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With the miniaturization of electronic-based devices, the foreseen potential of new optical nanoprobes and the assessment of eventual size and shape effects, elaboration of multifunctional noncentrosymmetric nanocrystals with ferroelectric, pyroelectric, piezoelectric, and nonlinear optical properties are the subject of an increasing research interest. Here, the recent achievements from the solution-based methods (coprecipitation in homogeneous and nanostructured media, sol-gel processes including various chemistries and hydro/solvothermal techniques) to prepare 0-D perovskite and nonperovskite oxides in the 5-500 nm size range are critically reviewed. To cover a representative list of covalent- and ionic-type materials, BaTiO

Hybrid nanoparticles composed of an efficient nonlinear optical core and a gold shell can enhance and tune the nonlinear optical emission thanks to the plasmonic effect. However the influence of an incomplete gold shell, i.e., isolated gold nano-islands, is still not well studied. Here LiNbO3 (LN) core nanoparticles of 45 nm were coated with various densities of gold nano-seeds (AuSeeds). As both LN and AuSeeds bear negative surface charge, a positively-charged polymer was first coated onto LN. The number of polymer chains per LN was evaluated at 1210 by XPS and confirmed by fluorescence titration. Then, the surface coverage percentage of AuSeeds onto LN was estimated to a maximum of 30% using ICP-AES. The addition of AuSeeds was also accompanied with surface charge reversal, the negative charge increasing with the higher amount of AuSeeds. Finally, the first hyperpolarizability decreased with the increase of AuSeeds density while depolarization values for Au-seeded LN were close to the one of bare LN, showing a predominance of the second harmonic volumic contribution. ispartof: NANOMATERIALS vol:11 issue:4 ispartof: location:Switzerland status: published

Phase-pure, highly crystalline sub-50 nm LiNbO3 nanocrystals were prepared from a non-aqueous solvothermal process for 72 h at 230 &deg, C and a commercial precursor solution of mixed lithium niobium ethoxide in its parent alcohol. A systematic variation of the reaction medium composition with the addition of different amounts of co-solvent including butanol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol resulted in the formation of nanocrystals of adjustable mean size and shape anisotropy, as demonstrated from XRD measurements and TEM imaging. Colloidal stability of ethanol- and water-based suspensions was evaluated from dynamic light scattering (DLS)/zeta potential studies and correlated with FTIR data. Thanks to the evolution in the nanocrystal size and shape distribution we observed, as well as to the available literature on the alkoxide chemistry, the reaction pathways and growth mechanisms were finally discussed with a special attention on the monomer formation rate, leading to the nucleation step. The polar, non-perovskite crystalline structure of LiNbO3 was also evidenced to play a major role in the nanocrystal shape anisotropy.

International audience; Whereas most of the reports on the nonlinear properties of micro- and nanostructures address the generation of distinct signals, such as second or third harmonic, here we demonstrate that the novel generation of dual output lasers recently developed for microscopy can readily increase the accessible parameter space and enable the simultaneous excitation and detection of multiple emission orders such as several harmonics and signals stemming from various sum and difference frequency mixing processes. This rich response, which in our case features 10 distinct emissions and encompasses the whole spectral range from the deep ultraviolet to the short-wave infrared region, is demonstrated using various nonlinear oxide nanomaterials while being characterized and simulated temporally and spectrally. Notably, we show that the response is conserved when the particles are embedded in biological media opening the way to novel biolabeling and phototriggering strategies.

We introduce a nonlinear all-optical theranostics protocol based on the excitation wavelength decoupling between imaging and photoinduced damage of human cancer cells labeled by bismuth ferrite (BFO) harmonic nanoparticles (HNPs). To characterize the damage process, we rely on a scheme for in situ temperature monitoring based on upconversion nanoparticles: by spectrally resolving the emission of silica coated NaGdF4:Yb3+/Er3+ nanoparticles in close vicinity of a BFO HNP, we show that the photointeraction upon NIR-I excitation at high irradiance is associated with a temperature increase >100 °C. The observed laser–cell interaction implies a permanent change of the BFO nonlinear optical properties, which can be used as a proxy to read out the outcome of a theranostics procedure combining imaging at 980 nm and selective cell damage at 830 nm. The approach has potential applications to monitor and treat lesions within NIR light penetration depth in tissues.

