Fluorescence Resonance Energy Transfer Mechanism Research Articles

Turn-On fluorescence resonance energy transfer (FRET)-based electrospun fibrous membranes: Rapid and ultrasensitive test strips for on-site detection of Mercury (II) ion

Creation of a highly sensitive test strip that can provide simple, rapid, and high-throughput determination of Hg2+ levels in consumer goods and industrial waste is extremely challenging since the portability and convenience of the paper-based platform often come at the expense of inferior sensitivity. In this work, a fluorescent electrospun fibrous membrane that can report mercury contamination down to sub-ppb level in less than a minute is developed. The key success of this user-friendly device relies on the design of novel mercury-favored organic dye (NF06) that displays specific fluorescence enhancement – “Turn-On” positive results – through fluorescence resonance energy transfer (FRET) mechanism and exhibits extremely large Stokes shift of 248 nm. The surface chemistry of the cellulose acetate(CA)/polycaprolactone(PCL) electrospun fibers on which the NF06 sensor is immobilized has been found to efficiently facilitate the FRET operation of the sensor. As a result, the detection limit of this NF06 strip reaches 0.309 ppb (0.697 nM), approximately an order of magnitude lower than the maximum mercury level permitted in drinking water (2 ppb) recommended by the US Environment Protection Agency. Instrument-free visual readout of Hg2+ level-dependent fluorescence enhancement after dipping the strips in Hg2+-spiked drinking water and skin whitening serum demonstrates that these low-cost test strips could certainly be used by general consumers for safety evaluation as well as by regulatory agencies for large-scale screening of a variety of commercial products without the need for expensive and highly sensitive detectors.

Fluorescent nitrogen-doped carbon dots for high selective detecting p-nitrophenol through FRET mechanism

A facile, friendly and one-step hydrothermal protocol was used to synthesize nitrogen-doped carbon dots (N-CDs) by utilizing hexamethylenetetramine and ethanediamine as the carbon and nitrogen sources. It demonstrated good water solubility and fluorescence properties were stable, whether in acidic or alkaline. Quantum yield (QY) of N-CDs was 8.3% at an excitation wavelength of 325 nm with maximum emission at 425 nm. The fluorescence of N-CDs achieved very high fluorescence quenching of 60% in the detection of p-nitrophenol (p-NP) in aqueous medium via fluorescence resonance energy transfer (FRET) mechanisms. Under optimum conditions, fluorescence probs of N-CDs had strong selectivity to p-NP, and the fluorescence intensity was linearly proportional to p-NP concentration from 0.5 to 70.0 μM with a detection limit of 0.201 μM. The corresponding cell experiments were also performed, indicating that the prepared N-CDs possessed low cytotoxicity and good biocompatibility. Meanwhile, the N-CDs can be used for the determination of p-NP in river water and industrial wastewater.

Visual-afterglow dual-mode immunochromatographic strip for 17β-estradiol detection in milk

The continuous intake of 17β-estradiol (E2) residue from animal-derived food may pose a threat to the health of consumers, so the rapid screen and detection of E2 is very necessary. Although visual immunochromatographic strip (ICS) has played a great role in food safety control such as the screen of many food contaminants, it cannot meet the requirements for E2 detection due to the insufficient sensitivity of traditional visual ICS and the low concentration range of estrogen in food. Here, we developed a dual-mode ICS strategy to achieve rapid and highly sensitive detection of E2. Based on the visual detection mode of a competitive ICS, the afterglow detection mode working in fluorescence resonance energy transfer mechanism was introduced by using the afterglow particles (APs) as energy donor and gold nanoparticles (AuNPs) as energy acceptor. In this method, large APs of micron size with superior afterglow were applied as the test zone-fixed fluorescence signal source, thus the contradiction between migration and afterglow characteristics was skillfully resolved. In addition, a 6 W UV lamp was used as the light source to excite APs, and a smartphone was used to capture an image of 0.5 s after the UV light was turned off to effectively remove the autofluorescence from the strips and improve the signal-to-noise ratio. The limit of detection of this afterglow mode was 0.5 ng/mL, twenty times more sensitive than that of visual mode (10 ng/mL). The strategy has been successfully applied to the detection of estradiol in milk and verified by HPLC–FLD.

