Luminescence Response Research Articles

Evaluation of TL and OSL responses of CaF2:Tm for electron beam processing dosimetry

The thermoluminescence (TL) and infrared stimulated luminescence (IRSL) responses of in-house produced CaF2:Tm dosimeters are investigated in this work, envisaging their application in electron beam (EB) radiation processing. The irradiations were performed at an industrial EB accelerator (1.5 MeV) covering a dose rate range of 2–8 kGy/s and dose up to 10 kGy. In general, the TL glow curves display four peaks, termed as peaks 2, 3, 4, and 5, corresponding to temperatures at ~150, 200, 240, and 300 °C, respectively. The intensity of the low-temperature peaks (2 and 3) grows with the dose, while the others remain constant (saturated). Nevertheless, an evident dose effect on the glow curves manifests in decreased peak3/peak2 ratio with increasing doses.The CW-IRSL curves exhibit similar patterns with an initial signal increase, followed by an exponential decay. Instead of the normal monotonic decays, these peak-shaped curves might be due to the charge capture competition between empty shallow traps and recombination centers. Both TL and IRSL intensities increase linearly with doses up to 6 kGy, and for higher doses, they become sub-linear with a saturation trend around 10 kGy. Another common feature of TL/IRSL response is its dose rate dependence, being more sensitive at higher dose rates. Despite being dose-rate dependent, the CaF2:Tm dosimeters might be suitable for EB processing dosimetry. However, for their use as routine dosimeters, relevant dosimetric characteristics, such as fading and response reproducibility, have to be investigated. Work in this direction is underway.

Composition-Thermometric Properties Correlations in Homodinuclear Eu3+ Luminescent Complexes.

A family of homodinuclear Ln3+ (Ln3+ = Gd3+, Eu3+) luminescent complexes with the general formula [Ln2(β-diketonato)6(N-oxide)y] has been developed to study the effect of the β-diketonato and N-oxide ligands on their thermometric properties. The investigated complexes are [Ln2(tta)6(pyrzMO)2] (Ln = Eu (1·C7H8), Gd (5)), [Ln2(dbm)6(pyrzMO)2] (Ln = Eu (2), Gd (6)), [Ln2(bta)6(pyrzMO)2] (Ln = Eu (3), Gd (7)), [Ln2(hfac)6(pyrzMO)3] (Ln = Eu (4), Gd (8)) (pyrzMO = pyrazine N-oxide, Htta = thenoyltrifluoroacetone, Hdbm = dibenzoylmethane, Hbta = benzoyltrifluoroacetone, Hhfac = hexafluoroacetylacetone, C7H8 = toluene), and their 4,4′-bipyridine N-oxide (bipyMO) analogues. Europium complexes emit a bright red light under UV radiation at room temperature, whose intensity displays a strong temperature (T) dependence between 223 and 373 K. This remarkable variation is exploited to develop a series of luminescent thermometers by using the integrated intensity of the 5D0 → 7F2 europium transition as the thermometric parameter (Δ). The effect of different β-diketonato and N-oxide ligands is investigated with particular regard to the shape of thermometer calibration (Δ vs T) and relative thermal sensitivity curves: i.e.. the change in Δ per degree of temperature variation usually indicated as Sr (% K–1). The thermometric properties are determined by the presence of two nonradiative deactivation channels, back energy transfer (BEnT) from Eu3+ to the ligand triplet levels and ligand to metal charge transfer (LMCT). In the complexes bearing tta and dbm ligands, whose triplet energy is ca. 20000 cm–1, both deactivation channels are active in the same temperature range, and both contribute to determine the thermometric properties. Conversely, with bta and hfac ligands the response of the europium luminescence to temperature variation is ruled by LMCT channels since the high triplet energy (>21400 cm–1) makes BEnT ineffective in the investigated temperature range.

