This licentiate thesis addresses two important aspects of the van der Waals and the Casimir-Polder ground-state and excited-state (resonance) interactions between two atoms or molecules. The first is the finite-size effect and the second is the non-perturbative effect. Going beyond the usual assumption of atoms and molecules as point particles and adopting a description of finite size, the divergence inherent in such interaction energies in the limit of zero separation distance between the two interacting atoms or molecules is removed. The attainment of finite interaction energy at such close separation distance facilitates the estimation of van der Waals force contribution to the binding energy of the molecules, and towards surfaces. This is particularly important for noble atoms. We investigate in detail for a pair of helium (He) atoms and krypton (Kr) atoms, and for a pair of methane (CH4) molecules considering its environmental importance. The application of finite size further leads to finite self energies of the atoms. The expression of the interaction energy, as is discussed in detail in this thesis, typically contains a logarithmic factor of the form ln(1-x). Formerly, in evaluating the interaction energies, this factor is customarily series-expanded and truncated in the leading order with certain assumptions. This thesis explores the effect of using the full expression, which we refer to as the non-perturbative (or, the non-expanded) theory, analytically wherever possible as well as numerically. The combined application of the finite-size theory and the non-perturbative theory results in as much as 100% correction in the self energy of atoms in vacuum. This may give rise to significant physical consequences, for example, in the permeabilities of atoms across dielectric membranes. The non-perturbative theory, in addition, exhibits interesting behaviour in the retarded resonance interaction. / <p>QC 20160509</p>

No description available.

The environmental fate and transport of engineered nanomaterials have been broadly investigated and evaluated in many published studies. Silver nanoparticles (AgNPs) represent one of the most widely manufactured nanomaterials. They are currently being incorporated into a wide range of consumer products due to their purported antimicrobial properties. However, either the AgNPs themselves or dissolved Ag+ ions has a significant potential for the environmental release. The safety issues for nanoparticles are continuously being tested because of their potential danger to the environment and human health. Studies have explored the toxicity of AgNPs to a variety of organisms and have shown such toxicity is primarily driven by Ag+ ion release. Dissolution of nanoparticles is an important process that alters their properties and is a critical step in determining their safety. Therefore, studying nanoparticles' dissolution can help in the current move towards safer design and application of nanoparticles. This research endeavor sought to acquire comprehensive kinetic data of AgNP dissolution to aid in the development of quantitative risk assessments of AgNP fate. To evaluate the dissolution process in the absence of nanoparticle aggregation, AgNP arrays were produced on glass substrates using nanosphere lithography (NSL). Changes in the size and shape of the prepared AgNP arrays were monitored during the dissolution process by atomic force microscopy (AFM). The dissolution of AgNP is affected by both internal and external factors. First, surface coating effects were investigated by using three different coating agents (BSA, PEG1000, and PEG5000). Capping agent effects nanoparticle transformation rate by blocking reactants from the nanoparticle surface. Coatings prevented dissolution to different extents due to the various way they were attached to the AgNP surface. Evidence for the existence of bonds between the coating agents and the AgNPs was obtained by surface enhanced Raman spectroscopy. Moreover, to study the size effects on AgNP dissolution, small, medium, and large sized AgNPs were used. The surrounding medium and temperature were the two variables that were included in the size effects study. Relationships were established between medium concentration and dissolution rate for three different sized AgNP samples. By using the Arrhenius equation to plot the reaction constant vs. reaction temperature, the activation energy of AgNPs of different sizes were obtained and compared. / Doctor of Philosophy / Nanomaterials, defined as materials with at least one characteristic dimension less than 100 nm, often have useful attributes that are distinct from the bulk material. The novel physical, chemical, and biological properties enable the promising applications in various manufacturing industry. Silver nanoparticles (AgNPs) represent one of the most widely manufactured nanomaterials and has been used as the antimicrobial agent in a wide range of consumer products. However, either the AgNPs themselves or dissolved Ag+ ions has a significant potential for the environmental release. The environmental fate and transport of AgNPs drawn considerable attentions because of the potential danger to environment and human health. Dissolution of nanoparticles is an important process that alters their properties and is a critical step in determining their safety. Ag+ ions migrate from the nanoparticle surface to the bulk solution when an AgNP dissolves. Studying nanoparticles' dissolution can help in the current move towards safer design and application of nanoparticles. This research aimed to acquire comprehensive kinetic data of AgNP dissolution to aid in the development of quantitative risk assessments of AgNP fate. AgNP arrays were produced on glass substrates using nanosphere lithography (NSL) and changes in the size and shape during the dissolution process were monitored by atomic force microscopy (AFM). First, surface coating effects were investigated by using three different coating agents. Coatings prevented dissolution to different extents due to the various way they were attached to the AgNP surface. Moreover, small, medium, and large sized AgNPs were used to study the size effects on AgNP dissolution. The surrounding medium concentration and temperature were the two variables that were included in the size effects study.