A Simple Determination of Trinitrotoluene (TNT) Based on Fluorescence Quenching of Rhodamine 110 with FRET Mechanism.

Sensitive and selective detection of nitroaromatic explosives is an important issue in regard to human health, environment, public security and military issues. In this study, a simple and sensitive fluorescence quenching - based assay utilizing Rhodamine 110 as fluorophore probe was developed for the determination of trinitrotoluene (TNT). This sensitive fluorometric method could measure the decrease in fluorescence of Rhodamine 110 (λex = 490nm, λem = 521nm) owing to the primary amine groups of Rhodamine 110 (different from other rhodamines) capable of donor-acceptor interaction with TNT. The resulting TNT-amine complex can strongly quench the fluorescence emission of Rhodamine 110 by fluorescence resonance energy transfer (FRET) which occurs as the excited Rhodamine 110 fluorophore (donor) transfers its energy to TNT (acceptor) by non-radiative dipole-dipole interaction. Fluorescence quenching varied linearly with TNT concentration, with LOD and the LOQ of 0.71 and 2.38mg L- 1 TNT, respectively. Similar explosives, common soil ions, and possible camouflage materials were found not to interfere with the proposed method, offering significant advantages with its easy methodology, low-cost, sensitivity, and rapidity of analysis. FRET mechanism based on dye donor-TNT acceptor interaction.

Multichannel Electron Transmission and Fluorescence Resonance Energy Transfer in In2S3/Au/rGO Composite for CO2 Photoreduction.

Efficient electron transmission is an important step in the process of CO2 photoreduction. In this paper, a multi-interface-contacted In2S3/Au/reduced graphene oxide (rGO) photocatalyst with the fluorescence resonance energy transfer (FRET) mechanism has been successfully prepared by the solvothermal, self-assembly, and hydrothermal reduction processes. Photocatalytic CO2 reduction experiments showed that the In2S3/Au/rGO (IAr-3) composite exhibited excellent photoreduction performance and photocatalytic stability. The yields of CO and CH4 obtained after the photoreduction process with IAr-3 as the catalyst were around 4 and 6 times higher than those of pure In2S3, respectively. Photoelectrochemical analysis showed that the multi-interface contact and FRET mechanism greatly improved the generation, transmission, and separation efficiency of carriers photogenerated within the photocatalyst. In situ FTIR test was applied to analyze the photocatalytic CO2 reduction process. 13C isotope tracer test confirmed that the carbon source of CO and CH4 was the CO2 molecules in the photoreduction process rather than the decomposition of catalyst or TEOA. A potential enhanced photocatalytic mechanism has been discussed in total.

Influence of bovine hemoglobin on the disruption of fluorescence resonance energy transfer between zinc sulfide quantum dots and fluorescent silica nanoparticles

Herein, the fluorescence resonance energy transfer (FRET) system composed of Zinc sulfide quantum dots (ZnS QDs) and fluorescent silica nanoparticles (FS) and the influence of bovine hemoglobin (BHb) on the system were studied using spectroscopy. UV–vis, SEM and XRD were used to characterize ZnS QDs. FT-IR spectroscopy, Zeta potential, DLS and fluorescence spectroscopy confirmed the synthesis of FS. The mechanism and efficiency of FRET in aqueous solution and BHb solution has been analyzed by fluorescence spectroscopy and Förster's non-radiative energy transfer theory, which implied that in the absence of BHb, there is dynamic quenching between ZnS QDs and FS. In the presence of BHb, it is static quenching. And BHb interfered with the stability of the ZnS QDs-FS FRET system and reduced FRET efficiency. Moreover, steady-state, synchronous fluorescence spectra and Raman spectroscopy showed that ZnS QDs caused an increase of hydrophilicity of the chromophore microenvironment, and FS may induce heme degradation to form fluorescent heme product, resulting in increased fluorescence intensity. This investigation will be significant in exploring the toxicity profile of ZnS QDs-FS FRET system for their in vivo.

