Search

Transparent glasses are ideal and robust hosts for a range of emission centers, while the simultaneous manipulation of the temporal and spectral characteristics of emission remains a tremendous challenge for inorganic glasses. Here, the development and functionalization of melt‐quenched transparent coordinate polymer glasses with a tailorable ultralong room‐temperature phosphorescence are demonstrated. Dynamic modulation of the phosphorescence is achieved by utilization of the high molecular rigidity and manipulation of the spin‐orbital coupling effects within the glass systems. By introducing dye molecules into the glasses, Phosphorescence resonance energy transfer from the glass matrix to the dye molecules is exploited and controllable multicolor long‐lived luminescence is demonstrated. Further design of the component and concentration of the encapsulated dyes allows for wavelength‐tunable long‐lived delayed fluorescence via an efficient delayed sensitization process, featuring a tunable emission spectrum covering a wide range from 520 to 630 nm. Leveraging the multiple spectral tuning channels of the hybrid glass, multi‐mode optical information storage, and dynamic anti‐counterfeiting applications are further demonstrated. This work provides a new hybrid material platform and design methodology for realizing lifetime‐adjustable and wavelength‐tunable long‐lived luminescence, which can find wide applications in time‐rsesolved information display, high‐density information storage, and dynamic anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Flexible regulation of bandgap of perovskite nanocrystals (PNCs) is fundamentally critical for desirable optoelectronic functions and applications. Here, regulating chemical composition and emission wavelength of PNCs in glass by a simple heat‐treatment process are reported, which is established to rely on the thermal‐trigger phase separation and ion exchange. The first principle calculations are overall performed to reveal the mechanism of bandgap engineering and optimization of emission performance. The PNCs exhibit excellent stability against thermal, ultraviolet irradiation, and organic molecules. The bandgap of PNCs in the heat‐treated glass can also be re‐modulated by ultrafast laser irradiation. Ultrafast laser direct writing of multi‐color patterns and holographic dynamic displays are achieved, which hold great potential in the application of encryption‐decryption and emissive devices. [ABSTRACT FROM AUTHOR]

The fabrication of multicolor luminescent glass with simultaneous controlling of the distribution of emission colors within a monolithic medium has been a tremendous challenge, which, however, could be attractive for diverse photonic applications from optical storage to information encryption. Here, a space‐selective doping method based on a stereolithographic technique is designed, enabling the control of the doping domain of the active luminescence ions, such as Eu3+, Ce3+, Tb3+, and Pr3+, in 3D‐printed single silica glasses. The printed glass shows intense multicolor luminescence, and the interface between the two doping areas is invisible under natural light. By using this technique, multicolor luminescent glass with pre‐designed emission color distribution is fabricated, which enables facile and nondestructive decryption strategies based on photoluminescence under controlled excitation conditions. Besides, the extending of this strategy by using a femtosecond laser for photopolymerization dramatically improves the printing resolution down to the few‐micron scale, enabling the multi‐dimensional optical storage and encryption in miniaturized glass items. This work not only delineates the potential applications of multicolor luminescent glass for multi‐dimensional anti‐counterfeiting and information storage, but also opens up new avenues for prospective applications in sensing, lasers, and displays based on glasses with spatially engineered optical responses. [ABSTRACT FROM AUTHOR]

In recent years, inorganic lead halide perovskite quantum dots have been used in various optoelectronic fields for their excellent luminescence properties, such as narrow emission bands, ultra‐wide tunable emission wavelength, and high quantum efficiency. In this paper, different from luminescence optimization in most research, luminescence degradation of perovskite quantum dots is addressed by femtosecond laser irradiation and successfully used for three‐dimensional data storage in CsPbBr3 quantum dots doped glass. Photoluminescence (PL) degradation can be finely modulated by adjusting the laser parameters. PL degradation mechanism, investigated by optical spectroscopy and morphology characterization, is attributed to laser‐induced decomposition, recrystallization, and defection of CsPbBr3 quantum dots. Laser‐induced PL degradation and the followed PL recovery by heat treatment are repeated for several cycles, showing good reversibility. Multilayer PL degradation patterns are written into the glass and read out without crosstalk, indicating high‐reliability 3D optical storage characteristics. Amazingly, PL degradation can be induced by just a low‐energy single laser pulse with estimated subpicosecond writing time per bit, demonstrating its potential in high‐speed, low‐power consumption 3D optical storage. [ABSTRACT FROM AUTHOR]

The information burst in modern society poses new challenges to information preservation technology, both in storage efficiency, capacity, and security. Multi‐dimensional optical data storage based on the femtosecond laser direct writing technique is a promising way to face these challenges. Herein, a new optical storage method based on femtosecond laser‐induced local darkening of CdSe quantum dots doped glass is reported. Photoluminescence image and spectrum indicate that highly luminescent well‐crystallized CdSe quantum dots can be amorphized by a single femtosecond laser pulse and reconstructed by thermal treatment, resulting in reversible luminescence modulation, in which the luminous efficacy of CdSe quantum dots in glass matrix was well recovered after each cycle of writing and erasing. Complicated patterns written inside the glass and multi‐layer information are also successfully inscribed and well demonstrated. Data bit could be written by just one 380 fs single pulse with pulse energy as low as 100 nJ. The present work provides a potential way for three‐dimensional optical information storage and data encryption with low power consumption, fast writing speed, large capacity, and high security. [ABSTRACT FROM AUTHOR]

