Luminescent Organic-inorganic Hybrid Materials Research Articles

Functional mobile-based two-factor authentication by photonic physical unclonable functions

Given the rapid expansion of the Internet of Things and because of the concerns around counterfeited goods, secure and resilient cryptographic systems are in high demand. Due to the development of digital ecosystems, mobile applications for transactions require fast and reliable methods to generate secure cryptographic keys, such as Physical Unclonable Functions (PUFs). We demonstrate a compact and reliable photonic PUF device able to be applied in mobile-based authentication. A miniaturized, energy-efficient, and low-cost token was forged of flexible luminescent organic–inorganic hybrid materials doped with lanthanides, displaying unique challenge–response pairs (CRPs) for two-factor authentication. Under laser irradiation in the red spectral region, a speckle pattern is attained and accessed through conventional charge-coupled cameras, and under ultraviolet light-emitting diodes, it displays a luminescent pattern accessed through hyperspectral imaging and converted to a random intensity-based pattern, ensuring the two-factor authentication. This methodology features the use of a discrete cosine transform to enable a low-cost and semi-compact encryption system suited for speckle and luminescence-based CRPs. The PUF evaluation and the authentication protocol required the analysis of multiple CRPs from different tokens, establishing an optimal cryptographic key size (128 bits) and an optimal decision threshold level that minimizes the error probability.

Crystal structures, proton conductivities and luminescence of two organic-inorganic hybrid materials based on Keggin-type clusters and Cu(II)/Cu(I)-bis(hydroxymethyl)-2,2′-bipyridine complexes

Two proton-conductive and luminescent organic-inorganic hybrid materials, {[Cu(II)(bhmbpy)(H2O)(Cl)0.5(CH3CN)]2[PW(VI) 10W(V) 2O39]}·4H2O(1) and {H2[Cu(I)(bhmbpy)2(Cl)Cu(I)(bhmbpy)2][PW12O40]}·7H2O (2) (where bhmbpy is bis(hydroxymethyl)-2,2′-bipyridine), were synthesized at room temperature. The two products were characterized by infrared spectroscopy, X-ray single-crystal diffraction, X-ray powder diffraction, elemental and thermogravimetric analyses. The proton conductivities and luminescence of 1 and 2 were studied by using alternating-current impedance spectroscopy and luminescence spectroscopy, respectively. X-ray diffraction analysis revealed that 1 includes a decorated polyanion chain {[Cu(II)(bhmbpy)(H2O)(Cl)0.5(CH3CN)]2[PW(VI) 10W(V) 2O39]}n and forms a three-dimensional network structure depending on short Cl…Cl contacts and hydrogen-bonding interactions. X-ray diffraction analysis revealed that 2 includes a butterfly-like bi-nuclear copper cluster unit with a Cl-bridge, [Cu(I)(bhmbpy)2(Cl)Cu(I)(bhmbpy)2]+, and forms a three-dimensional network structure depending on hydrogen-bonding interactions. [PW12O40]3– anions fill in the network based on hydrogen-bonding and electrostatic interactions. In them, the bhmbpy acts as a bidentate nitrogen donor ligand in the chelating fashion to coordinate with the Cu(II) center in 1 and the Cu(I) center in 2. The bhmbpy in 2 successfully constrains the Cu(I) within a rigid environment in a tetragonal-pyramidal geometry. The two compounds exhibit good proton conductivity (10−4 S·cm−1) at 100 °C in the relative humidity range 35–98%. Their luminescence behaviors in the solid state at room temperature have also been investigated. Upon excitation at 384 nm, 1 exhibits three emission peaks centered at 439, 507 and 566 nm. When excited at 364 nm, 2 displays three emission peaks centered at 443, 501 and 553 nm.

Eu-phen Bonded Titanium Oxo-Clusters, Precursors for a Facile Preparation of High Luminescent Materials and Films.