Enhancmentation of Photo-Thermal Lens of Fluorescence Molecules by Fluorescence Resonance Energy Transfer Mechanism.

The photo-thermal lens technique is based on the measurement of the gradient temperature that is produced in an illuminated sample by laser beam as a result of non-radiative relaxation. The sensitivity of photo-thermal lens is higher than conventional absorption techniques, due to the direct measurement of absorbed energy. However, the main drawback of the photo-thermal lens technique is the inability to measure molecules that release their excess energy of absorption in the form of radiation relaxation. In fluorescence molecules, because their excess energy is released by radiation, the photo-thermal lens is insignificant. In this research, we aim to increase the photo-thermal lens sensitivity of the fluorescence molecules by selecting the appropriate acceptor for the fluorescence molecules as the donor. We investigated the effect of the presence of AuNPs on the photo-thermal lens of di-triazene (DTA) as fluorescence molecules. We observed that AuNPs enhanced the photo-thermal lens of DTA. The quantum yield of DTA was calculated to be 90.45%. The energy transfer from DTA to AuNPs occurs by fluorescence resonance energy transfer (FRET) mechanism. The FRET efficiency was 83.43%. In the presence of AuNPs, the photo-thermal lens of the DTA was amplified by four times more. The calibration curve of DTA is linear in the range of 0.1 to 110ng/mL. The limited of detection (LOD) value of 0.08ng/mL is calculated.

A Fluorescent Sensor for Daunorubicin Determination Using 808 nm-excited Upconversion Nanoparticles

Daunorubicin is a common antineoplastic agent used for the treatment of lymphoma and acute leukemia. Here, we report an 808 nm-excited, citric acid coated, core–shell upconversion fluorescent sensor for daunorubicin (DAU) detection in aqueous solutions. The designed Nd3+ doped core–shell structure significantly raises the upconversion fluorescence intensity, while the presence of citric acid ligands helps to reduce the surface quenching effect exerted by water and improve the dispersibility. The upconversion fluorescence of nanoparticles is efficiently quenched in the presence of DAU via a fluorescence resonance energy transfer mechanism. The dynamic quenching constant was 1.58 × 104 M−1. The fluorescence intensity ratio showed a good linear response to DAU concentration in the range of 0.1 μM to 70 μM with a detection limit of 0.06 μM. The sensing method was simple, rapid, and low-cost and was further applied to determine the levels of DAU in urine with spike recoveries from 97.3% to 101.5%. The proposed fluorescent sensor holds great potential for in vivo imaging and detection of DAU.

A singlet oxygen self-reporting photosensitizer for cancer phototherapy.

Photodynamic cancer therapy has attracted great attention with the increasing threat of tumors, and improving its therapeutic efficacy is highly desirable. However, due to the highly efficient intersystem crossing potency to generate singlet oxygen (1O2), high-efficiency photosensitizers often suffer from weak fluorescence and excess injury to normal tissue. To overcome these obstacles, here we show a reliable self-reporting strategy for real-time monitoring of therapeutic progression. As a proof of concept, a molecular dyad is designed by connecting benzo[a]phenoselenazinium (NBSe) to rhodamine (Rh), namely Rh-NBSe, where the fluorescence of the Rh unit is initially suppressed by the fluorescence resonance energy transfer mechanism, but enabled to recover as feedback signal once the reaction with photosensitized 1O2 takes place. The observed fluorescence increases by irradiation in vitro and in vivo successfully reflect the real-time 1O2 generation speed in photodynamic therapy. In addition, the favorable therapeutic advantages of Rh-NBSe are also verified, for example, the high ΦΔ (0.8) and the low IC50 (0.2 μM, 6 J cm−2). Based on the therapeutic ability and real-time 1O2 self-reporting ability, Rh-NBSe demonstrates significant potential for self-regulating phototherapy.

