be attributed to the enhancement of the respiration and metabolism by the addition of SCDs, which helped to relieve seed dormancy and promote germination. This work supplied a novel nanomaterials for seed treatment, which could enhance the respiration during germination and showed considerable prospect in biological technology and farming production.

Multifaceted Approaches to Engineer Fluorescence in Nanomaterials via a Focused Laser Beam

Fluorescent nanomaterials have long been recognized as essential contributors to the advancement of material technologies. Over the years, the rapid expansion in this massive selection of materials has led to the emergence of systems with tunable and unique fluorescent properties, occupying pivotal roles across niche areas in imaging, photonics, micro-encryption, and steganographic applications. In recent years, research interest in the translation of laser-based operations towards the production and modulation of nanomaterial fluorescence has been reignited, owing to its ease of operation and low cost. In this paper, we summarize the assortment of laser operations for the fabrication, modification, and spatial positioning of various fluorescent nanomaterials, ranging from metallic nanoparticles, carbon dots, 2D ultrathin films to wide-bandgap nanomaterials, and upconversion nanocrystals. In addition, we evaluate the importance of laser-modified fluorescence for various applications and offer our perspective on the role of laser-based techniques in the forthcoming advancement of nanomaterials.

ONE-POT SYNTHESIS OF CARBON QUANTUM DOTS AND THEIR APPLICATION AS A FLUORESCENT INKS

A facile, low cost, and one-pot hydrothermal reaction method is utilized to synthesized highly stable and durable carbon quantum dots (CQDs) by using laurus nobilis leaves as a carbon source. Laurus nobilis leaves were subjected to hydrothermal reaction at 175 °C for 10 h. The color of obtained CQDs under UV-light is bright blue fluorescence. The excitation dependent fluorescent emission of the prepared CQDs was observed and the obtained CQDs gives maximum emission at 425 nm when excited at 344 nm. The absorption peak of the CQDs is located at 279 nm. Furthermore, the synthesized CQDs can be consumed as a fluorescent ink for security, encryption and information storage applications. Combining with good stability and water solubility, unique fluorescence properties and its low-cost, CQDs can also be used as a next generation fluorescent ink alternative to traditional fluorescent ink for anti-counterfeiting.

Influence of precursor chemistry in the property of carbon nanodots and its application for the degradation of methyl orange

Carbon nanodots (CNDs) are interesting materials from renewable sources that exhibit unique fluorescence property. This study reports that sulfated carrageenan (ᴋ-, ɩ-, λ-) as carbon precursors for CNDs impart unique properties not observed in a non-sulfated source. Hydrothermal process afforded CNDs having quasi-spherical shapes (TEM), nano sizes (TEM: 3.8 nm; DLS 1.0–2.3 nm), luminous green property under UV light, and presence of sulfur in CNDs (EDS, FTIR). The CNDs were embedded in a carrageenan film matrix to prevent its aggregation and to improve its stability affording brown-colored free-standing films that have better stability (zeta potential) compared to bare CNDs in solution. The CNDs from carrageenan exhibited unique acidic property in water, which is not observed in CNDs from galactose indicating that the sulfate-laden carrageenan precursor imparts unique property to the CNDs. Degradation activity on methyl orange (MO) dye was only observed for CNDs derived from carrageenan and not from galactose confirming the critical role of precursor chemistry in imparting unique acidic properties to the resulting CNDs. The study demonstrated the difference in the carrageenan-based CNDs compared to those prepared from simple sugar and showed its application for the degradation of dyes without the need for direct exposure to sunlight.

Colorimetric and Fluorescent Dual-Modality Sensing Platform Based on Fluorescent Nanozyme.

Compared with natural enzymes, nanozymes based on carbonaceous nanomaterials are advantages due to high stability, good biocompatibility, and the possibility of multifunctionalities through materials engineering at an atomic level. Herein, we present a sensing platform using a nitrogen-doped graphene quantum dot (NGQD) as a highly efficient fluorescent peroxidase mimic, which enables a colorimetric/fluorescent dual-modality platform for detection of hydrogen peroxide (H2O2) and biomolecules (ascorbic acid-AA, acid phosphatase-ACP) with high sensitivity. NGQD is synthesized using a simple hydrothermal process, which has advantages of high production yield and potential for large-scale preparation. NGQD with uniform size (3.0 ± 0.6 nm) and a single-layer graphene structure exhibits bright and stable fluorescence. N-doping and ultrasmall size endow NGQD with high peroxidase-mimicking activity with an obviously reduced Michaelis–Menten constant (K m) in comparison with natural horseradish peroxidase. Taking advantages of both high nanozyme activity and unique fluorescence property of NGQD, a colorimetric and fluorescent dual-modality platform capable of detecting H2O2 and biomolecules (AA, ACP) with high sensitivity is developed as the proof-of-concept demonstration. Furthermore, the mechanisms underlying the nanozyme activity and biosensing are investigated.

