Fluorescence Enhancement Research Articles

Design, synthesis, and antibacterial evaluation of a thiazole-based schiff base with fluorescence sensing for Cu2+ ions

ABSTRACT A novel thiazole-based heterocyclic Schiff base (TSB) was designed and synthesised. The synthesised Schiff base was structurally characterised by using fluorescence, FT-IR and 1H NMR. After structural characterisation, the sensing properties of TSB were investigated towards different metal ions such as such as Cr3+, Hg2+, Cu2+, Cd2+, Co2+, Ni2+, Zn2+, Ag+, Mg2+, Ca2+, Li+, Na+, and K+. A significant fluorescence enhancement were observed in the fluorescence emission of TSB at 584 nm upon interaction with Cu2+ ions as compared to other due to formation of TSB-Cu 2+ complex. The 2:1 binding mode between TSB and Cu2+ ions was confirmed by Job`s plot using fluorescence spectroscopy. The limit of detection (LOD) was calculated to be 0.0051 ppm (0.081 µM). The chemosensor TSB effectively detected Cu2+ in various environmental samples, demonstrating high recovery rates ranging from 88.0 ± 0.35% to 107.0 ± 0.47%. The antibacterial activity of Schiff base TSB and its complex TSB-Cu 2+ was also evaluated against various bacterial strain. The results showed that TSB exhibited good antibacterial activity, with the highest zone of inhibition reaching 13.54 ± 0.35 nm. In contrast, the TSB-Cu 2+ complex consistently demonstrated improved antibacterial activity, with the highest zone of inhibition recorded at 15.38 ± 0.72 nm.

Role of Oxygen Defects in Eliciting a Divergent Fluorescence Response of Single-Walled Carbon Nanotubes to Dopamine and Serotonin.

Modulating the optical response of fluorescent nanoparticles through rational modification of their surface chemistry can yield distinct optical signatures upon the interaction with structurally related molecules. Herein, we present a method for tuning the fluorescence response of single-walled carbon nanotubes (SWCNTs) toward dopamine (DA) and serotonin, two structurally related monoamine-hydroxylated aromatic neurotransmitters, by introducing oxygen defects into (6,5) chirality-enriched SWCNTs suspended by sodium cholate (SC). This modification facilitated opposite optical responses toward these neurotransmitters, where DA distinctly increased the fluorescence of the defect-induced emission of SWCNTs (D-SWCNTs) 6-fold, while serotonin notably decreased it. In contrast, pristine, defect-free SWCNTs exhibited similar optical responses to both neurotransmitters. The underlying mechanisms for the divergent fluorescence response were found to be polydopamine (PDA) surface adsorption in the case of the fluorescence enhancement in response to DA, while the fluorescence decrease in response to serotonin was attributed to enhanced solvent relaxation effects in the presence of defects. Importantly, the divergent optical response of D-SWCNTs to DA and serotonin, via the introduction of defects, was validated in complex biological environments such as serum. Further, the generality of our approach was confirmed by the demonstrations of a divergent fluorescence response of D-SWCNTs suspended by an additional dispersant, namely lipid-polyethylene glycol (PEG). This study offers promising avenues for the broad applicability of surface functionalization of SWCNTs to achieve divergent responses toward structurally related molecules and advance applications in sensing, imaging, and diagnostic technologies.

Bioimaging potential: Comparative study of ZnO nanoparticles synthesized via green and chemical routes

Zinc Oxide Nanoparticles (ZnO NPs) were synthesized through chemical and green synthesis methods employing Ficus religiosa (peepal) leaf extract. The synthesized nanoparticles underwent comprehensive characterization using various techniques such as Powder X-ray Diffractometry (PXRD), Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Photoluminescence (PL), UV–visible Spectroscopy, and Spectroscopic Ellipsometry. The PXRD analysis confirmed a hexagonal wurtzite structure with excellent crystallinity in the product. UV–visible studies indicated band gap energies of 3.13 eV and 2.7 eV for green-synthesized and chemically synthesized ZnO NPs, respectively. There was notable augmentation in the fluorescence characteristics of ZnO NPs derived through green synthesis when compared to chemically synthesized NPs. This observed enhancement in fluorescence renders the green-synthesized ZnO NPs particularly advantageous for bio-imaging.