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International audience; We report the microwave-assisted hydrothermal synthesis of α-La(IO3)3 nanocrystals doped with Yb 3+ and Er 3+ ions, along with their structural and optical characterizations. 50-nm sized α-La0.9-xYb0.1Erx(IO3)3 nanocrystals with x = 0.005, 0.01 and 0.02 were synthesized and dispersed in ethylene glycol. The as-obtained suspensions exhibit both Second Harmonic Generation (SHG) signal and up-conversion photoluminescence (UC-PL) without interplay between the two signals under near-infrared resonant excitation. The relative intensity of SHG and UC-PL emission can be modulated according to the excitation wavelength. The most intense UC-PL signal is obtained from a 980-nm excitation, thanks to the sensitization of Er 3+ by Yb 3+. 2

The absence of photobleaching, blinking, and saturation combined with a high contrast provides unique advantages of higher-harmonic generating nanoparticles over fluorescent probes, allowing for prolonged correlation spectroscopy studies. We apply the coherent intensity fluctuation model to study the mobility of second harmonic generating nanoparticles. A concise protocol is presented for quantifying the diffusion coefficient from a single spectroscopy measurement without the need for separate point-spread-function calibrations. The technique's applicability is illustrated on nominally 56 nm LiNbO3 nanoparticles. We perform label-free raster image correlation spectroscopy imaging in aqueous suspension and spatiotemporal image correlation spectroscopy in A549 human lung carcinoma cells. In good agreement with the expected theoretical result, the measured diffusion coefficient in water at room temperature is (7.5 +/- 0.3) mu m(2)/s. The diffusion coefficient in the cells is more than 10(3) times lower and heterogeneous, with an average of (3.7 +/- 1.5) X 10(-3) mu m(2)/s. This research was supported by the Research Foundation Flanders (Fonds Wetenschappelijk Onderzoek, project G092915FWO) and by the Interuniversity Attraction Poles Program (IAP FS2 P7/05, Functional Supramolecular Systems) initiated by the Belgian Science Policy Office. The authors are grateful to Prof. Dr. J. D'Haen for the SEM image, to Dr. N. Smisdom for fruitful discussions, and to Dr. R. Paesen and Dr. N. Smisdom for the design of the polarization unit. Research in P.P.'s laboratory was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Preparation of stable BiFeO3 nanocrystal suspensions through a simple, low-cost precipitation technique is described. Amorphous precursors are first precipitated from metal nitrate salts in highly basic KOH solutions, and a short high-temperature annealing step is then performed to induce crystallization. Nanoparticles are characterized by X-ray diffraction (XRD), TEM, DLS and ζ-potential measurements, and the synthesis conditions optimized after a systematic variation of the KOH concentration within the range of 1–12 M. The presence of residual impurities (mainly Bi25FeO39 and Bi2Fe4O9) quantified from XRD and mean nanocrystal size is found to be strongly influenced by the initial KOH solution content. A concentration at about 3–4 M is optimal in terms of BiFeO3 phase-purity and nanocrystal size. Stability of aqueous dispersions of the amorphous precursors and of the purest crystallized nanoparticles is also characterized between pH = 2 and pH = 13. After preparation of stable, almost phase-pure BiFeO3 nanocrystal suspensions, second and third harmonic scattering (SHS and THS) at excitation wavelengths of 1064 nm and 1250 nm are reported from nonlinear optical scattering measurements and compared with other recently published literature values.

