Resonance Energy Transfer Mechanism Research Articles

High-speed tracking of coalescence and mixing of optically controlled droplets

We are presenting an all-optical platform for on-demand and nonintrusive studies of coalescence of micron-sized liquid droplets in air. The platform has the purpose to mimic the airborne conditions occurring in typical environments where droplet interactions are involved. By means of the Förster resonance energy transfer mechanism, we have been able to track the dynamics of two coalescing glycerol droplets, with a radius of ∼10µm and a temporal resolution of 86µs. At the onset of coalescence, a fast mixing is observed. Such an effect depletes the fluorescence of the donor fluorophore to half its initial intensity on a timescale below the temporal resolution of our platform, whereas a complete mixing is observed to occur on a timescale of seconds. The experimental platform design and findings facilitate an increased understanding of the microphysics of collisions, coalescence, and the subsequent mixing/diffusion of droplets on the micrometer lengthscale and the microsecond timescale. Published by the American Physical Society 2024

Novel energy exchange behaviors and mechanisms in nonlinear acoustic metamaterials with multiple nonlinear resonators

Wave-wave interactions in a nonlinear metamaterial or structure with two propagating waves can induce energy exchange within the nonlinear systems. The effects of nonlinear resonators on these interactions and energy exchanges in a nonlinear acoustic metamaterial have not been extensively studied in the literature. In this paper, a nonlinear monatomic acoustic metamaterial with multiple nonlinear resonators (NMAM-MNR) is constructed to investigate the new behaviors and mechanisms introduced by these nonlinear resonators. Stability analyses reveal that stability can be tuned by adjusting the number of nonlinear resonators and by selecting different intensities or masses of the resonators and the chain. Additionally, direct numerical simulations are performed to study the novel energy exchange behaviors and mechanisms in NMAM-MNR systems. The results demonstrate that the degree and frequency of energy exchange can be tuned by altering the mass ratios, stiffness ratios, intensities, and natural frequencies of the nonlinear resonators and the chain. The influence of mass and stiffness ratios on the time taken for the B-wave magnitude to first reach its maximum value in NMAM-MNR systems is also studied, showing that the rate of energy exchange induced by wave-wave interactions can be tuned by changing the stiffness and mass ratios of multiple nonlinear resonators. These properties have potential applications in the fields of energy harvesters, waveguides, and resonant energy transfer mechanisms.

Preparation of Carbon Quantum Dot with Copper Nanoparticles Using Mugwort Leaves as Carbon Source to Construct FRET Fluorescent Sensor for Melamine Detection

AbstractCarbon quantum dots (CQDs) have gained extensive attention due to their excellent properties and wide applications. In this study, we selected the common Chinese herb mugwort as the carbon source and employed the microwave heating method to synthesize CQDs with a quantum yield of 13.54 %. These CQDs exhibited blue fluorescence under UV light irradiation. Furthermore, we constructed a fluorescence resonance energy transfer (FRET) mechanism by combining CQDs with copper nanoparticles (CuNPs) for the detection of melamine. The detection limit for melamine was determined to be 0.83 nmol/L, with a linear range of 1–100 nmol/L. The results demonstrated the potential of this sensing system for the sensitive and selective detection of melamine.

Comparative investigation on carbon dots and chloride fluxes modified ZnAl2O4:Cr3+ nanophosphors for temperature sensing, cutting-edge forensic, anti-counterfeiting and w-LEDs applications

