Blue Fluorescence Emission Research Articles

Stable All‐Fluorescence White Organic Light‐Emitting Diodes with High Efficiency and High CRI

AbstractWhite organic light‐emitting diodes (WOLEDs) have been regarded as the candidates for next‐generation flat‐panel displays and solid‐state lighting due to their low cost. However, it is still challenging to achieve two‐component WOLEDs with high efficiency, high color index (CRI), and long lifetime. Here, high‐performance all‐fluorescence WOLEDs based on a blue fluorescent emitter and an orange thermally activated delayed fluorescent (TADF) emitter are demonstrated. The optimized all‐fluorescence WOLED with two EMLs presents the maximum external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 23.4%, 40.2 cd A−1, and 33.2 lm W−1, corresponding to a maximum CRI value of 83.1 and Commission Internationale de L'Eclairage (CIE) coordinate of (0.30, 0.31). To further improve the device stability, the all‐fluorescence WOLEDs with three EMLs and tandem structure are constructed, respectively. Under the premise of ensuring efficiency, in going from the two‐EMLs to the three‐EMLs and the tandem structure, the LT50 (time to 50% of the initial luminance) of all‐fluorescence WOLEDs increase from 601 to 714 h and 1622 h at an initial luminance of 1000 cd m−2. These strategies and results present new insight into the design of all‐fluorescence WOLEDs with high efficiency, high CRI, and extended lifetime.

A blue fluorescent waterborne polyurethane-based Zn(ii) complex with antibacterial activity

Abstract Polymer-based transition metal complexes have attracted much attention in many fields of application. In this article, a fluorescent polymer-based transition metal complex was prepared by bonding the transition metal complex with the polymer. First, Schiff base salicylaldehyde ethanolamine (HL) as a ligand was prepared by the reaction of salicylaldehyde with ethanolamine. Then, salicylaldehyde glycolamine Zn(ii) transition metal complexes (ZnL2) were synthesized with HL and Zn2+ as the central ion. Finally, a blue fluorescent waterborne-based polyurethane Zn(ii) complex (ZnL2-WPU) with an antibacterial function was prepared with ZnL2 as a chain extender by modified acetone method. The characteristics of fluorescence, heat stability, and bacteriostasis were characterized. Compared with ZnL2, the UV–vis absorption peak of ZnL2-WPU shows a blue shift of about 20 nm. ZnL2-WPU has a strong blue fluorescence emission at 450 nm, and the intensity increases significantly with ZnL2 content. Surprisingly, the fluorescence lifetime of ZnL2-WPU is obviously increased, reaching more than one time that of ZnL2. Interestingly, the antibacterial efficiency of ZnL2-WPU against E. coli reached an incredible 99%. More importantly, ZnL2-WPU uses water as the dispersing medium, which is more environmentally friendly.

Spectroscopic properties of a fluorescent pyrene-quinoline-based bisoxime-type sensor and its application to the detection of Cu2+ ion in real water samples

Fluorescent sensors are efficient and convenient tools for metal ions analysis. Herein, a new fluorescent pyrene-quinoline-based bisoxime-type sensor PQS, possessing the monomer to excimer emission switching feature, was synthesized and the sensing ability toward Cu2+ was throughly studied. Interestingly, the blue emission of monomer PQS in dilute solution converted to the green fluorescence of excimer in aggregated state. Meanwhile, the blue fluorescence emission of sensor PQS quenched in the existence of Cu2+ with no apparent response toward other competitive cations. The plausible complexation ratio 1:1 of sensor PQS to Cu2+ was substantiated by Job's plot, mass spectrometric analysis combined with the density functional theory calculation. Furthermore, PQS coated paper strips were prepared and used for the rapid and convenient monitoring Cu2+ in a visible manner.

