An inorganic–organic hybrid photochromic material with fast response to hard and soft X-rays at room temperature

A series of inorganic–organic hybrid double-tartaric bridging mono-lanthanide substituted phosphotungstates with a general formula of [N(CH3)4]6K3H7[Ln(C4H2O6)(α-PW11O39)]2·27H2O (Ln = Dy for 1Dy, Er for 2Er, and Yb for 3Yb) have been synthesized by the reactions of K14[P2W19O69(H2O)]·24H2O and LnCl3·6H2O in the presence of tartaric acid and tetramethyl ammonium counterions in an aqueous medium. Crystal structure analyses reveal that 1Dy–3Yb are isomorphic and are all built from two mono-lanthanide substituted Keggin polyoxoanion fragments joined together by two tartaric ligands. 1Dy–3Yb exhibit reversible photochromism and they can change from white (for 1Dy and 3Yb) or pink (for 2Er) to blue upon UV irradiation and then their colors gradually recover in the dark for about five days. The solid-state photoluminescence spectra of 1Dy–3Yb display their characteristic emissions of lanthanide components based on their 4f–4f transitions. Moreover, the fluorescence of 1Dy displays an effectively switchable behaviour when exposed to UV light, the intensity of the emission band at 573 nm gradually weakens as the irradiation time increases and the intensity drops to 2.4% of the original intensity after 30 minutes. It is noteworthy that the frequency dependence of the ac-susceptibility was found for 1Dy, suggesting a typical single-molecule magnet (SMM) behavior with an energy barrier of 20 K.

Magnetic double-tartaric bridging mono-lanthanide substituted phosphotungstates with photochromic and switchable luminescence properties

Three zinc-viologen compounds, namely, {[Zn(Mebpy)(Hbtc)Cl]·2H2O}n (1), {[Zn3(Cebpy)2(Hbtc) (H2btc)2 (OH)2]·4H2O}n (2), and {[Zn4(Cebpy)2(IPA)3(OH)2]·2H2O}n (3) (Mebpy = N-methyl-4,4'-bipyridinium, Cebpy = N-carboxyethyl-4,4'-bipyridinium, H3btc = 1,3,5-benzenetricarboxylic acid, and H2IPA = isophthalic acid) have been constructed from aromatic carboxylic acid and viologen-derived ligands. In compound 1, the Hbtc2- ligands bridge Zn2+ cations to form a 1D fence-like chain with the Mebpy+ ligand suspended on the chains. Compound 2 possesses a 2D (4, 4) double-layered grid structure based on linear trinuclear Zn3O2 cluster units. The structure of compound 3 can be described as a 3D open-framework based on tetranuclear Zn4O2 cluster units and helical chains with helical channels. All three compounds display photochromic properties from pale yellow to dark blue after being irradiated by a xenon lamp with different photoresponsive rates. Compounds 2 and 3 can be deposited in paper simply by coating them with a solution of ethanol. The papers can be used as inkless and erasable print media. In addition, the photo-modulated luminescence of these compounds was also investigated.

Three viologen-derived Zn-organic materials: photochromism, photomodulated fluorescence, and inkless and erasable prints

The detection of the oxygen molecule is of particular interest due to various applications in chemical, biological, and environmental areas, and the typical materials of detecting O2 such as Clark-type electodes and optical oxygen sensors suffer from disadvantages such as insensitivity or usage of expensive instrument. In this paper, we present a nonporous two-dimensional viologen-based metal–organic frameworks consisting of pseudo-left- and right-handed helical chains [Cd(CPBPY)(o-BDC)(H2O)]·H2O (CPBPY = N-(3-carboxyphenyl)-4,4′-bipyridinium, o-BDC = o-benzenedicarboxylate) (1) that exhibits a slow photochromism under a vacuum, inert atmosphere, and even exposure to oxygen, and a three-dimensional porous 6-connected pcu topological metal–organic framework [Cd3(CPBPY)2(BDC)3]·DMF·H2O (BDC = 1,4-benzenedicarboxylate) (2), which displays rapid photochromism only under a vacuum or inert atmosphere. The photochromic product 2′ can quickly and conveniently detect O2 by naked eye recognition of color change. Th...

Photochromic Porous and Nonporous Viologen-Based Metal–Organic Frameworks for Visually Detecting Oxygen

Octahedron-shaped three-shell Ln14-substituted polyoxotungstogermanates encapsulating a W4O15 cluster: luminescence and frequency dependent magnetic properties.