Optical Activity of Chiral Metal Nanoclusters

ConspectusThe emerging chirality in nanomaterials represents one of the most dynamic areas in modern science. Although many novel chiral nanomaterials have been reported, the origin of their chirality and related optical activity have been not unveiled unambiguously. Thanks to the fast development of noble metal cluster chemistry, the structures of many chiral nanoclusters (CNCs) have been precisely determined and their chirality origin has been decoded as four different levels including chiral ligand, helix staple motif, asymmetry metal kernel, and chiral arrangement of organic ligands. Generally, the strong optical activity associated with the electron transitions of the noble metal core is popularly reported among CNCs protected by chiral ligands, following the so-called “outside-in” chirality transfer theory, namely, from organic ligand to metal core. Exceptionally, inherent chiral structures are discerned inside CNCs consisting of achiral ligands, such as the helix staples found in Au38(SR)24 and Au102(SR)44 (SR = thiolate) and the chiral metal kernel existing in Au20(PP3)4Cl4 (PP3 = tris(2-(diphenylphosphino)ethyl) phosphine). These chiral nanostructures induce distinct optical activity and even present reversed chirality transformation in the case of Au38(SR)24 (i.e., from chiral core structure to organic ligand). In the past decade, our group has carried out extensive research work on preparation, enantioseparation, optical activity, and application of chiral inorganic nanostructures. As representatives, enantiopure right-handed and left-handed Au20(PP3)4Cl4 clusters of intrinsic kernel chirality were acquired through an innovative supramolecular self-assembly method and their circular dichroism (CD) feature involving only the metal core was systematically studied; Au3[R/S-Tol-BINAP]3Cl (R/S-Tol-BINAP: R/S-2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl) clusters with the smallest metal-atom number among the reported CNCs were designed and synthesized by using the privileged chiral Tol-BINAP ligand, which exhibited not only strongly enhanced CD signal also remarkable circular polarized luminescence (CPL) response as self-assembled into monodispersed nanocubes.In this Account, we aim at reviewing the fast development of CNCs featuring strong chiral attributes and optical activity. We will briefly introduce the preparation methods of CNCs, such as direct synthesis, ligand exchange, and enantioseparation. In the following parts, the commonly used tools for characterizing the chirality of CNCs are summarized, including CD, vibrational circular dichroism (VCD), CPL, single X-ray diffraction, nuclear magnetic resonance (NMR), and theoretical prediction. Then, the optical activity of CNCs will be systematically discussed, especially their CD, VCD, and CPL activity along with their chirality origin. Finally, future strategies for fabricating CNCs possessing strong optical activity as well as potential chirality-related applications will be proposed. We believe that this Account will trigger more research interest to not only study the amazing optical activity of CNCs but also employ them in many fields.

STRUCTURE AND LUMINESCENT PROPERTIES OF EUROPIUM(III) COORDINATION POLYMERS WITH THIOPHENE LIGANDS

Three new metal-organic frameworks based on sulfur-containing 2,2′-bithiophene-5,5′-dicarboxylic acid (H2btdc) and thieno[3,2-b]thiophene-2,5-dicarboxylic acid (H2ttdc) are obtained. Their compositions are: [Eu(DMF)2(NO3)(btdc)]·DMF (1), [Eu2(H2O)2(DMF)(btdc)3]·H2O·3DMF (2), and [Eu2(DMF)4(ttdc)3]· 4DMF (3). Structures of the compounds are determined by single crystal X-ray diffraction: 1 is a layered compound whereas 2 and 3 have a three-dimensional framework with channel-like pores. The specific volume of cavities in the structures of 1-3 varies from 34% to 37%. Compounds 2 and 3 are characterized by IR spectroscopy, elemental and thermogravimetric analyses. The luminescent properties of solid samples of 3 are studied and a luminescent response (a threefold excess of the luminescence quantum yield of the 3⊃cyclohexane adduct in comparison with 3⊃benzene) is revealed.

