Tunable green laser source based on frequency mixing of pump and laser radiation from a Nd:YVO4 crystal operating at 1342 nm with an intracavity KTP crystal

We report on cw tunable green laser light generation from a Nd:YVO4 laser operating at 1342 nm. Visible radiation was produced by a frequency mixing of pump and laser radiation inside an intracavity KTP crystal. When Nd:YVO4 was diode pumped, green laser was tunable from 503 to 505 nm. The green tuning range increases up to 22 nm when a Ti:sapphire laser is used as the pump source. In nonoptimal conditions, and for a pump power of 650 mW, green power was above 3 mW and close to 0.1 mW for Ti:sapphire and diode pumping, respectively.     

Comparison of total ozone measurements from a differential optical absorption filter instrument and a Dobson spectrophotometer

Measures of total ozone at Lisbon in July 1996 taken with a differential optical absorption filter instrument (UAM-DOAF) and a Dobson spectrophotometer are compared. Correlation of the UAM-DOAF measures and NOAATOVS data from April to October 1996 and NASA Earth Probe TOMS data from July to October 1996 for Madrid (40 N, 3 W) are given. Results show that the UAM-DOAF instrument can be used with approximately a 3 per cent error in estimating short-term total ozone variations.     

Intratumoral Thermal Reading During Photo‐Thermal Therapy by Multifunctional Fluorescent Nanoparticles

The tremendous development of nanotechnology is bringing us closer to the dream of clinical application of nanoparticles in photothermal therapies of tumors. This requires the use of specific nanoparticles that must be highly biocompatible, efficient light‐to‐heat converters and fluorescent markers. Temperature reading by the heating nanoparticles during therapy appears of paramount importance to keep at a minimum the collateral damage that could arise from undesirable excessive heating. In this work, this thermally controlled therapy is possible by using Nd³⁺ ion‐doped LaF₃ nanocrystals. Because of the particular optical features of Nd³⁺ ions at high doping concentrations, these nanoparticles are capable of in vivo photothermal heating, fluorescent tumor localization and intratumoral thermal sensing. The successful photothermal therapy experiments here presented highlight the importance of controlling therapy parameters based on intratumoral temperature measurements instead of on the traditionally used skin temperature measurements. In fact, significant differences between intratumoral and skin temperatures do exist and could lead to the appearance of excessive collateral damage. These results open a new avenue for the real application of nano­particle‐based photothermal therapy at clinical level.     

PbS/CdS/ZnS Quantum Dots: A Multifunctional Platform for In Vivo Near‐Infrared Low‐Dose Fluorescence Imaging

Over the past decade, near‐infrared (NIR)‐emitting nanoparticles have increasingly been investigated in biomedical research for use as fluorescent imaging probes. Here, high‐quality water‐dispersible core/shell/shell PbS/CdS/ZnS quantum dots (hereafter QDs) as NIR imaging probes fabricated through a rapid, cost‐effective microwave‐assisted cation exchange procedure are reported. These QDs have proven to be water dispersible, stable, and are expected to be nontoxic, resulting from the growth of an outer ZnS shell and the simultaneous surface functionalization with mercaptopropionic acid ligands. Care is taken to design the emission wavelength of the QDs probe lying within the second biological window (1000–1350 nm), which leads to higher penetration depths because of the low extinction coefficient of biological tissues in this spectral range. Furthermore, their intense fluorescence emission enables to follow the real‐time evolution of QD biodistribution among different organs of living mice, after low‐dose intravenous administration. In this paper, QD platform has proven to be capable (ex vivo and in vitro) of high‐resolution thermal sensing in the physiological temperature range. The investigation, together with the lack of noticeable toxicity from these PbS/CdS/ZnS QDs after preliminary studies, paves the way for their use as outstanding multifunctional probes both for in vitro and in vivo applications in biomedicine.