Incorporation of Eu complexes into various organic or inorganic matrixes is one of the acceptable strategies to obtain displaying materials having practical applications. In this work, we report a convenient approach to preparing high luminescent organic-inorganic hybrid materials and films from the europium-titanium oxo-clusters (EuTOCs) having photoactive antenna ligands. Three Eu2Ti4 oxo-clusters were synthesized and crystallographically characterized. They are the first reported lanthanide-TOCs coordinated with 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy) as photoactive ligands, Eu2Ti4O6(phen)2(pa)10 (1) (pa = propionate), Eu2Ti4O6(bpy)2(pa)10 (2), and Eu2Ti4O6(phen)2(MA)10 (3) (MA = methacrylate). Benefitting from the photoactive antenna ligands and the rigid cluster structures, these clusters showed bright red luminescence with quantum yield in the range of 60-80% and long lifetime up to 3.0 ms. Unlike those physically mixed polymeric materials, the MA coordinated compound 3 can be self-polymerized to form a brilliant luminescent film. The film coated slide was used to develop a fluorescence sensor for biomolecule ascorbic acid (AA). The low detection limit and reusable properties suggest great potential for such EuTOC films in real applications.

Luminescent materials of covalent grafting lanthanide complexes to the synthetic clays

Lanthanide complex-based luminescent organic-inorganic hybrid materials are highly interesting for a broad range of application fields. The combination of lanthanide complexes with the synthetic clay, Laponite, is now attracting the interest of scientists due to the unique features of the synthetic clay. However, most of the reported literature are involved with the adsorption of lanthanide complexes on the clay particles. Taking the covalent incorporation of lanthanide complex into clay and satisfying the further coordinate with central lanthanide ion into account, herein, we reported a facile strategy of covalent grafting lanthanide complexes to the clay via the reaction of the terminal triethoxy groups of triethoxysilylated ligand (phenSi) and the surface OH groups of the clay. The successful grafting of the complexes was confirmed by the FT-IR spectra, 29Si solid-state NMR spectra and the luminescent data. And the nitrogen atoms of Phen moieties which are covalently grafted to the clay provide the chance to prepare luminescent hybrid materials with larger coordination number.

Novel luminescent lanthanide(iii) hybrid materials: fluorescence sensing of fluoride ions and N,N-dimethylformamide.

Two novel luminescent organic-inorganic hybrid materials, Ln(L-SBA15)3phen (Ln = Eu, Tb), were designed and synthesized. The organic ligand phenylurea was modified by the silane coupling agent 3-(triethoxysilyl)propyl isocyanate (TESPIC) to form a precursor (L), which was covalently bonded onto a mesoporous SBA-15 backbone to form mesoporous L-SBA15 through co-hydrolysis and co-condensation reactions. 1,10-Phenanthroline monohydrate (phen) was selected as the second ligand to improve the luminescence of the final products, and the two mesoporous hybrid materials Ln(L-SBA15)3phen were obtained after the coordination reaction between the organic ligands (phen and L-SBA15) and Ln(iii) ions. Both the mesoporous hybrid materials were examined by Fourier transform infrared spectroscopy, transmission electron microscopy, small-angle X-ray diffraction, N2 adsorption-desorption curves, and photoluminescence spectroscopy. The results show that both the hybrid materials showed highly ordered mesoporous structures, high surface areas, and excellent photophysical properties (long luminescence lifetimes and high quantum efficiencies). Furthermore, the fluorescence sensing properties of the materials were investigated systematically, and the hybrid materials were revealed to be promising examples of dual functional materials with good ability to sense fluoride ions and a small organic molecule N,N-dimethylformamide.

Luminescent hybrid materials based on (8-hydroxyquinoline)-substituted metal-organic complexes and lead-borate glasses

Novel luminescent organic-inorganic hybrid materials based on 8-hydroxyquinoline metal complexes (Liq, Kq, Naq, Rbq, Mgq2, Srq2, Znq2, Scq3, Alq3, Gaq3, and Inq3) have been synthesized by a high temperature exchange reaction with 80PbF2–20B2O3 inorganic low-melting glass. The mechanical and optical properties, transmission spectra, emission an excitation photoluminescence, and luminescence kinetic of hybrid materials were studied. All hybrid materials showed a wide luminescence band in the range 400–700 nm.