We demonstrate the simultaneous generation of second, third, and fourth harmonic from a single dielectric Bismuth Ferrite nanoparticle excited by a telecom fiber laser at 1560 nm. We first characterize the signals associated with different nonlinear orders in terms of spectrum, excitation intensity dependence, and relative signal strengths. Successively, on the basis of the polarization-resolved emission curves of the three harmonics, we discuss the interplay of susceptibility tensor components at the different orders and we show how polarization can be used as an optical handle to control the relative frequency conversion properties., Comment: include S.I. section at the end of the main pdf file

We present two new synthetic routes for bismuth ferrite harmonic nanoparticles (BiFeO3 HNPs). Both phase-pure and mixed phase BiFeO3 materials were produced after improvement of the solvent evaporation and sol-gel combustion routes. Metal nitrates with a series of dicarboxylic acids (tartronic, tartaric and mucic) were used to promote crystallization. We found that the longer the carbon backbone with a hydroxyl group attached to each carbon, the lower the annealing temperature. We also demonstrate that nanocrystals more readily formed at a given temperature by adding glycerol but to the detriment of phase purity, whereas addition of NaCl in excess with mucic acid promotes the formation of phase-pure, monocrystalline nanoparticles. This effect was possibly associated with a better dispersion of the primary amorphous precursors and formation of intermediate complexes. The nanoparticles have been characterized by XRD, TEM, ζ-potential, photon correlation spectroscopy, two-photon microscopy and Hyper-Rayleigh Scattering measurements. The improved crystallization leads to BiFeO3 HNPs without defect-induced luminescence and with a very high averaged second harmonic efficiency (220 pm/V), almost triple the efficiency previously reported. This development of simple, scalable synthesis routes which yield phase-pure and, crucially, monocrystalline BiFeO3 HNPs demonstrates a significant advance in engineering the properties of nanocrystals for bio-imaging and diagnostics applications.

Hyper Rayleigh scattering (HRS) was used to measure the second-order nonlinear susceptibility, 𝝌(2), for liquid exfoliated WS2 monolayers. To the best of our knowledge, it is the first reported application of the HRS technique to assess the bulk-like 𝝌(2) of a two-dimensional (2D) material. The concentration-dependent HRS signal indicated a 4.90±0.30×10−25 esu first hyperpolarizability for 42 nm WS2 monolayers under 1064 nm laser irradiation using para-nitroaniline as an external reference. The corresponding value of 𝝌(2)𝒙𝒙𝒙 was calculated to be 460±28 pm V−1. This was within 46% of independent density functional theory predictions. Agreement with theory was improved over related microscopy-based approaches. These results support the use of HRS to evaluate 2D materials for nonlinear frequency mixing applications.

Potassium niobate (KNbO3) nanocrystals exhibiting good second harmonic generation properties were coated with dextran derivatives containing primary amine groups. The surface modification results from attractive electrostatic interaction between the aminodextran molecules and the negatively charged surface of bare KNbO3 nanocrystals. To avoid flocculation, a suspension of KNbO3 nanocrystals was firstly prepared and then added drop-wise to an aqueous solution of aminodextran. The as-prepared hybrid (AD-coated KNbO3) nanoparticles were then characterized by using various techniques including transmission electron microscopy (TEM), infrared analysis (FTIR), dynamic light scattering (DLS) and zeta potential measurements as a function of pH of the dispersion medium. Then, the prepared AD- coated KNbO3 nanoparticles were evaluated in vitro diagnostic application as biomarker for non-tumor lung-derived human cells. The obtained results showed that the aminodextran-coated KNbO3 nanoparticles were efficiently bound to the non-tumor lung-derived human cells, which was proved by using a commercial Nikon multi-photon imaging platform. In addition, AD-coated KNbO3 nanoparticles showed good optical contrast for the investigated cells, and consequently they can be efficiently used as contrast agents in the bio-imaging diagnostic domain.

We use Hyper Rayleigh Scattering and polarization resolved multiphoton microscopy to investigate simultaneously the second and third-order nonlinear response of Potassium Niobate and Bismuth Ferrite harmonic nanoparticles. We first derive the second-to-third harmonic intensity ratio for colloidal ensembles and estimate the average third-order efficiency of these two materials. Successively, we explore the orientation dependent tensorial response of individual nanoparticles fixed on a substrate. The multi-order polarization resolved emission curves are globally fitted with an analytical model to retrieve individual elements of susceptibility tensors.