Heteroatoms-doped carbon dots as dual probes for heavy metal detection

The utilization of l-cysteine in hydrothermal synthesis allows for the manufacture of carbon dots (CDs) that are doped with heteroatoms including oxygen, nitrogen, and sulfur (N, S, O-doped CDs). CDs have a particle size ranging from 1 to 3 nm, with an average particle size of 2.5 nm. N, S, and O-doped CDs display a blue fluorescence emission at a wavelength of 425 nm. It shows a reliance on the specific excitation wavelength between 320 and 500 nm. It has a selective quenching effect specifically with copper (Cu2+) ions when exposed to interactions with heavy metal ions, as compared to other metal ions. The assay has a limit of detection (LOD) of 2 μM and exhibits a linear correlation within the concentration range of 10–33.3 μM. The fluorescence mechanism was elucidated by employing various analytical techniques, such as transmission electron microscopy (TEM), high-resolution TEM , UV–Vis spectroscopy, zeta potential analysis, and conductometry. An analysis of the data reveals that Cu2+ ions exhibit a strong attraction to the external surface of N, S, and O-doped CDs, leading to the formation of aggregates. N, S, and O-doped CDs can be also used as probes for electrochemical investigations utilizing cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) to produce Nyquist and Bode plots. The electrochemical results offer substantiation for the interaction between Cu2+ ions and N, S, and O-doped CDs. Zero-dimensional carbon nanomaterials, i.e. CDs, can improve the detection of heavy metals using optical and electrochemical methods.

A Simple Method for Synthesizing Nitrogen-Doped Carbon Quantum Dots for Fluorescent "Turn off" Mercury (II) Ion Sensing.

Here, straightforward and environmentally friendly fluorescent nitrogen doped carbon quantum dots (N-CQDs) with a high blue fluorescence emission at 455nm are used for ultrasensitive Hg2+ ion detection. Folic acid and urea are used as carbon sources in the carbonization process. Two broad absorption bands at around 280 and 370nm from UV-Vis spectrum and characteristic absorption peaks from infrared spectrum confirms the successful synthesis of the N-CQDs. Energy dispersive X-Ray analysis confirmed the elemental composition of the N-CQDs. Transmission electron microscopy showed the homogeneous globular morphology of the N-CQDs with an average particle size of 65nm. Zeta potential measurement established the stability and surface charge of N-CQDs. Dynamic light scattering measurement showed the average size of N-CQDs. With the addition of Hg2+ ion to N-CQDs, the blue fluorescence emission is quenched. Moreover, the N-CQDs can be applied to real water sample such as pond water, river water, and tap water. The detection limit is approximately calculated to be 12 nM and linear range is 0-30 parts per billion.

Highly Efficient Blue Fluorescent Organic Light-Emitting Devices Based on λ5-Phosphinine Derivatives.

Although λ5-phosphinine derivatives are known as a promising class of blue fluorescent emitters, those photoluminescent quantum yield (PLQY) values have been reached up to 92 %, however, only a few examples have been explored as an emitter for blue organic light-emitting device (OLED), and the external quantum efficiency (EQE) has been below 2.4 % so far. In this study, we newly developed two types of blue λ5-phosphinine derivatives namely CN-COCF3 and CO2Me-CHO, and investigated the photophysical properties in the solid states. The photophysical analyses in solid state films suggested that the strong electron-accepting nature of these λ5-phosphinine derivatives caused the inferior PLQY values, and the exciplex formation with the host and neighboring materials should be avoided to improve the device efficiency. By choosing suitable host and neighboring materials with deep ionization potentials, we successfully realized efficient blue fluorescent OLEDs with EQE of over 4 % and CIE (0.14, 0.18). This is among the best in λ5-phosphinine-based blue OLEDs so far.

Development of a long-term fluorescent invisible marker using blue-emitting carbon dots

The development of novel anti-counterfeiting materials and technologies is vital in order to combat counterfeit activities, as existing technologies such as optical watermarking, micro-printing, laser holography, barcodes, RFID, and QR codes are widely known to counterfeiters and easily replicated. In particular, several challenges and issues, including high costs, low yields during synthesis, and the photo-bleaching effect associated with the use of luminescent materials in anti-counterfeiting applications are still need to be addressed. Carbon Dots (CDs) is a new emergent in carbon family with excellent luminescence properties. In this report, we describe a fast, cost-effective, and simple one-step heating method for synthesizing CDs. An invisible marker was produced by incorporating blue emitting CDs into the reservoir of a commercial sketch pen. The writings using the marker were not visible under normal light but emitted blue fluorescence under UV light (365 nm). The marker retained its fluorescence for up to six months without any decrease visible to the naked eye.