Cette thèse porte sur la description du processus de fissuration du béton soumis à des sollicitations mécaniques. L'objectif principal est d'améliorer la description macroscopique à l'aide d'un modèle continu. Un modèle décrivant de façon cohérente le comportement à la rupture du béton devrait au moins représenter : (i) la transition continu/discret et l'effet d'écran induit par une macrofissure, (ii) la discontinuité du déplacement, (iii) l'interaction entre le processus de fissuration et un bord libre (iv) il doit aussi être capable de reproduire la réponse mécanique obtenue expérimentalement. Dans un premier temps, nous avons fait une analyse comparative entre le modèle d'endommagement non-local classique et différents modèles continus améliorés proposés dans la littérature. Des outils de comparaison ont été proposés pour cette analyse : (i) du point de vue numérique, deux exemples considérant la rupture dynamique d'une barre (barre en traction et test d'écaillage) et (ii) du point de vue expérimental, une base de données issue d'une série d'essais sur des poutres homothétiques entaillées et non-entaillées en flexion trois points. Nous avons conclu que seule une combinaison entre différentes formulations peut rendre compte de tous les mécanismes mis en jeu lors du processus de fissuration. Elle inclue à la fois la façon dont l'information non-locale est transmise, la croissance de défauts et la description des effets de bord. Nous avons mis en évidence que son implémentation 2D ou 3D reste complexe et donc la comparaison avec des données expérimentales s'avère impossible. Dans un deuxième temps, nous avons choisi de changer l'échelle d'analyse pour connaitre en détail les mécanismes ayant lieu au sein de la mésostructure du béton (pâte, granulat, interface) à l'aide d'un modèle mésoscopique basé sur des éléments lattice. Cette analyse a permis de conclure que la prise en compte des interactions entre les composants de la mésostructure du béton fournit des résultats numériques plus proches de la réalité que ceux obtenus avec le modèle non-local macroscopique classique. Le mésomodèle est capable de représenter aussi bien la charge maximale (effet d'échelle) que la phase adoucissante pour toutes les tailles de poutre et pour toutes les géométries d'entaille. Nous avons transposé la prise en compte des interactions de l'échelle mésoscopique à l'échelle macroscopique au travers de la fonction poids d'un nouveau modèle non-local. Elle est estimée en décrivant le matériau comme étant un ensemble d'inclusions qui interagissent entre elles lors du chargement. Ces inclusions sont dilatées élastiquement et successivement afin de caractériser le transfert d'information au sein du matériau et de reconstruire la fonction poids du modèle proposé. Ce nouveau modèle est capable de décrire la transition continu/discret et l'effet d'écran, la discontinuité du déplacement et de retrouver un effet de bord cohérent avec les résultats de la micromécanique. Son implémentation en 2D est présentée et les premiers résultats de calculs illustrent la démarche. Finalement, nous revenons sur la modélisation mésoscopique du comportement du béton. Sa richesse en information peut conduire à une compréhension plus fine du processus de fissuration et de la création puis l'évolution de la zone d'élaboration. / This work focuses on the description of the process of cracking of concrete subjected to mechanical stresses. The main objective is to improve the understanding of the mechanisms involved using a continuous macroscopic model. A model describing consistently the fracture behavior of concrete should at least represent: (i) the continuous / discrete transition and the shielding effect induced by a macrocrack, (ii) the discontinuity of displacement, (iii) the interaction between the cracking process and a free boundary, (iv) it must also be able to reproduce the mechanical response obtained experimentally. At first, we made a comparative analysis of the classical non-local damage model and others improved continuous models proposed in the literature. Comparison tools have been proposed for this analysis: (i) from a numerical point of view, two examples considering the dynamic rupture of a bar (tensile test and spalling test) and (ii) from an experimental point of view, a database obtained from three-point bending test on notched and unnotched geometrically similar beams made from the same concrete formulation. We found that only a combination of this formulations may account for the different mechanisms involved in the process of cracking. It includes the transmission of the non-local information, the growing of voids and the description of boundary effects. We shown that its implementation in 2D or 3D remains complex and thus comparison with experimental results are impossible. In a second step, we decided to change the scale of analysis to precise the mechanisms which are taking place within the mesostructure of concrete using a mesomodel based