CsPbI3 perovskite quantum dots (QDs) doped borosilicate glass was prepared by the process of melt‐quenching and subsequent annealing. With the introduction of ZnO to the parent glass as the glass network intermediate, the optical properties of the resultant samples are dramatically enhanced. Both the photoluminescence (PL) intensity and photoluminescence quantum yield (PLQY) shows a strong dependence on ZnO concentration as ZnO is found to facilitate the precipitated of the QDs by reducing the connectivity of three‐dimensional glass network built from SiO4 tetrahedrons. The tunable visible‐band PL emission of the CsPbI3 QD‐doped glass could find potential applications in white LEDs and lasers. [ABSTRACT FROM AUTHOR]

Tetra‐valent manganese (Mn4+) has been regarded as an efficient non‐rare‐earth red‐light emitting ion, which has stimulated continued search of robust hosts and efficient synthetic methods to stabilize Mn4+ centers with strong photoluminescence. In this work, we demonstrate a facile synthetic method for Mn4+ doped glass‐ceramic (GC) based on crystallization‐induced oxidation state change in an oxide glass. The parent glass with a formula of LiNaGe4O9 is fabricated by melt‐quenching and crystallization is induced by thermal treatment in air. Oxidation of Mn2+ in glass to Mn4+ in the GC is confirmed by both optical spectroscopy and electron paramagnetic resonance (EPR) measurements. After thermal treatment, the characteristic reddish photoluminescence (PL) of Mn2+ in the glass centered at 611 nm disappears and a strong photoluminescence peak at 660 nm attributed to Mn4+ is observed. The conversion to Mn4+ after crystallization in the examined system may have strong implications for synthesis of Mn4+ doped phosphors which always requires rigorous control of the redox equilibrium during synthesis. [ABSTRACT FROM AUTHOR]

Lanthanide (Ln) activated systems are characterized by the rich line‐shaped emission spectra stemming from the parity‐forbidden inner shell f‐f transitions. This inherent nature of Ln ions efficiently stabilizes their emissions against environment perturbations, but always necessitates the use of strong and broadband sensitizer to achieve efficient emission. Here, based on a model near‐infrared (NIR) emitting system – NaYF4 : Nd3+ NPs, we demonstrate sensitized NIR emission by grafting the nanoparticle (NP) surfaces with a visible‐light active organic conjugated oligomer, 4,7‐(9,9′‐bis(4‐carboxybutyl)‐fluorenyl)‐2,1,3‐benzothiadiazole (OFBT). Photoluminescence (PL) emission, excitation and time‐resolved spectra confirm energy transfer from the OFBT molecules to nanoparticles across the organic/inorganic interfaces, and the efficiency of ET is quantitatively determined by the surface coverage of OFBT molecules and concentration of Ln ions in the NPs. By taking advantage of the environment‐sensitive binding strength of OFBT to NP surface, we further demonstrate high sensitivity of the NIR emission from the hybrid NPs to variations in pH and temperature, which is explained by the change in energy transfer efficiency from OFBT to NPs. Therefore, the developed nano‐hybrid systems are believed to have potential applications in sensing and detection in physiological environment. [ABSTRACT FROM AUTHOR]

Broadband and tunable near-infrared (NIR) emission of Ni2+ doped glass–ceramics (GCs) is highly attractive due to their potential to address the challenge of broadband optical amplification in the optical communication band. However, optical activity of Ni2+ in different glass matrix as well as nucleation and crystallization processes in relevant glasses have not been understood fully. Here, broadband NIR photoluminescence was realized through precipitation of LiGa5O8:Ni2+ nanocrystals (NCs) within an alkali gallium-silicate glass matrix by melt-quenching and successive heat treatment. Upon exciting by a 980 nm laser diode, we observed NIR photoluminescence band centered at ~ 1310 nm with full width at half maximum of wider than 300 nm, which was originated from 3T2g(3F) → 3A2g(3F) electronic transition of octahedral coordinated Ni2+ in LiGa5O8 NCs embedded in the GCs. Controlled precipitation of NCs, LiGa5O8:Ni2+ and Ga2O3:Ni2+ were achieved by tailoring the composition of alkali gallium-silicate glass matrix. ab initio molecular dynamics simulation was carried out to clarify the formation of nanophases in the glass system. We confirmed that optical properties of transparent GCs containing Ni2+ NCs can be realized by changing molar percentages of Ga2O3. Our results offer a new insight into the precipitation of NCs in oxide glasses and Ni2+ doped GCs, which may be applicable in the photonic fields, such as optical amplifier and laser. [ABSTRACT FROM AUTHOR]

Monolithic luminescent glass‐ceramic is highly desirable for solid‐state lighting as it is stable and robust, while in practical light‐emitting devices only a thin luminescent layer is used for more efficient excitation and light extraction. In this paper, Mn2+‐doped glass and glass‐ceramic with the composition of 60SiO2‐8Na2O–20ZnO–12Ga2O3 were fabricated by the conventional melt‐quenching technique. We observe that the crystallization of α‐Zn2SiO4 nanocrystals takes place on the glass surface with controllable thickness after heat treatment. The glass samples show typical red emission peaking at λ = 620 nm that can be ascribed to the spin‐forbidden 4T1g(G) → 6A1g(S) transition of Mn2+ (d5) located in the octahedral coordination site of the glass host. After surface crystallization this red emission is retained and a new green emission at 528 nm is observed through the control of the crystallization temperature and duration, thus offering tunable emission characteristics promising for the lighting application. This change in the visible emission is interpreted in terms of the change of coordination state of Mn2+ from octahedral in a glass matrix to tetrahedral in the surface precipitated α‐Zn2SiO4 crystals. [ABSTRACT FROM AUTHOR]