Lanthanide MOFs based portable fluorescence sensing platform: Quantitative and visual detection of ciprofloxacin and Al3+

In the current context of water environmental monitoring and pollution control, there's a crucial need for rapid and simple methods to detect multi-pollutant. We herein report an easy one-step hydrothermal synthesis method to produce Eu-based metal-organic frameworks (Eu MOFs), which was used as a fluorescent probe to detect the aquatic environmental pollutants of ciprofloxacin (CIP) and aluminum ions (Al3+). This fluorescent sensor enabled the cascade detection of CIP and Al3+ through fluorescence enhancement and ratio fluorescence response, respectively. The introduction of CIP significantly turned on the characteristic fluorescence of Eu MOFs at 595 nm and 616 nm through the “antenna effect”. Based on this, the sensor enables quantitative detection of CIP within a linear range of 0–120 μM with a LOD as low as 50.421 nM. In the presence of Al3+, the fluorescence emission of Eu MOFs-CIP was sharply turned off due to strong Al3+ coordination with CIP, while the blue fluorescence emission of CIP was remarkably enhanced. And thus allowing ratio fluorescence quantitative detection of Al3+ (LOD = 2.681 μM). The introduction of CIP and Al3+ in cascade resulted in distinct fluorescence color changes from colorless to red and eventually to blue, exhibiting pronounced fluorescence characteristics. This observable phenomenon enables the visual detection of CIP and Al3+ in both aqueous phase and paper test strips. By combining the analysis of fluorescence chromaticity with the use of a smartphone, the fluorescence color of test papers allows for simple quantitative determination, which provides a convenient and accessible approach for quantifying CIP and Al3+ in water environments.

Fluorimetric determination of tetracycline antibiotics in animal derived foods using boron and nitrogen co-doped ceria-based nanoparticles.

Aninnovative synthesis of boron and nitrogen co-doped ceria-based nanoparticles (B/N-CeFNPs) with bright blue fluorescence emission is reportedusing the hydrothermal method. Based on the aggregation-induced emission enhancement (AIEE) effect between B/N-CeFNPs and chlortetracycline (CTC), a rapid detection method for CTC through fluorescence enhancement was developed. In addition, through the electron transfer process (ET), fluorescence resonance energy transfer (FRET) effect and static quenching between B/N-CeFNPs and oxytetracycline (OTC), a ratio fluorescence strategy for detecting OTC was generated. The fluorescence of B/N-CeFNPs at 410nm can be effectively quenched by OTC, and new fluorescence emission appears at a wavelength of 500nm. B/N-CeFNPs showed good linear responses with CTC and OTC in the range 0.1-1 µM and 1-40 µM, respectively. This system was used to simultaneously detect the CTC and OTC in milk and honey, realizing multi-residues detection of TCs in actual samples by using the same ceria-based fluorescence nanomaterial.

“Steric Armor” Strategy of Blue Fluorescent Emitters against Photooxidation‐Induced Degradation

Comprehensive SummaryStability against oxygen is an important factor affecting the performance of organic semiconductor devices. Improving photooxidation stability can prolong the service life of the device and maintain the mechanical and photoelectric properties of the device. Generally, various encapsulation methods from molecular structure to macroscopic device level are used to improve photooxidation stability. Here, we adopted a crystallization strategy to allow 14H‐spiro[dibenzo[c,h]acridine‐7,9′‐uorene] (SFDBA) to pack tightly to resist fluorescence decay caused by oxidation. In this case, the inert group of SFDBA acts as a “steric armor”, protecting the photosensitive group from being attacked by oxygen. Therefore, compared with the fluorescence quenching of SFDBA powder under 2 h of sunlight, SFDBA crystal can maintain its fluorescence emission for more than 8 h under the same conditions. Furthermore, the photoluminescence quantum yields (PLQYs) of the crystalline film is 327% higher than that of the amorphous film. It shows that the crystallization strategy is an effective method to resist oxidation.

Water/Light Multiregulated Supramolecular Polypseudorotaxane Gel with Switchable Room-Temperature Phosphorescence.

Water/light regulated room-temperature phosphorescence (RTP) of polypseudorotaxane supramolecular gel is constructed by threading the poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) chain with the bromoaromatic aldehyde into mono-(6-ethylenediamine-6-deoxygenated)-β-cyclodextrin (ECD) cavities and further assembling with negatively charged Laponite XLG (CNS) and diarylethene derivative (DAE) through electrostatic interaction. This hydrogel exhibits significant blue fluorescence emission; instead, after lyophilization to xerogel, the system exhibits both blue fluorescence and yellow RTP based on the rigid network structure of the xerogel, which restricts the vibration of the phosphor and suppresses the nonradiative relaxation process. Interestingly, the addition of excess ECDs to the gel system can enhance the RTP emission. Furthermore, the reversible luminescence behavior can be adjusted by the photoresponsive isomerism of DAE and humidity. This polypseudorotaxane supramolecular gel system provides a novel strategy for constructing tunable RTP materials.