International audience; We have investigated nanocrystals of Fe(IO3)3 by polarization-sensitive second harmonic generation (SHG) microscopy. As the nonlinear optical properties of this material were only poorly characterized, we have first determined the relative values of the elements of its second-order susceptibility tensor, by the global fitting of the polarization-resolved SHG response of an ensemble of nanocrystals. This information allows one to optically retrieve the orientation of individual particles in the sample. The high SHG efficiency measured for nanocrystals of Fe(IO3)3 and their polar nature could make them very attractive for nonlinear microscopy of biological samples.

International audience; Fe(IO3)3 powders have been produced by co-precipitation of iron nitrate and iodic acid in aqueous solution. X ray diffraction studies show that the crystal structure is satisfactorily described in space group P63; the cell parameters and the atomic positions have been ascertained by Rietveld refinements. The nanometric size of the Fe(IO3)3 particles has been estimated from the full width at half maximum of the diffraction peaks and confirmed by atomic force microscopy observations. Although we find colour changes and small weight losses below 400 °C, the structure is found stable up to this temperature where it decomposes to form nanosized hematite α-Fe2O3 powder. Finally, Fe(IO3)3 nanopowder pellets exhibit second harmonic generation of the fundamental wavelength of a Nd:YAG laser.

response, often referred to as harmonicnanoparticles (HNPs). HNPs feature a series of properties which distinguish them from otherphotonics nanoprobes (quantum dots, up-conversion nanoparticles, noble metal particles). HNPsemission is inherently nonlinear and based on the efficient generation of harmonics as opposed tofluorescence or surface plasmon scattering. In addition, the fully coherent signal emitted byHNPs together with their polarization sensitive response and absence of resonant interactionmake them appealing for several applications ranging from multi-photon (infrared) microscopyand holography, to cell tracking and sensing.Keywords: multiphoton microscopy, second harmonic generation, third harmonic generation,nonlinear optics, nanophotonics, perovskites(Some figures may appear in colour only in the online journal)1. IntroductionSince the advent of ultrafast lasers in the early nineties andrelated availability of high peak power pulses at compara-tively low energies, the investigation of nonlinear opticalresponse have become a widespread activity resulting ininnovative applications. In particular, in the field of imagingthis has led to the introduction of multi-photon microscopy byW Webb [1]. This technique, as compared to one-photonexcited fluorescence microscopy, features increased imagingdepth, no out-of-focus bleaching, and spatial resolutioncomparable to confocal techniques without compromise insensitivity. The latest technological advancements in this fieldare related to its extension towards longer wavelengths,facilitated by the timely introduction of novel tunable sourcesin the 0.7–1.3 μm spectral range and new optical componentswith optimized performances in this region (microscopeobjectives, acousto-optic modulators, ...). Although these newinfrared tunable devices are supposedly more adapted forimaging through thick (living) samples because of reducedscattering [2–4], the available choice of imaging targets(fluorescent molecules, dyes) with two-photon absorptionbands >1200nm is very limited.Nanoparticle-based labelling, which is sometimes pre-ferred over other approaches for its superior photo-stability,brightness, and chemical selectivity usually requires two-photon interactions in the 700–900nm range, with a fewnotable exceptions [5]. However most optically active labelsmay suffer from bleaching and blinking and their use inbiological research might be prevented because of low bio-compatibility. For these reasons, since 2006, several researchgroups worldwide have proposed a complementary approach

The lithium iodate ionic conduction in the polar c-axis direction is studied between 35 and 470 K for crystals grown in various conditions. So far, to separate processes induced by the nature of electrodes, the impedance spectroscopy technique had been used at room temperature with both metallic and ideally polarizable insulating electrodes, so that a relaxation of space charges was clearly identified. Here, the temperature dependence of the hopping ionic conductivity exhibits quite different activation energies well related to the growth conditions. Following low-temperature Raman and thermodynamic experiments, a new approach based on a vacancy diffusion mechanism is proposed. Experimental conductivity results are then correlated with the valence, size and concentration of extrinsic impurities incorporated during the growth and analyzed by plasma spectroscopy. Finally, a discussion is made on still not well-understood phenomena such as the strong increase of photorefractivity or the enhancement of some Bragg reflections.