Ternary Organic Semiconductor Blend for High Photovoltaic Performance Under Both Indoor and Outdoor Operating Conditions

Ternary blend in Organic Photovoltaics (OPVs) have been known as a way to increase performance in both low light intensity and AM 1.5G conditions. We have conducted a comparative study on 2 Donors:1 Acceptor (2D:1A) blends and 1 Donor:2 Acceptors (1D:2A) blends; 1D:2A blends have the higher performance and thermal stability than 2D:1A blends. In particular, non-fullerene acceptor (NFA) used for the 1D:2A blends have a good effect on packing property and crystallinity. The 1D:2A with optimized morphology reduced charge recombination on various irradiation conditions while the efficiency of 2D:1A devices depends on the fluorescence resonance energy transfer mechanism. The synergistic effect of 1D:2A blend with NFAs secures better efficiency and sustainable photoelectric properties under both indoor and outdoor operation conditions. Our analysis of the experiments reveals that NFA optimizes the arrangement of molecules to build more efficient ternary bulk heterojunctions in 1D:2A blends. Finally, the optimized ternary OPVs show effectively high power conversion efficiency of over 25% in both 200 lux and 1000 lux light–emitting diode conditions and present new opportunities in various practical applications.

TNT sensor based on accumulation layer and effective distance of FRET mechanism with ultra-high sensitivity

Common methods of 2,4,6-trinitrotoluene (TNT) detection are based on direct detection to the concentration of TNT. If TNT can be accumulated first to increase partial concentration near the sensor and detected by sensing materials then, the detection performance can be significantly improved. As we know, fluorescence resonance energy transfer (FRET) is widely used as the sensing mechanism in TNT detection, which has an effective range of 10 nm. Based on this, we built an accumulation layer between sensing materials and TNT within effective range of FRET, where exists a large quantity of amino groups. The Amino groups can adsorb TNT and realize accumulation function. The accumulation and sensing layer played different roles in the detection of TNT based on distinct mechanism. Accumulation layer was realized by forming Meisenheimer complex between TNT and amino groups while sensing layer was realized by FRET. Via both two layers and mechanisms, the sensors achieved ultra-high sensitivity to TNT, with a limit of detection (LOD) of 0.6 nM and a linear range of 1–20 nM. Compared with pure graphene quantum dots (GQDs), the KSV of sensor in this work to TNT increased for about 14 times. The accumulation-detection path provides an effective method for the measurement of TNT with ultra-low concentration.

Synthesis of Cit-NaYF4: Yb, Tm@phenolic formaldehyde resin (PFR)@Au composites as an optical sensor for the detection of Cu(Ⅱ) ions

Abstract A facile hydrothermal method was employed to synthesize the core-shell structure up-conversion Cit-NaYF4:Yb, Tm (UC)@phenolic formaldehyde resin (PFR) nanoparticles (NPs). UC NPs can enhance the emission intensity of the PFR shell, which contributes to improving the fluorescence detection sensitivity of UC@PFR NPs. Au NPs were loaded onto the surface of PFR shell in situ through the good reduction of the hydroxyl group in PFR. The emission intensity of UC@PFR decreased greatly in the presence of Au nanoparticles due to fluorescence resonance energy transfer (FRET) mechanism between UC@PFR and Au NPs. However, the mixture of H2O2 and SCN− could prevent the decrease of emission intensity of UC@PFR@Au composites because of the oxidation reaction between H2O2 and Au nanoparticles in the presence of SCN−. Also, Cu2+ can prevent the oxidation reaction to occur, which results in the slight change of emission intensity of UC@PFR@Au in the presence of H2O2 and SCN−. Thus, the as-synthesized UC@PFR@Au particles were used to detect Cu2+ sensitivity. The good linear correlation equation between the fluorescence intensity of UC@PFR@Au particles and the concentration of Cu2+ in the range of 4–90 nM (R2 = 0.99) was established with the low detection limit (LOD) of 0.54 nM. Furthermore, the as-synthesized particles were employed to detect Cu2+ in the actual water sample with satisfying results.