Solvent-free synthesis of recyclable hydrophobic carbon dots for highly selective detecting curcumin in food samples

A highly selective fluorometric method was developed for the specific determination of curcumin (Cur) based on hydrophobic carbon dots (HB-CDs) derived from flaxseed oil by a solvent-free reaction. The as-prepared HB-CDs possessed blue fluorescence emission (at 425 nm) with a fluorescence quantum yield (QY) of 21.1 %. It was that the fluorescence of HB-CDs could be quantitatively quenched by Cur, and the fluorescence quenching mechanism was proved to be a combination of dynamic and static quenching. The detection limit of the method for Cur was 20 nM with a linear response range of 0.2–200 µM. Additionally, HB-CDs can be quickly recovered from the tested solutions through solvent change precipitation. The developed HB-CDs based fluorescent method has been successfully applied for real food samples analysis with satisfactory results.

Shedding light on the use of graphene oxide-thiosemicarbazone hybrids towards the rapid immobilisation of methylene blue and functional coumarins.

Coumarins, methylene blue derivatives, as well as related functional organic dyes have become prevalent tools in life sciences and biomedicine. Their intense blue fluorescence emission makes them ideal agents for a range of applications, yet an unwanted facet of the interesting biological properties of such probes presents a simultaneous environmental threat due to inherent toxicity and persistence in aqueous media. As such, significant research efforts now ought to focus on their removal from the environment, and the sustainable trapping onto widely available, water dispersible and processable adsorbent structures such as graphene oxides could be advantageous. Additionally, flat and aromatic bis(thiosemicarbazones) (BTSCs) have shown biocompatibility and chemotherapeutic potential, as well as intrinsic fluorescence, hence traceability in the environment and in living systems. A new palette of graphene oxide-based hierarchical supramolecular materials incorporating BTSCs were prepared, characterised, and reported hereby. We report on the supramolecular entrapping of several flat, aromatic fluorogenic molecules onto graphene oxide on basis of non-covalent interactions, by virtue of their structural features with potential to form aromatic stacks and H-bonds. The evaluations of the binding interactions in solution by between organic dyes (methylene blue and functional coumarins) and new graphene oxide-anchored Zn(ii) derivatised bis(thiosemicarbazones) nanohybrids were carried out by UV-Vis and fluorescence spectroscopies.

Dual-monomer solvatochromic probe system (DSPS) for effectively differentiating lipid raft cholesterol and active membrane cholesterol in the inner-leaflet plasma membrane.

Monitoring active membrane cholesterol and lipid raft cholesterol in the inner leaflet of the plasma membrane is significant for understanding the membrane function and cellular physiopathological processes. Limited by existing methods, it is difficult to differentiate active membrane cholesterol and lipid raft cholesterol. A novel dual-monomer solvatochromic probe system (DSPS) that targets two types of cholesterol was developed. Acrylodan-BG/SNAP-D4 composed of SNAP-D4 cholesterol-recognizing monomers and solvatochromic acrylodan-BG-sensing monomers exhibits excellent cholesterol detecting properties in terms of selectivity, accuracy, convenience and economic benefits. Cell imaging revealed that lipid raft cholesterol emitted blue fluorescence, whereas active membrane cholesterol (which partially bobbed in aqueous cytosol) displayed green fluorescence; both the fluorescence emissions increased or decreased in a cholesterol-dependent manner. This system provides a new technology for the determination of two types of cholesterol, which is beneficial for the further study of membrane function, intracellular cholesterol trafficking, and cell signaling.

Efficient deep blue fluorescent emitters based on bipolar phenanthroimidazole-carbazole hybrid for non-doped electroluminescent device with small CIEy