on lattice elements. This analysis shown that since the mesomodel intrinsically took into account the interactions evolution within the structure, it is able to provide relevant results when classical macroscopic non-local models failed. It is able to represent both the maximum load (size effect) and the softening regime whatever the beam size or the pre-notch geometry. In addition, we proposed a new non-local framework where the interactions were upscale from the mesoscale to the macroscale through a new weight function. This function is estimated by describing the material as a set of inclusions that interact upon loading. These inclusions are successively elastically dilated to characterize the transfer of information within the material and rebuild the non-local weight function. This new model is able to describe the continuous / discrete transition, the shielding effect and the discontinuity of displacement. The model has been implemented in 2D in a finite element code and first results shown its capabilities to reproduce experimental results in term of maximum loads. In a third step, the richness of the mesoscopic approach has been used to describe precisely the local process of failure in term of fracture process zone evolution.

Les verres métalliques massifs sont connus pour leurs propriétés de résistance mécanique supérieures par rapport aux matériaux cristallins, mais aussi par une fragilité macroscopique. Cependant, des effets d’échelle sur le comportement mécanique ont été parfois reportés de manière inattendue lors de la réduction des tailles des échantillons. Afin d’étudier de tels effets, on s’est intéressé aux propriétés mécaniques de films minces en verre métallique de composition Zr65Ni35 et d’épaisseurs entre 200 et 900 nm ; les films étant obtenus par pulvérisation cathodique. Le comportement mécanique de ces films a été étudié à la fois sur substrat Si et sur des films libres. On montre que les films avec composition Zr65Ni35 ont la même structure atomique comme indiqué par l'absence de décalage des pics de diffraction et par des valeurs constantes de la densité, des propriétés élastiques, et du volume d'activation. Cependant, les mécanismes de fissuration varient avec l’épaisseur du film sur substrat, mais que cette variation résulte essentiellement d’un effet de confinement de l’épaisseur sur le développement de la zone plastique. Les propriétés mécaniques des films libres ont été étudiées en utilisant notamment une technique originale de micro-traction actionnée par contrainte interne. Dans ces conditions, des déformations plastiques importantes (jusqu’à 10%) combinées à des niveaux de contraintes élevés (jusqu’à 3500 MPa) ont pu être obtenues et on a montré qu’un paramètre important dans le contrôle des propriétés était l’aire de la section du film pouvant influencer la capacité d’obtention d’une percolation des défauts mis en jeu lors de la déformation plastique. Cela a été confirmé par des valeurs constantes du volume d’activation, estimé en étudiant les phénomènes de relaxation de la contrainte. L'effet de la composition du film sur les propriétés mécaniques a également été analysé et, dans ce cas, les variations de comportement mécanique ont été reliées à des modifications de la structure atomique du verre métallique. / Bulk metallic glasses are known for their superior strength performances with respect to crystalline counterparts, but also for a macroscopically brittle behaviour. Nevertheless, mechanical size effects have surprisingly been reported when reducing the specimen dimensions. In order to study such effects, the mechanical properties of thin Zr65Ni35 metallic glass films – deposited by DC magnetron sputtering – have been investigated for thickness ranging from 200 up to 900 nm. The mechanical behavior was studied for films deposited on Si substrate and for freestanding films as well. Zr65Ni35 films exhibit the same atomic structure as indicated by the absence of shift of diffraction peaks and by the constant values of the mass density, elastic properties, and activation volume. However, the cracking mechanisms of the film on the substrate are thickness dependent, resulting from a thickness confinement effect on the development of the plastic zone. The mechanical properties of freestanding films were investigated using an original technique of micro-tension controlled by internal stresses. Homogeneous plastic strains (up to 10 %) combined with very high stresses (up to 3500 MPa) were attained. The specimen cross-sectional area was the key parameter affecting the probability to get percolation of defects involved in the plastic deformation as confirmed by the constant value of the activation volume estimated analyzing stress relaxation phenomena. The effect of the composition on the mechanical properties has been investigated as well and, in this case, the changes in mechanical behavior were preferentially attributed to modifications of the metallic glass atomic structure.