Striking luminescence phenomena of carbon dots and their applications as a double ratiometric fluorescence probes for H2S detection

Here, we report some new observations on the luminescence of carbon dots (CDs) that are passivated with polyethylene glycol, and explored them, for the first time, as highly sensitive H2S detection probe. The as-prepared CDs have an ultraviolet (UV) emission at 350 nm and a green emission at 540 nm when excited at 270 nm, but they have only a green emission at 523 nm when excited at 365 nm. As Na2S is added to the CDs, the UV emission decreases gradually, while the green emission increases slightly, and interestingly a new emission appears at 455 nm is increased linearly in intensity with the increase of Na2S concentration. The blue emission at 455 nm is from the intrinsic core of CDs, and the green emissions at 540 or 523 nm are from their surface states, while the UV emission at 350 nm is from the anchored PEG. Both the emission intensity ratios of F450/F350 and F455/F523 show an excellent linear relationship with the Na2S concentration in the range of 0–800 μM, and the detection limit estimated from both of them is approximately 7.0 nM, indicating our method is the most sensitive H2S CDs based detection method reported thus far. Furthermore, the detection was tested successfully for H2S imaging in live cells. We propose that the interactions of H2S with the CDs and the anchored ligands, as well as the energy transfer between the ligands and the CDs, are responsible for the luminescence responses for H2S detection. Our studies enrich the world of carbon dots with plenty of potential applications.

Construction of a nanoscale Yb(III) Schiff base complex with NIR luminescence response to anions and nitro explosives

A nanoscale Yb(III) complex [Yb6(L1)2(L2)4(OH)4(CF3SO3)2(DMF)2(EtOH)4]·2(CF3SO3)·2OH (1) with Schiff base ligand N,N′-bis(3-methoxysalicylidene)(binaphthyl)-1,4-diamine (H2L1) and salicylaldehyde ligand 3-methoxysalicylaldehyde (H2L2) was synthesized. Upon excitation of the ligand-centered absorption bands, 1 displays typical NIR luminescence of Yb(III). Interestingly, it shows lanthanide luminescence response to anions and nitro explosives, especially with high sensitivity to F− and PA. Meanwhile, the quenching effect of F− and PA to the lanthanide luminescence of 1 is not affected by the existence of other anions and explosives.

Synthesis of Near-Infrared Mechanoluminescence Material Via Organic Acid-Aided Process

