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Fluoran salicylaldehyde hydrazone metal complex(FSHMC) is a kind of recently reported photo-responsive system, which has the advantages of simple synthesis, multiple colors as well as distinct color change before and after UV light irradiation. However, the emission property of FSHMC is relatively unitary. In solid state, especially, only fluorescence quench is induced after UV light irradiation, which limits their applications. In this work, a typical aggregation-induced emission(AIE) moiety of tetraphenylethene(TPE) was introduced to the design of FSHMC. The obtained FSHMC, 2-Zn, exhibited reversible color and fluorescence changes upon UV light irradiation. Due to the AIE feature of compound 2, 2-Zn exhibited different emission changes upon UV light irradiation in THF and in solid matrix, because of the fluorescence resonance energy transfer(FRET) process from TPE moiety to rhodamine B moiety.

Based on a fluoran skeleton, we herein reported a new fluorescent probe FLACu for Cu2+ by facile modification of the spirolactone of dye 1 with phenylhydrazine. Taking advantage of the spirolactam moiety, FLACu only delivers a specific “off-on” fluorescence signal output towards Cu2+ when treated with various metal ions, which has been well elucidated as the result of spirolactam ring opening and hydrolysis processes induced by copper ion. Meanwhile, the limit of detection (LOD) for FLACu has been estimated to be 35.4 nM and a pH range of 5.0–9.0 is evaluated to be suitable for Cu2+ detection. Significantly, FLACu shows low cell cytotoxicity and can be further ultilzied in the detection of exogenous Cu2+ in the living Hela cells.

Responsive photonic crystals have attracted considerable attention. The responsiveness is usually achieved through the variation of reflection wavelengths based on Bragg diffraction. However, distinguishing external stimuli from intrinsic angle dependence is a challenge. Herein, a novel thermal-responsive photonic crystal was constructed based on the synergistic effect of the low-angle dependence of SnO2 inverse opals and a thermochromic phase change system. The organic thermochromic phase change system was obtained by mixing the fluoran dye (heat-sensitive red TF-R2), bisphenol A, and aliphatic alcohols in a certain proportion. By filling the thermochromic phase change system into SnO2 inverse opals, the thermal-responsive photonic crystal was fabricated. Through simple external thermal stimulation, the mutual transformation of low-angle-dependent structural color and pigmentary color is realized and inverse opal patterns can be displayed and hidden. The proposed system, while preventing the interference of the observation angle to the thermal stimulation, shows potential application prospect in the fields of anti-counterfeiting and information encryption fields.

Three component thermochromic dyes including fluoran type leuco dye, n-tetradecanol, and phenolphthaleinwere prepared and encapsulated in polymethylmethacrylate in this study. Nanoencapsulated system was prepared via oil in water emulsion polymerization technique. According to the morphological investigation by SEM, nanocapsules having spherical shape, compact morphology and lower average diameter around 200 nm were prepared successfully. UV–Visible Spectroscopy analysis and the photographs taken by a digital camera indicated that thermochromic systems and their nanocapsules exhibited reversible color change with thermal stimuli. They were green color at room temperature and lost their color at temperatures upon melting point of the thermochromic systems. In the study, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone were added to the thermochromic systems to investigate UV resistance of the colorants in the systems. The effect of the UV absorbers on UV resistance of the thermochromic systems was investigated by color measurements based on CIELab system after UV aging of the nanoencapsulated systems. The results proved that especially 2,4-dihydroxybenzophenone was an effective material for increasing UV resistance of the systems and had color developer property. Besides, both thermochromic systems and their nanoencapsulated derivatives exhibited thermal energy storage/releasing property. While thermochromic systems had a heat storage capacity of over 200 J/g, the heat storage capacity of their nanocapsulated derivatives had reached up to 180 J/g. Melting temperature of the solvent n-tetradecanol decreased slightly in the thermochromic systems and further in nanoencapsulated form due to the cryoscopic effect of the non-volatile solutes in the system.

A polystyrene (PS)-based fibrous color dosimeter, comprising a color former based on 2-(phenylamino)-6-(dipentylamino)-3-methylspiro[9H-xanthene-9,3&prime, phthalide] (Black305) fluoran leuco dye and a 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (MBTT) photoacid generator, was developed for visual detection of X-ray doses of 15 Gy and higher. The composite fiber was produced by using a centrifugal spinning method, and the obtained composite fiber exhibited a stable and uniform morphology with a fiber diameter of 10 &mu, m or less and had sufficient mechanical strength. As an example of practical application, we successfully processed the composite fiber into an apron and clearly and visually confirmed that the color change from yellow to black occurs on the surface of the fabric under X-ray exposure.

