Near-infrared Luminescence Intensity Research Articles

Highly efficient electroluminescence from SnO2 nanocrystals and Er3+ co-doped silica thin film via introducing Ca2.

Efficient and stable near-infrared silicon-based light source is a challenge for future optoelectronic integration and interconnection. In this paper, alkaline earth metal Ca2+ doped SiO2-SnO2: Er3+ films were prepared by sol-gel method. The oxygen vacancies introduced by the doped Ca2+ significantly increase the near-infrared luminescence intensity of Er3+ ions. It was found that the doping concentration of Sn precursors not only modulate the crystallinity of SnO2 nanocrystals but also enhance the luminescence performance of Er3+ ions. The stable electroluminescent devices based on SiO2-SnO2: Er3+/Ca2+ films exhibit the power efficiency as high as 1.04×10-2 with the external quantum efficiency exceeding 10%.

Study on preparation, optical properties and mechanism of Zn2SnO4:Cr3+ with high NIR luminescence intensity

In this work, Zn2SnO4:xCr3+ with high near-infrared luminescence intensity (broad emission centered at 800 nm and sharp emission at 703 nm) were successfully prepared by high temperature solid state method. Measurements indicated that the samples exhibited obvious photoluminescence as well as persistent luminescence properties. The results of X-ray diffraction indicated that high temperature facilitated the entry of Cr3+ into the Zn2SnO4 crystal lattice and formed replacement doping and promoted the luminescence efficiency of the samples. And, under the condition of 1450 °C and 0.002 at% Cr3+ concentration, sample with optimum NIR fluorescence properties was prepared. In the high-temperature sintering process, many defects of Zn2SnO4 were generated, which effectively promoted the formation of vacancies. The energy levels of these lattice defects (trap energy levels) facilitated the sub-stable trapping of electrons and produce afterglow properties. Analysis of luminescence mechanism reveals that the broad emission band centered at 800 nm and the sharp emission peak at 703 nm were derived from the energy level transitions of 4T2(4F)→4A2 and 2E→4A2 of Cr3+, respectively. Though, the long afterglow luminescence duration of Zn2SnO4:Cr3+ needs to be further improved compared with gallate-based NIR phosphors, Zn2SnO4:Cr3+ do have a promising application in bio-imaging due to its special NIR emission range.

In-situ formation of oleic acid amide ligand boosts persistent luminescence of zinc gallate nanoparticles toward efficient latent fingermark detection

Cr3+-doped zinc gallate (ZnGa2O4:Cr3+, ZGOC) nanomaterials feature with near-infrared emission and long afterglow properties. However, simultaneously controlling nanoparticle size and afterglow performance of ZGOC remains very challenging. A novel organic amine-stimulated solvothermal synthesis method for preparing ZGOC nanoparticles was demonstrated in this paper. Controllable synthesis of ZGOC nanoparticles was realized for uniform particle size distribution and excellent afterglow properties via adding different amines in organic phase system. Among them, by the triethylamine-stimulated solvothermal method, ZGOC nanoparticles are subsphaeroidal and narrow size distributed with an average particle size of about 11 nm. The near-infrared luminescence intensity of the nanoparticles was enhanced more than 7 times. The underneath organic amines stimulation mechanism was clarified as the in-situ formation of oleic acid amide ligand, consequently, enhancing the afterglow properties via combination results of surface defects passivation and ligand antenna effect. Furthermore, uniform particle size distribution and excellent afterglow properties make the prepared nanoparticles show great visualization in latent fingermark detection. The current finding of in-situ formation of oleic acid amide ligand offers guidance for the controllable synthesis of nanoparticles by the organic amines-stimulated solvothermal method.

Bright, small sizes and hydro-dispersive NIR persistent luminescence nanoparticles modified with Si and amino groups for enhanced bioimaging