Bi, Ga, and Al codoped germanium glass was prepared and its optical properties were investigated by absorption, photoluminescence excitation (PLE), and photoluminescence spectra. Two active centers which occupy strong and weak crystal field environment are identified by using the PLE spectrum. The tunable and ultrabroadband luminescence properties are originated from electron transitions of these two active centers. Internal optical gain around 1300 and 1560 nm has been detected. The wavelength-dependent internal gains excited with 808 and 980 nm laser diodes show different characteristics, and the relative flat optical amplification can be realized by choosing 980 nm pumping. [ABSTRACT FROM AUTHOR]

PbS quantum dot (QD)‐doped glasses were fabricated through melt‐quenching method. After heat treatment schedule, uniform QDs were precipitated in the glasses and near‐infrared emission covering 900‐1700 nm was obtained under excitation. From photoluminescence (PL) spectra and lifetime decay curves, the whole emission band of QD‐doped glasses consisted of emission from the 1S‐1S state and the trap state. While using excitation with higher energy, the full width at half maximum (FWHM) of QD‐doped glasses broadened because smaller QDs were excited. Energy transfer process among QDs was revealed by measuring the lifetime of different emission bands in PL spectrum and the energy transferred from smaller QDs with broader bandgap to bigger QDs with narrow bandgap. Temperature‐dependent PL and the corresponding lifetime decay curves of PbS QD‐doped glasses were analyzed. Temperature‐dependent bandgap structure of PbS QDs was obtained by using density functional theory (DFT) calculations. The results here give deep insight into optical properties of PbS QD‐doped glasses and it is beneficial to design and develop high‐performance QD‐based optoelectronic devices in theory. [ABSTRACT FROM AUTHOR]

Alkaline earth orthosilicates M2SiO4 (M = Ba, Sr and Ca) phosphors doped with Mn5+ ions have been prepared by the conventional solid-state reaction method. The crystal structures were verified by X-ray diffraction. By varying the host composition from Ba to Ca, the position shifting of photoluminescence emission bands corresponding to the 1E → 3A2 transition are induced by the increasing angular distortion and covalence. The nonradiative energy transfer becomes a dominant role in the photoluminescence process with substituting Ba2+ sites for smaller cations. The structural evolution and relevant luminescence mechanisms in (Ba1−xCax)2SiO4 phosphors also have been investigated in detail. It reveals that the chemical composition modification and structural variation can be an efficient approach to optimize the photoluminescence behaviors. [ABSTRACT FROM AUTHOR]

Abstract: Borosilicate glasses doped with PbSe quantum dots (QDs) were prepared by a conventional melt‐quenching process followed by heat treatment, which exhibit good thermal, chemical, and mechanical stabilities, and are amenable to fiber‐drawing. A broad near infrared (NIR) photoluminescence (PL) emission (1070‐1330 nm) band with large full‐width at half‐maximum (FWHM) values (189‐266 nm) and notable Stokes shift (100‐210 nm) was observed, which depended on the B2O3 concentration. The PL lifetime was about 1.42‐2.44 μs, and it showed a clear decrease with increasing the QDs size. The planar [BO3] triangle units forming the two‐dimensional (2D) glass network structure clearly increased with increasing B2O3 concentration, which could accelerate the movement of Pb2+ and Se2− ions and facilitate the growth of PbSe QDs. The tunable broadband NIR PL emission of the PbSe QD‐doped borosilicate glass may find potential application in ultra‐wideband fiber amplifiers. [ABSTRACT FROM AUTHOR]

Abstract: A novel non‐rare‐earth doped phosphor La2MgGeO6:Mn4+ (LMG:Mn4+) with near‐infrared (NIR) long persistent luminescence (LPL) was successfully synthesized by solid‐state reaction. The phosphors can be effectively excited using ultraviolet light, followed by a sharp deep‐red emission peaking at 708 nm, which is originated from 2Eg → 4A2g transition of Mn4+ ions. The luminescent performance was analyzed by photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The crystal field parameters were calculated to describe the environment of Mn4+ in LMG host. The LPL behaviors as well as the mechanisms were systematically discussed. This study suggests that the phosphors will broaden new horizons in designing and fabricating novel NIR long phosphorescent materials. [ABSTRACT FROM AUTHOR]

Controlled morphology modulation of graphene carbon nitride (g-C3N4) is successfully realized from bulk to 3D loose foam architecture via the blowing effect of a bubble, which can be controlled by heating rate. The loose foam network is comprised by spatially scaffolded few-atom-layer interconnected flakes with the large specific surface area, as supporters to prevent agglomeration and provide a pathway for electron/phonon transports. The photocatalytic performance of 3D foam strutted g-C3N4 toward RhB decomposition and hydrogen evolution is significantly enhanced with the morphology optimization while its excellent optoelectronic properties are maintained simultaneously. Herein, the ultrathin, mono-, and high-quality foam g-C3N4 interconnected flakes with controlled layer are facilely obtained through ultrasonic, thus overcoming the drawbacks of a traditional top-down approach, opening a wide horizon for diverse practical usages. Additionally, the layer control mechanism of 3D hierarchical structure has been explored by means of bubble growth kinetics analysis and the density functional theory calculations. [ABSTRACT FROM AUTHOR]