A mechanoluminescence (ML) material is a kind of phosphor. There has been attracting attention as a sensing material capable of two-dimensionally visualizing physical phenomena such as strain, stress, or load [1-5]. In particular, the ML material that emits near-infrared (NIR:0.75~1.0 μm) and short-wave infrared (SWIR:1.0~2.5 μm) luminescence has biological transparency and a wavelength range different from a room illumination and is expected to spread a new applying field [6-7]. To use the ML material for physical sensing technology using an inorganic-organic hybrid film mixed with resin, the diameter of the ML particle needs to be several micrometers or less. However, the ML material is commonly synthesized by a solid-state reaction method at a rather high temperature above 1400°C, resulting in the formation of large particle size. Such a large ML particle is pulverized under a mechanically milling process to reduce the particle size, producing crystal defects. The crystal defects are known to be one of the causes of the charge career trapped sites in the ML material, posing deterioration of the ML intensity as well as a decrease in the reproducibility of sensing characteristics. Thus, to develop an ML material having a high ML intensity, it is necessary to establish a synthetic method capable of lowering the sintering temperature. For a decrease in the sintering temperature of the functional oxides, it has been reported that it is effective to produce a precursor whose particle size and shape are controlled by a solution technique. Although there have been numerous reports regarding the solution technique, an organic acid-aided method is suitable for producing a complicated material with a multi-element composition because it desolvates an aqueous solution and remains all the metal compounds [8]. In the present study, therefore, we tried to synthesize ML material by using the organic acid-aided method and evaluated both optical properties under visible light and near-infrared regions. Among various ML materials reported, we selected SrAl2O4 co-doped with Eu, Cr, and Nd ions (SAOEuCrNd) which emits both NIR and SWIR luminescence [7] and selected malic acid as a representative organic acid. For comparison, SrAl2O4 doped with Eu (SAOEu), SrAl2O4 co-doped with Eu,Cr (SAOEuCr), or Eu,Nd (SAOEuNd) were also synthesized by using the same synthetic method. The synthesized ML materials were evaluated by various analysis instruments.From x-ray diffraction (XRD) patterns of the synthesized ML materials, all the diffraction peaks coincided with those of the monoclinic SrAl2O4 (PDF no. 34-0379). This indicates that monoclinic SrAl2O4 can be synthesized by the organic acid-aided method even by using various luminescent center ions. The photoluminescence (PL) spectra of all the synthesized ML materials exhibited a broad emission which is centered at approximately 520 nm under excitation at 365 nm. On the other hand, Nd-doped ML materials such as SAOEuNd and SAOEuCrNd showed several peaks at around 900, 1100, and 1400 nm under excitation at 365 nm. The PL intensities under NIR and SWIR regions for SAOEuCrNd were much higher than those for SAOEuNd. Logically, it is reasonable to expect that Cr ion behaved as a sensitizer such as an energy transfer mechanism of YAG:Cr,Nd. Finally, we evaluated the ML intensity under NIR and SWIR regions for the synthesized ML materials by using a lab-built system comprising Si image sensor and optical filter (pass long wavelengths >750 nm). As a result, Nd-doped ML materials showed ML response toward the tensile strain and the ML intensity increased with increasing the tensile strain, although there is no luminescence response toward the tensile strain for SAOEu. Especially, SAOEuCrNd exhibited the highest ML intensity. Thus, the SAOEuCrNd synthesized by the organic acid-aided method using metal nitrates and malic acid is a promising candidate for ML materials which emits both NIR and SWIR luminescence.[1] C.N. Xu, T. Watanabe, M. Akiyama, X.G. Zheng, Appl. Phys. Lett., 74(9), 1236 (1999).[2] C.N. Xu, T. Watanabe, M. Akiyama, X.G. Zheng, Appl. Phys. Lett., 74(17), 2414 (1999).[3] A. Yoshida, L. Liu, D. Tu, S. Kainuma, C.N. Xu, J. Disaster Res., 12, 506 (2017).[4] N. Terasaki, Y. Fujio, S. Horiuchi, and H. Akiyama, Int. J. Adhes. Adhes., 93, 40 (2019).[5] Y. Fujio, C. N. Xu, Y. Sakata, N. Ueno, N. Terasaki, J. Alloys Compd., 41, 154900 (2020).[6] D. Tu, C.N. Xu, S. Kamimura, Y. Horibe, H. Oshiro, L. Zhang, Y. Ishii, K. Hyodo, G. Marriott, N. Ueno, X.G. Zheng, Adv. Mater., 1908083 (2020).[7] N. Terasaki, C.N. Xu, WO 2015033648, September 9, 2013.[8] Y. Teraoka, H. Kakebayashi, I. Moriguchi, S. Kagawa, Chem. Lett., 20(4), 673 (1991).

Microwave-Assisted Synthesis of Chalcopyrite/Silver Phosphate Composites with Enhanced Degradation of Rhodamine B under Photo-Fenton Process.

A new composite by coupling chalcopyrite (CuFeS2) with silver phosphate (Ag3PO4) (CuFeS2/Ag3PO4) was proposed by using a cyclic microwave heating method. The prepared composites were characterized by scanning and transmission electron microscopy and X-ray diffraction, Fourier-transform infrared, UV–Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. Under optimum conditions and 2.5 W irradiation (wavelength length > 420 nm, power density = 0.38 Wcm−2), 96% of rhodamine B (RhB) was degraded by CuFeS2/Ag3PO4 within a 1 min photo-Fenton reaction, better than the performance of Ag3PO4 (25% degradation within 10 min), CuFeS2 (87.7% degradation within 1 min), and mechanically mixed CuFeS2/Ag3PO4 catalyst. RhB degradation mainly depended on the amount of hydroxyl radicals generated from the Fenton reaction. The degradation mechanism of CuFeS2/Ag3PO4 from the photo-Fenton reaction was deduced using a free radical trapping experiment, the chemical reaction of coumarin, and photocurrent and luminescence response. The incorporation of CuFeS2 in Ag3PO4 enhanced the charge separation of Ag3PO4 and reduced Ag3PO4 photocorrosion as the photogenerated electrons on Ag3PO4 were transferred to regenerate Cu2+/Fe3+ ions produced from the Fenton reaction to Cu+/Fe2+ ions, thus simultaneously maintaining the CuFeS2 intact. This demonstrates the synergistic effect on material stability. However, hydroxyl radicals were produced by both the photogenerated holes of Ag3PO4 and the Fenton reaction of CuFeS2 as another synergistic effect in catalysis. Notably, the degradation performance and the reusability of CuFeS2/Ag3PO4 were promoted. The practical applications of this new material were demonstrated from the effective performance of CuFeS2/Ag3PO4 composites in degrading various dyestuffs (90–98.9% degradation within 10 min) and dyes in environmental water samples (tap water, river water, pond water, seawater, treated wastewater) through enhanced the Fenton reaction under sunlight irradiation.