Near-infrared (NIR) persistent luminescence nanoparticles (PLNPs) with high brightness, small sizes, good hydro-dispersivity, and intrinsic surface-functional groups are desirable in biological applications. In this work, Cr3+-doped zinc gallogermanates Zn1+x Ga2−2x Ge x O4:Cr (ZGGC) PLNPs were hydrothermally synthesized via 3-aminopropyltriethoxysilane (APTES) as an additive, or APTES and cetyltrimethylammonium bromide (CTAB) as two co-additives. Addition of APTES not only dramatically enhances the 696 nm NIR luminescence intensity, but also obviously decreases the particle size and introduces amino groups. In particular, the x = 0.1 series ZGGC (ZGGC0.1) with the addition of n moles equivalent APTES (ZGGC0.1-nA) had smaller particle sizes than the x = 0.2 counterpart (ZGGC0.2-nA). The NIR afterglow intensities increased with the APTES introduction. The ZGGC0.2-2.5A sample (also named as ZGGC, Si, -NH2) exhibited maximum luminescence intensities both in solid and aqueous states. With APTES, Si atom is doped and –NH2 groups are modified, the trap depth and density become larger, and the afterglow intensities and decay time are significantly enhanced. More notably, co-addition of CTAB (ZGGC0.2-2.5A-C) (also named as ZGGC, Si, −NH2’) further enhances hydro-dispersivity and luminescence intensity, decreases particle sizes, and results in more prominent amino groups. The trap density is drastically higher than that without CTAB (i.e. ZGGC0.2-2.5A). Change of Cr3+ microenvironment in the crystal and more defects introduction contribute to the enhanced brightness. As expected, the ZGGC,Si,-NH2’ PLNPs possess excellent biocompatibility, deep tissue penetration and distinguished bioimaging properties, and rechargeability with orange LED light. The ZGGC,Si,-NH2’ PLNPs should provide to be an excellent nanomaterial for various functionalization and bioimaging applications.

Influence of Plasmonic Gold Nanoparticles on the Optical Properties of Oxide Glasses Doped with Rare-Earth Ions

We report on the thermally-induced precipitation of gold plasmonic nanoparticles in phosphate and silicate glasses, doped with Eu3+ and Er3+ ions. We studied the structure and optical properties of glasses under the heat treatment below and above glass transition temperature. The heat treatment of the glass at temperatures above transition is shown to facilitate the formation of plasmonic gold nanoparticles and decrease near-infrared luminescence intensity of the ions. The formation of pre-plasmonic gold nanoparticles under the low-temperature heat-treatment leads to the increase of luminescence intensity through the energy transfer process. We showed that nanophase separation in silicate glasses allows precise tuning of localized surface plasmon resonance spectral position of gold nanoparticles and paves the way for the development of new glass-based materials for photonics applications.

Investigation of Er:Bi4Ge3O12 single crystals emitting near-infrared luminescence for scintillation detectors

0.1%, 0.5%, and 1% Er:Bi4Ge3O12 (BGO) single crystals were grown by the floating zone method, and the structural, optical, and scintillation properties were investigated. From the X-ray diffraction analyses, all the obtained crystals were confirmed to be in the single phase of BGO. The crystals exhibited photoluminescence and scintillation due to the 4f–4f transitions of Er3+ peaking at ~550 and 1540 nm as well as an emission band due to the 3P1–1S0 transitions of Bi3+ across 400–600 nm. The photoluminescence quantum yields of the NIR emission (1429–1677 nm) were 50.6%, 85.8%, and 69.0% for the 0.1%, 0.5%, and 1% Er-doped crystals, respectively. The scintillation decay curves were measured in the spectral range from UV to NIR, and the decay time constants of the visible–NIR luminescence were confirmed to be consistent with the known values of Er3+. The afterglow level at 20 ms after X-ray irradiation was 12.0–25.4 ppm, which is similar to the value of Nd:BGO. All the crystals showed a good linearity between the near-infrared luminescence intensity and X-ray exposure dose rate, and the lowest detectable dose rate was 0.006 Gy/h in all the crystals.

Downshifting energy transfer enhancement in Ce3+, Er3+-codoped YAG photonic crystals

This paper reports fabrication of Ce 3+ /Er 3+ -codoped YAG(Y 3 Al 5 O 12 ) downshifting photonic crystals. The effect of the photonic band gap on the downshifting Ce 3+ -Er 3+ energy transfer was studied. The Ce 3+ -Er 3+ energy transfer was enhanced because of suppressed spontaneous yellow emission of Ce 3+ . Results obtained in this work will be valuable for the foundational study of sensitized downshifting emission modification and application of downshifting optical devices in near-infrared (NIR) lasers materials. • YAG: Ce, Er with inverse opal structure was fabricated to modify the quantum cutting energy transfer by the sol-gel method. • The Ce–Er downshifting energy transfer efficiency is enhanced by suppressing the emission of Ce 3+ by photonic band gap. • The Ce 3+ .→Er 3+ energy transfer was enhanced to 38.8% and the near-infrared luminescence intensity of Er 3+ is enhanced.