Low-dimensional magnetic systems are of interest due to several new effects and modifications that occur at sizes below the average domain grain boundary within the bulk material. Molecule-like magnetite (Fe3O4) nanoparticles, with sizes ranging from one to two nm were synthesized and characterized in order to investigate new properties arising from quantum size effects. These small systems will provide opportunities to investigate magnetism of zero-dimension systems. A zero-dimensional object is usually called a quantum dot or artificial atom because its electronic states are few and sharply separated in energy, resembling those within an atom. Since the surface to volume ratio is the highest for zero-dimensional systems, most of the changes to magnetic behavior will be observed in ultra-fine magnetic particles. Chemically functional magnetic nanoparticles, comprised of a Fe3O4 magnetite core encased in a thin aliphatic carboxylate, have been prepared by sequential high temperature decomposition of organometallic compounds in a coordinating solvent. In this work, aliphatic carboxylic acid chain length, reaction temperature and duration were varied to produce small core diameters. In order to correlate size effects with changes in particle formation, it is important to have a through understanding of the structural components. This includes studies of the core size, surface effects, decomposition, electronic properties and magnetic behavior. Quantum size effects were observed in the (Fe3O4)X(carboxylate)Y monolayer protected clusters (MPCs) when the average core diameter was ≤ 2.0 nm, evidenced by a blue shifted absorbance band maxima, suggesting the onset of quantum confinement. These (Fe3O4)X(carboxylate)Y MPCs also posses a complex interplay between surface and finite size effects, which govern the magnetic properties of these zero-dimensional systems. These MPCs are all superparamagnetic above their blocking temperatures with total magnetic anisotropy values greater than the bulk value due to an increase in surface and magnetocrystalline anisotropy. A non-linear decrease in saturation magnetization (MS) [Bohr Magneton] per cluster) as a function of the reciprocal of core radius have been attributed to surface effects such as a magnetically inactive layer or an increase in spin disorder as core diameter decreases. The reduced core dimensions of these MPCs make them ideal candidates for further investigation of quantum magnetic systems.

