Exceptional Photostability Research Articles

Thiele's Fluorocarbons: Stable Diradicaloids with Efficient Visible-to-Near-Infrared Fluorescence from a Zwitterionic Excited State.

Thiele's hydrocarbon was the first synthesized diradicaloid in the search for stable open-shell structures, but it remains sensitive to oxygen and light. We here report the synthesis of Thiele's fluorocarbon (TFC) and its derivatives exhibiting exceptional thermal, oxidative, and photostability. TFCs have remarkable luminescent properties with yellow to NIR fluorescence and up to 100% quantum yields. X-ray crystallography and ESR spectroscopy confirm their closed-shell quinoidal ground state. As expected from their symmetric nonpolar structure, the TFCs' absorption spectra show no solvent effect, but their emission reveals an extraordinarily large Stokes shift which increases with solvent polarity (from 0.9 eV in cyclohexane to 1.5 eV in acetonitrile). We show that this behavior is a result of sudden polarization, leading to a zwitterionic excited state.

Solid-state fluorescence from bioplastic nanocomposite embedded with intentional zinc doped carbon quantum dots synthesized from Brassica juncea flower extract for applications in UV-tube down-conversion

The enhancement of solid-state fluorescence from nanocomposite bioplastics containing intentionally Zn-doped carbon quantum dots (CQDs) has been reported. For the synthesis of CQDs from Brassica juncea flower extract, an economical, ecologically sustainable, and one-step hydrothermal method was used. The morphological, structural, and physicochemical properties were examined. The quasi-circular shaped CQDs, with an average diameter of 4.7 nm, were discovered to emit yellow-greenish fluorescence upon UV stimulation, to have exceptional photostability, and to be highly water soluble, with a quantum yield of up to 18%. Furthermore, a commercial UVC-tube wrapped with bioplastic nanocomposite emitted a greenish-yellow colour where intentionally Zn-doped CQDs@bioplastic nanocomposite emits more intensely than an unintentional one with CIE chromatic coordinates (0.39, 0.56 vs. 0.29, 0.55).

Bright Tunable Multicolor Graphene Quantum Dots for Light-Emitting Devices and Anticounterfeiting Applications

The development of multicolor tunable emission graphene quantum dots (GQDs) is important for their application in photoelectric devices and multicolor anticounterfeiting. Herein, we synthesize blue (B-GQDs), green (G-GQDs), and red GQDs (R-GQDs) via a solvothermal reaction. The B-, G-, and R-GQDs exhibit excitation-independent behavior, excellent fluorescence properties, and exceptional photostability. The relative quantum yields (QYs) for the B-, G-, and R-GQDs are 68, 62, and 27%, respectively. Structural characterization and theoretical calculations indicate that the quantum size effect adjusts the red shift of emission from B-GQDs to G-GQDs, and the increased content of oxygen and C═N bonds are answerable for the red emission of R-GQDs. Then, we apply the prepared multicolor GQDs as a fluorescent ink for pattern printing and multicolor anticounterfeiting. Moreover, B-, G-, and R-colors and white light-emitting diodes (LEDs) are fabricated by ultraviolet radiation as excitation. The white LEDs exhibit a color coordinate of (0.335, 0.343), a high color rendering index of 95, and a correlated color temperature of 4835 K. This research successfully expands the potential application of GQDs in the reliable anticounterfeiting, information security, and high color rendering index GQD-based LEDs.

Quantum Dot-Based Molecular Beacons for Quantitative Detection of Nucleic Acids with CRISPR/Cas(N) Nucleases.