Bismuth Ferrite (BFO) nanoparticles (BFO-NP) display interesting optical (nonlinear response) and magnetic properties which make them amenable for bio-oriented applications as intra- and extra membrane contrast agents. Due to the relatively recent availability of this material in well dispersed nanometric form, its biocompatibility was not known to date. In this study, we present a thorough assessment of the effects of in vitro exposure of human adenocarcinoma (A549), lung squamous carcinoma (NCI-H520), and acute monocytic leukemia (THP-1) cell lines to uncoated and poly(ethylene glycol)-coated BFO-NP in the form of cytotoxicity, haemolytic response and biocompatibility. Our results support the attractiveness of the functional-BFO towards biomedical applications focused on advanced diagnostic imaging., Word Count: 109 Complete Word Count (body text and figure legends) : 4886 Number of Figures: 6 Number of Tables: 0 Number of reference: 45

Second Harmonic Generation (SHG) from BiFeO3 nanocrystals is investigated for the first time to determine their potential as biomarkers for multiphoton imaging. Nanocrystals are produced by an auto-combustion method with 2-amino-2-hydroxymethyl-propane-1,3-diol as a fuel. Stable colloidal suspensions with mean particle diameters in the range 100–120 nm are then obtained after wet-milling and sonication steps. SHG properties are determined using two complementary experimental techniques, Hyper Rayleigh Scattering and nonlinear polarization microscopy. BiFeO3 shows a very high second harmonic efficiency with an averaged hdi coefficient of 79612 pm/V. From the nonlinear polarization response of individual nanocrystals, relative values of the independent dij coefficients are also determined and compared with recent theoretical and experimental studies. Additionally, the particles show a moderate magnetic response, which is attributed to gamma-Fe2O3 impurities. A combination of high nonlinear optical efficiency and magnetic response within the same particle is of great interest for future bio-imaging and diagnostic applications.

Matériaux et Outils pour la Santé; International audience; Hydrophobic room-temperature ionic liquids were used to remove KNbO3 and BaTiO3 nanoparticles from water at 25 uC. A very good extraction efficiency was obtained with distribution coefficients as high as 500. After extraction, toxicity of the aqueous phase containing residual amounts of nanoparticles and ionic liquids was assessed using Vibrio fischeri. A preliminary investigation of the toxicity mechanism was carried out with propidium iodide tests. A key result is that the simultaneous presence of a small amount of nanoparticles and ionic liquid in water can result in adverse toxicological effects compared to aqueous solutions containing solely nanoparticles or ionic liquids.

We demonstrate the possibility to excite second-harmonic (SH) active Fe(IO(3))(3) nanocrystals with two distinct laser sources at 800 and 1550 nm, and we show, by a complementary experimental and numerical study, how the wavelength flexibility inherent to non-phase-matched SH nanoparticles can be efficiently exploited to increase imaging penetration depth of markers embedded in biological samples.

The ability of pellets made up of compressed iron iodate nanocrystals to frequency-double the whole visible spectrum is demonstrated. We suggest their use for complete characterization of intense ultrabroadband laser pulses.

International audience; We present a technique to characterize ultrashort pulses at the focal plane of a high numerical aperture objective with unprecedented spatial resolution, by performing a FROG measurement with a single nanocrystal as nonlinear medium. This approach can be extended to develop novel phase-sensitive techniques in laser scanning microscopy, probing the microscopic environment by monitoring phase and amplitude distortions of femtosecond laser pulses.