A new fluorescent probe Lyso-Fl has been facilely prepared by an esterification reaction of spironolactone fluoran dye Rdi with ethanol, which shows viscosity-selective response by fluorescence. The new probe delivers obvious fluorescence signal enhancement when environmental viscosity changes from 1.01 cP (water) to 1256 cP (98% glycerol). And, both the emission intensity (575 nm) and fluorescence lifetime of Lyso-Fl exhibit individually good linear relationships with the solution viscosity. Besides, Lyso-Fl gives a selective response to viscosity among various biological species and exhibits pH-independent (1–10) fluorescent signals towards viscosity. More importantly, Lyso-Fl shows low cytotoxicity and can be utilized for monitoring of dexamethasone-stimulated viscosity enhancement by cell imaging with excellent lysosome-targeted performance, promoting it a promising fluorescent probe for lysosomal viscosity detection.

In the present study, eight self-thermochromic fluorans (STC1-STC8) were synthesized, and their reversible thermochromic properties were investigated without the use of a color developer. This work demonstrated the role of the phenol group on ring c on the thermochromic reversibility of the fluorans. Furthermore, the two-component mixtures that contained fluorans and methyl stearate were used to examine the thermochromic behaviors of the fluorans with steady heating and cooling rates. The thermochromic properties of the fluorans were evaluated using solid-state UV-Vis, reflectance and FT-IR spectroscopic techniques. DFT calculations were conducted to justify the optical behaviors of the fluorans in their spirolactam forms (STC1-STC8) and cationic forms (STC1+- STC8+). Finally, STC1 was successfully microencapsulated and applied in acrylic fiber to use as thermal indicators.

Bifunctional fluorescent probes with dual-emission response attract extensive attention. A novel fluorescent probe FP, a hybrid of fluoran and phenothiazine, has been designed and synthesized for selective sensing of Fe3+ and ClO− with dual-emission changes, which involes mechanisms of Fe3+-promoted spirolactone ring opening and ClO−-induced oxidation of phenothiazine moiety, respectively. In addition, the detection limits for Fe3+ and ClO− were estimated to be 49.1 and 35.9 nM, respectively. Significantly, FP can be employed as an tracer for the detection of Fe3+ ions within living HeLa cells by fluorescence imaging.

Dynamic control of solar transmission by photovoltaic-powered electrochromic smart windows is an up-and-coming approach towards the reduction of energy consumption in buildings. Selectively-absorbing transparent organic solar cells are capable of exhibiting excellent visible-light transparency as well as respectable power conversion efficiencies. This work presents three different transparent small-molecule solar cells (TSCs) with an area of 2.52 cm2, two of which are UV-absorbing and one of which absorbs in the NIR, each in combination with an organic electrochromic device (EC). The NIR-absorbing TSC uses a BDP-OMe:C60 combination, and has a power conversion efficiency of 4% with an average visible light transmission (AVT) of 40%. The two UV-harvesting systems, α-6T/B4PYMPM and NPB:B4PYMPM, each have an AVT of 50–65%, as well as high open-circuit voltages of 1.5–2.0 V. We demonstrate that these photogenerated voltages are sufficient to power a fluoran dye-based organic EC, which has excellent optical properties: its color ranges from highly transparent to deep black, and its on/off contrast ratio is higher than 80% in the range between 390 nm and 640 nm. Self-powered smart windows made by the combination of TSCs and ECs provide a way to significantly reduce energy consumption from air conditioning and lighting, towards zero-energy buildings.

Fluoran dyes, a large family of colourants, have been widely used as thermosensitive dyes in print industry by taking advantage of the thermo-controlled interconversions between the colorless spirolactone and the colored zwitterion forms. But few attentions have been paid to their fluorescence properties. In this paper, the fluorescence regulation of 4-aminobenzofluoran dye 1 by introducing of electron-deficient acetyl group to tune the energy level of the highest occupied molecular orbital (HOMO) of the amino group has been carried out. Based on this strategy, the N-acetylated product BF derived from its precursor 1 shows stable UV–Vis and fluorescence spectra in water from pH 1.0 to 12.0 due to the blocking of the photoinduced electron transfer (PET) process from the amino group to the excited state of fluoran chromophore. Moreover, BF is cell permeable and can be used as signal reporter for the design of fluorescence probes by taking advantage of the fluorescence controlled mechanism of the ring opening and closing chemical processes of the spirolactone platform. By using BF as precursor, a highly sensitive and selective fluorescent probe BF-Cu for Cu2+ was synthesized by introducing a Cu2+-responsive water soluble 2-hydroxylethyl hydrazine functional group. We expect that the fluorescence recovery of fluoran dyes via the regulation of the HOMO energy level of the amino group enable an additional synthetic effort on the development of fluorescence fluoran dyes and expansion of their applications.