A novel Cr3+ doped ZnAl2O4 is synthesized by grafting carbon dots (CDs) and chloride fluxes (NaCl, KCl, NH4Cl) through the solid-state reaction method. Upon excitation at 530 nm wavelength, the Cr3+ ions in the ZAO NPs emit red light due to the influence of a strong crystal field. This red emission arises from the electric dipole 2Eg→4A2g of the Cr3+ ions. Among the chloride fluxes examined, NH4Cl had a significant impact on the PL intensity. Notably, when CDs are incorporated into the ZAO:7Cr3+/NH4Cl NPs, a remarkable increase of 17.25-folds in photoluminescence (PL) intensity is observed. This enhancement is substantially higher than that of CDs alone (11.23-folds) and NH4Cl alone (3.82-folds). The increased PL intensity is attributed to the Förster resonance energy transfer (FRET) mechanism. Furthermore, the addition of CDs (5 wt.%) enhanced the colour purity (CP) of ZAO:7Cr3+/NH4Cl NCs to 99.8%, achieving a high Internal quantum efficiency (IQE) of 93.4 %. Notably, the CDs (5 wt.%)@ZAO:7Cr3+/NH4Cl NCs maintained 92.43 % of their emission intensity even at 420 K, demonstrating exceptional thermal stability compared to ZAO:7Cr3+ NPs. Moreover, the NPs holds promise for optical thermometry, boasting a high relative sensitivity (Sr) of 6.74 × 10-2 %K-1 across a temperature range spanning from 300 to 480 K. Moreover, the latent fingerprints (LFPs) developed using CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs demonstrate remarkable selectivity and high contrast. Under UV irradiation, the structural features of LFPs at levels I–III are clearly visible. In addition, the strong red fluorescence emitted by CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs makes them suitable for applications in AC. CDs(5 wt.%)@ZAO:7Cr3+ NCs exhibit significant potential for w-LED fabrication, achieving a correlated colour temperature (CCT) of 5517 K, a CIE coordinate of (0.332, 0.331), and a high colour rendering index (CRI) of Ra = 94, outperforming ZAO:7Cr3+/NH4Cl NPs. Overall results clearly demonstrates that, CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs are effective for applications in optical thermometry, dactyloscopy, w-LEDs, and AC.

Smartphone-assisted ratiometric fluorescent sensor to quantitatively detect curcumin in traditional Chinese medicine based on Förster resonance energy transfer.

A ratiometric fluorescence sensor (Fe-MIL-88-NH2/curcumin) based on luminescent metal-organic frameworks (LMOFs) for the determination of curcumin was constructed. Upon the addition of curcumin, the 535-nm emission of curcumin was enhanced, while the fluorescence emission at 438nm was quenched, under 367-nm excitation. This sensor demonstrated a broad linear range from 1.5 to 40μM, a low detection limit of 35nM, and a fast response time of at most 30s. We verified the Förster resonance energy transfer (FRET) mechanism between donor (Fe-MIL-88-NH2) and acceptor (curcumin), which further proved the selectivity of theapproach. The sensing system enabled the detection of curcumin in the traditional Chinese medicine (TCM)Turmeric. A smartphone-assisted sensing platform was prepared to visually detect curcumin in a portable manner. This study represents the first attempt to fabricate LMOFs for ratiometric fluorescence detection of curcumin, which has promising potential for application in TCM.

Enhanced Sensitivity and Accuracy of Tb3+-Functionalized Zirconium-Based Bimetallic MOF for Visual Detection of Malachite Green in Fish.

The ratiometric fluorescent probe UiO-OH@Tb, a zirconium-based MOF functionalized with Tb3+, was synthesized using a hydrothermal method. This probe employs the fluorescence resonance energy transfer (FRET) mechanism between Tb3+ and malachite green (MG) for the double-inverse signal ratiometric fluorescence detection of MG. The probe's color shifts from lime green to blue with an increasing concentration of MG. In contrast, the monometallic MOFs' (UiO-OH) probe shows only blue fluorescence quenching due to the inner filter effect (IFE) after interacting with MG. Additionally, the composite fluorescent probe (UiO-OH@Tb) exhibits superior sensitivity, with a detection limit (LOD) of 0.19 μM, which is significantly lower than that of the monometallic MOFs (25 μM). Moreover, the content of MG can be detected on-site (LOD = 0.94 μM) using the RGB function of smartphones. Hence, the UiO-OH@Tb probe is proven to be an ideal material for MG detection, demonstrating significant practical value in real-world applications.

Liposomal fusion of plant-based extracellular vesicles to enhance skin anti-inflammation

This study reports a hybrid extracellular vesicle (EV)/liposome system developed through vesicular membrane fusion between anti-inflammatory Hydrangea macrophylla leaf EVs (HML-EVs) and terpinen-4-ol/azelamide monoethanolamine-loaded liposomes. Successful liposomal fusion between HML-EVs and terpinen-4-ol/azelamide monoethanolamine-loaded-liposome membranes, confirmed using the two-color fluorescence resonance energy transfer mechanism, enabled the scaled production of a stable hybrid HML-EV/liposome dispersion at a length scale of 100–200 nm. We show that the hybrid EV/liposome significantly inhibits apoptosis by nitric oxide and tumor necrosis factor-α production. Furthermore, HML-EV/liposomes can inhibit the synthesis of protease-activated receptor-2, interleukin-6, c-Jun, and thymic stromal lymphopoietin, thus exhibiting anti-inflammatory performance. These findings highlight that the hybrid EV/liposome system established in this study alleviates skin irritation and improves skin anti-inflammation.

