UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .

Advanced Nanoarchitectures for Solar Photocatalytic Applications

Upconversion luminescent materials: advances and applications.

Photon upconversion is promising for applications such as biological imaging, data storage or solar cells. Here, we have investigated upconversion processes in a broad range of gadolinium-based nanoparticles of varying composition. We show that by rational design of a core-shell structure with a set of lanthanide ions incorporated into separated layers at precisely defined concentrations, efficient upconversion emission can be realized through gadolinium sublattice-mediated energy migration for a wide range of lanthanide activators without long-lived intermediary energy states. Furthermore, the use of the core-shell structure allows the elimination of deleterious cross-relaxation. This effect enables fine-tuning of upconversion emission through trapping of the migrating energy by the activators. Indeed, the findings described here suggest a general approach to constructing a new class of luminescent materials with tunable upconversion emissions by controlled manipulation of energy transfer within a nanoscopic region.

Tuning upconversion through energy migration in core–shell nanoparticles

Rare-earth upconversion nanophosphors (UCNPs), when excited by continuous-wave near-infrared light, exhibit a unique narrow photoluminescence with higher energy. Such special upconversion luminescence makes UCNPs promising as bioimaging probes with attractive features, such as no auto-fluorescence from biological samples and a large penetration depth. As a result, UCNPs have emerged as novel imaging agents for small animals. In this critical review, recent reports regarding the synthesis of water-soluble UCNPs and their surface modification and bioconjugation chemistry are summarized. The applications of UCNPs for small-animal imaging, including tumor-targeted imaging, lymphatic imaging, vascular imaging and cell tracking are reviewed in detail. The exploration of UCNPs as multifunctional nanoscale carriers for integrated imaging and therapy is also presented. The biodistribution and toxicology of UCNPs are further described. Finally, we discuss the challenges and opportunities in the development of UCNP-based nanoplatforms for small-animal imaging (276 references).

Upconversion nanophosphors for small-animal imaging

Synthesis, Luminescent Properties, and Biomedical Applications Shili Gai,†,‡ Chunxia Li,† Piaoping Yang,*,‡ and Jun Lin*,† †State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China ‡Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin, 150001, P. R. China

Recent Progress in Rare Earth Micro/Nanocrystals: Soft Chemical Synthesis, Luminescent Properties, and Biomedical Applications

Near-infrared photocatalysis based on YF3 : Yb3+,Tm3+/TiO2 core/shell nanoparticles

Monodisperse β-NaYF4:Yb,Tm nanocrystals (nanospheres and nanoplates) with a uniform size were successfully synthesized. By tuning the ratios of solvent, reaction temperature, and reaction time, we manipulated their phase, shape, and size in the range of 30–400 nm. As a chelating agent and shape modifier, oleic acid (OA) was introduced into the reaction mixtures and played a key role in fine-tuning the nanocrystals. Possible mechanisms were proposed for forming the products with various architectures. Spectral analysis showed that the β-NaYF4:Yb,Tm nanocrystals were excellent materials for intense ultraviolet and blue upconversion luminescence. Here, we demonstrate that, under 980 nm excitation, the intense 5-photon upconversion fluorescence (290 nm and 345 nm) from the 1I6 level of Tm3+ ions is much stronger than the 4-photon upconversion fluorescence (361 nm and 451 nm) from the 1D2 level and the 3-photon upconversion fluorescence (474 nm) from the 1G4 level. The analysis of the temporal evolution of UC luminescence suggests that long lifetimes benefit the intense ultraviolet upconversion luminescence.

Greatly enhanced size-tunable ultraviolet upconversion luminescence of monodisperse β-NaYF4:Yb,Tm nanocrystals

Synthesis and field emission of MoO3 nanoflowers by a microwave hydrothermal route

Water soluble YVO4:Ln3+ and YVO4:Ln3+/Ba2+ (Ln = Ce, Dy, Eu, and Sm) nanocrystals were synthesized by a polyvinylpyrrolidone-assisted hydrothermal method. Under the excitation of the host absorption, phosphors can emit blue light for YVO4:Ce3+/Ba2+, yellow light for YVO4:Dy3+/Ba2+, red light for YVO4:Eu3+/Ba2+, and reddish orange light for YVO4:Sm3+/Ba2+. In comparison with those of YVO4:Ln3+ nanocrystals, the emissions of YVO4:Ln3+/Ba2+ are greatly enhanced. Furthermore, the excitation spectra of YVO4:Eu3+/Ba2+ and YVO4:Dy3+/Ba2+ show the similar features, which are different from those of YVO4:Sm3+/Ba2+ and YVO4:Ce3+/Ba2+.

Enhanced Photoluminescence of Water Soluble YVO4:Ln3+ (Ln = Eu, Dy, Sm, and Ce) Nanocrystals by Ba2+ Doping

Yb3+, Er3+, and Tm3+-codoped Gd2O3 nanotubes were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 °C. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), upconversion (UC) emission spectra, and kinetic decay were used to characterize the samples. Bright white UC luminescence in the nanotubes was observed under diode laser excitation of 980 nm. The white light consists of the blue (1G4 → 3H6 of Tm3+), green (2H11/2/4S3/2 → 4I15/2 of Er3+), and red (4F9/2 → 4I15/2 of Er3+) UC emissions. As the excitation power density changed in the range of 20–200 W cm−2, the calculated CIE color coordinates shift only slightly and fall well within the white region. This material may be a potential candidate for applications of color displays, lighting and photonics.

Daisheng Zhang

Papers

Near-infrared photocatalysis based on YF3 : Yb3+,Tm3+/TiO2 core/shell nanoparticles

Greatly enhanced size-tunable ultraviolet upconversion luminescence of monodisperse β-NaYF4:Yb,Tm nanocrystals

Synthesis and field emission of MoO3 nanoflowers by a microwave hydrothermal route

Enhanced Photoluminescence of Water Soluble YVO4:Ln3+ (Ln = Eu, Dy, Sm, and Ce) Nanocrystals by Ba2+ Doping

Bright white upconversion emission from Yb3+, Er3+, and Tm3+-codoped Gd2O3 nanotubes