A novel fluoran-based fluorescent probe 2 has been designed and synthesized by using a strategy of blocking the intramolecular photoinduced electron transfer (PET) process. The probe keeps a ring-closed spirolactone structure in aqueous buffer solution. However, the oxidation of the probe by ClO − perturbs a new equilibrium of the structural interconversion between the nonfluorescent spirolactone and the fluorescent ring-opened zwitterion, which generates a highly selective fluorescent probe for ClO − . Meanwhile, the probe is cell membrane permeable and can be utilized as fluorescent probe for imaging ClO − in living cells.

Traditional solar power applications largely avoid using the infrared spectrum. Nevertheless, this region makes up about 45% of the solar power spectrum and therefore represents an untapped resource. Temperature control of buildings represents a significant cost for both businesses and private consumers. We are interested in developing thermochromic materials for building coatings to help moderate solar infrared absorption and thereby offset temperature control costs for buildings. Our initial effort in this study has been to characterize materials which might represent starting points for our research. We previously designed and 3D-printed an optical test platform to perform reflectance measurements with an ultraviolet-visible-near infrared spectrometer over a spectral range from 200–1000nm. The test platform temperature can be adjusted in real time using Peltier modules. In this study, a sample of microencapsulated 7-anilino-3-diethylamino-6-methyl fluoran was studied by diffuse reflectance spectroscopy from 15-40 degrees Celsius. Scanning electron microscopy was used to characterize the dye particles. Temperature and spectral data were monitored while the sample temperature was adjusted. The visible diffuse reflectance from the sample increased from around 15% below the transition to more than 40% above the transition. A modification of this fluoran which extends the switching behavior into the infrared may be viable for passive thermo-optical switching in building coatings.

Fluoran dyes have been widely used as chromogenic reagents in piezochromic and thermochromic materials due to their intrinsic halochromic properties. However, reports on fluoran-based photochromic materials are still rare. In this work, a series of fluoran salicylaldehyde hydrazone Zn(II) complexes (1-Zn, 2-Zn and 3-Zn) were facilely prepared. The complexes exhibited excellent reversible photochromism with remarkable fatigue resistance both in solution and in a solid matrix. Due to the multiple colors of the fluoran parts, these complexes exhibited different colors after UV light irradiation. Particularly, a black color was obtained for 3-Zn, which is relatively infrequent because black photochromism systems are still very uncommon. The photochromic mechanism was proposed, where the tautomerism from the enol form to the keto form in the salicylaldehyde hydrazone moiety was induced by UV light irradiation, accompanied by a spirolactam ring-opening reaction and yielding colored products. A smaller group adjacent to the spirolactam ring was favorable for the stability of the colored products. The influences of different metal ions and solvents on the photochromism of these complexes were also studied. Moreover, patterns were successfully visualized in thin layer silica gel that was impregnated with the complexes after UV light irradiation, which suggested that they can be promising candidates for photo-patterning.

A polystyrene (PS)-based composite resin dosimeter (CRD) film comprising 2-(phenylamino)-6-(dipentylamino)-3-methylspiro[9H-xanthene-9,3'-phthalide] (Black305) fluoran leuco dye, cerium-doped yttrium aluminum perovskite YAlO3:Ce (YAP:Ce) scintillator, and 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (MBTT) photoacid generator was developed for the visualization of X-ray exposure doses in the range of 18-170 Gy. The color of the CRD film changed from yellow to black within this range based on the X-ray exposure dose. A CRD film based on Black305/YAP:Ce/MBTT/PS could be used to produce a dosimeter with various color change sensitivities by controlling the thermodynamic parameters of the constituent materials. A CRD film is a promising tool for measuring the X-ray exposure dose and can be used as an alternative to the existing radiochromic dosimeters.

