Doped CaTiO3 Research Articles

Copper doping induced band structure and morphology transformation in CaTiO3 for textile dye photodegradation applications

Semiconductor metal oxides with a wide bandgap like CaTiO3 can be exploited into an efficient visible light photocatalyst via cation doping. The type of dopant and the site of doping is known to greatly influence the photocatalytic activity of a material. Based on the intricacies of the density functional theory electronic structure study, we delve into the optimization of one-pot solvothermal synthesis to obtain Cu doped CaTiO3 nanocuboids. Doping of copper not only resulted in change in the electronic structure of the material but also led to change in the morphology. The uneven nanostep architecture resulted in increase in the surface area of the catalyst, which led to more active sites for the adsorption of the dyes and subsequent degradation. The reduced band gap and decreased recombination of charge carriers made the copper doped calcium titanate an efficient photocatalyst for degradation of both cationic (99.7% degradation of MV dye in 120 minutes) and anionic (99.8% degradation of RB in 45 minutes) dyes.

Upconversion, downshifting, quantum cutting and back energy trasfer from Yb3+ to Er3+ in Er3+/Yb3+ co-doped CaTiO3 phosphor, intense NIR generation for communication

The perovskite based phosphor materials are widely used to increase the efficiency of solar cells. In this work, Er3+ doped and Er3+/Yb3+ co-doped CaTiO3 perovskite phosphor samples have been synthesized by solid state reaction technique at 1473 K. The phosphor samples show orthorhombic phase with Pnma (62) space group. The average crystallites and particles size of CaTiO3 are increased in presence of Er3+ and Yb3+ ions. Er3+ doped CaTiO3 phosphor samples give downshifting emission under 379 nm excitation. Though upconversion emission is seen in Er3+ under 980 nm excitation without Yb3+ ions in this host. The emission intensity of Er3+ ion is enhanced by 46 and 16 times for green and red emissions, respectively in presence of Yb3+. An intense quantum cutting (QC) emission is observed at 980 nm in presence of Yb3+ in CaTiO3:0.5Er3+ phosphor under 379 nm excitation. The QC efficiency has been found to be 119 % for CaTiO3:0.5Er3+/5 Yb3+ phosphor. Further an interesting phenomenon of back energy transfer (BEnT) from Yb3+ to Er3+ giving an intense NIR emission from Er3+ at 1002 and 1550 nm have been observed. The phosphor sample also shows an intrinsic optical bistablity (IOB) by upconversion. Thus, the prepared phosphor samples may be useful to increase the efficiency of c-Si solar cell, NIR emission for communication, bistable material and green light emitting source.

Multicolor tunable emission through energy transfer in Dy3+/Ho3+ co-doped CaTiO3 phosphors with high thermal stability for solid state lighting applications

The exploration of multicolor emitting phosphors with single phase is extremely important for n-UV chip excited LED/WLED’s and multicolor display devices. In this paper, Dy3+, Ho3+ singly doped and Dy3+/Ho3+ co-doped CaTiO3 phosphor materials have been synthesized by solid state reaction method at 1473 K. The synthesized materials were characterized by XRD, FE-SEM, EDX, FTIR, PL and lifetime measurements. The PL emission spectra of Dy3+ doped CaTiO3 phosphors give intense blue and yellow emissions under UV excitation, while the PL emission spectra of Ho3+ doped CaTiO3 phosphor show intense green emission under UV/blue excitations. Further, to get the multicolor emission including white light, Dy3+ and Ho3+ were co-doped simultaneously in CaTiO3 host. It is found that alongwith colored and white light emissions, it also shows energy transfer from Dy3+ to Ho3+ with 367 nm and from Ho3+ to Dy3+ under 362 nm excitations. The energy transfer efficiency is found to be 67.76% and 69.39% for CaTiO3:4Dy3+/3Ho3+ and CaTiO3:3Ho3+/5Dy3+ phosphors, respectively. The CIE color coordinates, CCT and color purity of the phosphors have been calculated, which show color tunability from whitish to deep green via greenish yellow color. The lifetime of 4F9/2 level of Dy3+ ion and 5S2 level of Ho3+ ion is decreased in presence of Ho3+ and Dy3+ ions, respectively. This is due to energy transfer from Dy3+ to Ho3+ ions and vice versa. A temperature dependent photoluminescence studied of CaTiO3:4Dy3+/2Ho3+ phosphor show a high thermal stability (82% at 423 K of initial temperature 303 K) in the temperature range 303–483 K with activation energy 0.17 eV. The PLQY are 30%, 33% and 35% for CaTiO3:4Dy3+, CaTiO3:4Dy3+/2Ho3+ and CaTiO3:3Ho3+ phosphors, respectively. Hence, Dy3+, Ho3+ singly doped and Dy3+/Ho3+ co-doped CaTiO3 phosphor materials can be used in the field of single matrix perovskite color tunable phosphors which may be used in multicolor display devices, n-UV chip excited LED/WLED’s and photodynamic therapy for the cancer treatment.