Strategies utilizing the CRISPR/Cas nucleases Cas13 and Cas12 have shown great promise in the development of highly sensitive and rapid diagnostic assays for the detection of pathogenic nucleic acids. The most common approaches utilizing fluorophore-quencher molecular beacons require strand amplification strategies or highly sensitive optical setups to overcome the limitations of the readout. Here, we demonstrate a flexible strategy for assembling highly luminescent and colorimetric quantum dot-nucleic acid hairpin (QD-HP) molecular beacons for use in CRISPR/Cas diagnostics. This strategy utilizes a chimeric peptide-peptide nucleic acid (peptide-PNA) to conjugate fluorescently labeled DNA or RNA hairpins to ZnS-coated QDs. QDs are particularly promising alternatives for molecular beacons due to their greater brightness, strong UV absorbance with large emission offset, exceptional photostability, and potential for multiplexing due to their sharp emission peaks. Using Förster resonance energy transfer (FRET), we have developed ratiometric reporters capable of pM target detection (without nucleotide amplification) for both target DNA and RNA, and we further demonstrated their capabilities for multiplexing and camera-phone detection. The flexibility of this system is imparted by the dual functionality of the QD as both a FRET donor and a central nanoscaffold for arranging nucleic acids and fluorescent acceptors on its surface. This method also provides a generalized approach that could be applied for use in other CRISPR/Cas nuclease systems.

AIEgens: Next Generation Signaling Source for Immunoassays?

Luminogens with aggregation-induced emission (AIEgens) properties have numerous broad applications in fields of chemical and biological analyses due to their exceptional photostability, excellent signal reliability, high quantum yield, and large Stokes' shift. In particular, AIEgens also bring new blood for immunoassay. Since publication of the first 2004 paper, AIEgens-based immunoassays have received significant attention because of their high sensitivity, specificity, accuracy, and reliability. However, until now, there have been no comprehensive literature reviews focused on the evolving field of AIEgens-based immunoassays. Thus, we have extensively reviewed AIEgens-based immunoassays from their basic working principles to specific applications. We focus on several fundamental elements of AIEgens-based immunoassays, including the typical structures of AIEgens, emission mechanism of AIEgens probes, function of AIEgens in immunoassays, and platform of AIEgens-based immunoassays. Then, the representative applications of AIEgens-based immunoassays in food safety, medical diagnostics, and environmental monitoring are explored. Thus, proposals on how to further improve the AIEgens-based immunoassay performance are also discussed, as well as future challenges and perspectives, aiming to provide brief and valid guidelines for choosing suitable AIEgens-based immunoassays according to specific application requirements.

How the Way a Naphthalimide Unit is Implemented Affects the Photophysical and -catalytic Properties of Cu(I) Photosensitizers.

Driven by the great potential of solar energy conversion this study comprises the evaluation and comparison of two different design approaches for the improvement of copper based photosensitizers. In particular, the distinction between the effects of a covalently linked and a directly fused naphthalimide unit was assessed. For this purpose, the two heteroleptic Cu(I) complexes CuNIphen (NIphen = 5-(1,8-naphthalimide)-1,10-phenanthroline) and Cubiipo (biipo = 16H-benzo-[4′,5′]-isoquinolino-[2′,1′,:1,2]-imidazo-[4,5-f]-[1,10]-phenanthroline-16-one) were prepared and compared with the novel unsubstituted reference compound Cuphen (phen = 1,10-phenanthroline). Beside a comprehensive structural characterization, including two-dimensional nuclear magnetic resonance spectroscopy and X-ray analysis, a combination of electrochemistry, steady-state and time-resolved spectroscopy was used to determine the electrochemical and photophysical properties in detail. The nature of the excited states was further examined by (time-dependent) density functional theory (TD-DFT) calculations. It was found that CuNIphen exhibits a greatly enhanced absorption in the visible and a strong dependency of the excited state lifetimes on the chosen solvent. For example, the lifetime of CuNIphen extends from 0.37 µs in CH2Cl2 to 19.24 µs in MeCN, while it decreases from 128.39 to 2.6 µs in Cubiipo. Furthermore, CuNIphen has an exceptional photostability, allowing for an efficient and repetitive production of singlet oxygen with quantum yields of about 32%.

Tailoring Functional Terminals on Solution-Processable Fullerene Electron Transporting Materials for High Performance Perovskite Solar Cells.