Cooperative upconversion luminescence (CUCL) occurs in spectral regions in which single ions do not have energy levels. However, all results reported so far are concentrated on luminescence properties from Yb3+ ions-doped various hosts. Here, we report the observation of nonlinear negative transmittance (NNT) at continuous-wavelength (CW) 980-nm laser diodes (LDs) pumping in silicate oxyfluoride glass ceramics (GCs)-containing CaF2:Yb3+ nanocrystals. The unique optical nonlinearity is analyzed based on energy-level transitions, dynamic evolution, rate equation, and power transmission equation, which can be explained as the cooperative optical absorption for the intense CUCL of Yb3+ ions. The NNT in the CaF2:Yb3+ nanocrystals-embedded GCs can be tailored with the power of a CW 980-nm LDs, which possesses potential for the development of future optical limiters and switches. [ABSTRACT FROM AUTHOR]

Transfer of energy occurs endlessly in our universe by means of radiation. Compared to energy transfer (ET) in free space, in solid state materials the transfer of energy occurs in a rather confined manner, which is usually mediated by real or virtual particles, including not only photons, but also electrons, phonons, and excitons. In the present review, we discuss the recent advances in optical ET by resonance mediated with photons in solid materials as well as their nanoscale counterparts, with focus on the photoluminescence behavior pertaining to ET between optically active centers, such as rare earth (RE) ions. This review begins with a brief discussion on the classification of optical ET together with an overview of the theoretical formulations and experimental method for the examination of ET. We will then present a comprehensive discussion on the ET in practical systems in which normal photoluminescence, upconversion and quantum cutting resulted from ET involving metal ions, QDs, organic species, 2D materials and plasmonic nanostructures. Diverse ET systems are therefore simply categorized into cases of ion–ion interactions and non-ion interactions. Special attention has been paid to the progress in the manipulation of spatially confined ET in nanostructured systems including core–shell structures, as well as the ET in multiple exciton generation found in QDs and organic molecules, which behave quite similarly to resonance ET between metal ion centers. Afterwards, we will discuss the broad spectrum of applications of ET in the aforementioned systems, including solid state lighting, solar energy utilization, bio-imaging and diagnosis, and sensing. In the closing part, along with a short summary, we discuss further research focus regarding the problems and possible future directions of optical ET in solids. [ABSTRACT FROM AUTHOR]

A reddish orange emission Sr2P2O7:Sm3+ phosphor is prepared by the solid-state reaction method in air, and the crystal structure and luminescence properties of phosphors are investigated. Sr2P2O7:Sm3+ phosphor shows Commission International de I'Eclairage (CIE) chromaticity coordinates (x = 0.5753, y = 0.4147). White light-emitting diodes (W-LEDs) fabricated using Sr2P2O7:Sm3+ phosphor etc. show CIE chromaticity coordinates (x = 0.3471, y = 0.3124). These results indicate that Sr2P2O7:Sm3+ phosphor could be a potential suitable reddish orange emitting phosphor candidate for W-LEDs with excitation of a ~400 nm n-UV LED chip. [ABSTRACT FROM AUTHOR]

The trivalent green element of bismuth, when doped into different compounds, can produce multiple emissions in ultraviolet, blue, green or even yellow spectral regimes. The emission adjustability comes from the susceptibility of bismuth naked 6s electrons to the crystal field particularly surrounding Bi3+. However, this has never been observed in a single compound. In this work, we report that broadly tunable bismuth emission indeed occurs even within the same host (CaMoO4) when the local microenvironment around Bi3+ is modified by intentional introduction of alkali ions. As the radius of the selected alkali ion decreases, the emission regularly blue-shifts from 586 to 554 nm, and its intensity is enhanced greatly. For instance, the integrated intensity for the Li+ and Bi3+ codoped sample is 4.46 times stronger than the Bi3+ single-doped sample upon excitation at 300 nm. Low-temperature photoluminescence spectra surprisingly reveal that energy transfer can partially take place from the MoO42- group to Bi3+ at lower temperature when excited into the charge transfer state of the MoO42- group, however, this does not occur at higher temperature. The mechanism needs further study. Dynamic luminescence analysis between 10 and 300 K implies a population dependence of the excited states 3P0 and 3P1 on temperature that is responsible for the evolution of the Bi3+ emission lifetime with temperature. [ABSTRACT FROM AUTHOR]

In this manuscript, we report an ultrabroadband luminescence covering the whole 1000-1800 nm in [ABSTRACT FROM AUTHOR]