Designing and construction of genetically encoded FRET-based nanosensor for qualitative analysis of digoxin

Nanobiotechnological improvements defined on the utilization of biological materials and principles have enormously partaken to revolutionize physical, chemical, and biological sciences. However, the exploration of plant nanobiotechnology is still in its outset. The search for novel tools to monitor plant biomolecules is an emerging issue for the nanobiotechnologists. Given this, a genetically encoded FRET-based nanobiosensor has been developed to monitor the popular plant cardiac glycoside – digoxin, which is used as the most common prescription drug for heart-related illnesses across the world. Digoxin is sourced from the leaves of the foxglove plant (Digitalis purpurea L.) and has a significant demand in the medical sector. Moreover, with the rising popularity of the herbal formulations in the global market, attention towards the authentication and quality control of the herbal drugs is important. Furthermore, digoxin has a very narrow therapeutic range, i.e., 0.6 nM - 2.6 nM. Therefore, strict monitoring of blood digoxin levels is necessary. Besides, previously used techniques for drug authentication and quantification of small-molecule drugs in blood samples are not the best choice available. The nanobiosensor is based on the FRET (Fluorescence Resonance Energy Transfer) mechanism, and it is constructed in such a way that it gives a changed FRET output in the presence of digoxin. Two fluorophores, enhanced cyan fluorescent protein (ECFP) and Venus, were attached on either end of the sensory domain - human nuclear receptor ROR-gamma (RORγt). The developed nanobiosensor was named as fluorescent indicator protein for digoxin, (FLIP-digoxin). The ligand binding affinity of FLIP-digoxin was calculated as 425 μM. Affinity mutants of the FLIP-digoxin were also generated to measure digoxin in wide concentration ranges. This sensor offers high-throughput qualitative analysis of digoxin in Digitalis preparations procured from local drug stores. It confirms the authenticity of the preparations through the detection of digoxin. The FLIP-1n was also able to monitor digoxin concentration in serum samples in lesser than 5 min. The nanobiosensor was found pH stable, digoxin-specific, non- interfered by the biological serum species and can perform high throughput screening of the Digitalis powder, infusion and tincture preparations.

Selective sensing of Mn2+ based on ZnCdS/ZnS QD/carboxymethyl chitosan/g-C3N4 nanosheet nanocomposite film by the conformational regulation of polymer chain

A novel film consisting of ZnCdS/ZnS quantum dots (QDs) and g-C3N4 nanosheets conjugated with carboxymethyl chitosan (CMCS) chains via weak bonds was built. The Mn2+ in contact with the composite film forced the chitosan to undergo conformational changes, resulting in the intermolecular complex R–COO–(Mn2+)–NH2–R, which enhanced the fluorescence. The film was developed for trace Mn2+ determination according to the fluorescence resonance energy transfer mechanism by the enhancement effect of the film. The sensor exhibited a good linearity (F = 2.0852C + 168.667) for Mn2+ at a concentration of 1.961 × 10−6–1.667 × 10−5 mol/L under certain conditions with a correlation coefficient of 0.9981. The film was successfully used to determine Mn2+ with recoveries in the range of 90%–107% in the real water samples. The proposed method provides a simple, facile, sensitive, and fast detection method for Mn2+.