Widely known as an excellent electron transporting material (ETM), pristine fullerene C60 plays a critical role in improving the photovoltaic performance of inverted structure perovskite solar cells (PSCs). However, the imperfect perovskite/C60 interface significantly limits the promotion of device performance and stability due to the weak coordination interactions between bare carbon cages and perovskite. Here, we designed and synthesized three functionalized fulleropyrrolidine ETMs (abbreviated as CEP, CEPE, and CECB), each of which was modified with the same primary terminal (cyanoethyl) and various secondary terminals (phenyl, phenethyl, and chlorobutyl). The resulting CECB-based PSC has a power conversion efficiency (PCE) over 19% and exceptional photo-stability over 1800 h. This work provides significant insight into the targeted terminal design of novel fullerene ETMs for efficient and stable PSCs.

Design of High-Performance Thermally Activated Delayed Fluorescence Emitters Containing s-Triazine and s-Heptazine with Molecular Orbital Visualization by STM

Materials exhibiting thermally activated delayed fluorescence (TADF) are now key components of some of the most advanced organic light-emitting diodes, photocatalysts, and bioimaging probes. Designing a TADF emitter requires a precise understanding of its frontier molecular orbitals (FMOs), yet rarely are these orbitals visualized experimentally. Here, we use scanning tunneling microscopy on Ag(111) to probe the electronic structures of high-performance TADF materials with different orbital landscapes based on s-triazine and s-heptazine acceptors. These materials exhibit room-temperature phosphorescence or thermally activated delayed fluorescence, deep-blue (452 nm) to red (615 nm) emission, near-unity photoluminescence quantum yields, exceptional photostability, and two-photon absorption cross sections as high as 2098 GM. Overall, this work demonstrates the potential of s-heptazines as optoelectronic materials, as well as the utility of direct FMO visualization in material design.

From Khoi-San indigenous knowledge to bioengineered CeO2 nanocrystals to exceptional UV-blocking green nanocosmetics

Single phase CeO2 nanocrystals were bio-synthesized using Hoodia gordonii natural extract as an effective chelating agent. The nanocrystals with an average diameter of 〈Ø〉 ~ 5–26 nm with 4+ electronic valence of Ce displayed a remarkable UV selectivity and an exceptional photostability. The diffuse reflectivity profile of such CeO2 exhibited a unique UV selectivity, in a form of a Heaviside function-like type profile in the solar spectrum. While the UV reflectivity is significantly low; within the range of 0.7%, it reaches 63% in the VIS and NIR. Their relative Reactive Oxygen Species (ROS) production was found to be < 1 within a wide range of concentration (0.5–1000 μg/ml). This exceptional photostability conjugated to a sound UV selectivity opens a potential horizon to a novel family of green nano-cosmetics by green nano-processing.

Self-Assembly of Nanodiamonds and Plasmonic Nanoparticles for Nanoscopy.

Nanodiamonds have emerged as promising agents for sensing and imaging due to their exceptional photostability and sensitivity to the local nanoscale environment. Here, we introduce a hybrid system composed of a nanodiamond containing nitrogen-vacancy center that is paired to a gold nanoparticle via DNA hybridization. Using multiphoton optical studies, we demonstrate that the harmonic mode emission generated in gold nanoparticles induces a coupled fluorescence emission in nanodiamonds. We show that the flickering of harmonic emission in gold nanoparticles directly influences the nanodiamonds’ emissions, resulting in stochastic blinking. By utilizing the stochastic emission fluctuations, we present a proof-of-principle experiment to demonstrate the potential application of the hybrid system for super-resolution microscopy. The introduced system may find applications in intracellular biosensing and bioimaging due to the DNA-based coupling mechanism and also the attractive characteristics of harmonic generation, such as low power, low background and tissue transparency.

Detection of Pesticides in Food by CDs Blue Luminescent Material with the Help of Fluorescence Quenching Study