International audience; In this paper we present the fabrication and characterization of nanocomposite materials based on crystalline nanoparticles dispersed in an oligomer matrix (DGEBA, used in epoxy resin). Two types of nanoparticles are used. Al2O3 nanoparticles, commercially available, allow us to carry out the fabrication process of the nanocomposites. This system (DGEBA+Al 2 O 3 ) is considered as a reference for the second one based on iron iodate nanoparticles fabricated by co-precipitation. The nanocomposite fabrication process is described. The dispersion step and the problems inherent to clusters destruction are underlined. Iron iodate nanoparticles are characterized by TEM, SEM, X-ray diffraction, Raman spectroscopy and EDX. Results point out that the nanoparticles have dimensions between 20 and 30 nm and present two different morphologies (ball and needle). Mechanical properties of the nanocomposite based on Al 2 O 3 are explored by Brillouin spectroscopy. An enhancement of the Young's modulus is observed with a very weak mass percentage of nanoparticles (3%), the glass transition is also shifted from 247 K to 251 K. X-ray diffraction measurement on iron iodate nanocomposite demonstrates that nanoparticles remain in the same phase (P6 3 ) after the nanocomposite preparation process. This result is of great importance in order to achieve piezoelectric and ferroelectric applications.

Inorganic nanoparticles (NPs) have emerged as promising tools in biomedical applications, owing to their inherent physicochemical properties and their ease of functionalization. In all potential applications, the surface functionalization strategy is a key step to ensure that NPs are able to overcome the barriers encountered in physiological media, while introducing specific reactive moieties to enable post-functionalization. Silanization appears as a versatile NP-coating strategy, due to the biocompatibility and stability of silica, thus justifying the need for robust and well controlled silanization protocols. Herein, we describe a procedure for the silica coating of harmonic metal oxide NPs (LiNbO3, LNO) using a water-in-oil microemulsion (W/O ME) approach. Through optimized ME conditions, the silanization of LNO NPs was achieved by the condensation of silica precursors (TEOS, APTES derivatives) on the oxide surface, resulting in the formation of coated NPs displaying carboxyl (LNO@COOH) or azide (LNO@N3) reactive moieties. LNO@COOH NPs were further conjugated to an unnatural azido-containing small peptide to obtain silica-coated LNO NPs (LNO@Talys), displaying both azide and carboxyl moieties, which are well suited for biomedical applications due to the orthogonality of their surface functional groups, their colloidal stability in aqueous medium, and their anti-fouling properties.

International audience; Background: Harmonic Nanoparticles are a new family of exogenous markers for multiphoton imaging exerting optical contrast by second harmonic (SH) generation. In this tutorial, we present the application of Hyper-Rayleigh Scattering (HRS) for a quantitative assessment of the nonlinear optical properties of these particles and discuss the underlying theory and some crucial experimental aspects. Methods: The second harmonic properties of BaTiO3, KNbO3, KiTiOPO4 (KTP), LiNbO3 and ZnO nanocrystals (NCs) are investigated by HRS measurements after careful preparation and characterization of colloidal suspensions. Results: A detailed analysis of the experimental results is presented with emphasis on the theoretical background and on the influence of some experimental parameters including the accurate determination of the nanocrystal size and concentration. The SH generation efficiency and averaged nonlinear optical coefficients are then derived and compared for six different types of NCs. Conclusions: After preparation of colloidal NC suspensions and careful examination of their size, concentration and possible aggregation state, HRS appears as a valuable tool to quantitatively assess the SH efficiency ofnoncentrosymmetric NCs. All the investigated nanomaterials show high SH conversion efficiencies, demonstrating a good potential for bio-labelling applications.