Multifunctional rhodamine B appended ROMP derived fluorescent probe detects Al3+ and selectively labels lysosomes in live cells

There a few reports of rhodamine-based fluorescent sensors for selective detection of only Al3+, due to the challenge of identifying a suitable ligand for binding Al3+ ion. The use of fluorophore moieties appended to a polymer backbone for sensing applications is far from mature. Here, we report a new fluorescent probe/monomer 4 and its ROMP derived polymer P for specific detection of Al3+ ions. Both monomer 4 and its polymer P exhibit high selectivity toward only Al3+ with no interference from other metal ions, having a limit detection of 0.5 and 2.1 µM, respectively. The reversible recognition of monomer 4 and P for Al3+ was also proved in presence of Na2EDTA by both UV–Vis and fluorometric titration. The experimental data indicates the behavior of 4 and P toward Al3+ is pH independent in medium conditions. In addition, the switch-on luminescence response of 4 at acidic pH (0 < 5.0), allowed us to specifically stain lysosomes (pH ~ 4.5–5.0) in live cells.

Novel Platinum(II) Complex-based Luminescent Probe for Detection of Hypochlorite in Cancer Cells.

Hypochlorite (ClO⁻) is of great importance either for the metabolism of living organisms or as disinfectant in daily life. However, improper concentration levels of ClO⁻ lead to serious health problems including erythrocyte damage, cardiovascular problems, neuron degeneration, lung/kidney injury and cancer. Therefore, a sensitive and selective detection method is required for the visualization and measurement of ClO⁻. In this work, a novel platinum(II) complex-based luminescent probe Pt-CHO was synthesized and utilized to detect ClO⁻. This "turn-off" probe exhibits high sensitivity, excellent selectivity, good pH stability, low limit of detection and instantaneous response ability. Moreover, the luminescent response is caused by the oxidation of aldehyde into carboxyl groups combined with the coordination of hydroxyl groups at the Pt center, which is rarely reported. The cell imaging of HeLa cells proved the considerable potential of the probe for ClO⁻ imaging in living cells.

Thermal stability improvement of sprayable fast-responding pressure-sensitive paint for measurement above 100 °C

The thermal stability of sprayable fast-responding Pressure-Sensitive Paint (fast PSP) was investigated to explore the possibility for application in turbomachinery and hypersonic research with temperature above 100 °C. The first part of the study focused on a widely-used Polymer Ceramic PSP (PC-PSP). The effects of thermal degradation on its key sensing properties, including luminescent intensity, pressure sensitivity and response time, were examined for a temperature range from 60 to 100 °C. Severe degradation in intensity and pressure sensitivity was found as temperature reached 70 °C or higher, which would cause failure of PSP application in these conditions. Subsequently, a fast-responding Mesoporous-Particle PSP (MP-PSP) was developed which did not show degradation effects until 140 °C. The greatly improved thermal stability of MP-PSP was attributed to: selection of polymer with higher glass transition temperature (polystyrene) to delay the saturation effect of oxygen quenching as temperature increased; porous and hollow structure of particles for luminophore deposition that minimizes polymer–luminophore interaction. This new paint formulation has significantly raised the upper temperature limit of fast PSP and offers more opportunities for applications in harsh environment.