Environmental contamination has modified the approach to life of the folks in many ways all round the world. Food science suggests that the science of food which has food elements, their behaviour underneath completely different environmental conditions, method of harvest, milling, exposure to heat, cold, acid, alkalis etc. Today, the sphere of food science has progressed from basic physical, chemical and biological reactions that turn up throughout process to the fields of biotechnology, food engineering, packaging and its result on the patron. Luminescence and visual radiation phenomena have really fascinating ideas in technology. Light-weight materials have really various and distinctive properties, that are a magnet for various scientists to do and do the analysis throughout this field to implement in numerous sectors. Once the invention year in analysis of carbon dots in 2004, the study of carbon dots unreal, together with whole completely different fluorescent properties of carbon dots. It’s varied and valuable properties like water solubility, stable fluorescent property, exceptional photostability, high sensitivity with low toxicity, which can be apply in varied disciplines of research areas. This text explains the transient introduction of varied toxic materials and their effects. It explains the transient introduction and history of food science together with nutrition and digestions of food. It conjointly describes the various properties of food. The article is additionally mentioning the detection of various hazardous/poisonous materials by CDs with inherent literature survey. This text represents the transient introduction of pesticides and basic info of visible light extinction study. Through that, the venturesome material will be simply detected in varied food beverages.

High internal phase Pickering emulsions stabilized by egg yolk low density lipoprotein for delivery of curcumin

Egg yolk low density lipoprotein (LDL) was used to prepare high internal phase Pickering emulsions (HIPEs) and its role as a stabilizer was comprehensively studied in this work. LDL exists as homogenous nanoparticles with an average size of 49 nm and amphiphilic nature, having a contact angle close to 90°. HIPEs were studied by varying compositions of 75%–90% oil phase and 25%–10% aqueous phase containing 0.5%–2% LDL. Rheological measurement, confocal laser scanning and optical microscopes imaging together with digital photos revealed the solid gel network, the strength of which was dependent upon oil volume fraction and LDL concentration. Optimal formulation of HIPEs was found as 80% oil and 2% LDL concentration, which exhibited small droplets under 10 µm with negligible aggregations, even after four weeks storage under refrigeration or heating at 90 ℃ for 30 min. After three freeze-thawing cycles, the HIPEs were demulsified losing their gel structure, but a simple re-homogenization was able to reconstitute the gel network identical to original microstructure. Encapsulation of curcumin into Pickering HIPEs provided exceptional photostability (around 80% retention rate) against ultraviolet radiation and improved its bioaccessibility from 10% to 50% during in vitro digestion. Our findings may bring new opportunities to design semi-solid foods using natural and edible ingredients.

Surfactant-chaperoned donor-acceptor-donor NIR-II dye strategy efficiently circumvents intermolecular aggregation to afford enhanced bioimaging contrast.

Fluorescence emission in the near-infrared-II (NIR-II) optical window affords reduced autofluorescence and light scattering, enabling deep-tissue visualization for both disease detection and surgical navigation. Small-molecule NIR-II dyes are preferable for clinical bioimaging applications, as the flexibility in their molecular synthesis allows for precise control of their optical and pharmacokinetic properties. Among the various types of dye, donor-acceptor-donor-based (D-A-D) dyes demonstrate exceptional photostability, whereas the frequently used PEGylation approach does not keep their intrinsic brightness enough in water environments due to their inherent effect of self-assembly. Here, we demonstrate that the commercially-available surfactants can serve as a dispersant to prevent molecular aggregation of PEGylated D-A-D dyes. Due to the favorable energetics for co-assembly between D-A-D dyes and surfactants, the formed surfactant-chaperoned dye strategy dramatically increases dye brightness. Accordingly, this effect provides remarkably improved performance for in vivo bioimaging applications. In parallel, we also investigate the D-A-D dye uptake and signal enhancement properties in the liver of murine models and demonstrate that the lumen-lining Kupffer cells can potentially disassemble PEGylated D-A-D aggregates such that their inherent brightness is restored. This phenomenon is similar to the surfactant-chaperoned dye strategy and our investigations provide a positive addition to better use of the current NIR-II fluorophores, especially for visualizing high-brightness required events.

Preparation, characterization, evaluation and mechanistic study of organic polymer nano-photocatalysts for solar fuel production.