Efficient capture and dual-model fluorescence detection of ReO4− using a TPE-based pyridinium network

99Technetium is one of the highly radioactive contaminants in nuclear wastewater. ReO4− is an ideal substitute for the safe handling of 99TcO4−, its efficient capture and detection are also significant for scarce rhenium resource recovery. However, designing novel materials for the efficient capture and detection of ReO4− and 99TcO4− is still very challenging. Herein, we establish dual-model fluorescence detection for ReO4− via quick ion exchange by a TPE-based cationic polymeric network (TPDC). TPDC displays good sensor performance for ReO4− accompanying the fluorescence enhancement as well as I− accompanying the fluorescence quenching (on-off). Interestingly, the quenched fluorescence can be reopened by ReO4− (off-on) with a slight increase in the detection limit. Moreover, the adsorption capacity for ReO4− reaches 804.2 mg g−1 and the adsorption equilibrium is achieved within 2 min with a kd value of 6.225×105 mL g−1. This work provides a multifunctional material that manifests efficient capture and dual-model fluorescence detection for ReO4− via quick ion exchange accompanying separate or continuous fluorescence change.

Rational design of 1, 2, 4, 5-tetraphenyl-1H-imidazole-based AIEgens with tunable intramolecular charge transfer and restricted intramolecular rotation processes for multifunctional sensing

Aggregation-induced emission fluorogens (AIEgens) with intramolecular charge transfer (ICT) characteristic are widely used in the detection of various analytes owing to their highly tunable fluorescence emission properties. However, facilely synthesis of AIEgens with ICT characteristic for multiple sensing is still rare and limited in use. In this work, two new AIEgens of 1,2-bis(4-alkoxycarbonylphenyl)-4,5-bis(4-methoxyphenyl)-1H-imidazole (AMI) and its hydrolyzed derivative 1,2-bis(4-carboxylphenyl)-4,5-bis(4-methoxyphenyl)-1H-imidazole (CMI) were facilely synthesized with donor-π-acceptor (D-π-A) structures. The tunable ICT and restricted intramolecular rotation (RIR) processes endow them multifunctional sensing performances. AMI could serve as a reversible fluorescent thermometer, in which a positive linear correlation between fluorescence intensities and temperatures from 20 °C to 60 °C was obtained. Meanwhile, owning to the specific interaction between carboxyl groups and Al(III) ions, CMI was successfully served as a “turn-on” fluorescent chemosensor for detecting Al(III) in aqueous solutions under a neutral condition with high sensitivity and selectivity. Mechanism study showed that the formation of aggregation states of coordination polymers between CMI and Al(III) was responsible for the fluorescence enhancement. What is more, the sensing process could be applied for detecting Al(III) in real water samples and on solid test papers, which implied its potential application values. Furthermore, the aggregation-induced emission (AIE) characteristic also made fluorescence emissions of CMI suitable for specific pH sensing. This work provides an efficient strategy for the construction of multifunctional fluorescence chemosensors based on AIEgens.

A Turn-On Fluorescence Probe Based on GSH-Protected Silver Nanoclusters for the Selective Detection of Pb2.

Glutathione-protected silver nanoclusters (GSH-AgNCs) with good photostability were successfully synthesized through a one-pot heating process. The resultant GSH-AgNCs with an average diameter of ~1.6 nm exhibit red fluorescence (λem = 650 nm), and the fluorescence is excitation independent. Strong aggregation-induced emission (AIE) effect was observed in GSH-AgNCs, which can be induced by solvent and metal ions. In particular, a specific fluorescence enhancement was detected upon interaction with lead ions (Pb2+). A fluorescent probe was designed for off-on detection of Pb2+ based on as-synthesized GSH-AgNCs. Under the optimum parameters, two linear response intervals were found between the relative fluorescence intensity and the concentration of Pb2+ in the range of 10-250 μM (R2 = 0.9900) and 400-1000 μM (R2 = 0.9930). Significant fluorescence color evolutions observed under UV light, resulting in a semiquantitative visual detection of Pb2+. A possible detection mechanism based on the interaction between GSH-AgNCs and Pb2+ is discussed.