Photocatalytic and optical properties of (Mg:La) CaTiO3: Insights from first principles studies

Calcium titanate (CaTiO3) is widely employed in optoelectronic devices and the ceramic industry. The photocatalytic properties of calcium titanate are affected by substitution with transition metals. In this study, the simultaneous inclusion of Mg and La in CaTiO3 was investigated using density functional theory and the generalized gradient approximation functional of Perdew–Burke–Erzenhoff. Including elements had important effects on the structural, photocatalytic, optical, and electronic properties of semiconductor materials. Mg and La were introduced at the calcium sites at a ratio of 2:1. The effects of including Mg and La on the band structure, structural parameters, and optical properties, such as the absorption, static dielectric constant, and reflectivity, were elucidated in detail and clear correlations were also established between them. Co-doping had significant effects on the structural and electronic parameters. The band gap increased due to occupation of states in the conduction band. The static dielectric function decreased from 6 to 3.2, and the static refractive index with doping was 1.8. The reflectivity decreased from less than 20% in case of pure CaTiO3 to less than 10% with co-doping. Clear correlations were established between the electronic properties, such as the band gap and lattice parameter, and the optical properties in order to understand the results obtained. Water splitting was investigated for the pure and doped CaTiO3 in the ultraviolet and visible ranges. Pure and (Mg, La)–CaTiO3 exhibited oxygen evolution reaction activity. The materials are clearly lead-free and suitable for green energy applications because of their photocatalytic activities, and they also have an ideal band gap range for solar cell applications.

White light emission via Pb2+ to Dy3+ energy transfer mechanism in CaTiO3 phosphor

CaTiO3 activated Pb2+ and Dy3+ with different doping concentrations were prepared by combustion technique. The prepared phosphors were characterized by XRD, SEM, and photoluminescence (PL) techniques. The Pb2+ doped CaTiO3 phosphor exhibits broad n-UV emission. The effect of varying Pb2+ doping concentration on PL result and critical transfer distance were studied. The PL spectra of CaTiO3:(Pb2+,Dy3+) exhibit characteristic Dy3+ emission in blue (483 nm) and yellow (578 nm) region. At higher concentration of Dy3+ in CaTiO3:(Pb3+,Dy3+) phosphor, efficient energy transfer occur from Pb2+ to Dy3+. The CIE chromaticity study showed CaTiO3:(Pb3+,Dy3+) phosphor emits light in white region, which can be useful white phosphor for ultraviolet convertible white-light emitting devices.