Fabrication of PAA coated green-emitting AuNCs for construction of label-free FRET assembly for specific recognition of T-2 toxin

In view of numerous encouraging requisitions, toxins quantification is an imperative research field of food safety. Herein, we synthesized a green-emitting l-arginine@6-aza-2-thiothymine-protected gold nanocluster (Arg@ATT-AuNCs) through host-guest assemblages. The Arg@ATT-AuNCs were capped with polyacrylic acid (PAA) to construct the PAA@Arg@ATT-AuNCs nanoparticles (NPs). The fluorescent and visual detection of T-2 (trichothecenes A) is based on PAA@Arg@ATT-AuNCs NPs and PDDA-aggregated-AuNPs assembly. In the absence of a target, electrostatic interaction of the aptamer-PDDA complex prevents the aggregation of AuNPs. The scattered AuNPs (absorbance at 520 nm) can quench the fluorescence intensity (F.I) of PAA@Arg@ATT-AuNCs NPs (emission at 530 nm) following FRET (Fluorescence resonance energy transfer) mechanism. The target addition leads in toxin-aptamer assemblies and succeeding PDDA is free to aggregate AuNPs (absorbance at 665 nm), resulted in recovered F.I. The developed bioassay sensitively used for quantification of T-2 with LOD of 0.57 pg mL−1 (0.001−100 ng mL−1). Spiking analysis reveals the robustness and efficiency of bioassay in maize and highly correlated with the standard ELISA method. We envision that the present study will substantively contribute to synthesize new core-shell NCs and may be considered as a new method for onsite detection.

A novel strategy for detection of small molecules based on aptamer/gold nanoparticles/graphitic carbon nitride nanosheets as fluorescent biosensor

Herein, a novel ultrasensitive strategy has been developed by designing a label free fluorescent nano-aptasensor for monitoring of small moecules in human plasma. In this nano-aptasensor, graphitic carbon nitride nanosheets were used as fluorescent probe. The fluorescence intensity of the probe was decreased by interaction between graphitic carbon nitride nanosheets and label-free aptamer/gold nanoparticles conjugate, via Fluorescence resonance energy transfer mechanism. Upon addition of the analyte, the fluorescence of graphitic carbon nitride nanosheets was restored due to the aptamer/analyte interaction, and the aggregation of gold nanoparticles in the presence of salt. The influence of various factors on sensing method was investigated, and under the approved conditions, the fluorescence signal showed a linear relation with Digoxin concentration in the range of 10–500 ng L−1 with limit of detection down to 3.2 ng L−1 relative standard deviations for 25, 100 and 500 ng L−1 of analyte concentrations were 2.6, 4.0 and 6.5%, respectively. This strategy provided a simple, rapid, cost effective and reproducible experimental model, with successful application for determination of Digoxin in plasma samples without any pretreatment steps.

Reversible spiropyran-based chemosensor with pH-switches and application for bioimaging in living cells, Pseudomonas aeruginosa and zebrafish

Intracellular pH was tightly regulated in many biological processes in which cells must control pH changes within a precise range. Hence, tracing intracellular pH variation was important for understanding the physiological and pathological processes. Although fluorescent probes can be a necessary tool for detecting changes in pH, there are many limitations to existing probes, such as background interference, large cytotoxicity, and poor permeability, which need to be urgently overcome. In this work, a ratiometric and colorimetric chemosensor based on spiropyran (SP-DCCH) was fabricated for monitoring pH change using fluorescence resonance energy transfer mechanism. SP-DCCH has demonstrated the advantages of high sensitivity and selectivity, outstanding permeability and hypotoxicity. Moreover, SP-DCCH displays a pH-sensitive response from 1.68 to 7.21 (pKa = 4.87) and a linear response from pH 3.81 to 6.01, which was desirable for detecting pH change in living biosystem. As expected, the results confirmed that the response signal was pH-dependent and regulated via switchable forms between spiropyran and merocyanine. Spectacularly, SP-DCCH has successfully realized sensing and mapping pH in living cells, P. aeruginosa and zebrafish. The above results exhibited that SP-DCCH could be a powerful tool for sensing and visualizing pH in living systems.