Construction of two lanthanide schiff base complexes: Chiral “triple-decker” structure and NIR luminescent response towards anions

Two 4f and 3d-4f complexes [Yb3L3(OAc)3] (1) and [Zn2NdL2(OAc)3] (2) were constructed from Schiff base ligand N,N′-bis(3-methoxysalicylidene)(4-methylphenylene)-1,2-diamine (H2L). 1 shows a chiral “triple-decker” structure with Yb3+ ions sandwiched between the alternating layers of Schiff base ligands, while 2 exhibits a “cross” structure with the Nd3+ ion clipped by two ZnL groups. Open 3D channel structures running along the a-axis are formed in the solid state of 1 and 2. Excited by ligand-centered absorption bands, 1 and 2 show typical NIR emission of Yb3+ and Nd3+, respectively. Interestingly, 2 exhibits lanthanide luminescent response towards anions, especially to CN− and OAc− at ppm level.

One Nanoscale Zn(II)-Nd(III) Complex With Schiff Base Ligand: NIR Luminescent Sensing of Anions and Nitro Explosives.

One Zn-Nd complex [Zn2Nd4L2(OAc)10(OH)2(CH3OH)2] (1) was synthesized from Schiff base ligand bis(3-methoxysalicylidene)ethylene-1,2-phenylenediamine (H2L). 1 shows nanoscale rectangular structure with sizes of about 0.8 × 1.1 × 2.8 nm. 1 exhibits typical near-infrared luminescence of Nd(III) under the excitation of UV-visible light. Further study shows that the complex displays luminescent response behavior to anions and nitro explosives, especially with high sensitivity to H2 and 2,4,6-trinitrophenol.

Luminescent sensors based on coordination polymers with adjustable emissions for detecting biomarker of pollutant ethylbenzene and styrene

Sensitive luminescent probes for phenylglyoxylic acid (PGA), which is a biomarker of ethylbenzene and styrene (EB/S) representing the internal dose of EB/S exposure, have been constructed on the basis of newly designed luminescent coordination polymers (LCPs). Three isostructural LCPs with different lanthanide centers were solvothermally synthesized and fully characterized. All the LCPs 1–3 display strong regulated emissions by the adjustable metal–organic coordination interactions. Among LCPs 1–3, the fabricated LCP 2 can quantitatively detect PGA with the highest sensitivity in physiologically relevant ranges. The mechanism study of luminescent responses toward PGA further explains the excellent sensitivity and selectivity of LCP 2 for sensing PGA. The facile, accurate, fast, and recyclable sensing system relying on LCP materials provides a convenient approach for developing sensing platforms with adjustable emissions for assessment of the intoxication level of EB/S.

Kinetics of the Luminescence Response of Self-Assembled Ge(Si) Nanoislands Embedded in Two-Dimensional Photonic Crystals

The results of studies of the spectral and kinetic characteristics of the photoluminescence of photonic crystals formed on the basis of structures with self-assembled Ge(Si) nanoislands are reported. The experimentally observed enhancement of the photoluminescence-signal intensity of the nanoislands in the spectral range 1.1–1.6 μm due to interaction with the radiative modes of photonic crystals in the vicinity of the Γ point of the Brillouin zone and the effect of such interaction on the probability of radiative recombination in Ge(Si) nanoislands are considered.

Construction of a Nano‐rectangular Zn(II)‐Yb(III) Complex with Near‐Infrared Luminescent Response towards Metal Ions

Summary of main observation and conclusionOne six‐metal Zn(II)‐Yb(III) complex [Zn2Yb4L2(OAc)10(OH)2(CH3OH)2] (1) was constructed from Schiff base ligand bis(3‐methoxysalicylidene)ethylene‐1,2‐phenylenediamine (H2L). 1 shows a nanoscale rectangular structure with dimensions of approximately 0.8 nm × 1.1 nm × 2.8 nm. Excited by ligand‐centered absorption bands, 1 shows typical near‐infrared emission of Yb3+ ion. Interestingly, 1 exhibits lanthanide luminescent response towards metal ions, especially to Cd2+ at ppm level.