Zirconia-based luminescent organic-inorganic hybrid materials with ternary europium (III) complexes bonded

In this work, a novel red-emitting organic-inorganic hybrid material with europium (III) lanthanide β-diketonate complexes linked to a zirconia was reported, which was realized by adduct formation with zirconia-tethered terpyridine moieties. Luminescence enhancement of the hybrid material has been observed compared with pure Eu(tta)3·2H2O. Transparent and strongly luminescent thin films based on PMMA were also prepared at room temperature, which are highly luminescent under UV-light irradiation and possess a promising prospect in the area of optics.

Improvement in the emission properties of a luminescent anionic dye intercalated between the lamellae of zinc hydroxide-layered

A luminescent green anionic dye, 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium, has been intercalated between the layers of the zinc hydroxide-layered (here named as ZHL-layered-NO3) using an anion exchange technique to produce new luminescent organic–inorganic hybrid materials with interesting photoemission properties. X-ray diffraction, FTIR, UV–vis spectroscopic and scanning electron microscopic studies have shown the incorporation of the luminescent anionic dye between the layers of the inorganic host. X-ray diffraction studies revealed increases in the basal spacing of ZHL-layered hybrid after the intercalation of the green dye using different time intercalation. The interlayer spacing increased from 0.98nm in the pristine ZHL-layered NO3 to 3.54, 3.18 and 3.62nm in the ZHL-layered/Py-SO3−3 composites at 12, 24 and 48h of time intercalation, respectively. Photophysical properties of these new luminescent hybrids (ZHL-layered/Py-SO3−3) were also investigated using the UV–vis absorption, steady-state and dynamic fluorescence spectroscopies. All hybrid materials presented UV–vis absorption bands and photoemission at green region due to the presence of the anionic dye in the galleries of the inorganic layered. For the material produced at 12h of time intercalation, a higher quantum yield photoluminescence (ϕPL=13.0%) was observed compared to the pure dye solid (ϕPL=1.0%). This result was attributed to the confinement of the anionic species in the host two-dimensional gallery. These observations open new opportunities for the use of this organic dye immobilized in alternative layered compound for electronic devices or for sensors.

Luminescent sol–gel materials based on lanthanide aminopolycarboxylates (Ln = Nd, Eu, Tb, Yb)

Luminescent organic–inorganic hybrid materials containing immobilized lanthanide(III) complexes (Ln = Nd, Eu, Tb, Yb) with modified ethylenediaminetetraacetic and diethylenetriaminepentaacetic acid were synthesized by sol–gel method. Obtained hybrids exhibit 4f-luminescence in the visible (Eu(III) and Tb(III)) and IR-region (Nd(III) and Yb(III)). The influence of the hybrid matrix on the lanthanide luminescence was established and it was shown, that the location of resonance level of Eu(III) is optimal for efficient energy transfer from matrix, while in the case of Tb(III) energy transfer does not occur and Tb(III) is able to absorb energy only due to its own week f–f transitions. It was also established that the inorganic matrix leads to elimination of nonradiative energy losses and increase of 4f-luminescence lifetimes. Covalent binding of Ln(III) aminopolycarboxylates in the matrix allows to consider obtained materials as promising for creation of photo- and chemically-stable luminescent sensors.

Luminescent organic–inorganic hybrid materials based on lanthanide containing ionic liquids and sylilated β-diketone

In this work, we report the luminescent organic–inorganic hybrid materials prepared by hydrolysis and condensation of sylilated β-diketone under acid conditions in the presence of carboxyl-functionalized ionic liquid in which Eu3+ ions are coordinated to the oxygen atoms of carboxylate groups from the ionic liquids. The obtained materials were characterized with FT-IR, TG and photoluminescence spectroscopy. FT-IR spectra imply that Eu3+ ions are still coordinated to the ionic liquid in the hybrid materials. Excitation and emission spectra demonstrate that the energy transfer occurs from the β-diketone molecules covalently bonded with silica to Eu3+ ions. The Eu3+ (5D0) quantum efficiency value of the hybrid materials has been estimated based on the emission spectrum and the value of lifetime. A large value of ratio (16.44) between the intensities of the 5D0→7F2 and 5D0→7F1 transition and high value of 5D0 quantum efficiency (51.01%) are obtained.

