Upconversion nanoparticles in biological labeling, imaging, and therapy

Nanoparticles for highly efficient multiphoton fluorescence bioimaging

In this paper, we demonstrate for the first time that the new class of fluoride-based inorganic upconverting nanoparticles, NaYF4:Er3+, Yb3+, are the most efficient multiphoton excited fluorescent nanoparticles developed to date. The near-infrared-to-visible conversion efficiency of the aforementioned nanoparticles surpasses that of CdSe quantum dots and gold nanorods, which are the commercially available inorganic fluorescent nanoprobes presently used for multiphoton fluorescence bioimaging. The results presented here open new perspectives for the implementation of fluorescence tomography by multiphoton fluorescence imaging.

Self-aligned nanolithography by selective polymer dissolution

We report a novel approach to the fabrication of self-aligned nanoscale trench structures in a thin polymer layer covering on conductive materials. By passing AC current through a polymer-coated nanowire in the presence of an appropriate solvent, a self-aligned nanotrench is formed in the polymer overlayer as a result of accelerated dissolution while the rest of the device remains covered. Similar results have been achieved for polymer-coated graphene ribbons. Such polymer-protected devices in which only the active component is exposed should find important applications as electrical sensors in aqueous solutions, particularly in cases where parasitic ionic currents often obscure sensing signals.

Upconverting luminescent nanoparticles for use in bioconjugation and bioimaging

Upconverting luminescent nanoparticles (UCNPs) display the unique property of emitting visible light following photoexcitation with near-infrared laser light. This results in features such as virtually zero autofluorescence of (biological) matter and easy separation of the emission peaks from stray light. Other features include rather narrow emission bands, very high chemical stability, the lack of bleaching, and the absence of blinking effects. This article reviews the work performed in the past few years with UCNPs in terms of surface modifications, bioconjugation, and optical (cellular) imaging.