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Orientador: Italo Odone Mazali / Dissertação ( mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T04:18:17Z (GMT). No. of bitstreams: 1 Correa_DeleonNascimento_M.pdf: 2416044 bytes, checksum: 1853938c864df0a03a91908eb0f6353b (MD5) Previous issue date: 2009 / Resumo: Este trabalho reporta o estudo e o desenvolvimento da metodologia de síntese e de caracterização de nanopartículas isoladas e nanopartículas heteroestruturadas caroço@casca (NCC) envolvendo os óxidos semicondutores (TiO2, CeO2 e SnO2) impregnados em suporte poroso funcional (vidro poroso Vycor ¿ PVG). Empregou-se a metodologia de Ciclos de Impregnação-Decomposição (CID) alternados de compostos metalorgânicos, a partir da técnica de decomposição de precursores metalogânicos (MOD). A metodologia CID prosseguiu com a impregnação dos compostos metalorgânicos di-(propóxido)-di-(2-etilhexanoato) de titânio (IV) [Ti(OnPr)2(hex)2], 2-etilhexanoato de cério (III) [Ce(hex)2] e 2-etilhexanoato de estanho (II) [Sn(hex)2] no PVG em condições controladas. Os estudos das curvas de ganho de massa cumulativo em função de cada CID evidenciaram que para 3 CID os sistemas responderam com um ganho cumulativo de massa de 17,5% (PVG/3SnO2), 4,3% (PVG/3CeO2) e 2,5% (PVG/3TiO2) com a concentração inicial dos precursores de partida de 0,75 molL. O efeito de confinamento quântico foi descrito pelo Modelo da Aproximação da Massa Efetiva (MAME), observado experimentalmente na borda de absorção dos espectros de refletância difusa, DRS, e pelo Modelo de Confinamento de Fônons (MCF), no deslocamento dos modos vibracionais nos espectros Raman. O tamanho de cristalito para a amostra PVG/3TiO2 por TEM e Raman/MCF foi de 4,7 e 4,9 nm, respectivamente, mostrando boa aproximação. O sistema PVG/xTiO2 apresentou variações sistemáticas (blue shift) da energia da banda proibida (Eg*) do TiO2 (óxido de titânio anatásio) nos espectros DRS, evidenciando que Eg* é uma função direta do tamanho de partícula (Eg* = f(2r)) e da metodologia CID. O raio de Bohr, aB, descrito na literatura para a aplicabilidade do MAME ao sistema PVG/xTiO2 não reproduziu a função Eg* = f(2r) de acordo com os resultados TEM. A Partir dos espectros Raman e DRS e os dados teóricos MCF, realizou-se a determinação empírica do aB de 6,4 nm para os cristalitos de TiO2 impregnados no PVG, constituindo nova metodologia para determinação do tamanho de cristalito das amostras PVG/xTiO2. A aplicabilidade do MAME ao sistema PVG/xCeO2 não ofereceu sucesso, pois os cristalitos de CeO2 sofrem acoplamento elétrons-fônons sofrendo um red shift da borda de absorção do espectro DRS. A média de tamanho de cristalito obtida por TEM e estimado por espectroscopia Raman e associado ao MCF está em torno de 5,0 nm para amostras de PVG/5CeO2 0,75-1,0 molL do precursor Ce(hex)3. Os resultados obtidos por DRS para o sistema PVG/xSnO2 demonstraram que o efeito de confinamento quântico ocorre apenas para precursores de concentração abaixo de 0,25 molL. A média de tamanho encontrado para as imagens TEM das amostras PVG/1SnO2 0,10 molL e PVG/1SnO2 0,25 molL é de 3,5 e 5,8 nm e a associação DRS/MAME 3,8 e 4,6 nm, respectivamente. Sobre a obtenção das NCC, as amostras PVG/xTiO2@yCeO2 e PVG/xCeO2@TiO2 (x = 3, 5 e 7 e y = 3, 5 e 7) demonstraram mudança da inclinação da reta de ganho de massa cumulativo após a alternância dos precursores Ti(OnPr)2(hex)2 e Ce(hex)3 A partir das estimativas das Eg* para as amostras PVG/3TiO2@xCeO2 (x = 1, 2 e 3) comparadas com as amostras PVG@xCeO2, relacionou-se tais energias com a formação das NCC. A NCC PVG/3TiO2@3CeO2, 0,75 molL apresentou tamanho de cristalito de 6,9 nm, constituindo um caroço de TiO2 de até 4,7 nm (Raman/MCF, TEM e DRS/MAME) e uma casca de CeO2 inseridos pelos 3 CID do precursor de cério (PVG/3CeO2 constitui 4,1 nm pelo MCF) nucleando sobre o caroço PVG/3TiO2 corroborando com os dados descritos pelo ganho de massa cumulativo com a mudança da inclinação da reta. Observou-se que o sistema PVG/5CeO2@3TiO2 constituiu