Cr3+-doped LiInSiO4 phosphors were prepared by a solid-state reaction method. X-ray diffraction measurement was carried out for crystalline phase identification. Absorption, photoluminescence, excitation, and time-resolved spectra were measured to investigate the optical properties of the phosphors. Two broadband near-infrared emissions centered at 920 and 1172 nm were observed. Time-resolved spectra show that the emission at 1172 nm decays more quickly than the emission at 920 nm. The electron spin resonance spectra exhibit a broad resonance signal at g = 1.96 because of exchange-coupled Cr3+ pairs. The value of Dq/B for low and intermediate crystal fields was evaluated. We suggest that Cr3+ incorporated into different octahedral sites of the crystal is responsible for the different near-infrared luminescence. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present the photoluminescence properties of Eu3+, Tb3+ and Tm3+-doped oxyfluoride alumino-silicate glasses and glass ceramics. The X-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of these glasses have been carried out, to confirm their structure and thermal stability. Compared to Eu3+, Tb3+ and Tm3+-doped glasses, their respective glass ceramics have shown stronger emissions due to the presence of LiGdF4 crystalline phase. For Eu3+-doped glass and glass ceramics, five emission bands centered at 578nm (5D0 → 7F0), 592nm (5D0 → 7F1), 614nm (5D0 → 7F2), 652nm (5D0 → 7F3) and 698nm (5D0 → 7F4) have been observed with 394nm (5D0 → 7L6) excitation wavelength. Of them, 614nm (5D0 → 7F2) has shown bright reddish-orange emission. With regard to the Tb3+-doped glass and glass ceramic, four emission bands centered at 491nm (5D4 → 7F6), 545nm (5D4 → 7F5), 587nm (5D4 → 7F4) and 622nm (5D4 → 7F3) have been observed with an excitation at 377nm (3F6 → 5G6) wavelength. Of them, 545nm (5D4 → 7F5) has shown bright green emission. Emission bands of 1G4 → 3F4 (650nm) and 3F3 → 3H6 (708nm) transitions for the Tm3+:glass and glass ceramic, with an excitation at 3H6 → 1G4 (469nm) have been observed. The stimulated emission cross-sections of all the emission bands of Eu3+, Tb3+ and Tm3+:glasses and glass ceramics have been computed based on their measured full-width at half maximum (FWHM, Δλ) and lifetimes (τ m). [Copyright &y& Elsevier]

Abstract: In this paper, we present the photoluminescence properties of Pr3+, Sm3+ and Dy3+-doped transparent oxyfluoride alumino-silicate glasses. These glasses have shown strong emission and absorption bands in visible and near-infrared (NIR) region. From the measured absorption spectra, Judd–Ofelt (J–O) intensity parameters (Ω 2, Ω 4 and Ω 6) have been calculated for all the studied ions. For Pr3+-doped glass, emission bands centered at 532nm (3P0 → 3H5), 615nm (3P0 → 3H6) and 647nm (3P0 → 3F2) have been observed with 486nm (3H4 → 3P0) excitation wavelength. Of them, 647nm (3P0 → 3F2) has shown bright red emission. Emission bands of 4G5/2 → 6H5/2 (563nm), 4G5/2 → 6H7/2 (599nm) 4G5/2 → 6H9/2 (645nm) and 707nm (4G5/2 → 6H11/2) for the Sm3+:glass, with excitation at 6H5/2 → 4F7/2 (403nm) have been recorded. Of them, 4G5/2 → 6H7/2 (599nm) has shown a bright orange emission. With regard to the Dy3+:glass, a bright fluorescent yellow emission at 575nm (4F9/2 → 6H13/2) and blue emission at 484nm (4F9/2 → 6H15/2) have been observed, apart from 4F9/2 → 6H11/2 (663nm) emission transition with an excitation at 388nm (6H15/2 → 4I13/2 + 4F7/2) wavelength. The stimulated emission cross-sections of all the emission bands of Pr3+, Sm3+ and Dy3+:glasses have been computed based on their measured full-width at half maximum (FWHM, Δλ) and measured lifetimes (τ m). [Copyright &y& Elsevier]

The nonlinear optical crystal Ba2TiSi2O8 is induced three-dimensionally inside a glass by a femtosecond pulse laser with 800 nm, 250 kHz, and 150 fs. Micro-Raman and photoluminescence spectra confirm that crystals can grow in the focal point of the laser beam. Continuous crystalline lines were written through moving the focal point of the laser beam inside the glass. The results demonstrate a convenient method to engrave three-dimensional patterns of crystals with nonlinear optical properties for integrated optical devices. [ABSTRACT FROM AUTHOR]

Polymeric g‐C3N4 with controllable photoluminescence emission wavelength in the whole visible light range (450–650 nm) is synthesized through the one‐step molecular doping during the thermal condensation process of g‐C3N4 conjugated framework, which opens up its application beyond the conventional catalysis scopes. By adjusting the doped content of hetero‐molecules, the modified g‐C3N4 with the optical properties controlled according to the demand of practical applications can be facilely and largely obtained. It overcomes the limitation of the narrow adjusting range of conventional g‐C3N4 on optical properties and makes it become more promising for applications in solid‐state displays. The corresponding multiple‐color g‐C3N4‐based LED devices and the white‐light LEDs with high quality can be obtained as supported by experiments and theoretical calculations. Moreover, the effect of doped molecule on the π‐conjugated system of g‐C3N4 is systematically studied here, and the tunable luminescence mechanism is proposed. [ABSTRACT FROM AUTHOR]