A conjugated gold nanoparticle-azacyanine off-on-off fluorescence probe for sensitive and selective detection of G-quadruplexes

G-quadruplex secondary structures have gained significant recognition due to the discovery of their involvement in regulation of gene expression and their association with many diseases such as cancer and neurological disorders. Consequently, the need for the recognition and characterization of G-quadruplex structures has increased considerably. Here, we present a rapid, facile and sensitive off-on-off in vitro platform for G-quadruplex detection, based on the gold nanoparticle-azacyanine5 (AuNP-Aza5) conjugated fluorescence probe. The conjugated probe is governed by Fluorescence Resonance Energy Transfer (FRET) mechanism between the fluorophore molecule, Aza5, and AuNPs. The fluorescence of Aza5 that was hindered by AuNPs (off), was restored in the presence of L-cysteine (on) until the addition of a G-quadruplex structure (off). The developed sensing platform selectively responds to G-quadruplex structures formed within the promoter regions of VEGF-Pu22, K-RAS, C-myc and BCL-2. It doesn’t exhibit a similar response to the other secondary structures such as single, double or triple stranded nucleic acid structures. The detailed investigation of the probe with VEGF-Pu22 as a model G-quadruplex structure revealed a linear response between the concentration range of 0.032–0.347 μM with a detection limit of 12.66 nM.

A glutathione-responsive photosensitizer with fluorescence resonance energy transfer characteristics for imaging-guided targeting photodynamic therapy

Here, we have synthesized and characterized a novel activatable photosensitizer (PS) 8a in which two well-designed boron dipyrromethene (BODIPY) derivatives are utilized as the photosensitizing fluorophore and quencher respectively, which are connected by a disulfide linker via two successive Cu (І) catalyzed click reactions. The fluorescence emission and singlet oxygen production of 8a are suppressed via intramolecular fluorescence resonance energy transfer (FRET) from the excited BODIPY-based PS part to quencher unit, but both of them can be simultaneously switched on by cancer-related biothiol glutathione (GSH) in phosphate buffered saline (PBS) solution with 0.05% Tween 80 as a result of cleavage of disulfide. Also, 8a exhibits a bright fluorescence image and a substantial ROS production in A549 human lung adenocarcinoma, HeLa human cervical carcinoma and H22 mouse hepatoma cells having a relatively high concentration of GSH, thereby leading to a significant photocytotoxicity, with IC50 values as low as 0.44 μM, 0.67 μM and 0.48 μM, respectively. In addition, the photosensitizer can be effectively activated and imaged in H22 transplanted hepatoma tumors of mice and shows a strong inhibition on tumor growth. All these results suggest that such a GSH-responsive photosensitizer based on FRET mechanism may provide a new strategy for tumor-targeted and fluorescence imaging-guided cancer therapy.

Surfactant-assisted synthesis of fluorescent SmCrO3 nanopowder and its application for fast detection of nitroaromatic and nitramine explosives in solution

In this work, SmCrO3 nanopowder was synthesized via sol gel route assisted by citric acid and cetyltrimethylammonium bromide (CTAB) in water. The obtained SmCrO3 perovskite oxide nanopowder exhibits strong fluorescence at near-UV and visible regions in polar solvents such as ethyl acetate (EtOAc), tetrahydrofuran (THF) and ethyl methyl ketone (EMK) that its fluorescence could be strongly quenched by nitro explosives such as TNP, TNT, HMX and RDX at room temperature. Thus, the prepared fluorescent nanopowder was used as chemosensor for selective detection of nitro explosives. The lowest detection limit (6.0 × 10−8 M) was observed for HMX and the highest detection limit (9.6 × 10−7 M) was obtained for TNP in THF solvent. The obtained results confirm that the quenching effect of the nitro explosives on the fluorescence signal of the SmCrO3 nanopowder can be take place fluorescence resonance energy transfer (FRET) mechanism. This rare earth orthochromite based perovskite will introduce a new group of inorganic compounds that potentially can be effective for rapid and sensitive sensing for trace value of the nitro explosives. In addition, due to great chemical and thermal stability of chromite perovskite structures, these chemosensors can be easily recovered.