Recently, plasmonic copper sulfide (Cu2-xS) nanocrystals (NCs) have attracted much attention as materials for photothermal therapy (PTT). Previous reports have correlated photoinduced cell death to the photothermal heat mechanism of these NCs, and no evidence of their photodynamic properties has been reported yet. Herein we have prepared physiologically stable near-infrared (NIR) plasmonic copper sulfide NCs and analyzed their photothermal and photodynamic properties, including therapeutic potential in cultured melanoma cells and a murine melanoma model. Interestingly, we observe that, besides a high PTT efficacy, these copper sulfide NCs additionally possess intrinsic NIR induced photodynamic activity, whereupon they generate high levels of reactive oxygen species. Furthermore, in vitro and in vivo acute toxic responses of copper sulfide NCs were also elicited. This study highlights a mechanism of NIR light induced cancer therapy, which could pave the way toward more effective nanotherapeutics.

Gold nanorods (AuNRs) are eligible for a variety of biological applications including cell imaging, sensing, and photothermal therapy thanks to their optical properties. The aim of this work is to show how AuNRs could be employed as non-photobleachable optical contrast agents for biomedical applications. In order to demonstrate the feasibility of their use as optical trackers, we employed two-photon emission confocal microscopy on cells incubated with PEGylated AuNRs. Remarkably, AuNRs were localized mostly in the perinuclear zone and microscopy characterization showed the presence of a considerable number of rods inside cell nuclei. Furthermore, we estimated the toxicity and the efficiency of cellular uptake of the PEGylated AuNRs as a function of administered dose on HeLa/3T3 cell lines and on zebrafish during development, employed as an in vivo model. Eventually, we observed good agreement between in vivo and in vitro experiments. The employed AuNRs were prepared through a photochemical protocol here improved by tuning the amount of the cationic surfactant cetyltrimethylammonium bromide for the achievement of AuNRs at two different aspect ratios. Furthermore we also investigated if the AuNR aspect ratio influenced the toxicity and the efficiency of cellular uptake of the PEGylated AuNRs in HeLa/3T3 cell lines and in zebrafish embryos.

In this work, we demonstrate that the photoluminescence emission of CdSe/CdS spherical core/rod like shell nanorods can be completely inhibited by using low-energy femtosecond laser pulses at 720 nm. A combined analysis of optical confocal microscopy images and transmission electron microscope micrographs reveals the presence of different power regimes in the nanocrystals photodegradation process. The photoluminescence inhibition of the nanorods is found to start at a power range in which no apparent structural damage occurs to the nanorods after irradiation. This suggests the presence of a photochemical transformation of the nanocrystals that is of potential interest for application in optical data storage. This is because in recording systems based on photochemical processes the photoexcited volume can be effectively confined within the diffraction-limited laser focus. We indeed demonstrate that the recorded mark can be scaled down to a few nanorods, or even to a single nanorod, without crosstalk between adjacent nanostructures separated by the optical resolution of the instrument used. Finally, the intensities required for inhibiting the emission of nanorods and for avoiding any peripheral thermal damage of the hosting polymer matrix are determined (200−360 GW/cm 2 ), and the mechanism underlying the photochemical process is discussed.

The future of optical data storage and the search for next generation high-density technologies have become a topic of lively debate. Three dimensional (3D) optical data storage, a relatively new technique which enables hundredslayer data recording in a hard memory, seems a viable candidate for this role. In this work, we report on 3D optical data storage in photochromic compounds. The recording medium used in the experiments was a photochromic diarylethenes derivative embedded in different host polymers. Multi-photon processes capability of triggering photochemical reactions and physical changes with micrometer-sized resolution in three dimensions offers a wellsuited means to achieve volumetric storage densities. A commercial microscope coupled to pulsed NIR and CW lasers have been used to write, read and erase data in our prototype memories. Information was recorded within the volume of the media via a multi-photon process achieving high localized photoconversion and the fluorescence emission from the photoconverted molecules when excited by a 405 nm laser diode was the readout signal. It is also shown that data recorded in such a medium can be selectively erased by irradiating with 514 nm CW laser light giving the chance to write new data in the formerly used memory space. These storage media, thus, have good potentials to achieve volumetric storage of data although they certainly deserve further optimization work to achieve high number of superposed layers and to assure durability of the written data under readout conditions.

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