Nd3+ co-doped CsPbBr 3 perovskite quantum dots (PQDs) glasses were prepared by conventional melt-quenching followed by a thermal treatment process. With the introduction of Nd 2 O 3 to the parent glass, the optical properties of the CsPbBr 3 PQDs are significantly improved. The energy transfer from CsPbBr 3 PQDs to Nd3+ ions was investigated and confirmed by excitation and emission spectra. The results show that visible excitation band width for the near-infrared (NIR) emission of Nd3+ ions is significantly increased in the presence of PQDs. The strategy for modulation of the optical properties by the energy transfer between rare earth ions and PQDs in the glass matrix could be further utilized for spectral engineering of photonic glasses for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Bi-doped (60-x)GeO2-xSiO2-15B2O3-20MgO-5Al2O3-0.5Bi2O3 (x = 0, 5, 10, 15,20, 25 mol%)glasses were prepared by a conventional melt-quenching process. A broad near-infrared (NIR) photoluminescence (PL) band from Bi centers centered around 1100 nm with a large full-width-at-half-maximum value (~ 195 nm) was observed under excitation at 700 nm. Along with the increase of SiO2 concentration, the NIR PL intensity and the quantum yield (44.1-51.2%) increase first and then decrease, and the PL lifetime increases from 409 to 464 µs. The spectroscopic properties can be interpreted in terms of Bi centers with different valence states, which were confirmed by two-dimension photoluminescence excitation map spectra. The dependence of optical properties on SiO2 concentration is mainly attributed to the change of the optical basicity among different samples. This Bi-doped B2O3-GeO2-SiO2 glass could find potential application in fiber amplifier and laser due to the efficient and tunable broad NIR luminescence. [ABSTRACT FROM AUTHOR]

Abstract: NIR luminescence phosphors Sr2CeO4:Yb3+, M + (M +=Li+, Na+, K+) were synthesized by conventional solid-state method in the present paper. The prepared phosphors are characterized by XRD and fluorescence spectrometer. Under UV light excitation, the NIR emission intensity of Yb3+:2F5/2→2F7/2 around 1μm of Sr2CeO4:Yb3+ is strengthened significantly by introducing appropriate alkali metal cations dopants (Li+, Na+, K+) into the crystalline lattice. The relevant mechanisms have been discussed in detail. The peculiar optical properties make Sr2CeO4:Yb3+, M + (M +=Li+, Na+, K+) promising for potential application in the high efficiency silicon-based solar cells. [Copyright &y& Elsevier]

Abstract: This paper report on the absorption and photoluminescence properties of Pr3+, Nd3+ and Ni2+ ions doped tellurite glasses. The X-ray diffraction (XRD) and differential scanning calorimetry (DSC) profiles of the host glass matrix have been carried out, to confirm its structure and thermal stability. From the measured absorption spectra, Judd–Ofelt (J–O) intensity parameters (Ω 2, Ω 4 and Ω 6) have been calculated for the rare-earth ions doped glasses and B, C, Dq parameters for transition metal ion-doped glass, respectively. The near infrared emission spectrum of Nd3+ ions doped glass has shown full width at half maximum (FWHM) around 50nm (for 4F3/2 → 4I9/2 transition), 50nm (for 4F3/2 → 4I11/2 transition) and 70nm (for 4F3/2 → 4I13/2 transition), respectively. Decay measurements were also carried out for Pr3+, Nd3+ and Ni2+ ions doped glasses. These glasses with better thermal stability and bright visible luminescence should have potential applications in optoelectronic materials and broadband amplifiers. [Copyright &y& Elsevier]

Abstract: In this paper, we report on the absorption and photoluminescence properties of Tm3+/Dy3+ ions co-doped oxyfluoride germanate glasses for white light emission. The X-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of the host glass have been carried out to confirm its structure and thermal stability. From the measured absorption spectra, Judd–Ofelt (J–O) intensity parameters (Ω 2, Ω 4 and Ω 6) have been evaluated for Tm3+ and Dy3+ ions. A combination of blue, yellow and red emissions has emerged in these glasses, which allows the observation of bright white light when the glasses are excited by the ultraviolet light. The white light luminescence colour could be changed by varying the excitation wavelength. Also, various colours of luminescence, including white light, can be easily tuned by adjusting the concentrations of Tm3+ or Dy3+ ions in the co-doped glasses. Concentration quenching effect was also investigated and possible energy transfer mechanism from Dy3+→Tm3+ ions was explained which is also confirmed by the decay lifetime measurements. [Copyright &y& Elsevier]

Carbon quantum dots (CQDs) with multi-color emission are synthesized through hydrothermal method by varying the ratio of citric acid (CA) and urea, the solvent (water, ethyl alcohol, and dimethylformamide), the hydrothermal temperature, and reaction time. The CQDs emit bright fluorescence which can be gradually tuned from blue to red continuously, almost covering the whole visible spectrum. The emission peaks of the CQDs shift from 450 nm to 650 nm with the surface groups and structures changing. Importantly, all solid state CQDs@SiO 2 nanophosphors are successfully synthesized by reversed-phase micromulsion method. Based on these solid state phosphors, multi-color CQDs@SiO 2 phosphors-based light-emitting diodes (LED) and white light-emitting diode (WLED) with a Commission Internationale de L' Eclairage (CIE) value of (0.3497, 0.3045) are fabricated in a low-cost, environment-friendly way. [ABSTRACT FROM AUTHOR]

A novel single-phased tunable emitting phosphor Ba 9 Lu 2 Si 6 O 24 :Bi 3+ ,Eu 3+ (BLSO:Bi 3+ ,Eu 3+ ) was successfully prepared via a simple solid-state approach. The main excitation peaks range from 320 to 400 nm of BLSO:Bi 3+ were identified by photoluminescence characterization, indicating BLSO:Bi 3+ viable for ultraviolet (UV) excitation. Emission spectra show that Bi 3+ occupies at least two nonequivalent sites in BLSO host, and display broad emission peaks at 410 and 490 nm when excited by UV light, respectively. As red emitting center Eu 3+ was introduced into BLSO:Bi 3+ , significant energy transfer (ET) occurs from Bi 3+ to Eu 3+ through a dipole-dipole mechanism. The ET efficiency reaches 97.57%. By varying the doped ratio of Bi 3+ and Eu 3+ , tunable light and white emission can be easily realized. Results indicate that BLSO:Bi 3+ ,Eu 3+ is a potential tunable emission phosphor in UV excited W-LEDs. [ABSTRACT FROM AUTHOR]