A new extended-π-conjugated naphthorhodamine dye, 9′-diethylamino-2′-hydroxyl-benzo[a]fluoran (1) with a carboxylic acid-functional group was designed and synthesized. Compared to Rhodamine B, the emission wavelength of 1 was extended to ca. 600 nm, and its fluorescence properties could be controlled by the key carboxylic acid-functional group. By taking advantage of 1, we synthesized a new far-red bioimaging dye 2-ethyl-9′-diethylimino-2′-hydroxyl- benzo[a]fluoran (2) by esterification of 1, which could selectively stain mitochondria. Moreover, encouraged by the spirocyclization switching mechanism platform, we successfully constructed a new fluorescent probe 9′-diethylamino-2′-hydroxyl-benzo[a]fluoran hydrazine (3), the hydrazide derivative of 1, for Hg2+ with good selectivity. These results suggest that the new naphthorhodamine dye could be used as a platform to construct fluorescent probes and bioimaging reagents.

In the present study, six tert-butyl substituted fluorans have been synthesized, and their reversible thermochromic properties have been investigated. This work is the first direct demonstration of the role of the substituent on the lactone concerning the thermochromic reversibility of the fluoran. The electron donating substituents induced greater chromic effects than the electron withdrawing substituents. Furthermore, the three-component mixtures that contained fluorans, bisphenol-A, and methyl stearate or 1-dodecanol were used to examine the thermochromic behavior of the fluorans as bulk samples with steady heating and cooling process. The thermochromic properties of the fluorans were evaluated using solid-state UV–Vis, reflectance and FT-IR spectroscopic techniques. DFT calculations were conducted to rationalize the optical behavior of the fluoran in spirolactam form and cationic form. Finally, one of the synthesized fluoran has been successfully converted into the form of a test paper similar to pH paper and acrylic fiber tape for use as thermal indicators.

An electroswitching device that enables modulation of both emission and coloration was obtained by combining luminesncent/electrochromic (EC) molecules of a fluoran molecule (Yellow-1) and 1,4-benzoquinone (BQ). Electroswitching of emission and coloration was achieved by the reversible electrochemically induced closing and opening of the lactone ring in Yellow-1. Neutral Yellow-1 was colorless and did not exhibit any fluorescence, while oxidized Yellow-1 (lactone ring-opened form) was yellow and displayed green fluorescence because of its extended, planar, and conjugated system. In order to achieve quick response time and high reversibility of the electroswitching optical device for modulating both emission and coloration, a BQ molecule was introduced as a bifunctional material. The inclusion of a redox-active moiety on the auxiliary electrode maintained the charge balance and acted as an EC molecule (transparent/yellow in neutral/reduced state, respectively). BQ acted as a bifunctional molecule, leading to quick and stable switching of both emission and coloration.

A novel black crystalline composite was prepared using a fluoran dye and a bisphenol S derivative for high performance thermal paper. This composite can be potentially applied as a functional black ink without near-infrared absorption. In addition, the coloured structure of the fluoran dye with the developer was successfully analysed.

A new N-heterocyclic fluoran based dye BiF is facilely prepared in high yield by reaction of 5-methoxybenzimidazole and 2-(4-diethylamino-2-hydroxy)benzoylbenzoic acid in concentrated H2SO4, which keeps stable optical signals in water at pH values ranging from 4 to 10 and exhibits good living cell membrane permeability. By modification of the spirolactone in molecule BiF, a fluorescent probe BiF–Cu with specific and sensitive response to Cu2+ has been further developed, which contains a six-membered spirolic hydroxyethylhydrazide moiety that can be selectively triggered by Cu2+ among various metal ions through a specific cascade reaction of Cu2+-promoted spirolactam ring-opening and hydrolysis. A limit of detection for Cu2+ is calculated as 7.12 × 10−8 mol/L. In addition, the utilization of BiF–Cu for bioimaging Cu2+ in L929 cells demonstrates its living cell membrane permeability and makes it promising candidate for monitoring Cu2+ by cell imaging technology.