A protein structure-dependent fluorescent probe for hemoglobin monitoring and controllable imaging in living cells.

A novel protein structure-dependent non-covalent fluorescent probe, DDBM, was developed. It exhibited selective fluorescence "turn-off" responsiveness to bovine hemoglobin (BHb). This responsiveness depended on the interaction between the probe and BHb, with the methoxynaphthalene group significantly contributing to the sensitivity. Non-covalent interactions played a crucial role in stabilizing the binding of DDBM with BHb. DDBM demonstrated a robust anti-interference capability in its BHb responsiveness. Interestingly, the BHb responsiveness of DDBM could be modulated by ibuprofen. Additionally, DDBM exhibited favorable fluorescence enhancement sensitivity to bovine serum albumin (BSA), coupled with a robust anti-interference capability. These distinctive properties of DDBM enabled it to dynamically trace the metabolism of hemoglobin (Hb) and further achieve Hb-mediated precise controllable live cell imaging.

Detection of dithiocarbamate pesticide residues in tea by colorimetric and fluorescent double-mode probe regulated by tyrosinase

In this study, a colorimetric/fluorescent double-mode probe for sensitive detection of dithiocarbamates (DTCs) pesticides residues was constructed based on the fluorescence controllable property of Mn3+-sealed metal-organic framework (MnMOF), the chromogenic reaction of enzyme reaction products, and inhibition of tyrosinase activity by DTCs. DTCs inhibited the activity of tyrosinase and impeded the consumption of catechol (CC), thereby weakening the colorimetric signal. The redox reaction between residual CC and MnMOF led to backbone collapse and release of free porphyrin (TCPP), which caused fluorescence enhancement of the probe solution. As the concentration of DTCs increased, the color of probe solution gradually transitioned from reddish brown to light pink in daylight, and the red fluorescence was gradually enhanced under 365 nm UV light. Under the optimal conditions and using zineb as a representative of DTCs, the probe achieved the sensitive response to zineb over the concentration range of 0.03 ∼ 1.1 μg mL−1. The detection limits were 9.23 ng mL−1 and 5.95 ng mL−1 in colorimetric and fluorescent modes, respectively. The practical applicability of the probe was demonstrated by the detection of zineb residues in tea. In this study, a simple, sensitive, and reliable double-mode analysis platform was established for the identification of DTCs residues in tea, which is of great significance for ensuring the quality and safety of tea and human health.

Construction of pyridine-functionalized metal-organic frameworks for the detection of flazasulfuron.

Two novel Cu-based metal-organic frameworks (MOFs), namely, poly[[aquadichlorido[μ4-4'-(pyridin-4-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylato][μ3-4'-(pyridin-4-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylato]tricopper(II)] monohydrate], {[Cu3(C22H12N4O4)2Cl2(H2O)]·H2O}n or {[Cu3(PTP)2Cl2(H2O)]·H2O}n, (I), and poly[[diaquabis[μ2-4'-(pyridin-3-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylato]bis(μ2-terephthalato)tricopper(II)] dihydrate], {[Cu3(C22H12N4O4)2(C8H4O4)2(H2O)2]·2H2O}n or {[Cu3(BDC)2(MTP)2(H2O)2]·2H2O}n, (II), have been synthesized successfully with 4'-(pyridin-4-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylic acid (H2PTP) and 4'-(pyridin-3-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylic acid (H2MTP) as the ligands, respectively. Crystal structure analysis reveals that (II) possesses a 2D coordinated layer structure, in which adjacent 2D coordination layers are linked into 3D frameworks through π-π interactions, while the structure of (I) displays dual coordination layers, in which adjacent coordination layers are connected into a 3D framework through hydrogen-bonding interactions. The photophysical properties of the two MOFs were investigated by fluorescence spectroscopy. Complex (II) shows an obvious `turn-on' fluorescence enhancement effect towards flazasulfuron and its potential application for sensing flazasulfuron in water with high selectivity and sensitivity was also investigated in detail.