Abstract: A novel non‐rare‐earth doped phosphor La2MgGeO6:Mn4+ (LMG:Mn4+) with near‐infrared (NIR) long persistent luminescence (LPL) was successfully synthesized by solid‐state reaction. The phosphors can be effectively excited using ultraviolet light, followed by a sharp deep‐red emission peaking at 708 nm, which is originated from 2Eg → 4A2g transition of Mn4+ ions. The luminescent performance was analyzed by photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The crystal field parameters were calculated to describe the environment of Mn4+ in LMG host. The LPL behaviors as well as the mechanisms were systematically discussed. This study suggests that the phosphors will broaden new horizons in designing and fabricating novel NIR long phosphorescent materials. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mono-dispersed ZnS: Mn nanocrystals were synthesized by a hydrothermal route. [•] Photoluminescence of nanocrystals were studied by steady and transient state spectra. [•] A novel energy transfer mechanism of ZnS: Mn nanocrystals was proposed. [ABSTRACT FROM AUTHOR]

Abstract: We report on a simple method for fabricating ultra-small nanodiamonds (NDs) with size tunability and uniformity by femtosecond laser ablation in solution. Photoluminescence (PL) is tailored in a broad range from ultra-violet (UV) to red region through adjusting the carbon sources or solutions. The NDs also emit multiphoton luminescence. Comprehensive discussions based on the anomalous PL behavior and well-defined absorption and excitation peaks suggest that UV emission originates from radiative recombination through intrinsic direct transitions between highly localized π states and blue or green emission originates from radiative recombination through defect energy trapping states. [Copyright &y& Elsevier]

Abstract: Silicate glasses containing PbS quantum dots (QDs) with narrow size distribution were prepared through heat treatment. Transmission electron microscopy (TEM) results show that spherical PbS QDs are densely dispersed in the glassy matrix. Using ZnS–PbO to replace PbS as precursor of PbS QDs, the size distribution of PbS QDs in glasses becomes more uniform. Tunable infrared luminescence from 1100 to 2200nm has been obtained by controlling the glassy matrix and preparation parameters. Obvious optical amplification at communication windows of 1.55μm and 1.33μm is probed, and the PbS QDs doped glasses using ZnS–PbO as precursor exhibit larger optical amplification. The PbS QDs doped glasses with intense optical amplification are considered to be promising candidate as gain medium for broadband fiber amplifier and tunable fiber laser. [Copyright &y& Elsevier]

Abstract: Ever since the discovery of ultra-broadband near-infrared (NIR) photoluminescence (PL) from Bi-doped silicate glass, this class of materials and corresponding devices have experienced rapid progress. This is mainly driven by the suggested use in broadband optical amplifiers and novel lasers for future telecommunication networks. Currently, it appears that the optical bandwidth which is provided by Bi-doped glasses and crystals cannot be achieved by any rare-earth (RE) based amplifier, or by the combination of multiple RE-doped devices. However, the nature of the optically active NIR emission centers remains highly debated. The present paper critically reviews the various arguments and models which have been proposed in this context over the last decade. From the overall conclusions, the major open questions are identified. [Copyright &y& Elsevier]

Abstract: Three individual primary colors were generated from only one piece of Er3+–Eu3+ co-doped oxygen-deficient germanate glass under UV light irradiation. Blue, green, and red emissions were originated from Ge-related oxygen-deficient defect centers (GODCs), Er3+ ions, and Eu3+ ions, respectively. Detailed photoluminescence spectra, decay curve analyses, and electron paramagnetic resonance measurements were carried and the results indicate the existence of energy transfer between Er3+ and Eu3+ ions, GODCs and Eu3+ ions. [Copyright &y& Elsevier]

Abstract: We report on the luminescence properties of reduced SrO–Al2O3–GeO2 glasses. Metal Al instead of corresponding oxide (Al2O3) is added into SrO–Al2O3–GeO2 glasses in order to control the oxygen-deficient defects. The obtained transparent glass samples, in which Ge2+ defects are stable, emit bright blue, white, and red light when excited by 300, 335 and 370nm ultraviolet light, respectively. Quantities of the defects can be controlled by adjusting the amount of metal Al, resulting in tunable luminescence from blue to white and to red. The origins of different luminescence centers are discussed and the color coordinates of the photoluminescence spectra are also calculated. [Copyright &y& Elsevier]

Abstract: Eu-doped and Eu/Al-codoped high silica glasses (HSGs) are prepared by infiltration and densification method. Absorption, photoluminescence and electron spin resonance (ESR) spectra of the Eu-doped high silica glasses (HSGs) are measured and the results indicate the reduction of Eu3+ to Eu2+ ions partly in Eu/Al-codoped HSGs. Energy transfer between Eu2+ ions and Eu3+ ions is observed and this transfer enhances the intensity of Eu3+ ions. The reduction mechanism is also discussed. [Copyright &y& Elsevier]