Hg2+ Detection with Rational Design of DNA-Templated Fluorescent Silver Nanoclusters

Atomically precise silver nanoclusters (AgNCs) are small nanostructures consisting of only a few atoms of silver. The combination of AgNCs with cytosine-rich single-stranded oligonucleotides results in DNA-templated silver nanoclusters (DNA-AgNCs). DNA-AgNCs are highly luminescent and can be engineered with reproducible and unique fluorescent properties. Furthermore, using nucleic acids as templates for the synthesis of AgNCs provides additional practical benefits by expanding optical activity beyond the visible spectral range and creating the possibility for color tunability. In this study, we explore DNA oligonucleotides designed to fold into hairpin-loop (HL) structures which modulate optical properties of AgNCs based on the size of the loop containing different number of cytosines (HL-CN). Depending on the size of the loop, AgNCs can be manufactured to have either single or multiple emissive states. Such hairpin-loop structures provide an additional stability for AgNCs and further control over the base composition of the loop, allowing for the rational design of AgNCs’ optical properties. We demonstrate the potential of AgNCs in detecting Hg2+ by utilizing the HL-C13 design and its variants HL-T2C11, HL-T4C9, and HL-T6C7. The replacement of cytosines with thymines in the loop was intended to serve as an additional sink for mercury ions extending the detectable range of Hg2+. While AgNC@HL-T0C13 exhibits an interpretable quenching curve, AgNC@HL-T6C7 provides the largest detectable range of Hg2+. The results presented herein suggest that it is possible to use a rational design of DNA-AgNCs based on the composition of loop sequence in HL structures for creating biosensors to detect heavy metals, particularly Hg2+.

DNA-Templated Fluorescent Silver Nanoclusters Inhibit Bacterial Growth While Being Non-Toxic to Mammalian Cells.

Silver has a long history of antibacterial effectiveness. The combination of atomically precise metal nanoclusters with the field of nucleic acid nanotechnology has given rise to DNA-templated silver nanoclusters (DNA-AgNCs) which can be engineered with reproducible and unique fluorescent properties and antibacterial activity. Furthermore, cytosine-rich single-stranded DNA oligonucleotides designed to fold into hairpin structures improve the stability of AgNCs and additionally modulate their antibacterial properties and the quality of observed fluorescent signals. In this work, we characterize the sequence-specific fluorescence and composition of four representative DNA-AgNCs, compare their corresponding antibacterial effectiveness at different pH, and assess cytotoxicity to several mammalian cell lines.

Fluorescent carbon dots derived from magnolia withered leaves for promoting growth and fluorescent labeling of bean sprouts

As a nano-fertilizer, carbon dots have good application prospects in crop planting. And its unique fluorescent properties and low toxicity make it become a good biomarker material. In this paper, CDs is prepared by a facile synthesis method. Mung bean as a model plant, and gradient concentration of N-CDs solution for breeding bean sprouts. The results show that 0.15 mg⋅L−1 carbon point solution can promote plant growth. At the same time, we also reveal that carbon dots segmented migration in bean sprouts, discuss the transfer path of carbon dots in bean sprouts, and find that the absorption of carbon dots solution by bean sprouts is linear, and its R2=0.98. We find that carbon dots can maintain good fluorescence properties in bean sprouts. A metabolic residue experiment is carried out and it is found that the carbon dots still exist in the bean sprouts after 24 h.

Self-Assembled Nanorods of Phenylboronic Acid Functionalized Pyrene for In Situ Two-Photon Imaging of Cell Surface Sialic Acids and Photodynamic Therapy.

Sialic acid (SA) plays important roles in various biological and pathological processes. Methods for monitoring and detection of SA are of great significance in terms of fundamental research, cancer diagnostics, and therapeutics, which are still limited until now. Here, a phenylboronic acid (PBA)-functionalized pyrene derivative, 4-(4-(pyren-1-yl)butyramido)phenylboronic acid (Py-PBA), was synthesized and used as a building block for self-assembling into hydrophilic nanorods. The Py-PBA nanorods (Py-PBA NRs) featured highly specific and efficient imaging of SA on living cells with the advantages of excellent fluorescence stability, good biocompatibility, and unique two-photon fluorescence properties. Meanwhile, the assembled Py-PBA NRs could efficiently generate 1O2 under two-photon irradiation, making it an excellent candidate for photodynamic therapy. This nanoplatform realized in situ recognition and two-photon imaging of SA on the cell surface as well as effective cancer cell therapy, providing a potential method for simple and selective analysis of SA in living cells and a new prospect for image-guided therapy.