In this work, four bipolar deep-blue emitting materials of 2-(4-(9H-carbazol-9-yl)phenyl)-1-(4-methylphenyl)-1H-phenanthro[9,10-d]imidazole (MePPIM-Cz), 2-(4-(9H-carbazol-9-yl)phenyl)-1-(4-chlorophenyl)-1H-phenanthro [9,10-d]imidazole (ClPPIM-Cz), 2-(4-(9H-carbazol-9-yl)phenyl)-1-(4-tert-butyl phenyl)-1H-phenanthro[9,10-d]imidazole (BuPPIM-Cz) and 2-(4-(9H-carbazol-9-yl) phenyl)-1-(4-(trifluoromethyl)phenyl)-1H-phenanthro[9,10-d]imidazole (TFMPPIM-Cz) based on phenanthroimidazole and carbazole group have been designed and synthesized by introducing different electron active substitutions into the N1 position of phenanthroimidazole. The thermal, photophysical, electrochemical and computational properties of four compounds were investigated. All compounds exhibited the deep blue emission and good thermal stability with glass transition temperature (Tg) in range of 126°C–137 °C. Single carrier devices were also fabricated and demonstrated that the four compounds have bipolar transporting properties. The non-doped organic light emitting diodes (OLEDs) based on MePPIM-Cz, ClPPIM-Cz, BuPPIM-Cz and TFMPPIM-Cz showed deep blue emission with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.07), (0.16, 0.06), (0.16, 0.05) and (0.16, 0.10) and the maximum external quantum efficiencies (EQEmax) of 2.67%, 2.24%, 1.81% and 1.09%, respectively. The CIE coordinates of MePPIM-Cz, ClPPIM-Cz and BuPPIM-Cz is extremely close to the National Television System Committee (NTSC) standard blue CIE of (0.14, 0.08), which is very significant for high color purity full-color display.

Chameleon-like Photoluminescent Janus Nanoparticles as Full-Color Multicomponent Organic Nanoinks: Combination of Förster Resonance Energy Transfer and Photochromism for Encryption and Anticounterfeiting with Multilevel Authentication.

Increasing the security by the multilevel authentication mechanism was the most significant challenge in recent years for the development of anticounterfeiting inks based on photoluminescent nanomaterials. For this purpose, the greatest strategy is the use of multicomponent organic materials and a combination of Förster resonance energy transfer (FRET) with the intelligent behavior of photochromic compounds like spiropyran. Here, the hydroxyl-functionalized polymer nanoparticles were synthesized by emulsion copolymerization of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) in different compositions (0-30 wt % of HEMA). Results illustrated that the size of the nanoparticles changed from 64 to 204 nm, and a morphology evolution from spherical to Janus shape was observed by increasing the concentration of HEMA. Photoluminescent inks with red, green, and blue (RGB) fluorescence emissions were prepared by modification of nanoparticles containing 15 wt % of HEMA with spiropyran, fluorescein, and coumarin, respectively. To develop dual-color and multicolor photoluminescent inks that display static and dynamic emission, RGB latex samples were mixed together in different ratios and printed on cellulosic paper. Results display that the fluorescence emission of developed inks can be photoswitched between different statuses, including white to blue, green to blue, green to red/orange, purple to pink, and white to pink, utilizing the FRET phenomenon, photochromism, and a combination of both phenomena. Samples containing spiropyran displayed dynamic color changes in the emission to red, orange, and pink depending on the composition. Hence, developed dual-color and multicolor photoluminescent inks were used for printing of security tags and also painting of some hand-drawn artworks, which obtained results indicating high printability, maximum fluorescence intensity, high resolution, and fast responsivity upon UV-light irradiations of 254 nm (for static mode) and 365 nm (for dynamic mode). In addition, the multilevel authentication mechanism by a static emission under UV-light irradiation of 254 nm, a dynamic emission under UV-light irradiation of 365 nm, and photochromic color change was observed, resulting in increasing the security of developed inks. Actually, developed multicolor photoluminescent inks are the most efficient candidates for developing a new category of chameleon-like high-security anticounterfeiting inks that have tunable optical properties and complex multilevel authentication mechanisms.

Green synthesis of elephant manure-derived carbon dots and multifunctional applications: Metal sensing, antioxidant, and rice plant promotion

Carbon dots, the carbon nanomaterials, have been greatly developed for several applications including fluorescent sensors for metal ion detection, antioxidant activity, and plant growth promotion due to their excellent photophysical properties, non-toxicity, and high quantum yield. Therefore, this research focused on the synthesis of multifunctional carbon dots from elephant manure via green hydrothermal synthesis owing to its chemical composition of cellulose, hemicellulose, and lignin. The as-synthesized carbon dots exhibited blue fluorescence emission under UV light and the excitation wavelength-dependent fluorescence enhancement. Carbon dots could be further used as a “turn-off” fluorescence sensor for Hg2+ detection as a part of environmental monitoring. Furthermore, the as-synthesized carbon dots containing high phenolic content showed the antioxidant activity and promoted rice growth with an increase in the characteristic aroma compound (2-acetyl-1-pyrroline), confirmed by GC–MS analysis.