Commonly called the "silicon of photonics", lithium niobate (LiNbO3) at the nanoscale is the subject of this work. These so-called harmonic nanocrystals, due to their non-centrosymmetric crystal structure and excellent non-linear optical properties, can be used as contrast agents in multiphoton biomedical imaging for better diagnosis and targeted release of therapeutic agents. The synthesis of LiNbO3 nanocrystals under solvothermal conditions, from alkoxide precursors, is described with a special focus on the fine understanding of reaction mechanisms. Ultimately, this understanding aims to better control the nanocrystal size and shape polydispersity by modifying nucleation and growth rates as desired.For non-aqueous syntheses, since water is neither added nor generated in the reaction medium, it is shown that thermal decomposition of the chosen ethoxide precursor governs the formation kinetics of the monomers and leads, in this case, to the production of nano-platelets. On the other hand, a controlled addition of glycols, such as butane-1,4-diol and pentane-1,5-diol, makes it possible to prepare quasi-spherical nanocrystals with a smaller size and shape distribution due to a better carbocation stability, thus favoring a shorter and more intense nucleation step.For the hydrolytic route, the variation of the hydrolysis rate h leads either to polymeric gels (h1) whose solvothermal treatment produces nanocrystals of low and high polydispersity, respectively. Compared to the international state of the art and to well-known perovskites with (pseudo)-cubic crystal structure, it seems that the specific reticular system of LiNbO3 is to be related to the stronger shape anisotropy of nanocrystals obtained under our synthesis conditions., Communément appelé le « silicium de la photonique », le niobate de lithium (LiNbO3) sous forme nanométrique fait l’objet de ce travail. De tels nanocristaux, dits harmoniques en raison de leur structure cristalline non centrosymétrique et de leurs excellentes propriétés optiques non linéaires, peuvent être utilisés comme agents de contraste en imagerie biomédicale multiphotonique pour un meilleur diagnostic et un relargage ciblé d’agents thérapeutiques.La synthèse de nanocristaux de LiNbO3 en conditions solvothermales, à partir de précurseurs alcoxydes, est décrite avec une attention toute particulière à la compréhension fine des mécanismes réactionnels. À terme, cette compréhension a pour but de mieux contrôler les polydispersités de taille et de forme des nanocristaux en modifiant à souhait les vitesses de nucléation et de croissance.Pour les synthèses non aqueuses, l’eau n’étant ni ajoutée ni générée dans le milieu réactionnel, il est démontré que la décomposition thermique du précurseur ethoxide mixte choisi gouverne la cinétique de génération des monomères et conduit, dans ce cas, à la formation de nano-plaquettes. Un ajout contrôlé de glycols, comme le butane-1,4-diol et le pentane-1,5-diol, permet par contre de préparer des nanocristaux de forme quasi-sphérique avec une faible distribution en taille et forme en raison d’une meilleure stabilité des carbocations, favorisant ainsi une étape de nucléation plus courte et intense. Pour la voie hydrolytique, la variation du taux d’hydrolyse h conduit soit à des gels polymériques (h1) dont le traitement solvothermal produit des nanocristaux de faible et de forte polydispersité, respectivement. Par rapport à l’état de l’art international et aux pérovskites bien connues de structure cristalline (pseudo)-cubique, il semble que le système réticulaire propre à LiNbO3 est à relier à la plus forte anisotropie de forme des nanocristaux obtenus pour nos conditions de synthèse.

Harmonic nanocrystals with a non-centrosymmetric crystalline structure have nonlinearoptical properties that are particularly interesting for use as optical markers inbiomedical imaging.The Hyper-Rayleigh scattering technique currently used to quantify the secondharmonic response of nanoparticles in suspension has been extended in this work todetermine the third order non-linear susceptibility of different nanomaterials (BiFeO3,ZnO, KNbO3 and LiNbO3). Furthermore, the development of an experimental set-upbased on a wavelength-tunable source has allowed probing the non-linear opticalresonances of the 2nd order (for excitation between 700 nm and 1300 nm) of thesedifferent materials. The spectral response of WS2 nanosheets has also been studiedusing the same system. Finally, we have demonstrated the detection of fourthharmonic signals from a single BiFeO3 nanoparticle using a multiphotonicmicroscopy device combined with a Telecom laser source for future integration ofthese nanoparticles as frequency conversion elements for nanophotonics.; Les nanocristaux harmoniques de structure cristalline non centrosymétrique possèdentdes propriétés optiques non linéaires intéressantes notamment pour une utilisationcomme marqueurs optiques en imagerie biomédicale.La technique de diffusion Hyper-Rayleigh habituellement utilisée pour quantifier laréponse de deuxième harmonique de nanoparticules en suspension a été étendue dansce travail pour déterminer la susceptibilité non linéaire d’ordre 3 de différentsnanomatériaux (BiFeO3, ZnO, KNbO3 et LiNbO3). D’autre part, le développementd’un montage expérimental basé sur une source accordable en longueur d’onde apermis de sonder les résonances optiques non linéaires d’ordre 2 (pour une excitationcomprise entre 700 nm et 1300 nm) de ces différents matériaux. La réponse spectralede nanofeuillets de WS2 a également été étudiée à l’aide du même système. Enfin,nous avons démontré la détection de signaux de quatrième harmonique d’unenanoparticule unique de BiFeO3 à l’aide d’un dispositif de microscopiemultiphotonique associé à une source laser Telecom pour une future intégration deces nanoparticules comme éléments de conversion de fréquence pour lananophotonique.