Abstract: Photoluminescence properties of Sm3+, Dy3+, and Tm3+-doped transparent oxyfluoride silicate glass ceramics containing CaF2 nanocrystals were reported. Emission bands of 4G5/2 → 6H5/2 (562nm), 4G5/2 → 6H7/2 (598nm), 4G5/2 → 6H9/2 (645nm) and 4G5/2 → 6H11/2 (706nm) for the Sm3+: glass and glass ceramic, with an excitation at 6H5/2 → 4F7/2 (402nm) have been recorded. Of them, 4G5/2 → 6H7/2 (598nm) has shown a bright orange emission. With regard to the Dy3+: glass, a bright fluorescent yellow emission at 575nm (4F9/2 → 6H13/2) and blue emission at 481nm (4F9/2 → 6H15/2) have been observed, apart from 662nm (4F9/2 → 6H11/2) emission transition with an excitation at 386nm (6H15/2 → 4I13/2 + 4F7/2) wavelength. Emission bands of 1G4 → 3F4 (650nm) and 1G4 → 3H5 (795nm) transitions for the Tm3+: glass and glass ceramic, with an excitation at 3H6 → 1G4 (467nm) have been observed. Of them, 1G4 → 3F4 (650nm) has shown bright red emission. Decay lifetime measurements were also carried out for all the observed Sm3+, Dy3+, and Tm3+-doped glass and glass ceramic emission bands. [Copyright &y& Elsevier]

Abstract: We report on highly efficient broadband near-infrared photoluminescence (PL) in Ni2+-doped glass ceramics (GCs) films fabricated by annealing Si/Ni2+-doped glass superlattices (SNGS). Over two orders of magnitude enhancement of PL can be achieved in comparison with that from the annealed glass film. The PL lifetime of the annealed SNGS is several milliseconds, which is much longer than those of bulk GCs. The strong PL enhancement results from the formation of high-quality cordierite nanocrystals because the Si layers act as Si source for the crystal growth. This technique can be extended to fabricate other types of high-quality GCs films. [Copyright &y& Elsevier]

Abstract: We report a method for the selective introduction of fluorescent Ag nanoclusters in glass. Extinction and photoluminescence spectra show that a fraction of the Ag atoms are generated through femtosecond laser induced multiphoton reduction and then aggregate to form Ag nanoclusters after heat treatment. Red luminescence from the irradiated region is observed under blue or green laser excitation. The fluorescence can be attributed to interband transitions within Ag nanoclusters. This method provides a novel route to fabricate fluorescent nanomaterials in 3D transparent materials. [Copyright &y& Elsevier]

Abstract: Rare-earth ternary chelates Eu X Gd1− X (TFA)3(TPPO)2 (, 0.3, 0.4,…,1.0) were synthesized in gel glasses via in situ technique. Corresponding pure chelates were also synthesized for a comparative investigation and were characterized with Fourier transform infrared (FTIR) absorption spectra and elemental analysis. Photoluminescence (PL) properties of the in situ chelates in gel glasses and the pure chelates have been studied comparatively. It is found that the enhanced luminescence of Eu3+ ions by Gd3+ ions (energy transfer from Gd3+ ions to Eu3+ ions) occurs in both pure and in situ ternary chelates. [Copyright &y& Elsevier]

Investigating the nature of two-/multi-wavelength light excitation effects in optical materials such as their mechanisms, materials composition, and opto-electronic behaviors is crucial for observing the photophysical and photochemical performance for their applications. Recently, this research area has received extensive attention owing to its remarkable optical performance, capability of tunable fluorescence emission, tailorable photochemical reaction, controllable electron population, and driving of novel photophysical and photochemical phenomena, which are promising for emerging applications in broad areas of spectroscopy, photophysics, photochemistry, opto-electronics, biophysics, as well as environmental and materials science. In this work, we review recent progress in the interdisciplinary studies of photoluminescence mechanisms, emitting centers, host material system, optical setups and characterization techniques, and application fields for the optical materials by two-/multi-wavelength light excitation effects. In the first part, we introduce the latest progress of two-/multi-wavelength light excitation effects in optical materials, from their fundamentals to their applications. In the second part, we present the dominant two-/multi-wavelength excited photoluminescence mechanisms, including excited state absorption, stimulated emission depletion (STED), ground state depletion, and more STED-inspired models. Moreover, we outline recent progress in optically active centers and host material classification, and their intrinsic connections between tunable microstructures and applications for different material systems based on two-/multi-wavelength light excitation effects. Optical measurement setups and characterization techniques for broad application fields are reviewed and summarized. By emphasizing the progress of emerging photoluminescence properties in optical materials and their application prospects based on two-/multi-wavelength light excitation effects, involving three-dimensional displays, lasers, STED super-resolution nanoscopy, photolithography and optical data storage, ultraviolet bacteriostatic agents, solar cells, and optical switches are explained. Finally, we discuss the present achievements and remaining questions and provide perspectives for future research directions. [ABSTRACT FROM AUTHOR]

Abstract: Water-soluble CdTe quantum dots (QDs) with green and yellow emission are prepared in aqueous solution using thioglycolic acid (TGA) as stabilizing agent. The as-obtained CdTe QDs are characterized by absorption and photoluminescence spectra. Strong emission is observed when the CdTe QDs are excited by an 800nm femtosecond laser. The ln–ln relations between the integral intensity of CdTe QDs and the excitation power are investigated, and the results indicate that the upconversion luminescence is a two-photon assisted process via a virtual energy state. [ABSTRACT FROM AUTHOR]