Incoherent ultrafast energy transfer in phycocyanin 620 from Thermosynechococcus vulcanus revealed by polarization-controlled two dimensional electronic spectroscopy.

Phycocyanin 620 (PC620) is the outermost light-harvesting complex in phycobilisome of cyanobacteria, engaged in light collection and energy transfer to the core antenna, allophycocyanin. Recently, long-lived exciton-vibrational coherences have been observed in allophycocyanin, accounting for the coherent energy transfer [Zhu et al., Nat. Commun. 15, 3171 (2024)]. PC620 has a nearly identical spatial location of three α84-β84 phycocyanobilin pigment pairs to those in allophycocyanin, inferring an existence of possible coherent energy transfer pathways. However, whether PC620 undergoes coherent or incoherent energy transfer remains debated. Furthermore, accurate determination of energy transfer rates in PC620 is still necessary owing to the spectral overlap and broadening in conventional time-resolved spectroscopic measurements. In this work, the energy transfer process within PC620 was directly resolved by polarization-controlled two dimensional electronic spectroscopy (2DES) and global analysis. The results show that the energy transfer from α84 to the adjacent β84 has a lifetime constant of 400fs, from β155 to β84 of 6-8ps, and from β155 to α84 of 66ps, fully conforming to the Förster resonance energy transfer mechanism. The circular dichroism spectrum also reveals that the α84-β84 pigment pair does not form excitonic dimer, and the observed oscillatory signals are confirmed to be vibrational coherence, excluding the exciton-vibrational coupling. Nodal line slope analysis of 2DES further reveals that all the vibrational modes participate in the energy dissipation of the excited states. Our results consolidate that the ultrafast energy transfer process in PC620 is incoherent, where the twisted conformation of α84 is suggested as the main cause for preventing the formation of α84-β84 excitonic dimer in contrast to allophycocyanin.

Heavy-Atom-Free Covalent Organic Frameworks for Organic Room-Temperature Phosphorescence via Förster and Dexter Energy Transfer Mechanism.

Covalent organic frameworks (COFs), with their accessible nanoscale porosity, selectable building blocks, and precisely engineered topology, offer unique benefits in the design of room-temperature phosphorescent (RTP) materials. However, their potential has been limited by phosphorescence quenching caused by interlayer π-π stacking interactions. This paper presents a novel strategy to enhance RTP in heavy-atom-free COFs by employing a donor-acceptor (D-A) system that leverages the Förster resonance energy transfer (FRET) and Dexter energy transfer (DET) mechanisms. Among the materials investigated, the best-performing COF exhibits a phosphorescence lifetime of 4.35ms at room temperature. Spectral analysis, structural analysis, and theoretical calculations indicate the presence of intralayer FRET processes as well as interlayer DET processes within the D-A COF system. Potential anti-counterfeiting applications are explored by exploiting the unique phosphorescent properties of these materials. Additionally, the inherent permanent porosity of COFs presents new opportunities for future development and application. This strategy offers many promising prospects for advancing the RTP technology in COF materials and broadens their potential applications in various fields.

Nucleic acid-functionalized upconversion luminescence biosensor based on strand displacement-mediated signal amplification for the detection of trivalent chromium ions