Perovskite-based solar cells fabricated from TiO2 nanoparticles hybridized with biomaterials from mollusc and diatoms

Perovskite solar cells (PVSCs) convert solar energy into electrical energy. Current study employs fabrication of PVSCs using calcium titanate (CaTiO3) prepared by co-precipitation of TiO2 nanoparticle (NP) and CaCO3 NP with later synthesized from mollusc shell. Furthermore, frustules of diatom, Nitzschia palea were used to prepare silica doped CaTiO3 (Si-CaTiO3) nanocomposite. CaTiO3 NP and Si-CaTiO3 nanocomposites film were made on fluorine doped tin oxide (FTO) glass plate using spin coater separately for two different kinds of PVSCs tested at different intensities of light. The perovskite materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray (EDX) spectroscopy. Thickness of the film was measured by profilometer. The maximum power density (PDmax) of CaTiO3 made PVSCs was 0.235 mW/m2 under white LED light and 0.041 mW/m2 in broad spectrum light. Whereas, PDmax of PVSCs with Si-CaTiO3 was higher about 0.0083 mW/m2 in broad spectrum light and was 0.0039 mW/m2 in white LED light. This is due to the fact that CaTiO3 allowed blue and red light in broad spectrum to pass through it without being absorbed compared to white LED light which gets reflected. On the offset, in PVSC made of Si-CaTiO3 since diatoms frustules are made up of nanoporous architecture it increases the overall porosity of PVSC making them potentially more efficient in broad spectrum of light compared to white LED light.

Charge compensation assisted enhancement of photoluminescence in (Li+, Mg2+, Sr2+) doped CaTiO3: Eu/Dy/xGd for WLEDs applications

A series of CaTiO3: Eu3+, Eu3+/Dy3+, Eu3+/Dy3+/xGd3+, and Eu3+/Dy3+/Gd3+/M (M = Li+, Mg2+, Sr2+) perovskite micro phosphors have been prepared via solid-state reaction method. The structural, morphological, and spectral properties were systematically characterized by XRD, MEB, FT-IR, UV-V absorption, PL, and PLE. The prepared micro powders exhibited a single-phase orthorhombic structure with Pbnm space group. The MEB images revealed grain size ranging from 5 to 20 μm. The CaTiO3 band gap energy decreases by introducing the doping elements and changes from 3.581 eV for the undoped to 2.847 eV for Eu/Dy/Gd/Li doped sample. The photoluminescence properties of Eu3+, Eu3+/Dy3+, and Eu3+/Dy3+/xGd3+ doped CaTiO3 phosphors were investigated through excitation and emission spectra. Under 365 nm excitation, Eu3+/Dy3+ co-doped samples exhibit blue emission, which is turned to near white region by introducing Gd3+ ions. In order to enhance the luminescence properties, (Li+, Mg2+, Sr2+) ions are doped into CaTiO3 Eu3+/Dy3+/Gd3+ phosphors to ensure the host charge compensation. The charge compensators not only provide luminescence enhancement but also modify the local environment of the lanthanide ions and then adjust the emission to tune the ratio of each color in the spectrum. The photometric parameters such as CIE-coordinate and correlated color temperature (CCT) were calculated, which depend on the ion charge and on the ionic radii. These perovskite phosphors can be applied for solid-state lighting applications.

Exploration of the novel structures and electronic properties for Nd3+ doped CaTiO3

Rare-earth neodymium ions (Nd3+) doped CaTiO3 crystal shows excellent light-emitting properties which give rise to the development of new-generation laser devices. However, the structural evolutions of the trivalent Nd3+ doped CaTiO3 (CaTiO3:Nd) crystal are still not clear. Herein, we report a systematic first-principles study on the geometrical structures and electronic properties of CaTiO3:Nd. Based on the crystal structure analysis by particle swarm optimization (CALYPSO) method combined with density functional theory, we uncover a novel layered grid structure with Pm space group. The Ca2+ ion in the host crystal is replaced by the Nd3+ ion. The simulated XRD spectrums match fairly well with the experimental data, which demonstrating the validity of the obtained ground state structure. The calculated band structures manifest that the conduction band pass through the Fermi level, suggesting a conductive character of CaTiO3:Nd. The results of density of states (DOS) demonstrate that the impurity Nd3+ ions can trigger a phase transition of CaTiO3 from semiconductor to conductor. The analysis of electron localization function (ELF) for CaTiO3:Nd indicates that the interaction between Ca-O is mainly ionic bond. These results could provide significant insights for exploring new laser materials.