A bionic palladium metal-organic framework based on a fluorescence sensing enhancement mechanism for sensitive detection of phorate.

We have developed a biomimetic fluorescent nanoprobe (Pd-MOF) that can accurately identify phorate at a fixed wavelength for rapid, sensitive and selective detection. Pd-MOF was a nanoparticle (260.00 ± 27.83 nm) based on the linkage of Pd metal and a TCPP organic framework. It could detect phorate according to the fluorescence principles similar to that of the bioluminescence of Chrysaora pacifica (substance interaction and chromophore fluorescence enhancement). When phorate molecules enter the pores of Pd-MOF and interact with each other, the energy transfer process is stimulated, and the fluorescence signal is significantly enhanced, thereby improving the detection sensitivity. According to shift of the white line in the XANES energy spectrum and the DFT results, phorate increased the energy gap of Pd-MOF from 0.025 eV to 0.046 eV, enhanced the stability of the system, and thus achieved fluorescence enhancement. The sensitivity of Pd-MOF was due to its much smaller energy gap (<80 times) than other metal MOFs and thus it was easier to get excited. The linear detection range for the phorate of the nanoprobe in the water system was 0.01-100 ppb, and the detection limit was 0.0017 ppb. The response time of the Pd-MOF nanoprobe to phorate was 45 seconds. The detection of phorate in tap water, pear and cabbage samples showed that the recovery rates were in the range of 87.69-106.12%, and the relative standard deviation (RSD) was less than 11.16%, which verified the possibility of Pd-MOF nanoprobe in practical application. The sensitive and specific recognition of phorate by Pd-MOF nanoprobe and the development of a phorate test strip (Pd-MOF@paper) confirmed its potential application in pesticide residue detection.

Cadmium(II) and zinc(II) frameworks with a benzothiadiazole-based ligand as a turn-on fluorescence sensor for dopamine

Two new luminescent metal-organic frameworks (MOFs), [Cd3(AIBTD)4(HCOO)2(DMF)2] (Cd-MOF) and [Zn(AIBTD)(AA)] (Zn-MOF) (DMF = N,N-dimethylformamide, AA = acetate), were prepared by solvothermal reactions of 4-(7-(1H-imidazol-1-yl)benzo[c][1, 2, 5]thiadiazol-4-yl)benzoic acid (HAIBTD) possessing an emissive benzothiadiazole (BTD) moiety with cadmium nitrate and zinc nitrate, respectively. Single-crystal X-ray diffraction analyses show that Cd-MOF and Zn-MOF possess different two-dimensional (2D) networks and form three-dimensional (3D) frameworks with different stacking modes. Their fluorescence sensing ability for dopamine was studied and it was found that both Cd-MOF and Zn-MOF show fluorescence enhancement in DMF. The turn-on effect may be attributed to the absorbance-caused enhancement (ACE). The results indicate that Cd-MOF and Zn-MOF have potential as fluorescent sensors for dopamine.

Unravelling the intricacies of fluorescence enhancement in heptamethine cyanine dyes induced by heavy halogen atoms

The classic heavy-atom effect refers to the photophysical phenomenon observed in fluorophores, where the interaction with heavy atoms quenches fluorescence emission. Many fluorophores containing heavy halogen atoms, such as xanthenes, BODIPYs, porphyrins, and anthracenes, adhere to this effect, while the photophysical behavior of others, e.g. halogenated heptamethine cyanine dyes, is poorly studied having contradicting results. In this study, we explored for the first time unexpected fluorescence enhancement induced by heavy halogen atoms in heptamethine dyes, contrasting the classic heavy-atom effect. To this end, a series of novel heptamethine cyanine dyes were synthesized and their photophysical properties were experimentally and theoretically investigated. Heavy halogen atoms were found to significantly affect the fluorescence behaviour of heptamethine dyes depending on the number and position of the attached halogens. Thus, the introduction of bromine and iodine atoms at the non-conjugated positions to the chromophore moieties led to an increase in the fluorescence quantum yields, which contradicts the classic principle and could be explained by heavy halogen-induced vibration restrictions. The value of halogen atom-promoted singlet oxygen generation quantum yield ΦΔ is also not straightforward and depends on the number, position and weight of the halogen atom. The breaking of the classic heavy-atom effect in halogenated heptamethine dyes provides an effective strategy to substantially increase the fluorescence intensity of long-wavelength cyanine dyes, providing new functional advantages for fluorescence imaging, diagnostics, and photodynamic therapy, among other applications.

