Redox-Responsive Photochromism and Fluorescence Modulation of Two 3D Metal-Organic Hybrids Derived from a Triamine-Based Polycarboxylate Ligand

Future prospects of luminescent nanomaterial based security inks: from synthesis to anti-counterfeiting applications

Counterfeiting of valuable documents, currency and branded products is a challenging problem that has serious economic, security and health ramifications for governments, businesses and consumers all over the world. It is estimated that counterfeiting represents a multi-billion dollar underground economy with counterfeit products being produced on a large scale every year. Counterfeiting is an increasingly high-tech crime and calls for high-tech solutions to prevent and deter the acts of counterfeiting. The present review briefly outlines and addresses the key challenges in this area, including the above mentioned concerns for anti-counterfeiting applications. This article describes a unique combination of all possible kinds of security ink formulations based on lanthanide doped luminescent nanomaterials, quantum dots (semiconductor and carbon based), metal organic frameworks as well as plasmonic nanomaterials for their possible use in anti-counterfeiting applications. Moreover, in this review, we have briefly discussed and described the historical background of luminescent nanomaterials, basic concepts and detailed synthesis methods along with their characterization. Furthermore, we have also discussed the methods adopted for the fabrication and design of luminescent security inks, various security printing techniques and their anti-counterfeiting applications.

Photoelectric properties and potential nitro derivatives sensing by a highly luminescent of Zn(ii) and Cd(ii) metal–organic frameworks assembled by the flexible hexapodal ligand, 1,3,5-triazine-2,4,6-triamine hexaacetic acid

The luminescent quenching of coordination polymers 1 and 2 were especially obvious with the increasing of the nitro derivatives concentration, indicating 1 and 2 have very high sensitivity sensing properties.

A Photochromic Copolymer Hydrogel Contact Lens: From Synthesis to Application

A photochromic poly(2-hydroxyl-ethyl methacrylate-N-vinylpyrrolidone-spironaphthoxazine) hydrogel (p(HEMA-NVP-SPO)) has been designed and synthesized by free radical polymerization in this work. The chemical and structural information of hydrogels was investigated by IR spectra, equilibrium water content (EWC), and SEM. The IR spectra confirmed successful synthesis of copolymer. The domain of NVP contributed to not only EWC but also inner structure of hydrogel, while SPO had little influence on these properties of hydrogel. The photochromic behaviors of hydrogel including photochromic properties and thermal fading kinetics were systematically studied and compared with hydrogel made by immersing method. Results showed that when SPO was incorporated in hydrogel by polymerization, maximum absorbance wavelength got shorter, and the relaxation half-life became longer. In addition, salicylic acid as a drug model could be loaded into hydrogel by immersing method, and its sustained drug release in a given period was dependent on the characteristics of solution and loading time.

Stabilizing and color tuning pyrazine radicals by coordination for photochromism

This work reports the first photochromic pyrazine-based compound that can undergo photoinduced charge separation and yield stable pyrazine radicals.

Tunable two-color luminescence and host-guest energy transfer of fluorescent chromophores encapsulated in metal-organic frameworks

Co-assembly of chromophore guests with host matrices can afford materials which have photofunctionalities different from those of individual components. Compared with clay and zeolite materials, the use of metal–organic frameworks (MOFs) as a host structure for fabricating luminescent host–guest materials is still at an early stage. Herein, we report the incorporation of a laser dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), into stilbene-based and naphthalene-based MOF systems. The resulting materials exhibit blue/red two-color emission, and the intensity ratio of blue to red fluorescence varies in different planes within the MOF crystal as detected by 3D confocal fluorescence microscopy. The observed changes in ratiometric fluorescence suggest the occurrence of energy transfer from MOF host to DCM molecules, which can be further confirmed by periodic density functional theoretical (DFT) calculations. Moreover, selective changes in luminescence behavior are observed on treating the guest@MOF samples with volatile organic compounds (methanol, acetone and toluene), indicating that these host–guest systems have potential applications as fluorescence sensors. It can be expected that by rational selection of MOF hosts and guest chromophores with suitable emissive colors and energy levels, a wide variety of multi-color luminescent and energy-transfer systems can readily be prepared in a similar manner.

Metal–organic frameworks based on flexible ligands (FL-MOFs): structures and applications

This review presents the recent developments on FL-MOFs, including their structures and applications in gas adsorption, catalysis and proton conduction.

Molecular packing, crystal to crystal transformation, electron transfer behaviour, and photochromic and fluorescent properties of three hydrogen-bonded supramolecular complexes containing benzenecarboxylate donors and viologen acceptors

Structures of three D–A supramolecular systems and their photoresponsive characteristics are investigated.

A series of metal–organic frameworks containing diverse secondary building units derived from a flexible triazine-based tetracarboxylic ligand

Five new coordination polymers containing diverse SBUs derived from a flexible triazine-based tetracarboxylic acid have been solvothermally synthesized and characterized.

Highly stable photoresponsive complex framework formation involves unusual selective hydrogenation of a pyridine derivative

The self-assembly of the zinc ion with the ligand PYPDB in-situ generated from an unusual selective hydrogenation process produces a highly stable photoactive complex Zn(PYPDB)₂ displaying interesting long range electron transfer behavior in the conjugated ring system.