Production of renewable fuels from solar energy and abundant resourses, such as water and carbon dioxide, via photocatalytic reactions is seen as a promising strategy to adequately address the climate challenge. Photocatalytic systems based on organic polymer nanoparticles (PNPs) are seen as one avenue to transform solar energy into hydrogen and other solar fuels. Semiconducting PNPs are light-harvesting materials with exceptional optical properties, photostability, low cost and low cytotoxity, whose performance surpasses conventional organic dyes and inorganic semiconductors. This review introduces the optimization strategies for the preparation methods of PNP via cocatalyst loading and morphology tuning. We present an analysis on how the preparative methods will impact the physico-chemical properties of these materials, and thus the catalytic activity. A list of experimental techniques is presented for characterization of the physico-chemical properties (optical, morphological, electrochemical and catalytic properties) of PNPs. We provide detailed analysis of PNP photochemistry during photocatalysis with focus on the mechanistic understanding of processes of internal charge generation and transport to the catalyst. This tutorial review provides the reader with the guidelines on current strategies used to optimize PNP performance highlighting the future directions of polymer nano-photocatalysts development.

Morphology and Phase Engineering of MoS2 Cocatalyst for High-Efficiency Hydrogen Evolution: One-Step Clean Synthesis and Comparative Studies

Effective separation and transfer of photoexcited carriers are essential for photocatalysis, which could be optimized by the rational design of morphology and phase structure. Herein, using NH4HCO3 as intercalating and orienting agents, few-layer vertical-standing multiphasic MoS2 nanosheets (VM-MoS2) were successfully constructed along the longitudinal axis of CdS nanorods via a green hydrothermal method. The growth mechanism of VM-MoS2 on CdS nanorods was demonstrated to include the competitive adsorption of HCO3– and Mo7O246– anions on the protonated CdS, and the intercalation of NH4+ cations. Moreover, the impacts of the morphology and phase structure of the MoS2 cocatalyst on the photocatalytic H2 evolution (PHE) performance of CdS were carefully compared. It is found that the VM-MoS2 nanosheets can not only expose abundant active sites, but also allow the supporter to harvest the light effectively. Additionally, the metallic 1T-MoS2 in VM-MoS2 would help the interface transfer of photogenerated electrons and act as photoelectron entrepots and catalytically active sites for H2 evolution. With the VM-MoS2 cocatalyst, the as-synthesized CdS@VM-MoS2 shows an outstanding PHE rate of ∼40.1 mmol·h–1·g–1 under visible-light irradiation. Interestingly, integrating with the 2H-MoS2 phase will make the metastable 1T-MoS2 more stable, leading to the exceptional photostability of CdS@VM-MoS2 nanocomposite.

Physical Stability, Rheology, Thermal Conductivity and Optical and Corrosion Properties of a Graphene Quantum Dot Fluid

Because of their unique and tunable photoluminescence properties, exceptional physicochemical properties, high photostability, biocompatibility and small size, Graphene quantum dots (GQDs) have received a lot of attention. However, insufficient investigations have been carried out on GQD fluids. In this paper, the properties of a prepared GQD fluid are studied experimentally, involving the physical stability, rheology, thermal conductivity, optical properties and corrosion characteristics. It is found that a highly physically stable GQD fluid could be easily achieved because the selected GQDs are well dispersed. It is also found that the addition of GQDs had a slight effect on the base fluid viscosity, but it could significantly increase the thermal conductivity of the fluid. In addition, the investigation of the optical properties shows that the GQD fluid exhibited high absorption to sunlight. The transmittance of ultraviolet and near-infrared light is close to zero. In contrast, the transmittance of GQDs to visible light is high at low weight concentrations, but significantly decreases with the increase of the proportion of GQDs. The corrosion characteristics of the copper and carbon steel samples in the selected GQD fluid or deionized water were experimentally investigated. It is found that the selected GQD fluid can greatly accelerate the corrosion of copper. However, nearly the same corrosion rate is observed for carbon steel in the GQD fluid as that in deionized water. The high stability, low viscosity, enhanced thermal conductivity and unique optical and corrosion properties allowed the GQD fluid to have excellent potential for applications in the energy sector.