Construction of a High-Nuclearity Elliptical Yb(III) Nanoring: NIR Luminescent Response to Metal Ions and Nitro Explosives.

One 14-metal Yb(III) nanoring [Yb14(HL)2L20(DMF)8(H2O)8] (1) with a size of about 1.1 × 2.5 × 2.7 nm was synthesized from a tridentate ligand. Under the excitation of ligand absorption bands, 1 exhibits the NIR luminescence of Yb(III) and displays high luminescence sensitivity and selectivity to Co(II), Cu(II), and 2,4,6-trinitrophenol (PA) at the parts per million level. The KSV values of 1 to Co(II), Cu(II), and PA are 6.0 × 104 M-1, 3.8 × 104 M-1, and 6.9 × 104 M-1, respectively. 1 exhibits high luminescent sensitivity to PA even in the presence of other explosives.

Electrofluorochromic Device Based on a Redox-Active Europium(III) Complex

Electrofluorochromism owing to redox reactions on the center europium (Eu) ion in ionic liquids is examined for the helicate complexes (abbreviated as EuL) with a hexadentate pyridine derivative. Typical electrofluorochromism requires extra electroactive units complementing intra- or intermolecular energy transfer to quench fluorophores. Herein, an unprecedentedly simplified electrofluorochromic system overcoming such issues is demonstrated by utilizing reversible electrochemistry of EuL between Eu3+ and Eu2+, which accompanies large emission transition. A three-electrode electrochemical switching device is facilely prepared with an ionic liquid [BMIM][PF6] and EuL mixture. Benefiting from the stable helical coordinated structure of the ligand in [BMIM][PF6], highly enhanced red fluorescence of EuL with small quantity (≤1 wt %) is utilized. Rapid response and large contrast of luminescence are achieved: the emission is drastically quenched at the reduced state (Eu2+) and it is successfully restored by subsequent oxidation (Eu3+). The reversible fluctuation of excitation and emission spectra of an electrofluorochromic device is achieved in the potential window within ±2 V. The device affords excellent optoelectric properties in terms of well-controlled luminescence switching depending on the applied potentials and its durability. This work paves an efficient and smart way toward Eu luminescence control in optoelectronic devices.

Ion-beam induced luminescence and optical response measurement setup at IGCAR: First experimental results

A multipurpose novel experimental setup has been developed for the in situ measurements of ion-beam induced luminescence, optical response, and time-resolved photoluminescence spectroscopy of materials. A low-energy ion accelerator (terminal voltage of 150 kV) has been coupled with the spectrometer for the experiments. Measurements show a drastic increase in the luminescence intensity at 425 nm with the maximum fluence of 120 keV He+ ion irradiation on pure monoclinic ZrO2 samples. The maximum luminescence intensity is found to increase systematically with the ion fluences. An excess of oxygen defects in irradiated ZrO2 samples is thought to be the reason for the increase in the luminescence intensity. In addition, the He+ ion-beam induced increase in optical responses at 425 nm in Ag+ ion-exchanged soda glass samples, for example, has been observed on ion irradiation. The unique in situ experimental setup demonstrates and opens new opportunities to study irradiation controllable defects in materials and ion-beam induced optical responses in glass samples.

Correlation between thermoluminescence and optically stimulated luminescence responses of natural alexandrite

Luminescent properties of alexandrite crystals (BeAl2O4:Cr3+) are studied. Partial readouts of thermoluminescence (TL) and optically stimulated luminescence (OSL) signals were obtained to infer the relations of OSL and TL trapping centers. Four TL peaks were studied; their intensities decrease at different rates by illumination with blue OSL light. The OSL curve shows two-time components (exponential decay constants 3.15 and 28.4 s). The short time component is preferentially diminished when the sample is heated to temperatures from 363 to 513 K. About 50% of the whole TL intensity remains after a complete 300s OSL readout.