Novel luminescent lanthanide complexes covalently linked to a terpyridine-functionalized silica network

Novel luminescent organic–inorganic hybrid materials consisting of lanthanide (Eu 3+, Tb 3+) complexes covalently bonded to a silica-based network have been obtained by a sol–gel approach. A new monomer has been synthesized by the thiol-ene photopolymerization between γ-mercaptopropyltrimethoxysilane and 4′-allyloxy-2,2′:6′,2″-terpyridine. The monomer is afterward submitted to complexation with lanthanide ions and used as the siloxane network precursor. FT-IR, DR, SEM, luminescence spectra and decay analysis, as well as luminescence quantum yields, were used to characterize the obtained hybrid materials. Excitation at the ligand absorption wavelength (333 nm) resulted in strong emission of the lanthanide ions: Eu 3+ 5D 0– 7F J ( J = 0–4) and Tb 3+ 5D 4– 7F J ( J = 6, 5, 4, 3) emission lines due to efficient energy transfer from the ligands to the lanthanide ions. When the Eu 3+ and Tb 3+ ions were incorporated into the same hybrid material, only the simple addition spectra from the two metal centers was observed, which indicated bimetallic complex was not formed.

Molecular design of luminescent organic-inorganic hybrid materials activated by europium (III) ions

Abstract Luminescent hybrid materials consisting in rare-earth (Eu 3+ , Gd 3+ ) organic complexes covalently attached to a silica-based network have been obtained by a sol–gel process. Four dicarboxylic acids with different aromatic subunits (dipicolinic acid, 4-phenyl-2,6-pyridinedicarboxylic acid, 4-(phenylethynyl)-2,6-pyridinedicarboxylic acid and 2,6-Bis(3-carboxy-1-pyrazolyl)pyridine) have been chosen as ligands for Ln 3+ ions. They were grafted to 3-aminopropyltriethoxysilane (APTES) to give organically modified alkoxysilanes that were used as molecular precursors for the preparation of hybrid materials. Ln 3+ first coordination sphere, composition of the siloxane matrix and connection between the organic and inorganic parts have been characterized by infrared spectroscopy, by 13 C 29 Si solid-state NMR as well as by elemental analyses. UV excitation in the organic component resulted in strong emission from Eu 3+ ions due to an efficient ligand-to-metal energy transfer. As compared to reference organic molecules, hybrid samples exhibited similar emission properties under UV excitation in addition to mainly unchanged excited states lifetimes. However, by direct excitation of the Eu 3+ - 5 D 0 energy level, the presence of two different site distributions were evidenced in the four hybrid compounds. Emission features related to each of these site distributions and their respective attribution were investigated. Variations in the relative emission intensities were observed according to the nature of the organic chromophore. These variations were discussed in relation to the ATE (Absorption-Transfer-Emission) mechanism and to the relative energy positions of the ligand and the rare-earth ions respectively.

Use of polymeric resin in the formation of SiO 2 hybrid gels

A new organic–inorganic hybrid material with interpenetrating polymer networks was synthesized with a phase of SiO 2 made by sol–gel chemistry and an organic phase made from a polymeric resin obtained by polyesterification between metal chelate complexes (formed by metallic ions and α-hydroxycarboxylic acids) and a polyfunctional alcohol. One modification in this method consists in preparing organic polymers doped with europium III/dipicolinic acid or terbium III/1,2-phenylenedioxidiacetic acid complexes. Europium and terbium luminescent properties were used as probe to obtain structural information about the hybrid gel. To the organic polymers we added tetraorthosilicates to obtain transparent and luminescent organic–inorganic hybrid materials through the sol–gel process. Luminescent and infrared spectra and thermogravimetric properties were measured.