Improving luminescence behavior and glass stability of tellurium‐doped germanate glasses by modifying network topology

AbstractBroadband near‐infrared (NIR) luminescent materials are of great interest for their potential application in optical communication, remote sensing, imaging, and homeland security. Tellurium (Te) doped glasses were recently recognized as such a promising candidate due to their broadband NIR emission (700–1700 nm). However, the achievement of Te‐doped glasses with high luminescence efficiency and glass stability (GS) remains a daunting challenge. Here, the luminescence behavior and GS of Te‐doped germanate glasses are manipulated by tailoring the glass network topology. Te NIR luminescence is enhanced by tailoring topological cages in germanate glass network structure through varying glass network modifiers. Meanwhile, the GS of potassium germanate glass is significantly enhanced due to increased network connectivity caused by the co‐introduction of alkaline earth oxides. Finally, NIR luminescence intensity of the glass was further enhanced by optimizing the doping concentration of TeO2. The findings here could contribute to designing Te‐activated glasses with improved performance for application in optical amplifiers and tunable fiber lasers.

The effect of Li+ incorporation in Yb3+-Nd3+ co-doped CaF2 phosphors over the NIR photoluminescence emission excited under visible light

The structural and optical characteristics of Nd3+-Yb3+ doped CaF2 phosphors with and without the addition of Li+ ions are described in this work. The phosphors synthetized by hydrothermal and co-precipitation methods showed near-infrared (NIR) luminescence emission associated with inter-electronic transition of the Yb3+ ion in the range of 900–1050 nm via energy transfer process from Nd3+ ions under visible light excitation. The addition of Li+ to these phosphors resulted in an improvement of the NIR luminescence intensity by a factor up to 5. The effect of the incorporation of Li+ ions into the CaF2 crystallite structure, the reduction of luminescence quenching states, as well as the energy transfer mechanism involved are discussed.

Thermally-induced precipitation of gold nanoparticles in phosphate glass: effect on the optical properties of Er3+ ions

Gold nanoparticles incorporated in glass medium are the object of keen interest due to their unique properties induced by plasmonic effects: coloration, noticeable optical nonlinearity and rare earth ions photoluminescence enhancement. In this work, we examine the structure and optical properties of potassium aluminophosphate glasses doped with Er3+ ions and Au under the heat treatment below and above glass transition temperature. The heat treatment of the glass at temperatures above Tg is shown to facilitate the formation of plasmonic gold nanoparticles and decrease near-infrared luminescence intensity of Er3+ ions. On the contrary, a similar treatment of the studied glasses at temperatures below Tg doesn't induce plasmonic absorption and leads to the intensity enhancement of Er3+ luminescence. Formation of gold clusters in the glass treated at lower temperatures is supposed to enable the energy transfer process between clusters and rare-earth ions which is expressed in luminescence intensity enhancement.

Effects of forming gas annealing on luminescence properties of erbium silicate thin films

While hydrogen passivation has led to enhanced luminescence in many erbium doped materials, its effects on Er oxides/silicates compounds has rarely been demonstrated. Here we report effects of forming gas annealing on the luminescence properties in such Er compound materials. A broad band photoluminescence in the ultraviolet/visible range, likely arising from structural defects in the material, is significantly suppressed after forming gas annealing. Concurrently, the Er near-infrared luminescence intensity and its lifetime increase by about a factor of two and three, respectively. The samples are further characterized with Rutherford backscattering for composition information, optical absorption for optically excitable Er concentrations and extended x-ray absorption fine structures for Er local environments. We discuss the hydrogen passivation effects in the context of diffusion limited relaxation processes and suggest pathways to further improving near-infrared luminescence properties in Er compound materials.