BackgroundRapid industrial development has generated serious pollution, including the presence of toxic and harmful heavy metal ions. Among them, trivalent chromium ion (Cr3+) is a very important element that poses a threat to life and health in our industrial wastewater pollution. Thus, it is important to develop efficient fluorescence methods for Cr3+ detection. In this study, an upconversion luminescence biosensor for detecting Cr3+ was constructed based on a DNAzyme, strand displacement reaction (SDR), and DNA-functionalized upconversion nanoparticles (UCNPs). ResultsThe sulfonate-rich poly (sodium 4-styrene sulfonate) (PSS) was modified onto the surface of UCNPs, forming UCNPs@PSS. Then, NH2-Capture probe DNA (NH2-Cp) was further modified onto the UCNPs@PSS surface through sulfonylation, resulting in UCNPs@PSS@NH2-Cp. The DNAzyme activated by Cr3+ triggered the release of the primer probe (Pp), which initiated the SDR system cycle, thereby releasing a tetramethylrhodamine (TAMRA)-modified signal probe (TAMRA-Sp). Finally, UCNPs@PSS@NH2-Cp bound to TAMRA-Sp through complementary base pairing, causing UCNPs and TAMRA to approach each other. Because of the luminescence resonance energy transfer (LRET) mechanism, the upconversion luminescence (UCL) signal of the UCNPs was quenched by TAMRA, enabling the detection of Cr3+ by the change of I585/I545 ratio. This biosensor has good stability, selectivity, and sensitivity, with a linear range of 0.5–75 nM and a detection limit of 0.135 nM for Cr3+. Significance and noveltyFirstly, based on LRET between UCNPs and TAMRA, the quantitative analysis of Cr3+ is achieved through the changes of ratio fluorescence. Secondly, the specificity of the biosensor is improved by utilizing the specific recognition of DNA enzymes. Thirdly, the signal amplification technology of the SDR cycle greatly improves the sensitivity of biosensor. This biosensor will be useful for future environmental safety monitoring and biopsy of biological fluids.

Influence of carbon dots integrated in Pr3+ doped gahnite nanophosphor for thermal sensing, data fortification and fingerprint visualization analysis through YOLOv8x deep learning embedded model

The remarkable optical properties of carbon dots (CDs) render them highly promising as a versatile group of carbon-based nanomaterials. Integrating hydrothermally synthesized CDs into zinc aluminate doped with Pr3+ ions (ZnAl2O4:Pr3+) nanophosphors (ZAO:Pr3+ NPs) fabricated via the solution combustion (SC) technique holds great potential. The aim of synthesizing these nanocrystals (NCs) is to explore their potential uses in optical thermometry and anti-counterfeiting (AC) measures. The synthesized nanoparticles (NPs) and nanocomposites (NCs) underwent characterization using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra to verify their phase, morphology, particle size, oxidation state, and chemical composition. When excited at 447 nm, the Pr3+ doped ZAO: NPs exhibited an orange-red emission band at 614 nm. A remarkable enhancement in PL intensity, by a factor of 39.02 folds, is noted upon embedding CDs into the ZAO:Pr3+ NPs (CDs@ ZAO:Pr3+). The enhanced PL intensity can be ascribed to the Förster resonance energy transfer (FRET) mechanism. Even at a temperature of 423 K, the NPs retains 95.4% of its emission intensity compared to that at room temperature, showcasing exceptional thermal stability. The 5 wt% CDs@ZAO:1Pr3+ NCs demonstrate a high colour purity (CP) of 98.3%. Moreover, these NCs hold promise for optical thermometry applications across a broad temperature range spanning from 303 to 463 K. Utilizing the exceptional ZAO:1Pr3+ NPs and 5 wt% CDs@ZAO:1Pr3+ NCs, two representative white light emitting diodes (w-LEDs) have been successfully developed, boasting satisfactory luminous efficacy and colour-rendering index (CRI). This underscores their potential for high-performance w-LED applications. Simultaneously, a highly sensitive, non-contact optical thermometer has been engineered, featuring maximum relative sensitivities of approximately 44.51×10−4K−1 and 75.48×10−4K−1 at the emission intensities corresponding to 673, 693, 712 and 735 nm, respectively. We have developed a simple brush mode technique for creating a variety of patterns using the manufactured AC security ink. The latent fingerprints (LFPs) visualized using 5 wt% CDs@ZAO:1Pr3+ NCs exhibit excellent resolution and contrast, enabling the easy identification of fingerprint characteristics from levels I-III. Employing deep learning utilizing the YOLOv8x algorithm, fluorescence images of the revealed LFPs demonstrate remarkable alignment with standard controls, suggesting a high degree of similarity. In addition, the fabricated white light emitting diode (w-LED) boasts a favorable colour rendering index (Ra=87) alongside Commission International de L′Eclairage (CIE) coordinates (0.617, 0.376). Consequently, the inclusion of 5wt% CDs@ZAO:1Pr3+NPs showcases remarkable luminescent attributes and holds promising prospects across various applications.