Enhanced photoluminescence in a Eu3+ doped CaTiO3 perovskite phosphor via incorporation of alkali ions for white LEDs

Intense red photoluminescence has been observed in Eu3+/Z+ (Z+ = Li+, Na+ & K+) co-doped CaTiO3 perovskite phosphor materials, synthesized through high temperature solid-state reaction technique. The phosphor materials are structurally characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. All the compounds are crystalline with the orthorhombic phase. The crystallite and particle size of phosphor increase via incorporation of alkali ions. The vibrational groups in phosphor materials are studied by Fourier transform infrared (FTIR) technique. The diffuse reflectance spectra showed a number of peaks in the UV–visible regions due to different transitions of Eu3+ ion. The band gap (Eg) of the phosphor decreases on incorporation of alkali ions. The phosphor materials emit intense red color at 613 nm due to 5D0 → 7F2 transition of Eu3+ ion upon 398 nm and 466 nm excitation wavelengths. The intensity of red emission increases upto 12 mol% concentration of Eu3+ ions. On incorporation of alkali ions in the 12 mol% Eu3+: CaTiO3 phosphor, the emission intensity increases further due to crystallinity, charge compensation and the asymmetry created around the Eu3+ ions in the phosphor. The emission intensity is largest for the 12Eu3+/10Na+ co-doped CaTiO3 phosphor. The asymmetric ratio is higher for the 12Eu3+/10Na+ co-doped CaTiO3 phosphor. The lifetime of 5D0 level is enhanced via incorporation of alkali ions and it is also larger for the 12Eu3+/10Na+ co-doped CaTiO3 phosphor. The CIE color coordinates, correlated color temperature (CCT), color purity and color rendering index (CRI) calculations of the phosphors have also been carried out, which show pure red color in warm light region. Therefore, these synthesized perovskite phosphor materials can be advantageous for display devices, NUV excited red phosphors for making the tricolor phosphor converted WLEDs and blue LED chip-based WLEDs for solid state lighting applications.

A Highly Enhanced Photoluminescence of Eu3+-Activated CaTiO3 Phosphors via Selective A-Site and B-Site Cation Substitutions (Sr2+ and Sn4+)

Sr2+ and Sn4+ doped CaTiO3:Eu3+ phosphors were prepared by a high temperature solid-state method. X-ray diffraction characterization shows that the sample calcined at 1200°C is pure and has an orthorhombic crystal lattice. Photoluminescence (PL) measurement shows that CaTiO3:Eu3+ has five excitation peaks at 363 nm, 381 nm, 398 nm, 418 nm, and 466 nm, respectively corresponding to the transitions 7F0 → 5D4, 7F0 → 5L7, 7F0 → 5L6, 7F0 → 5D3 and 7F0 → 5D2 of Eu3+. The main emission peaks of CaTiO3:Eu3+ at 592 nm and 613 nm are ascribed to the 5D0 → 7FJ (J = 1, 2) transitions of Eu3+. In addition, PL emissions at 592 nm and 613 nm of CaTiO3:Eu3+ phosphors are enhanced remarkably through A-site substitution of Ca2+ with Sr2+ or B-site substitution of Ti4+ with Sn4+. Noticeably, the emission intensity of Ca(Ti,Sn)O3:Eu3+ is nearly three times higher than that of CaTiO3:Eu3+. The reason is that substitution of Ti4+ with Sn4+ induces a large lattice distortion, which promotes the 5D0 → 7F2 transition probability and thus enhances the emissions at 613 nm. It is also found that Sr2+ substitution narrows the optical bandgaps of CaTiO3:Eu3+ , while Sn4+ substitution widens them. In addition, chromatic purity of the phosphors shows a remarkable dependence on the asymmetric ratio.