A radiation colour former amino fluoran dye, Pergascript Orange (PGO), in a polyvinyl butyral solution containing a colour developer, hexachloroethane (HCE), was prepared and investigated for radiotherapy dosimetry of 60Co, 6 MV and 15 MV photons. PGO, a colourless dye, reacts with the acid produced upon radiation exposure of HCE, enabling the lactone ring to open and the orange colour of PGO to develop. The ring opening of PGO was confirmed by the appearance of a broad peak of OH− at 3360 cm−1, C O carboxylic peak at 1763 cm−1, and an iminium group peak at 1640 cm−1. The dose response of all prepared compositions was linear in the dose range of 1–20 Gy. Increasing HCE in the dosimeter matrix from 63 mM to 106 mM enhanced the radiation sensitivity by ≈58%. The radiation sensitivity of PGO-PVB (PGO-P) dosimeter is comparable with Fricke gel and higher than N-(Isobutoxymethyl) acrylamide polymer gel dosimeters. The experimental results reveal an energy-independent response (≈1.2% variation at 1σ) in the studied range of radiotherapy beam quality from 60Co beams to the beams from Linacs with a maximum energy of 15 MeV. Based on the theoretical study, this dosimeter is water equivalent from 80 keV to 10 MeV. The overall uncertainty was found to be 4.5% at the 95% confidence level, indicating the possibility of using PGO-P dosimeter in conventional radiotherapy dose verification.

In the present study, two fluoran molecules (TH1 and TH2) have been synthesized, and their reversible thermochromic properties have been investigated. This work demonstrates the thermochromic reversibility of the fluoran. Furthermore, the three-component mixtures that comprising fluorans (TH1/TH2), bisphenol-A (color developer), and methyl stearate a low melting solvent were used to examine the thermochromic behavior with sturdy heating and cooling rates and the thermochromic properties of the fluorans were detailed using UV-Vis, reflectance and FT-IR spectroscopic techniques. Finally, test strip similar to pH paper and acrylic fiber a versatile material used as thermal indicators also been successfully made from these two fluoran derivatives.

Two functionalized rhodamine based probes have been rational designed and synthesized. The probes have sufficiently high selectivity and sensitivity for the detection of Fe3+ ion both by fluorescence and ultraviolet spectroscopy with strong ability of anti-interference performance. The detection process has been shown to be reversible and involves the fluoran ring-opening upon complexation with Fe3+. The obvious fluorescence image obtained from confocal laser scanning microscopy of the detection of Fe3+ in living L929 cells demonstrate that the probes could contribute to significant breakthroughs in understanding the critically important functions of Fe3+ in related cells and biological organs.

The reductive alkylation of fluoran green base with hydroxybenzaldehydes gave novel fluorans that exhibited thermochromism, reversibly changing colour from very pale pink to deep green, in methyl stearate and in microcapsules containing methyl palmitate/isopropyl palmitate without the need of an added phenolic colour developer. Acylation of fluoran green base with O -acetylsalicyloyl chloride and subsequent cleavage of the acetyl group gave a new colour former bearing an o -hydroxybenzoyl moiety which also exhibited thermochromism, reversibly changing from colourless to red.

The utilization of a fluoran leuco sensitizer, 2-anilino-6-dibutyl amino-3-methylfluoran (ODB-2), for dye-sensitized solar cells (DSSCs) was investigated through the examination of the adsorption of ODB-2 molecules onto the surfaces of porous titanium dioxide (titania, TiO2) films and the photovoltaic properties of ODB-2-based DSSCs. Despite of the absence of the specific anchoring groups with titania, ODB-2 dye molecules were spontaneously adsorbed onto the titania surfaces because the lactone ring in ODB-2 was opened and changed into the carboxylic acid (-COOH) by releasing protons from the surfaces (TiOH2 + ) of titania, which consequently leads to the chemisorption reaction of ODB-2 molecules to the active sites of titania. DSSCs based on ODB-2 exhibited typical photovoltaic properties with an open-circuit voltage (VOC) of 0.19 V, a short-circuit current (JSC) of 0.30 mA·cm -2 , a fill factor (FF) of 37%, and a conversion efficiency (PCE) of 0.02%.

A multifunctional composite film that exhibited thermoresponsive absorption and emission was fabricated using a thermochromic fluoran dye, its developer, and a luminescent europium(III) complex. The emissions from and coloration of this composite film could be reversibly changed and maintained via the thermochromic reaction taking place within the fluoran dye–developer system. The coloration and decoloration of the composite film were caused by thermoresponsive control of the nanoscale aggregation of structures of the fluoran dye and its developer, whose molecular structure consisted of a long alkyl chain. The control of the phenomenon of photoluminescence could also be achieved via thermochromism, which was induced by intermolecular energy transfer from the Eu(III) ions in the excited state to the fluoran dye.