Facile synthesis of multifunctional carbon dots with 54.4% orange emission for label-free detection of morin and endogenous/exogenous hypochlorite

Carbon dots with long-wavelength emission (orange to red), high quantum yield (QY) and good biocompatibility are of great significance for biomedical applications, but achieving this is still a highly challenging task. In this work, multifunctional carbon dots with 54.4% orange emission (O-CDs) were prepared through one-pot solvothermal treatment of nileblueasulphate and citric acid as precursor for label-free recognition of morin and endogenous/exogenous hypochlorite (ClO-) and bioimaging in cellular and zebrafish. Morin can quench the luminescence of O-CDs by static quenching (SQ). The linear range is 5–125 μM and LOD is 0.84 μM. ClO- reduce the photoluminescence intensity of O-CDs via SQ. The linear range is 2.5–90 μM and LOD was 0.46 μM. In addition, The obtained O-CDs have successfully realized the monitoring of morin and endogenous/ exogenous ClO- in living cells and zebrafish owing to its superior biocompatibility, exceptional photostability and lower toxicity. This work opens up a novel opportunity for the development of long-wavelength emission multifunctional nanomaterial with high quantum yield based on CDs for biosensing, biolabeling and biomedical optical imaging.

COOH-Terminated Silicon Quantum Dots as a Highly Efficient Drug Nanocarrier for Targeted Tumor Cell Imaging.

Fluorescent silicon quantum dots (SiQDs) characterized by exceptional photostability and colloidal robustness as well as beneficial biocompatibility are fast becoming new pharmaceutical nanocarriers. With a view to efficiently loading cisplatin (CDDP) onto SiQDs, carboxylate group (COOH) terminated SiQDs were imperative because of chelate formation with CDDP. In this work, we employed a facial microwave irradiation route for rapidly synthesizing high-quality COOH-SiQDs through the use of 3-aminopropyl trimethoxy silane (APTMS) molecules to fulfil the role of silicon precursor and maleic acid (MA) as the agent for facilitating reduction. The SiQDs showed blue fluorescence with an associated photoluminescence quantum yield (PLQY) of 40.2%, the size of which was small at 3.2 ±0.6 nm, and long-lasting stability (an extensive range in pH (4-12) and concentrations of electrolytes reaching 3 Molarity of a solution of sodium chloride). As nanocarriers, carboxylic acids chelation generated a high loading of CDDP onto SiQDs (drug loading capacity, DLC up to 32.2% at pH = 9) and a drug release of CDDP up to 57.6% at pH = 5. Furthermore, the MTT assays demonstrated the non or low cytotoxicity of SiQDs and the role of the controlled release of SiQD-CDDP Finally, the prepared SiQD-CDDP were used for cell imaging, and further targeted labeling of some tumors after folic acid (FA) conjugation. These characteristics allow for the deployment of SiQDs as a highly efficient nanocarrier that facilitate the delivery of clinical drugs for the future.

Fluorescent ruby nanocrystals for biocompatible applications

Chromium-doped aluminum oxide (ruby) micro- and nanocrystals have shown a sharp and strong fluorescence emission that linearly depends on pressure and temperature. They also have an exceptional photostability and a high quantum efficiency. In spite of their widespread use as pressure sensors, only a few earlier studies have used ruby nanocrystals as efficient fluorescent bioimaging probes. However, their use at biocompatible excitation/detection wavelengths and toxicity assessment against human living cells remain unexplored. In this work, we show that ruby nanocrystals can be efficiently excited and detected within the biological transparency window. We also examined the biocompatibility of ruby nanocrystals in human living cells, which exhibited no detectable cytotoxicity. This makes ruby nanocrystals among the best alternative fluorescent probes for promising biological applications.

Photoswitchable Fluorescent Self-Assembled Metallacycles with High Photostability.

In this study, photoswitchable fluorescent supramolecular metallacycles with high fatigue-resistance have been constructed by coordination-driven self-assembly by using bithienylethene with dipyridyl units (BTE) as a coordination donor and a fluorescent di-platinum(II) (Pt-F) as a coordination acceptor. The photo-triggered reversible transformation between the ring-open and ring-closed form of the metallacycles was confirmed by 1 H NMR, 31 P NMR, and UV/Vis spectroscopy. This unique property enabled a reversible noninvasive "off-on" switching of fluorescence through efficient Förster resonance energy transfer (FRET). Importantly, the metallacycles remained structurally intact after up to 10 photoswitching cycles. The photoresponsive property and exceptional photostability of the metallacycles posit their potential promising application in optical switching, image storage, and super-resolution microscopy.