the systems described so far require UV-Vis light which limits their applications. Two-Photon Excitation (TPE) in the near-infrared region is a promising alternative to UV-vis light due to the many advantages TPE provides such as three dimensional spatial resolution, lower scattering losses, and deeper penetration in tissues.[ 16 ] Very few TPE-triggered MSN-based drug delivery systems have been described in the literature, [ 17,18 ] and only two very recent examples were reported with cytotoxic drug delivery in cancer cells. The fi rst example is based on coumarin cleavage and needed very high material concentration (1 mg mL −1 ) in cells and long time of irradiation (1 h) to observe a cancer cell killing effect.[ 19 ] The second was described by us and concerned nanoimpellers reconfi gured for TPE.[ 20 ] The system was effi cient in inducing cancer cell death under TPE. In this communication, we report an alternative MSN-azobenzene-based system with a high specifi c surface area and pore volume for TPE-triggered drug delivery in cancer cells. Furthermore, two-photon fl uorescence imaging in vitro was also performed (see Scheme 1 ). First of all, a novel two-photon paracyclophane-based fl uorophore (CF) possessing a high two-photon absorption cross-section was designed and fully characterized. (see the Supporting Information). The maximum emission of the fl uorophore was 415 nm in THF, with a quantum yield of 68% suitable for FRET with azobenzene ( Figure 1 ).The silylated fl uorophore (CF) was co-condensed with tetraethoxysilane (TEOS) and cetyltrimethylammonium bromide (CTAB) in basic media to lead to the two-photon fl uorescent MSN (MCF NPs). Mono-triethoxysilylated azobenzene was then grafted on the surface of the nanoparticles (MCF-AZO NPs). Then, the cargo was loaded in the pores of the MCF-AZO NPs. The supramolecular complexation of β-cyclodextrin was performed in ice-cooled conditions, in order to cap the porous surface to lead to the nanovalve (MCF-AZO@βCD NPs). As a control MCM-41 type MSN NPs were functionalized with azobenzene (MSN-AZO NPs) and β-cyclodextrin MSN-AZO@βCD NPs using the same procedure.The characterizations of the MCF NPs after surfactant removal confi rmed the monodispersity and mesoporosity of Drug Delivery

Porous silicon nanoparticles (pSiNPs) act as a sensitizer for the 2-photon excitation of a pendant porphyrin using NIR laser light, for imaging and photodynamic therapy. Mannose-functionalized pSiNPs can be vectorized to MCF-7 human breast cancer cells through a mannose receptor-mediated endocytosis mechanism to provide a 3-fold enhancement of the 2-photon PDT effect.

In this work, we describe the synthesis of new Mixed Periodic Mesoporous Organosilica Nanoparticles (MPMO NPs), combining the co-condensation of a tetra-trialkoxysilylated twophoton photosensitizer with bis-(triethoxysilyl)phenylene or ethylene. Novel gold core-MPMO shell systems are also described. The MPMO NPs are analyzed and characterized by multiple techniques, and are very efficient for anti-cancer drug delivery combined with two-photon therapy in MCF-7 breast cancer cells, leading down to 76% cancer cell death. MPMO NPs are thus very promising for nanomedicine applications.

A two-photon photosensitizer with four triethoxysilyl groups is synthesized through the click reaction. This photosensitizer allows the design of bridged silsesquioxane (BS) nanoparticles through a sol-gel process; moreover, gold core BS shells or BS nanoparticles decorated with gold nanospheres are synthesized. An enhancement of the two-photon properties is noted with gold and the nanoparticles are efficient for two-photon imaging and two-photon photodynamic therapy of cancer cells.

A diverse set of imidazole-and p-expanded imidazole derivatives displaying excited state intramolecular proton transfer (ESIPT) was designed and synthesized. The effect of structural variation on photophysical properties was studied in detail for nine dyes. The relationship between the structure and photophysical properties was thoroughly elucidated also by comparing with analogues with blocked ESIPT functionality. All but one of the obtained compounds exhibit ESIPT, as demonstrated by large Stokes shifts (6500-15 600 cm À1 ). The type of p-expansion strongly influences the overall optical phenomena: while typical p-expansion preserves ESIPT activity, the direct fusion of imidazole with a naphthalene unit at positions 4 and 5 results in dyes which do not exhibit ESIPT. The compound possessing an acidic NH group as part of an intramolecular hydrogen bond system has a much higher fluorescence quantum yield and Stokes shift than its analogue bearing an OH group. The occurrence of ESIPT for tosylamide analogues is less affected by the hydrogen-bonding ability of the solvents compared to the unprotected amines. Two-photon absorption cross-sections of the selected derivatives are in the range of 5-100 GM.

Structurally unique π-expanded diketopyrrolopyrroles (EDPP) were designed and synthesized. Strategic placement of a fluorene scaffold at the periphery of a diketopyrrolopyrrole through tandem Friedel-Crafts-dehydration reactions resulted in dyes with supreme solubility. The structure of the dyes was confirmed by X-ray crystallography verifying a nearly flattened arrangement of the ten fused rings. Despite the extended ring system, the dye still preserved good solubility and was further functionalized by using Pd-catalyzed coupling reactions, such as the Buchwald-Hartwig amination. Photophysical studies of these new functional dyes revealed that they possess enhanced properties when compared with expanded DPPs in terms of two-photon absorption cross-section. It is further demonstrated that in addition to the initial diacetals, the final electrophilic cyclization step can also be applied to diketones. By placing two amine groups at peripheral positions of the resulting dyes, values of two-photon absorption cross-section on the level of 2000 GM around 1000 nm were achieved, which in combination with high fluorescence quantum yield (Φfl ), generated a two-photon brightness of approximately 1600 GM. These characteristics in combination with strong red emission (665 nm) make these new π-expanded diketopyrrolopyrroles of major promise as two-photon dyes for bioimaging applications. Finally, the corresponding N-alkylated DPPs displayed a solid-state fluorescence.

The linear optical (LO) and nonlinear optical (NLO) properties of a series of isocyanurates functionalized by donor arms at the periphery are reported herein. These octupolar derivatives were obtained in a straightforward way from commercial isocyanate derivatives and were fully characterized. Although several of these compounds are known, those that exhibited the largest NLO activities are all new compounds. In terms of second-order activity, several of these derivatives exhibit remarkable activity/transparency tradeoffs. In terms of third-order activity, the longer derivatives with the stronger donor groups (X = NH(2), NMe(2), or NPh(2)) were shown to possess significant two-photon absorption cross sections. These strongly luminescent derivatives exhibit two-photon absorption cross sections up to 410 GM. DFT computations were also conducted to unravel their electronic structures and to rationalize their NLO properties. To our knowledge, the present study is the first concerned with the nonlinear optical properties of these original cyclotrimers.

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