Luminescence and energy transfer progress in Bi-Yb co-doped germanate glass

The Bi-doped and Bi-Yb co-doped germanate glasses were fabricated by high temperature melting-quenched technique. The absorption spectra, near-infrared (NIR) luminescence properties and decay time spectra are investigated. The results show that the NIR emission peak around 1030 nm of Yb3+ ions and two NIR emission bands around 1180 and 1300 nm of Bi ions are observed, under 690 nm LD excitation. Two NIR emission bands of Bi-related are ascribing in different Bi-related NIR emission centers, Bi0 for 1180 nm and Bi+ ion for 1300 nm, respectively. NIR luminescence intensity of Yb3+ ions, Bi0 and Bi+ ion is decreased. The full width at half maximum (FWHM) is broadening with the increasing in Yb2O3 concentration, and over 361 nm. The energy transfer (ET) among Yb3+, Bi0, and Bi+ NIR emission center is also investigated, under 690 nm LD excitation. It shows that Bi0 ion transfer energy to Bi+ and Yb3+ ions. The Yb3+ ion addition is benefit to Bi+ ions NIR luminescence. This could be the reason for broadening the FWHM. Yb–Bi codoped germanate glass is a promising material for broadband optical amplification.

Effects of copper ions on the near-infrared luminescence in Bi doped silicate glass via copper for sodium ion exchange

The copper (Cu) atoms were incorporated into the bismuth (Bi) doped silicate glasses by the copper for sodium (Cu–Na) ion exchange method. After the ion exchange process, the Cu ions were introduced into the glass matrix with different copper valence states, namely, Cu0, Cu+, and Cu2+. Bi3+ ions could be reduced to lower valence states of Bi containing Bi near infrared (NIR) active centers with the incorporation of the Cu ions, resulting in the enhancement of the Bi NIR luminescence intensity. During the heat treatment process, some lower valence states of Bi containing Bi NIR active centers could be oxidized, resulting in the attenuation of the NIR luminescence of Bi. Our research may extend the understanding of chemical environment modulation in Bi valence states and offer a valuable way to enhance the NIR luminescence intensity of Bi in glasses.

Optical temperature sensing based on the near-infrared emissions from Nd³⁺/Yb³⁺ codoped CaWO₄.

Under a 980 nm diode laser excitation, the near-infrared (NIR) emissions from Nd3+:4F7/2, 4F5/2, and 4F3/2 states in Nd3+/Yb3+ codoped CaWO4 powder were studied at temperatures ranging from 303 to 873 K. As the temperature increased, the NIR luminescence intensity was significantly enhanced and nearly 190-fold enhancement was achieved at 873 K compared with that at 303 K. By using the fluorescence intensity ratio technique, the thermometry behaviors through the NIR emissions were investigated. The results illustrate that the sensitivity and the accuracy achieved here are much higher than temperature sensors based on other rare earth ion doped materials.

LaPO4:Er microspheres with high NIR luminescent quantum yield

Er-doped LaPO4 microspheres have been synthesized by spray pyrolysis and the near infrared (NIR) properties have been characterized. It has been found that, following an adequate post-annealing treatment, the emission properties are remarkably improved. The NIR luminescence intensity is highly enhanced and its decay time increases to a value almost coincident with the reported radiative lifetime, which implies that the quantum yield approaches η ≈ 100%. This improvement in luminescence characteristics is probably related to the suppression of residual OH− radicals, that otherwise act as NIR luminescence quenchers, and to the increase in material's crystallinity.

Bulky Adamantanethiolate and Cyclohexanethiolate Ligands Favor Smaller Gold Nanoparticles with Altered Discrete Sizes

Use of bulky ligands (BLs) in the synthesis of metal nanoparticles (NPs) gives smaller core sizes, sharpens the size distribution, and alters the discrete sizes. For BLs, the highly curved surface of small NPs may facilitate growth, but as the size increases and the surface flattens, NP growth may terminate when the ligand monolayer blocks BLs from transporting metal atoms to the NP core. Batches of thiolate-stabilized Au NPs were synthesized using equimolar amounts of 1-adamantanethiol (AdSH), cyclohexanethiol (CySH), or n-hexanethiol (C6SH). The bulky CyS- and AdS-stabilized NPs have smaller, more monodisperse sizes than the C6S-stabilized NPs. As the bulkiness increases, the near-infrared luminescence intensity increases, which is characteristic of small Au NPs. Four new discrete sizes were measured by MALDI-TOF mass spectrometry, Au(30)(SAd)(18), Au(39)(SAd)(23), Au(65)(SCy)(30), and Au(67)(SCy)(30). No Au(25)(SAd)(18) was observed, which suggests that this structure would be too sterically crowded. Use of BLs may also lead to the discovery of new discrete sizes in other systems.