Pressure-Induced Structural Phase Transition and Fluorescence Enhancement of Double Perovskite Material Cs2NaHoCl6

Cs2NaHoCl6, a double perovskite material, has demonstrated extensive application potential in the fields of anti-counterfeiting and optoelectronics. The synthesis of Cs2NaHoCl6 crystals was achieved using a hydrothermal method, followed by the determination of their crystal structures through single crystal X-ray diffraction techniques. The material exhibits bright red fluorescence when exposed to ultraviolet light, confirming its excellent optical properties. An in situ high-pressure fluorescence experiment was conducted on Cs2NaHoCl6 up to 10 GPa at room temperature. The results indicate that the material possibly undergoes a structural phase transition within the pressure range of 6.9–7.9 GPa, which is accompanied by a significant enhancement in fluorescence. Geometric optimization based on density functional theory (DFT) revealed a significant decrease in the bond lengths and crystal volumes of Ho-Cl and Na-Cl across the predicted phase transition range. Furthermore, it was observed that the bond lengths of Na-Cl and Ho-Cl reach an equivalent state within this phase transition interval. The alteration in bond length may modify the local crystal field strength surrounding Ho3+, consequently affecting its electronic transition energy levels. This could be the primary factor contributing to the structural phase transition.

Preparation of Metal Nanocluster Supraparticles for Ultrasensitive Sensing of Tetracycline Based on Multiple Interactions between a Target and Sensor.

New strategies for enhancing the fluorescence emission of metal nanoclusters (MNCs) are very crucial for the highly sensitive sensing of food hazards. In this work, we prepared MNC supraparticles (Sc-CB/AuNCs) by simultaneously introducing cucurbit[7]uril (CB[7]) and Sc3+ ions into ATT-AuNCs for the first time. The obtained supraparticles exhibited strong emission enhancement due to synergistic aggregation-induced emission enhancement and restriction of intramolecular motion effects. Notably, the fluorescence of ATT-AuNCs was enhanced by 24-fold due to the combination of CB[7] and Sc3+ ions, and the quantum yield reached 69.1%. Moreover, we found that tetracycline (TC) could bind to the Sc-CB/AuNCs through simultaneous host-guest recognition and ionic complexation, which effectively quenched the Sc-CB/AuNCs through the synergy of photoinduced electron transfer and inner filter effect. Based on the above multiple interactions between TC and Sc-CB/AuNCs, an ultrasensitive sensing method for TC was constructed with an LOD of 0.3 nM. Furthermore, a portable fluorescent gel sensor was constructed and successfully used for TC detection in honey samples. The test took only 2 min. This work not only provided a simple and effective fluorescence enhancement strategy for MNCs but also offered a novel sensing strategy, which may largely extend the potential of host-guest recognition-based sensors for food and environmental hazards.

Two New Coordination Polymers: Crystal Structures and Fluorescence Properties.

A new Ni (II) metal-organic frameworks with the formula [Ni2(HL)2(H2O)4]∙3H2O (1) and a novel phenoxo-O bridged rare-earth dinuclear Schiff base complex with the formula [La2(dbm)4L·CH3OH] (2), where the HL2- is the partial deprotonated of the organic ligand H3L, and H2L is a bis-Schiff foundation ligand (H3L = 4,6-dioxo-1,4,5,6-tetrahydro-1,3,5-triazine-2-carboxylic acid, H2L = N, N'-bis (2-hydroxy-3-methoxybenzylidene) -propane-1,2-diamine, Hdbm = dibenzoylmethane), have been successfully generated under the solvothermal condition. The targeted product sample of 1 and 2 has been fully characterized by single-crystal X-ray data, elemental analysis, FT-IR, powder X-ray diffraction, and thermogravimetric analysis. Furthermore, fluorescence performance testing of the complexes revealed that in complex 1, H3L forms a rigid chain through coordination with Ni2+ ions and further forms a highly rigid three-dimensional framework within the hydrogen bond network, resulting in fluorescence enhancement of up to 13.7-fold, displaying deep blue fluorescence with CIE coordinates of (0.1626, 0.1375). In contrast, complex 2 forms only discrete zero-dimensional molecules and exhibits light blue fluorescence with CIE coordinates of (0.1744, 0.2306). This demonstrates their potential as fluorescent materials.