Intrinsic hydroquinone-functionalized aggregation-induced emission core shows redox and pH sensitivity

Aggregation-induced emission (AIE) fluorophores exhibit strong fluorescence in an aggregated state but emit no or weak fluorescence in dilute solutions. This emerging class of AIE optical materials comprise a variety of functionalities. Here an AIE luminescence core, 1-hydroquinol-1,2,2-triphenylethene (HQTPE), has been designed and synthesized. This AIE core is simple but is fundamentally important to chemistry because of its intrinsic redox and pH activities. The incorporation of hydroquinone (HQ) moiety into a common AIE core tetraphenylethene (TPE) yields HQTPE with unique fluorescent properties like nonlinear self-quenching over most other AIE-active fluorophores (AIEgens) so far reported. There are differences of photochemical properties between HQTPE, 1-benzoquinol-1,2,2-triphenylethene (QTPE, the oxidized counterpart) and its anions. Interestingly, as the solution concentration is increased, AIEgen HQTPE shows stronger fluorescence but QTPE exhibits rapid quenching of fluorescence in a nonlinear fashion, which are in agreement with theoretical studies. The fluorescence of HQTPE is also highly dependent on the pH value of media. We have further explored HQTPE as an ultrasensitive redox probe and efficient deoxidizer, which could lead to potential applications in health care, food security, environmental monitoring, optic and electronic devices.

Green-emissive carbon quantum dots with high fluorescence quantum yield: Preparation and cell imaging

High fluorescence quantum yield (QY), excellent fluorescence stability, and low toxicity are essential for a good cellular imaging fluorescent probe. Green-emissive carbon quantum dots (CQDs) with many advantages, such as unique fluorescence properties, anti-photobleaching, low toxicity, fine biocompatibility and high penetration depth in tissues, have been considered as a potential candidate in cell imaging fluorescent probes. Herein, N, S-codoped green-emissive CQDs (QY = 64.03%) were synthesized by the one-step hydrothermal method, with m-phenylenediamine as the carbon and nitrogen source, and L-cysteine as the nitrogen and sulfur dopant, under the optimum condition of 200 °C reaction for 2 h. Their luminescence was found to originate from the surface state. In light of the satisfactory photobleaching resistance and the low cytotoxicity, CQDs were used as a cell imaging probe for HeLa cell imaging. The results clearly indicate that cells can be labeled with CQDs, which can not only enter the cytoplasm, but also enter the nucleus through the nuclear pore, showing their broad application prospect in the field of cell imaging.

A new family of Ln-BTC-AC-FM framework intelligent materials: Precise synthesis, structure and characterization for fluorescence detecting of UO22+ and adsorbing dyes

The unique fluorescence properties of rare earth ions and subtle interactions with organic ligands make the target lanthanide metal-organic frameworks show potential development prospects in many fields. Based on this situation, a series of new lanthanide metal-organic frameworks Ln-BTC-AC-FM: (CH3)2NH2[Ln2(BTC)(AC)3(FM)], (Ln=Pr (1), Ce (2), Nd (3), Eu (4), Sm (5), Gd (6), Tb (7), Ho (8), Er (9) and Yb (10), H3BTC=1,3,5-benzenetricarboxylic acid) were synthesized through the reaction of triangular polycarboxylic acid ligand (H3BTC) and rare earth nitrate Ln(NO3)3·6H2O with mixed formic acid (FM) and glacial acetic acid (AC) system. Due to this new type of Ln-BTC-AC-FM MOFs have unique and excellent fluorescence properties, we selected (CH3)2NH2[Eu2(BTC)(AC)3(FM)] (4) to explore its detection performance for UO22+ in aqueous solution. The study found that 4 is a high-efficiency fluorescent probe, which has a good quenching effect on uranium solution, and the quenching rate can reach 98.01%. At the same time, 4 has a good fluorescent response to UO22+, with a higher KSV value of 8.56 × 103 M−1 and a lower detection limit of 4.12 μM. In addition, we also studied the adsorption properties of this series of Ln-BTC-AC-FM MOFs for dyes because of their novel three-dimensional microporous structures. The results showed that 4 has a good adsorption effect on Coomassie Brilliant Blue (CBB) and Eosin. Moreover, it was found that the dye adsorption process was proved to be a suitable pseudo-second-order kinetic model.

Superior spectral fluorescence signature of novel illuminated melamine resin for industrial explosive detection

It is widely-accepted that explosive materials are electron deficient. The exposure of fluorescent material to explosive vapors could hold back electron movement with fluorescence quenching. We report on the porous melamine-based resin (MF) as a novel sensing element regarding explosive vapors detection. MF resin's average pore diameter is 94.7 (Å) and, a surface area of 162 m2/g could effectively-adsorb explosive vapors via its porous structure. MF resin confirmed unique fluorescent properties over visible band 400–450 nm, and infrared band 700–800 nm when illuminated with 385 nm UV laser light. The fluorescence light signal was quenched as MF resin, and was subjected to ammonium nitrate (the most common industrial explosive material). These novel optical properties could be ascribed to wired series of π bonds, and lone pairs of an electron, along the macromolecule chain. The aligned series of electron donor sites could offer a high affinity to capture explosive molecules and could strengthen the chemosensory response. Fluorescence/quenching signal was precisely-recorded using hyperspectral imaging beside a 2D moving average filter.