Efficient near-infrared quantum splitting in YVO4:Ho3+ for photovoltaics

A sequential two-step near-infrared (NIR) quantum splitting (QS) has been demonstrated in a Ho3+-doped YVO4 phosphor, whereby one incident ultraviolet (UV)-to-visible photon, enabling Ho3+:5F4,5S2 excited, could be split efficiently into two NIR photons with emissions at 1015 and 1190nm, respectively. The involved NIR-QS mechanism has been analyzed in terms of the static–dynamic photoemission, monitored excitation spectra and time-resolved emission spectra. Internal quantum yield is obtained up to 112% on the basis of experimental and theoretical calculation results. It is found that the broadband [VO4]3− group as a sensitizer could efficiently transfer its energy to Ho3+ activator ions, thus dramatically enhancing the UV photo-response and the NIR luminescence intensity of the phosphor. Further development of this two-step two-photon NIR-QS phosphor may open up a new approach for enhancing the photo-response of photovoltaic cells, particular in the wavelength range of 250–560nm.

Ru(ii) sensitized lanthanide luminescence: synthesis, photophysical properties, and near-infrared luminescent determination of alpha-fetal protein (AFP)

A series of dinuclear compounds of [Ru(bpy)(2)(tpphz)Ln(TTA)(3)](PF(6))(2) (tpphz = tetrapyrido[3,2-a:2',3'-c:3'',2''-h:3''',4'''-j]phenazine; Ln = Er(III), Nd(III), Yb(III) and Gd(III); TTA = 2-thenoyltrifluoroacetone) have been prepared by attachment of a [Ln(TTA)(3)] fragment at the vacant diimine site of the luminescent mononuclear complex [Ru(bpy)(2)(tpphz)](PF(6))(2). In the solid state, in CH(2)Cl(2) solution and in Tris-HCl buffer solution of these dinuclear complexes Ru-Ln, sensitized near-infrared (NIR) luminescence is observed from Nd and Yb centres following excitation of the d-block unit, which results from the effective Ru → Ln (Ln = Nd, Yb) energy transfer, but no Er-based NIR luminescence is produced. The (3)MLCT (MLCT = metal to ligand charge transfer) emission is partly quenched in the Ru-Nd complex, slightly increased in the Ru-Yb complex, and is not changed in the Ru-Ercomplex. Interestingly, alpha-fetal protein (AFP) tends to decrease the NIR luminescence intensity of the Ru-Nd complex in Tris-HCl buffer solution. A novel NIR luminescent method for the determination of AFP was developed with a linear range of 0.5-18 ng mL(-1), and a detection limit of 0.2 ng mL(-1) based on 3 times the ratio of the signal-to-noise. Considering the attractive features, such as good selectivity, stability and rapidity, the proposed NIR luminescent method provides promising potential for AFP detection in clinical diagnosis and biomedical applications.

Infrared emission properties and energy transfer in ZnO–SiO 2:Yb 3+ composites

Intense near-infrared emission at 1 μm has been obtained in ZnO–SiO 2:Yb 3+ composites via a facile sol–gel method upon broadband ultraviolet light excitation. Systematic optical measurements including static and time-resolved photoluminescence have been performed to elucidate the energy transfer from ZnO quantum dots to Yb 3+ ions. The dependence of energy transfer efficiency on Yb 3+ concentration has been investigated in detail. Codoping with Li + ions leads to about twice enhancement of the near-infrared luminescence intensity around 1 μm at room temperature. The enhancement in the luminescence intensity could be mostly attributed to the modification of the local symmetry around Yb 3+ ions by codoping with Li + ions.

Spectral properties and broadband optical amplification of Yb-Bi codoped MgO-Al_2O_3-ZnO-SiO_2 glasses

We reported on the spectral properties of Yb-Bi codoped MgO-Al2O3-ZnO-SiO2 glasses. The near-infrared luminescence intensity in Yb-Bi codoped glass was ~31 times stronger than that of Bi-doped glass with 980 nm laser diode excitation. No optical amplification was observed in Bi-doped glass, while apparent broadband optical amplification between 1270 and 1340 nm was observed from Yb-Bi codoped glass with 980 nm laser diode excitation. The highest optical gain and gain coefficient at 1270 nm of Yb-Bi codoped silicate glass reached to 1.57 dB and 7.84 dB⋅cm−1, respectively. Yb-Bi codoped silicate glass is a promising candidate for broadband optical amplification.