Simultaneous visualization of lipid droplets and tracking of the endogenous hypochlorous acid in psoriatic mice models with a novel fluorescent probe in a wash-free fashion

Psoriasis is an autoimmune inflammation-related disease accompanied by a variety of complications. Reactive oxygen species (ROS) are modulators of inflammation, and their excessive production caused by oxidative/anti-oxidative imbalance has been observed in psoriatic patients. Hypochlorous acid (HOCl) is a ROS produced by myeloperoxidase (MPO) from chloride ions (Cl-) and hydrogen peroxide (H2O2). Endogenous HOCl has recently been studied as a potential biomarker of psoriasis underlying the necessity for the development of efficient analytical tools for its detection and real time monitoring. Herein, we designed a novel highly sensitive and selective coumarin-based fluorescent probe for HOCl detection, named CN2-CF3-S. The probe itself featured negligible fluorescence because of the heavy atom effect of the thiocarbonyl group. However, upon responding to HOCl a conversion to sulfur-free derivative CN2-CF3-O occurs, resulting in a dramatical fluorescent enhancement setting the detection limit for HOCl of 3.2 nM. The HOCl-recognition mechanism could be ascribed to the HOCl-triggered oxidative desulfurization process that agrees with liquid chromatography-mass spectrometry (LC-MS) analysis and density functional theory (DFT) computations. The probe’s design incorporated a synergistic combination of two structural features for efficient lipid droplets (LDs)-targeting imaging. An efficient push–pull system reinforced by the presence of two strongly electron-donating dimethylamino groups equipped CN2-CF3-O with pronounced solvatochromism realized through the enhanced blue-shifted emission in non-polar media. Meanwhile, the presence of trifluormethylphenyl moiety at the acceptor side led to an increased lipophilicity. The CN2-CF3-S probe has been successfully utilized to track the endogenous HOCl in cells and on skin of the psoriatic mice in a wash-free manner. As a result, we have demonstrated that the concentration of HOCl in skin might correlate positively with the degree of inflammation in psoriasis. Thus, CN2-CF3-S constitutes the first example of LDs-imaging fluorescent probe for detecting the psoriasis-linked HOCl, offering a convenient tool for further in-depth investigation of psoriasis pathophysiology.

Fluorescence Enhancement of Nonemissive Monodeprotonated Luteolin in a Poly(vinyl alcohol) Film.

Solid polymer matrixes can modulate the electronic states of embedded chromophores and have been widely used in flexible optoelectronic and optical materials. Luteolin is one of the most common natural flavonoids, and its neutral and monodeprotonated forms are nonemissive in aqueous solution induced by ultrafast excited-state proton transfer (ESPT) followed by nonradiative relaxation. In this study, we have incorporated luteolin into poly(vinyl alcohol) (PVA) films and studied their fluorescence behaviors. Neutral and one monodeprotonated luteolin coexist in the PVA film. Weak steady-state fluorescence of neutral luteolin peaking at about 440 nm is observed for the first time. In addition, the monodeprotonated luteolin in PVA film exhibits obvious fluorescence peaking at 500 nm, with a fluorescence quantum yield of as high as 0.4 and a fluorescence lifetime of as long as 2.4 ns. Time-dependent density functional theory calculations have determined that the ESPT of neutral luteolin is barrierless but that of monodeprotonated luteolin needs to surmount a barrier, explaining their distinct emission properties. These results indicate the modulation ability of the PVA film in both ground-state deprotonation and ESPT, broadening the application areas of the solid polymer matrix.

Pyrene Based Schiff Base for Cascade Fluorescent "On-Off" Detection of Aluminium(III) and Fluoride Ions and its Applications in Live Cells Imaging.