A novel photochromic and luminescent switchable hybrid of [(AV2+)(p-AV)(EuW10O36)]n·2nH2O (1; AV2+ = N,N′-bisaminopropyl-4,4′-bipyridinium bromide hydrobromide; p-AV = poly(1-ethyl-1′-butyl-4,4′-bipyridinium)) has been synthesized by combining a fluorescent POM with monomeric and in situ generated polymerized viologen molecules. Photochromic transformation of 1 from colorless to dark blue under UV-irradiation was observed due to its in situ generated polymeric viologen units, in which the coloration and decoloration time were both lower than 10 minutes. Especially, the decoloration process can be easily realized by exposure of 1 to humid air (95% relative humidity) within 5 minutes, which allows 1 to be used as a potential humidity sensitive material. The reversible coloration and decoloration process can be repeated for more than 40 cycles, which makes 1 an intriguing stable inorganic-viologen-based photochromic hybrid. Intermolecular fluorescence resonance energy transfer (FRET) from inorganic polyoxoanions to the organic photochromic component was observed and was responsible for the modulation of the red emission of 1 to its quenching state when it was under UV-irradiation. The photochromism and photomodulated fluorescence of 1 opens a new avenue for developing durable and quick-responsive smart optical materials based on polyoxometalate and viologen.

A durable and fast-responsive photochromic and switchable luminescent polyviologen–polyoxometalate hybrid

A novel solar ultraviolet sensitive composite film consisting of fluorescent polyoxometalate and viologen has been readily prepared on solid substrates using a drop casting method, and can be colored and bleached by photoreduction and air oxidation processes. A photoswitchable emission has also been observed with the fluorescence intensity returning to its original value after bleaching of the blue-colored film, which is due to the fluorescence resonance energy transfer (FRET) from the excited states of the Eu(III) ions to colored viologen. The decoloration process takes about 2.5 hours under ambient conditions but can be accelerated by humid air. The absorbance change of the composite film is less than 15% even after 8 cycles of variation between the colorless and blue color states. This is also the reason for the emission intensity change of the composite film. Thus, quick-responsive photochromism and switchable fluorescence are realized by a POM-viologen-based film which shows great potential to realize portable devices for solar ultraviolet detection.

A solar ultraviolet sensor based on fluorescent polyoxometalate and viologen

Polyoxometalate coordination induced controllable release of quinolone in hybrid film

The invention relates to a preparation method of visual ultraviolet intensity detection glue. The preparation method of the visual ultraviolet intensity detection glue solves the problem that an existing detection device is difficult to popularize due to complex circuits or processing technology. The preparation method of the visual ultraviolet intensity detection glue includes: 1, preparing gel; 2, spreading the gel; 3, arranging a color colorimetric card. The visual ultraviolet intensity detection glue prepared through the preparation method of the visual ultraviolet intensity detection glue can indicate intensity of ultraviolet light in sunlight through color change of a film, can achieve color changes after irradiation of the ultraviolet light, enables a person to distinguish the color changes through naked eyes, and is suitable for convenient and fast detection of the ultraviolet light in the outdoor sunlight, simple in structure, low in cost and easy to manufacture. The preparation method of the visual ultraviolet intensity detection glue is used to manufacture the visual ultraviolet intensity detection glue used to detect the intensity of the ultraviolet light.

Preparation method of visual ultraviolet intensity detection glue

The invention discloses a preparation method for ultraviolet test paper, and relates to the preparation method of test paper. The invention is to solve the problems that the existing ultraviolet intensity detection method is complex in implementing device, tedious and high in cost. The method includes the steps of: adding polyvinylpyrrolidone into water, adding purpurine and polyoxometallate, mixing uniformly, adding sodium polystyrenesulfonate, then adding polyethyleneimine to obtain mixed liquor; uniformly coating the filter paper with the mixed liquor, airing naturally, and thereby obtaining the ultraviolet test paper. When the ultraviolet test paper with high sensitivity prepared by the method of the invention is used for detecting the ultraviolet intensity, no complex electric circuits and devices are needed, and color comparison can be achieved only by a 6w small ultraviolet lamp in fluorescent color comparison, thus being simple and easy to implement and meanwhile greatly saving in time; considering from the view of production, more than 90% cost can be saved compared with the current test facilities. The invention belongs to the field of preparation of test paper.

Si Li

Papers

A durable and fast-responsive photochromic and switchable luminescent polyviologen–polyoxometalate hybrid

A solar ultraviolet sensor based on fluorescent polyoxometalate and viologen

Polyoxometalate coordination induced controllable release of quinolone in hybrid film

Preparation method of visual ultraviolet intensity detection glue

Preparation method for ultraviolet test paper