Non-centrosymetric nanocrystals show promising nonlinear optical properties for being used as optical labels in bio-imaging applications, with significant interest for observations of long duration and for penetration depth into biological tissues. The development of such biomarkers requires the determination of their nonlinear optical properties to select the best potential markers. In this thesis, Hyper-Rayleigh Scattering (HRS) technique is used to determine nonlinear efficiencies of several nanocystals (BaTiO3, KNbO3, KTP, LiNbO3, ZnO and BiFeO3). These ensemble measurements have been performed on nanocrystals suspensions, for which the influence of parameters such as size, concentration and aggregation state was discussed. BiFeO3nanocrystals offer the best nonlinear optical efficiency compared to other particles, showing their potential as efficient optical biomarkers. Polarisation-resolved measurements have also been performed to retrieve individual coefficients of the nonlinear tensor of the investigated materials and influent parameters such as nanocrystals shape have been identified., Les nanocristaux à structure non-centrosymétrique présentent des propriétés optiques non linéaires prometteuses pour une utilisation en tant que marqueurs optiques en imagerie biomédicale, avec un intérêt significatif en termes de suivi sur de longues durées et de profondeur de pénétration dans les tissus biologiques. Le développement de ces marqueurs nécessite la détermination de leurs efficacités optiques non linéaires afin de pouvoir sélectionner les nanocristaux les plus prometteurs. Pour cela, la technique de diffusion Hyper-Rayleigh a été adaptée à la caractérisation de suspensions de nanoparticules (BaTiO3, KNbO3, KTP, LiNbO3 et ZnO, BiFeO3) pour lesquelles l’influence de paramètres comme la taille, la concentration ou l’état d’agrégation a été analysée et discutée. Les nanocristaux de BiFeO3 possèdent une efficacité optique non linéaire largement supérieure aux autres particules, démontrant leur potentiel pour la réalisation de nano-sondes optiques particulièrement performantes. Des mesures résolues en polarisation ont également été mises en œuvre pour déterminer les coefficients optiques non linéaires indépendants des particules étudiées. Dans ce cadre, une étude a permis de mettre en évidence l’influence de la forme des nanocristaux sur cette réponse.

Exogenous biomarkers based on hybrid nanoparticles of controlled size and morphology with nonlinear optical properties were prepared as a contrast agent for second harmonic imaging and diagnosis of pathogenic cells. Iron iodate is one of the nonlinear materials for biomedical applications imaging due to its low toxicity to the immune system. These iron iodate nanoparticles were synthesized by inverse microemulsion and inverse miniemulsion with good control of size and morphology. Their in situ encapsulation was carried out by reverse miniemulsion polymerization. Encapsulation of potassium niobate was also conducted and their interaction with the biological environment has been reported by in vitro studies and second harmonic imaging., Des marqueurs biologiques exogènes à base de nanoparticules hybrides de taille et de morphologie contrôlées et ayant des propriétés optiques non-linéaires ont été préparés en tant qu’agent de contraste en imagerie de second harmonique et de diagnostic de cellules pathogènes. L’iodate de fer est l’un des matériaux non linéaires le plus sollicité pour des applications en imagerie biomédicale en raison de sa faible toxicité vis-à-vis du système immunitaire. Ces nanoparticules d’iodate de fer ont été synthétisées par microémulsion inverse et miniémulsion inverse avec un bon contrôle de taille et de morphologie. Leur encapsulation in situ a été réalisée par polymérisation en miniémulsion inverse. L’encapsulation de niobate de potassium a également été réalisée, leur interaction avec le milieu biologique a été reportée par des études in vitro en imagerie de seconde harmonique.