A Bifunctional Fluorescence Probe Based on AIE-ICT Strategy for Visual Detection of Cu(2+)/Co(2+) in Complex Matrix

Grind, shine and detect: mechanochemical synthesis of AIE-active polyaromatic amide and its application as molecular receptor of monovalent anions or nucleotides

A mechanochemical synthesis of novel polyaromatic amide consisting of 1,3,5-triphenylbenzene and 1,1',2,2'-tetraphenylethylene skeletons has been established. The designed mechanochemical approach using readily available and low-cost equipment allowed a twofold increase in reaction yield, a 350-fold reduction in reaction time and a significant reduction in the use of harmful reactants in comparison to the solution synthesis method. The parameters of Green Chemistry were used to highlight the advantages of the developed synthesis method over the solution-based approach. The title compound was found to exhibit attractive optical properties related to the Aggregation-induced emission (AIE) behaviour. Taking the advantage of AIE-active properties of the synthesized polyaromatic amide, its application as effective and versatile molecular receptor towards detection of monovalent anions, as well as bio-relevant anions - nucleotides, has been demonstrated. The values of the binding constants were at the satisfactory level of 104, the detection limit values were low and ranged from 0.2 μM to 19.9 μM.

Novel An Efficient Fluorescent Probe Based on Calix[4]triazacrown-5 With Naphthalimide Group for Co2+, Cd2+ and Dopamine Detection

A novel naphthalimide-substituted calix[4]triazacrown-5 (Nap-Calix) at cone conformation was designed and synthesized to employ as a fluorescent probe, which enables the simultaneously detection of Co2+ and Cd2+ metal ions as well as dopamine (DA). 1H-NMR, 13C-NMR, ESI-MS and elemental analysis techniques were carried out to characterize its structure. Cation binding property of Nap-Calix against various metal ions such as Ba2+, Co2+, Ni2+, Pb2+, Zn2+, and Cd2+ exhibited that the sensor selectively binds to Co2+ and Cd2+ metal ions with a remarkable affinity. Introduction of Co2+ and Cd2+ metal ions to a solution of Nap-Calix in DMF/water (1:1, v/v) resulted with a new emission band at 370 nm when excited at 283 nm. In addition, the fluorescence sensing affinity of the probe Nap-Calix against a catecholamine neurotransmitter (dopamine) was investigated in a wide range of concentration of DA (0-0.1 mmol L-1) in 50% DMF/PBS (pH = 5.0). The fluorescence intensity of Nap-Calix, with excitation/emission peaks at 283/327 nm, is highly enhanced by DA. It was also observed that Nap-Calix exhibits excellent fluorescence behavior towards DA with a very low detection limit as 0.21 µmol L-1.

ICT-based fluorescent probes for intracellular pH and biological species detection

Fluorescent probes, typically based on the intramolecular charge transfer (ICT) mechanism, have received considerable research attention in cell detection due to their non-invasiveness, fast response, easy regulation, high sensitivity, and low damage tolerance for in vivo bio-samples. Generally, intracellular pH and biological species such as various gases, metal ions, and anions constitute the foundation of cells and participate in the basic physiological processes, whose abnormal level can lead to poisoning, cardiovascular disease, and cancer in living organisms. Therefore, monitoring of their quantity plays an essential role in understanding the status of organisms and preventing, diagnosing, and treating diseases. In the last decades, remarkable progress has been made in developing ICT probes for the detection of biological elements. In this review, we highlight the recent ICT probes focusing primarily on the detection of intracellular pH, various gases (H2S, CO, H2O2, and NO), metal ions (Cu2+, Hg2+, Pb2+, Zn2+, and Al3+), and anions (ClO-, CN-, SO3 2-, and F-). In addition, we discuss the issues and limitations of ICT-based fluorescent probes for in vivo detection and explore the clinical translational potential and challenges of these materials, providing valuable guidance and insights for the design of fluorescent materials.

A Simple Schiff Base Probe for Quintuplicate-Metal Analytes with Four Emission-Wavelength Responses

A versatile mono-Schiff compound consisting of o-aminobenzene-hydroxyjulolidine (ABJ-MS) has been easily synthesized using a one-step reaction. ABJ-MS displays four diverse fluorescence responses to the addition of Zn2+/Al3+/Fe3+/Ag+, with the maximum fluorescence emission at 530 nm undergoing a hypsochromic shift to 502/490/440/430 nm, synchronously with the discriminating fluorescence enhancement being 10.6/22.8/2.6/7.1-fold, respectively. However, the addition of Cu2+ into ABJ-MS leads to an opposite behavior, namely, fluorescence quenching. Meanwhile, ABJ-MS also displays distinct absorption changes after adding these five metal ions due to different binding affinities between them and ABJ-MS, which gives ABJ-MS quite a versatile detecting nature for Cu2+/Zn2+/Al3+/Fe3+/Ag+. Moreover, ABJ-MS can mimic a series of versatile AND/OR/INH-consisting logic circuits on the basis of the Cu2+/Zn2+/Al3+/Fe3+/Ag+-mediated diverse optical responses. These will endow the smart ABJ-MS molecule and potential applications in the multi-analysis chemosensory and molecular logic material fields.