Dark brown Cr doped CaTiO3 pigments with high NIR reflectance

Some brown CaTiO3 pigments have been synthesized by calcining the depositions of CaCO3 and Cr dopant on the surface of TiO2 particles. The pigments have a pure phase composition of perovskite and a narrow size distribution ranging from 0.5 to 1.5 μm. These pigments have a low lightness and exhibit dark brown color due to the presence of Cr6+.The doped CaTiO3 pigment with 1% Cr has high NIR reflectance of 79.7% and high solar reflectance of 58%, and the doped pigment coating can lower 8.9 °C for the inner surface of ceramic tiles.

Promising red emission from functionalized Polypyrrole/CaTiO3:Eu3+ nano-composites for photonic applications

CaTiO3:Eu3+ luminescent nanoparticles (NPs) and Ppy/CaTiO3:Eu3+ nanocomposites (NCs) are synthesized via combustion and solution casting techniques respectively and their structural and optical properties are investigated. The powder X-ray diffraction patterns of the as-formed products show single orthorhombic phase. The crystallite size measurement is assessed utilizing Scherrer's technique and observed to be in the range of 40–45 nm. The impact of Eu3+ ions on luminescence properties of the produced nanophosphors is examined the outcomes are given in detail. The phosphors displayed splendid red emission at 398 nm excitation. The emission peaks observed at 540, 593, 615, 653, 696 and 706 nm (5D0→7Fj = 0, 1, 2, 3, 4, 5) are assigned to Eu3+ ions transitions. The electronic transition equivalent to 5D0→7F2 (615 nm) is robust than the magnetic dipole transition 5D0→7F1 of Eu3+ ions (596 nm). The CIE chromaticity co-ordinates are ascertained from emanation spectra, the obtained values are very close to NTSC standard value of red emission. Hence, the present phosphors are exceedingly valuable for display applications. The obtained results demonstrate that Ppy-assisted solution casting is an effective methodology for the synthesis of rare-earth doped CaTiO3:Eu3+ nanocomposites (NCs).

Processing, point defects and photoluminescence of Pr-CaTiO3 phosphors

Perovskite structured calcium titanate can be directly synthesized at room temperature. Other partial amorphous phase will have started to crystallize at 600 °C following the incorporation of Pr ion into the lattice. The doping mechanism is studied. The relationship between processing and point defects is found. The lattice cell expends with the annealing temperature until 900 °C, after that, contracts suddenly at 1000 °C and then tends to a constant at the temperature over 1100 °C. The mechanism of photoluminescence of Pr3+ doped CaTiO3 is set up. The powders have the red emission at 613 nm by the activation of UV light. The intensity of the emission increases with the annealing temperature till 1000 °C and then decreases, due to it has a correlation with the concentration of incorporated Pr ion. The decay time increases with the annealing temperature. The photoluminescence behavior is associated with the point defects which can be tailored by the processing of the powders, especially by the annealing temperatures.

Investigation of structural, spectral and photometric properties of CaTiO3:Dy3+ nanophosphors for the lighting applications

A series of perovskite CaTiO3:Dy3+ nanophosphors have been prepared via solid state reaction method in order to investigate the structural, spectral and photometric properties. The structural, morphological and spectral properties of prepared nanophosphors were systematically characterized by XRD, FESEM, EDX, Photoluminescence, PL decay time and UV-Visible spectroscopy. The novel CaTiO3:Dy3+ nanophosphors exhibited single phase orthorhombic structure with space group Pbnm. The high magnification FESEM images of prepared sample demonstrated the particle size in the range 220-240 nm. The photoluminescence properties of Dy3+ doped CaTiO3 nanophosphors were investigated through excitation, emission spectra and decay time by varying the concentration of activator (Dy3+). Under the excitation of 386 nm UV light, Dy3+ activated CaTiO3 nanophosphors exhibited its characteristic excellent intense emissions in blue and yellow region around the wavelength 484 and 575 nm due to the transition 4F9/2→6H15/2 and 4F9/2 → 6H13/2 respectively. The photometric parameters such as CIE-coordinate and correlated color temperature (CCT) was also calculated. The CIE- coordinate (0.28, 0.32) was found near white light and CCT value was found to be 9222.31 K for optimum composition Ca0.96TiO3:0.04Dy3+ which was useful for cold light emission. The affirmative experimental results indicated that the prepared nanophosphors could be the favorable candidate for lighting applications.