A fluorescent turn-on nanosensor for selective detection of L-morphine using D-cysteine-functionalized graphene quantum dots

Here, L- and D-cysteine-functionalized graphene quantum dots (L-/D-cys-GQDs) were designed with the aim of obtaining a selective fluorescent nanosensor to detect L-morphine. Citric acid was pyrolyzed to synthesize the GQDs, which were then functionalized with chiral L- and D-cys species using a thiol-ene click reaction between sulfur group of cysteine species and CC double bonds of GQDs. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopies (XPS) provides elemental analysis data which approved the presence of sulfur and nitrogen elements of L- and D-cysteine species on the surface of GQDs. Transmission electron microscopy (TEM) showed that the particle size of the modified GQDs ranges from 2 to 4.2 nm. The results of fluorescence spectroscopy showed that upon functionalization of GQDs with L-/D-cys the fluorescence intensity decreases as a result of Forster resonance energy transfer (FRET) mechanism. Interestingly, in the presence of L-morphine, the fluorescence intensity of D-cys-GQDs was selectively turned on as the FRET mechanism is ceased between the cysteine species and GQDs. Additional tests demonstrated that this nanosensor cannot interact with other drugs like methamphetamine or ibuprofen. As a result, it can serve as a cheap and precise nanosensor for identifying low quantities of L-morphine.

A Vector Nanoplatform for the Bioimaging of Deep-Seated Tumors.

Today, in preclinical studies, optical bioimaging based on luminescence and fluorescence is indispensable in studying the development of neoplastic transformations, the proliferative activity of the tumor, its metastatic potential, as well as the therapeutic effect of antitumor agents. In order to expand the capabilities of optical imaging, sensors based on the bioluminescence resonance energy transfer (BRET) mechanism and, therefore, independent of an external light source are being developed. A targeted nanoplatform based on HER2-specific liposomes whose internal environment contains a genetically encoded BRET sensor was developed in this study to visualize deep-seated tumors characterized by overexpression of human epidermal growth factor receptor type 2 (HER2). The BRET sensor is a hybrid protein consisting of the highly catalytic luciferase NanoLuc (an energy donor) and a LSSmKate1 red fluorescent protein with a large Stokes shift (an energy acceptor). During the bioimaging of disseminated intraperitoneal tumors formed by HER2-positive SKOV3.ip1cells of serous ovarian cystadenocarcinoma, it was shown that the developed system is applicable in detecting deep-seated tumors of a certain molecular profile. The developed system can become an efficient platform for optimizing preclinical studies of novel targeted drugs.

Robust and Efficient Out-of-Plane Exciton Transport in Two-Dimensional Perovskites via Ultrafast Förster Energy Transfer.

Two-dimensional (2D) perovskites, comprising inorganic semiconductor layers separated by organic spacers, hold promise for light harvesting and optoelectronic applications. Exciton transport in these materials is pivotal for device performance, often necessitating deliberate alignment of the inorganic layers with respect to the contacting layers to facilitate exciton transport. While much attention has focused on in-plane exciton transport, little has been paid to out-of-plane interlayer transport, which presumably is sluggish and unfavorable. Herein, by time-resolved photoluminescence, we unveil surprisingly efficient out-of-plane exciton transport in 2D perovskites, with diffusion coefficients (up to ∼0.1 cm2 s-1) and lengths (∼100 nm) merely a few times smaller or comparable to their in-plane counterparts. We unambiguously confirm that the out-of-plane exciton diffusion coefficient corresponds to a subpicosecond interlayer exciton transfer, governed by the Förster resonance energy transfer (FRET) mechanism. Intriguingly, in contrast to temperature-sensitive intralayer band-like transport, the interlayer exciton transport exhibits negligible temperature dependence, implying a lowest-lying bright exciton state in 2D perovskites, irrespective of spacer molecules. The robust and ultrafast interlayer exciton transport alleviates the constraints on crystal orientation that are crucial for the design of 2D perovskite-based light harvesting and optoelectronic devices.