An easy-to-prepare pyrene-based Schiff base PNZ was synthesized by condensing equimolar amount of 1-pyrenebutyric hydrazide with 2-hydroxy-naphthaldehyde, and employed as a fluorescent chemosensor for in-situ cascade detection of aluminium (Al3+) and fluoride (F-) ions. In DMSO:H2O (1 : 1, v/v), the weakly emissive PNZ showed a significant fluorescence enhancement at 455 nm selectively upon the addition of Al3+ due to the complexation-induced formation of a pyrene excimer. Schiff base PNZ and Al3+ formed a complex in 2 : 1 binding ratio with the estimated binding constants of K1:1=9826.01 M-1 and K2:1=3188.49 M-1. The sensing mechanism was explored by performing quantum mechanical calculations and 1H-NMR titration of PNZ with Al3+. The in-situ formed PNZ-Al3+ complex species enabled the fluorescent turn-off detection of F-. Using PNZ and PNZ-Al3+, the concentrations of Al3+ and F- ions can be detected down to 2.89×10-7 M and 1.88×10-7 M, respectively. The cytotoxicity of the PNZ and its ability to bioimage Al3+ and F- ions was examined in the human cervical cancer cell line. Finally, the receptor PNZ was applied for the quantification of Al3+ and F- ions in various real samples, such as tap water, river water, rainwater, mouthwash, and toothpaste.

Albumin-Chaperoned Deep-NIR Triarylmethane Dyes for High-Contrast In Vivo Imaging and Photothermal Therapy.

Fluorophores absorbing/emitting in the deep near-infrared (deep NIR) spectral region, that is, 800 nm and beyond, hold great promise for in vivo bioimaging, diagnosis, and phototherapy due to deeper tissue penetration. The bottleneck is the lack of bright, stable, and readily synthesized deep NIR fluorophores. Here, it is reported that the albumin-chaperon strategy is a viable one-for-all strategy to address these difficulties. A focused library of deep-NIR absorbing dyes (EA5) is easily synthesized via a two-step cascade. They are neither very stable nor bright in phosphate bufferdue to a propeller-type flexible scaffold. Through screening, EA5_c3 is found to exhibit a high affinity toward bovine serum albumin (BSA). Binding-associated structural rigidification resulted in a gigantic 26-fold fluorescence enhancement. The albumin chaperone also greatly improved the stability of EA5_c3 by shielding the bisbenzannulated triarylmethane core from nucleophilic or oxidative species. The resulting EA5_c3@BSA exhibits high biocompatibility. It offered high-resolution vasculature, lymph systems, tumors, and other tissue imaging with its bright deep NIR emission. At the same time, it exhibits prominent potential in photoacoustic imaging and photothermal treatment of subcutaneous and orthotopic breast tumors. These findings provide insights into robust and high-performance fluorophores with deep NIR regions for theranostic against aggressive cancers.

Biofuel-Driven Stepping Chiral Supramolecular Transfer Container.

Herein, we reported a biofuel-driven recyclable chiral supramolecular transfer container based on hexacationic triphenylamine cage and nucleotides. Possessing rotatable paddle rigid backbones, the artificial receptor effectively encapsulated nucleotides with a high binding constant up to 5.37×105 M-1 in water, displaying guest-induced efficient fluorescence enhancement with quantum yield increased from 6.5% to 16.6%. Especially, the achiral cage could effectively bind with adenosine triphosphate to activate chirality transfer from substrates to the single molecular container, giving circularly polarized luminescence at 575 nm and positive Cotton effect peaks with significant asymmetric factor (gabs = +6.4×10-4). Meanwhile, the adaptive chiral supramolecule not only has reversible thermal responsiveness but also could stepwise regulate chirality transfer by the catalysis of hexokinase and apyrase in tandem, showing recovery adaptive chirality after refueled, achieving dynamically regulated programmable multistate chiral luminescent supramolecules. Therefore, the biofuel-driven chiral supramolecular transfer container could be successfully applied in chiral logic gates and multilevel information encryption, providing new insight into intelligent chiral materials.