We report that non-contact optical temperature sensing can be achieved with the use of heavily Nd(3+) doped NaYF(4) nanoparticles. The temperature evaluation can be realized either by monitoring the absolute luminescence intensity or by measuring the intensity ratio of the two Stark components of the (4)F(3/2) multiplet in the Nd(3+) ions.

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Wide wavelength range (550-1600 nm) measurements of nonlinear optical properties of ca. 5 nm CdS quantum dots (QDs) colloidal solution were performed using the Z-scan technique with femtosecond laser pulses at 1 kHz. Parameters characterizing nonlinear absorption and nonlinear refraction were determined. Nonlinear absorption has the character of a two-, three- and four-photon process depending on the wavelength range, with the values of the relevant coefficients peaking at 750 nm, 1200 nm and 1500 nm, respectively. The order of the nonlinear processes was confirmed by measurements of the integral luminescence intensity vs. input excitation intensity. Maxima of the multi-photon absorption bands correspond to the second absorption band of the QDs. The maximum value of the two-photon absorption cross-section σ2 was estimated to be 7.2 × 10(-47) cm(4) s per QD at 750 nm.

Although efficient in heat generation, gold nanoparticles dedicated for photostimulated localized hyperthermia treatment (LHT) lack luminescent properties suitable for detection in heterogeneous and autofluorescent tissue. Here, we study and report the use of bifunctional luminescent neodymium (Nd 3+ ) ions doped α-NaYF 4 colloidal nanoparticles as potential nanoheaters suitable for LHT. Up to 35°C (0.8°C/mW@514.5 nm) temperature rise in ∼0.5 ml colloidal 25%Nd 3+ :NaYF 4 solution was achieved in comparison to around a 4°C rise for the undoped colloidal NaYF 4 . The maximum temperature (T max ) was linearly proportional to the concentration of Nd 3+ dopant. The time required to elevate temperature to 1/e × T max varied from 100 to 135 seconds. The proposed approach gives premises to the construction of multi-functional therapeutic agents detectable by means of fluorescence molecular imaging.A. Bednarkiewicz ( ) · W. Strek

At the core of luminescence color and lifetime tuning of rare earth doped upconverting nanoparticles (UCNPs), is the understanding of the impact of the particle architecture for commonly used sensitizer (S) and activator (A) ions. In this respect, a series of core@shell NaYF UCNPs doped with Yb and Ho ions are presented here, where the same dopant concentrations are distributed in different particle architectures following the scheme: YbHo core and YbHo@…, …@YbHo, Yb@Ho, Ho@Yb, YbHo@Yb, and Yb@YbHo core-shell NPs. As revealed by quantitative steady-state and time-resolved luminescence studies, the relative spatial distribution of the A and S ions in the UCNPs and their protection from surface quenching has a critical impact on their luminescence characteristics. Although the increased amount of Yb ions boosts UCNP performance by amplifying the absorption, the Yb ions can also efficiently dissipate the energy stored in the material through energy migration to the surface, thereby reducing the overall energy transfer efficiency to the activator ions. The results provide yet another proof that UC phosphor chemistry combined with materials engineering through intentional core@shell structures may help to fine-tune the luminescence features of UCNPs for their specific future applications in biosensing, bioimaging, photovoltaics, and display technologies.