A coumarin-naphthalimide-based ratiometric fluorescent probe for nitroxyl (HNO) based on an ICT-FRET mechanism

Nitroxyl (HNO) is an important reactive nitrogen that is associated with various states in physiology and pathology and plays a unique function in living systems. So, it is important to exploit fluorescent probes with high sensitivity and selectivity for sensing HNO. In this paper, a novel ratiometric fluorescent probe for HNO was developed utilizing intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) mechanisms. The probe selected coumarin as energy donor, naphthalimide as energy receptor and 2-(diphenylphosphino)benzoate as the sensing site for detecting HNO. When HNO was not present, the 2-(diphenylphosphino)benzoate unit of the probe restricted electron transfer and the ICT process could not occur, leading to the inhibition of FRET process as well. Thus, in the absence of HNO the probe displayed the intrinsic blue fluorescence of coumarin. When HNO was added, the HNO reacted with the 2-(diphenylphosphino)benzoate unit of the probe to yield a hydroxyl group which resulting in the opening of ICT process and the occurring of FRET process. Thus, after providing HNO the probe displayed yellow fluorescence. In addition, the probe showed good linearity in the ratio of fluorescence intensity at 545 nm and 472 nm (I545 nm/I472 nm) with a concentration of HNO (0.1–20 μM). The probe processed a detection limit of 0.014 μM and a response time of 4 min. The probe also specifically identified HNO over a wide pH scope (pH = 4.00–10.00), including physiological conditions. Cellular experiments had shown that this fluorescent probe was virtually non-cytotoxic and could be applied for ratiometric sensing of HNO in A549 cells.

Synthesis of P, N-dopped carbon nanosheets for highly sensitive fluorescence analysis of nitrofuran antibiotics in fish

The misuse of antibiotics has caused serious impacts on food safety and human health, making it crucial to develop rapidly and highly sensitive methods for detecting trace nitrofuran antibiotics (NFs). In this study, phosphorus, nitride-doped carbon nanosheets (PN/CNs) were synthesized using a simple hydrothermal method based on graphitic carbon nitride. This prepared material showed excellent water solubility and stable optical properties. A new fluorescence sensing platform based on PN/CNs was constructed for the highly sensitive detection of four NFs. This sensitivity was mainly attributed to the fluorescence resonance energy transfer (FRET) mechanism. The limits of detection for nitrofurazone, nitrofurantoin, furazolidone and furaltadone were determined to be 13.41, 15.24, 16.37 and 19.94 nM, respectively. The high sensitivity and selectivity of PN/CNs for these four NFs were thoroughly evaluated by the Stern-Volmer equation and FRET quenching efficiency. This proposed method exhibited high sensitivity and can be successfully applied to detect NFs in fish.

Click generated photochromic naphthalenediimide-dithienylethene diad: Application in deciphering secret codes

Photochromic molecules with efficient fluorescence switching capability remain a core research interest among the scientific community for the application in security technologies and anti-counterfeiting measures. A dithienylethene-naphthalene diimide diad was designed and synthesized using Cu(I) catalysed click reaction between a fluorescent core substituted naphthalene diimide (cNDI) and photochromic dithienylethene (DTE) molecule, which demonstrated excellent photocyclization (ksolution = 0.0359 s−1, ksolid = 0.0122 s−1) and photocycloreversion (ksolution = 0.01737 s−1, ksolid = 0.00456 s−1) dynamics with high fluorescence quantum yield (5o ΦF = 0.39, PSS ΦF = 0.05). The fluorescence property of the molecule was switched ‘on-off’ by UV and visible light irradiation respectively via Förster resonance energy transfer (FRET) mechanism in solution state as well as in solid state, which was further corroborated with DFT studies. In view of efficient fluorescence switching behaviour and high fatigue resistance properties (25 cycles), the molecule was successfully applied in secret code encryption-decryption purposes using barcode demonstrating real-life applicability of the molecule in security technologies.

A Renal Clearable Nano-Assembly with Förster Resonance Energy Transfer Amplified Superoxide Radical and Heat Generation to Overcome Hypoxia Resistance in Phototherapeutics.