Fluorans are popular leuco dyes that are used in various applications, such as carbonless-copy papers and thermal papers. Here, we describe unique leuco dyes in which two fluoran units are fused into a C2h structure (iso-aminobenzopyranoxanthenes; iso-ABPXs). iso-ABPXs exhibited a large two-step color change (colorless/pink and pink/blue-green) due to opening-closing of two spirolactone rings. The two-step equilibrium among the colorless, pink, and blue-green forms could be well controlled by adjusting acid concentration, solvent, and/or temperature.

We have investigated the Hg 2+ transport from Crystal Violet Lactone to Fluoran dye based on the association constant, K ass . Upon addition of Hg 2+ , the Crystal Violet Lactone shows a new peak at around 603 nm, and the color of the solution changed from colorless to blue. With the addition of Fluoran dye in this solution containing Crystal Violet Lactone and Hg 2+ , the absorption intensity of Fluoran dye at 447 nm and 586 nm was all increased. So the color of solution gradually became black from blue color. From the changes of the ratio A 586 /A 447 , it is apparent that the Hg 2+ in Crystal Violet Lactone–Hg 2+ was transported to colored Fluoran. The Hg 2+ transport from Crystal Violet Lactone to Fluoran dye was also carried out by the calculation of the association constant: the binding ability for the complex formation of Fluoran dye and Crystal Violet Lactone–Hg 2+ is much greater in CH 3 CN solution ( K ass = 3.0 × 10 4 M −1 ) than that of the Crystal Violet Lactone with Hg 2+ ( K ass = 1.2 × 10 3 M −1 ).

The palladium-catalysed amination of readily accessible bromofluorans and bromobenzo[a]fluorans has been accomplished with a series of anilines and morpholine. The resulting aminofluorans generated intense black shades upon formulation in methyl stearate containing bisphenol A. The route provides an alternative approach to various amino substituted fluorans without the need of a series of individual diphenylamine intermediates.

[Purpose] To show storage-resistant food internal quality changes such as canned food. [Method] By measuring the time-temperature-gray relational model of thermo-sensitive paper, compare it with the time-temperature-quality movement model of storage-resistant food. [Results] The analysis of the example show that: through controlling the production process and prescription of thermo-sensitive paper, adjusting the dosage of color-producing reagent, enabling the variation rule of gray match with the quality change of storage-resistant food. [Conclusions] Based colorless dyestuff 2-phenyl-3-methyl-6, 6-2 D-amino fluoran and 2, 2-bis (4-hydroxyphenyl) propane color developer thermo-sensitive system, through controlling the production process and prescription of thermo-sensitive paper to show the quality change of storage-resistant food.

A highly selective chemosensor based on fluoran dye for Fe(2+), 2'-anilino-3'-methyl-6'-dibuthylamino-N-((2'-(2''-ethylimino) methyl) naphthalen-2-ol) iso-indolin-1-one-fluoran (5), was designed and synthesized. The chemical structures of all the intermediates and the fluoran dye 5 are characterized by (1)H NMR, (13)C NMR, Ms and elemental analysis. Upon addition of Fe(2+), the fluoran dye 5 shows a new peak around 658nm in its absorption spectra, and the color of solution changed from colorless to greenish black. Whereas other ions including Mg(2+), Pb(2+), Ni(2+), Hg(2+), Cd(2+), Fe(3+), Cu(2+), Zn(2+) and Al(3+) and so on induced basically no spectral change, which constituted a Fe(2+) highly sensitive and selective colorimetric chemosensor by "naked eyes".

Crystal structure analysis was carried out on two novel, urea–urethane developers for high-performance thermo-sensitive paper. Crystals of the compounds displayed a multiple hydrogen-bonded network between the urea and urethane moieties, which stabilized the fluoran dyes, thereby imparting high fastness to printed images.

For the purpose of improving the visible method of γ-rays detection, detailed conditions with various acids have been examined for the color development of a fluoran-based black color former in acetonitrile. It is suggested that the protons (H + ), which may be produced from acid generators by γ-ray radiation, can be properly detected by the color development of the black color former containing proper kinds and concentrations of bases. Reversible decolorization through the interaction between Mg 2+ and polyamines (acyclic and macrocyclic) has been examined in order to reconfirm that the colored zwitterion is produced by the direct chemical interaction with Mg (ClO 4 ) 2 in the fluoran dye–acetonitrile solution.