Chiral benzo[ghi]perylene substituted [n]helicenes with strong blue fluorescent emission and circularly polarized luminescence

Chiral organic fluorescent molecules with circularly polarized luminescence (CPL) properties have attracted much attention for their potential applications in chiral optical and electronic devices. Benzo [ghi]perylene is one of the classical polycyclic aromatic hydrocarbons (PAHs) with good fluorescent properties and has many applications in the fields including optoelectronic devices and fluorescence probes. In this work, chiral benzo [ghi]perylene substituted [n]helicenes were directly obtained from chiral BINOL. The introduction of benzo [ghi]perylene structure greatly improved the fluorescent efficiency of the pristine helicene molecules. These benzo [ghi]perylene substituted [n]helicenes show strong blue fluorescent emission in organic solutions with good fluorescent quantum yields. These molecules could also exhibit moderate fluorescent emission in the solid-states. Based on the DFT calculations results, the HOMOs and LUMOs of these molecules are mainly contributed by benzo [ghi]perylene, which forms an orthogonal geometry with helicene moieties. The enantiomers of these molecules show opposite signals in CD and CPL spectra. The gabs and glum values could be increased with elongation of helicene structure. Compounds with [7]helicene moiety show relatively large gabs and glum values, which could reach up to 3.6 × 10−3 and 1.0 × 10−3, respectively. This work has provided a new strategy to develop chiral organic emitters through integration of benzo [ghi]perylene and helicene structures, which exhibit efficient fluorescent emission and intense CPL properties.

Assembly of two luminescent cadmium(II) 4,4'-phosphini Co-dibenzoate coordination polymers

Two new cadmium(II) coordination polymers [Cd(HL)(H2O)]·1.5H2O (1) and [Cd(HL)(4-bpmp)0.5]·2H2O (2) (H3L = 4,4'-phosphinicobis-dibenzoic acid, and 4-bpmp = N,N'-bis(4-pyridylmethyl)piperazine) have been synthesized by self-assembly of CdCl2 with 4,4'-phosphinicobis-dibenzoate, and N,N'-bis(4-pyridylmethyl)piperazine through solvothermal/hydrothermal method. Their structures were confirmed by X-ray single crystal diffraction, infrared spectrometer (IR), and powder X-ray diffraction (PXRD) and TGA techniques. Both compounds are in Pī space group and exhibited a 2D networks constructed from dinuclear [Cd2(POO)2] or paddle-wheel [Cd2(COO)2(POO)2] units, respectively. In 2, the Cd2+ is five-coordinated and shows a rare tetragonal pyramidal geometry. At room temperature, the compounds exhibit moderately intense blue and green fluorescence emission with peaks at 381 nm and 509 nm, respectively.
 KEY WORDS: Cadmium(II) compounds, Photoluminescence, Carboxyphosphinate ligand
 Bull. Chem. Soc. Ethiop. 2024, 38(1), 85-98. DOI: https://dx.doi.org/10.4314/bcse.v38i1.7

A value product after the hydrothermal treatment of sludge: Carbon quantum dots and its application

Carbon quantum dots (CQDs) are highly promising fluorescent nanomaterials with a wide range of applications. This study presented a novel, clean, hydrothermal carbonization (HTC) method for synthesizing fluorescent CQDs from sludge. A response surface design method was employed to optimize synthesis conditions, resulting in CQDs with excellent fluorescence properties. They were excited at 320 nm and emitted blue fluorescence at 450 nm under UV light. A mechanism for the formation of CQDs from sludge during HTC was proposed and revealed that the CQDs had an aromatic polymer structure with abundant oxygen-containing groups. X-ray photoelectron spectroscopy confirmed N and Fe doping of CQDs, which significantly improved their fluorescence properties. Additionally, a fluorescence quenching analysis showed that the CQDs selectively detected Pb2+ in the aqueous phase, indicating their potential application in Pb2+ detection. The photoinduced electron transfer (PET) arising from amino groups and other reductive functional groups has been shown to align with the quenching mechanism during the detection of Pb2+ by CQDs. This study provided a cost-effective and scalable approach that could be used to produce CQDs for the in situ detection of Pb2+ in wastewater.