Given that type I photosensitizers (PSs) possess a good hypoxic tolerance, developing an innovative tactic to construct type I PSs is crucially important, but remains a challenge. Herein, we present a smart molecular design strategy based on the Förster resonance energy transfer (FRET) mechanism to develop a type I photodynamic therapy (PDT) agent with an encouraging amplification effect for accurate hypoxic tumor therapy. Of note, benefiting from the FRET effect, the obtained nanostructured type I PDT agent (NanoPcSZ) with boosted light-harvesting ability not only amplifies superoxide radical (O2 •-) production but also promotes heat generation upon near-infrared light irradiation. These features facilitate NanoPcSZ to realize excellent phototherapeutic response under both normal and hypoxic environments. As a result, both in vitro and in vivo experiments achieved a remarkable improvement in therapeutic efficacy via the combined effect of photothermal action and type I photoreaction. Notably, NanoPcSZ can be eliminated from organs (including the liver, lung, spleen, and kidney) apart from the tumor site and excreted through urine within 24 h of its systemic administration. In this way, the potential biotoxicity of drug accumulation can be avoided and the biosafety can be further enhanced.

Construction of nitrogen-doped carbon dots-based fluorescence probe for rapid, efficient and sensitive detection of chlortetracycline

Antibiotics are widely used in clinical medicine due to their excellent antibacterial abilities. As typical emerging pollutants, their misuse can lead to excess antibiotics entering the environment, causing antimicrobial resistance and leading to serious health problems via food chain. Herein, a nano-fluorescent probe based on nitrogen-doped carbon dots (N-CDs) was constructed for the sensitive detection of chlortetracycline (CTC). N-CDs with stable fluorescence were synthesized by hydrothermal method using alizarin red and melamine as raw materials. The N-CDs exhibited significant independence to excitation wavelength. The fluorescence of N-CDs was significantly quenched by CTC ascribing to the fluorescence resonance energy transfer mechanism. The concentration of N-CDs, solution pH and incubation time were optimized to obtain the optimal detection parameters. Under optimal conditions, CTC exhibited excellent linearity over the range of 20–1200 μg/L, and the detection limit was 8.74 μg/L. The method was validated with actual water samples and achieved satisfied spiked recoveries of 97.6–102.6%. Therefore, the proposed method has significant application value in the detection of CTC in waters.

Investigating the influence of carbon dots on β-Ca2SiO4:Ce3+ phosphors derived from agro-waste for diverse applications

A series of blue-emitting composite based on 3 wt% carbon dots in β-Ca2SiO4:Ce3+ (3 wt% CDs@β-CSO:Ce3+) was synthesized through a hydrothermal method, aiming to enhance applications in latent fingerprint (LFP) detection, anti-counterfeiting (AC) measures, and optical thermometry. The X-ray diffraction (XRD) analysis confirmed that these phosphors possess a monoclinic crystal structure. Under 356 nm excitation, the Ce3+ doped β-Ca2SiO4 phosphors (β-CSO:Ce3+) display a broad blue emission peak at 431 nm, attributed to the 5d → 4f electric dipole transition of Ce3+, while the inclusion of Carbon dots (CDs) shifts this emission to 442 nm. This shift and the improved photoluminescence (PL) intensity are thought to result from the Fӧrster Resonance Energy Transfer (FRET) mechanism. The optimal concentration of Ce3+ ions was determined to be 5 mol%, as higher concentrations led to a decrease in emission intensity due to concentration quenching (CQ). Additionally, a fabricated white light diode using these phosphors achieved chromaticity coordinates of (0.344, 0.330) according to the Commission International de L'Eclairage (CIE), with the CIE, correlated colour temperature (CCT), and colour purity (CP) metrics indicating a bright green output with values of (0.1486, 0.0433), 1759 K, and 96.4%, respectively. The optimized 3 wt% CDs@β-CSO:5Ce3+ composite demonstrated a remarkable CP of 99.9%. Notably, the phosphors maintained 85.77% of their emission intensity at 423 K, showcasing exceptional thermal stability. A novel approach utilizing sketch pen and brush mode was developed to apply the optimized AC security ink, allowing for the creation of various intricate patterns. The resulting AC tags featured high resolution and durability. These findings underscore the 3wt%CDs@β-CSO:5Ce3+ composite as superior luminescent materials for use in fields requiring LFP, AC strategies, and optical thermometry.