NUV excited luminescence studies of Tb3+ in CaTiO3 nanophosphor for wLEDs

A series of Tb3+ doped CaTiO3 (1-9 mol%) nanophosphors were successfully synthesized by a low temperature solution combustion method using ODH as a fuel. The phase and morphology, of the prepared phosphors were characterized by using powder x-ray diffraction (PXRD) and Scanning electron microscopy (SEM) and confirms orthorhombic structure with porous morphology and the size of the crystallites are ∼ 40 nm. Photoluminescence (PL) emission was studied under 377 nm excitation wavelength. PL spectra consists of emission bands corresponding to transition 5D3→7F3 (458 nm) and 5D4→7Fj (j = 6, 5, 4, 3) transitions such as 5D4→7F6 (486 nm), 5D4→7F5 (541 nm), 5D4→7F4 (585 nm) and 5D4→7F3 (622 nm). Among these, the green emission corresponding to 5D4→7F5 (541 nm) transition was the most dominant and the same was confirmed by The CIE coordinates. Thus, the present nanophosphors can be served as an excellent material for solid state lighting applications and for wLEDs.

Oxygen permeation and stability of CaTi0.73Fe0.18Mg0.09O3−δ oxygen-transport membrane

Oxygen permeation membranes consisting of gastight mixed ionic-electronic conductors (MIEC) allow the diffusion of oxygen through the crystal lattice via oxygen vacancies. An extended screening of doped CaTiO3 materials is reported here with the aim of improving the ionic and the electronic conductivity of the material. The dopants were selected taking into account the ionic radii affinity and their aliovalence or multivalence. Moreover, this work presents the oxygen permeability of CaTi1−xFexO3−δ co-doped with Mg. The structural and electrochemical properties of the nominal perovskite CaTi0.73Fe0.18Mg0.09O3−δ (CTFM) are studied. X-ray diffraction demonstrates that the material crystallizes as a single perovskite structure with orthorhombic distorted symmetry, although the MgO segregates as a minor separated phase. The partial addition of Mg2+ to the perovskite results in an increase of oxygen vacancies, and therefore the total conductivity at high temperatures with respect to the non-doped CaTi0.8Fe0.2O3 (CTF). On the contrary, below 800°C the conductivity of CTFM is lower than for CTF, attributed to the lower amount of Fe in the CTFM. Permeation measurements were performed on CTFM gastight membranes of 900 μm thickness, reaching oxygen fluxes of up to 0.95mLmin−1cm−2 at 1000°C. Stability of the membrane to CO2 was evaluated by exposing the membrane to 15% CO2 in Ar atmosphere for 24h at 750°C and O2 fluxes were measured by using this atmosphere as sweep gas. Initial O2 fluxes were maintained after the CO2 treatment. In addition, thermogravimetric (TG) measurements performed on powder CTFM under dry CO2 (5% in Ar) did not show any carbonate formation, confirming the stability of the material in this atmosphere.

Structural and photoluminescence studies of red emitting CaTiO3:Eu3+ perovskite nanophosphors for lighting applications

Herein, the authors present the spectral studies with quantum efficiency of red emitting Eu3+ doped CaTiO3 downconverting phosphor synthesized by chemical co-precipitation method for the demonstration on the development of solid state lighting devices. The photoluminescence properties of Eu3+ doped CaTiO3 phosphors were investigated through changing the concentration of activator (Eu3+). The structural, morphological and optical properties are systematically characterized by the XRD, FTIR, FESEM, PL and UV–Vis spectroscopy. The synthesized phosphor revealed the single phase orthorhombic structure with space group Pbnm. The FESEM studies exhibited the irregular morphology of the obtained phosphor particles having grain size in the range 70–170 nm. Photoluminescence spectra of CaTiO3:Eu3+ nanophosphor revealed an intense red emission peak around wavelength 619 nm in the visible region upon the excitation of near-UV light at wavelength 397 nm due to 5D0 → 7F2 transition in Eu3+. The Judd–Ofelt intensity parameters were calculated and the quantum efficiency of optimized composition (for Ca0.95TiO3:0.05Eu3+) is found to be 17.46 %. The photometric characterization results revealed that the prepared phosphor can be a suitable candidate for application of solid state lighting devices.

Long-lived photoinduced charge-carriers in Er3 + doped CaTiO3 for photocatalytic H2 production under UV irradiation

The incorporation of Er3+ ions in the CaTiO3 structure provides an enhanced H2 photoproduction due to the formation of long-lived charge-carriers in the semiconductor. Nitroblue tetrazolium reaction, photoluminescence and time resolved microwave conductivity techniques were used to investigate the generation of the superoxide species and the lifetime of the charge-carriers. The improved photoactivity has been explained in terms of the dopant agent, finding that phenomena such as a higher concentration of the superoxide radicals, a more efficient separation of the photogenerated charge-carriers, and a slower recombination process take place in the Er3+ doped CaTiO3 compared to the undoped CaTiO3.

Mesoporous Red Nanophosphor CaTiO3:Pr3+ Fabricated by Sol-Gel

Uniform sphere-like mesoporous nanoparticles of Pr3+ doped CaTiO3 crystallines have been fabricated by sol-gel method. The decomposition process of the precursor, crystallization, particle sizes of CaTiO3 have been investigated by using thermal analysis, powder X-ray diffraction and transmission electron microscopy respectively. The mesoporous properties have been investigated by Brunauer-Emmett-Teller method, Barrett-Joyner-Halenda method, electron diffraction pattern, and high resolution TEM. The nanophosphor emits red luminescence under excitation of UV lamp. It is interesting to observe mesoporous structure in a luminescent material synthesized at a temperature as high as 600°C, which will provide an advance material with thermal stabilities possessing potential applications in photocatalysis, photoelectronic sensors, and optical devices.

Near-infrared luminescent CaTiO3:Nd3+ nanofibers with tunable and trackable drug release kinetics.

750-850 nm (NIR I) and 1000-1400 nm (NIR II) in the near infrared (NIR) spectra are two windows of optical transparency for biological tissues with the latter capable of penetrating tissue deeper. Monitoring drug release from the drug carrier is still a daunting challenge in the field of nanomedicine. To overcome such a challenge, we propose to use porous Nd3+-doped CaTiO3 nanofibers, which can be excited by NIR I to emit NIR II light, to carry drugs to test the concept of monitoring drug release from the nanofibers by detecting the NIR II emission intensity. Towards this end, we first used electrospinning to prepare porous Nd3+-doped CaTiO3 nanofibers by adding micelle-forming surfactant Pluronic F127, followed by annealing to remove the organic component. After a model drug, ibuprofen, was loaded into the porous nanofibers, the drug release from the nanofibers into the phosphate buffered saline (PBS) solution was monitored by detecting the NIR II emission from the nanofibers. We found that the release of the drug molecules from the nanofibers into the PBS solution triggers the quenching of NIR II emission by the hydroxyl groups in the surrounding media. Consequently, more drug release corresponded to more reduction in the intensity of the NIR II emission, allowing us to monitor the drug release by simply detecting the intensity of NIR II from the nanofibers. In addition, we demonstrated that tuning the amount of micelle-forming surfactant Pluronic F127 enabled us to tune the porosity of the nanofibers and thus the drug release kinetics. This study suggests that Nd3+ doped CaTiO3 nanostructures can serve as a promising drug delivery platform with the potential to monitor drug release kinetics by detecting the tissue-penetrating NIR emission.