uma borda de absorção em torno 3,23 eV, sendo uma evidência qualitativa do recobrimento e a formação de NCC PVG/5CeO2@3TiO2, pois, se as nanopartículas PVG/5CeO2 não estivessem sido encapadas ver-se-ia uma borda de absorção correspondendo a PVG/5CeO2 em torno de 3,17 eV. O sistema PVG/xCeO2@yTiO2 (x = 3, 5 e 7 e y = 3, 5 e 7) foi estudado por espectroscopia Raman. Os resultados mostraram deslocamentos sistemáticos do modo vibracional Eg do TiO2 dependentes da espessura da casca e a estabilização da banda T2g do CeO2 no caroço. Espectros Raman do sistema PVG/xTiO2@yCeO2 (x = 3, 5 e 7 e y = 3, 5 e 7) demonstraram a formação de bandas muitos deslocadas, quando o CeO2 se encontra na casca / Abstract: This work reports the development of a synthesis and characterization methodology for isolated nanoparticles and core-shell heterostructures nanoparticles (CSN), involving the semiconducting oxides (TiO2, CeO2 and SnO2) impregnated into a functional porous support (porous Vycor glass - PVG). The alternated impregnation¿decomposition cycle (ICD) methodology was applied from metallo-organic precursors by the used metalloorganic decomposition (MOD) technique. The ICD methodology used Ti (IV) di-(n-propoxy)-di-(2-ethylhexanoate) [Ti(OnPr)2(hex)2],.Ce(III) 2- ethylhexanoate [Ce(hex)3] and Sn(II) 2-ethylhexanoate [Sn(hex)2] impregnation into PVG in controlled conditions. The studies of the cumulative mass gain curves as functions of each ICD evidenced that, for 3 ICD, the systems had cumulative mass gains of 17.5% (PVG/3SnO2), 4.3% (PVG/3CeO2) e 2.5% (PVG/3TiO2) with initial precursor concentrations of 0.75 mol L. The quantum size effect was described by the effective mass approximation model (EMAM), observed experimentally in the absorption edge of the diffuse reflectance spectra (DRS), and by the phonon confinement model (PCM), in the vibrational modes of the Raman shift. The PVG/3TiO2 sample crystallite size was determined by TEM and Raman/PCM to be 4.7 and 4.9 nm, respectively, showing a good approach. The PVG/xTiO2 system showed systematic blue shift variations in the band gap energies (Eg*) in DRS spectra, showing that Eg* is a particle size function (Eg* = f(2r)) and ICD methodology. The Bohr radius (aB), described in literature for the EMAM application, did not describe the Eg* = f(2r) function for the PVG/xTiO2 system, in concordance with TEM data. From Raman and DRS spectra associated with PCM data, followed by the empirical aB determination for TiO2 (anatase titanium oxide) crystallites impregnated in PVG found to be 6.4 nm, constituting important methodology for crystallite size determination in PVG/xTiO2 samples. The EMAM on the PVG/xCeO2 system was not successful, the CeO2 crystallites suffers a red-shift in the DRS absorption edge as a result of effects arising from electron¿phonon coupling. The average crystallite size from TEM data and estimated by Raman spectroscopy associated with PCM are found to be around 5.0 nm for PVG/5CeO2 (0.75-1.0 mol L precursor concentration) samples. The DRS results for the PVG/xSnO2 system demonstrates that the quantum size effects occurs only below 0.25 molL precursors concentrations. The PVG/1SnO2 0.10 mol L and PVG/1SnO2 0.25 mol L average size found from TEM images were 3.5 and 5.8 nm, respectively, and the DRS/EMAM showed 3.8 and 4.6 nm, respectively. The PVG/xTiO2@yCeO2 and PVG/xCeO2@TiO2 (x = 3, 5 e 7 and y = 3, 5 e 7) CSN samples demonstrated an inclination change of the cumulative mass gain line with the Ti(OnPr)2(hex)2 and Ce(hex)3 precursor alternation. From the estimated Eg* for the PVG/3TiO2@xCeO2 (x = 1, 2 e 3) samples compared with PVG@xCeO2 samples, it was possible to relate the energies with the CSN formation. The PVG/3TiO2@3CeO2, 0.75 mol L CSN present a particles size of 6.9 nm, constituting a TiO2 core around 4.7 nm (Raman/PCM, TEM and DRS/EMAM) and a CeO2 shell insert from 3 ICD from cerium precursor (PVG/3CeO2 presents 4.12 nm by PCM). The data suggest that the CeO2 shell nucleated around the PVG/3TiO2 core, corroborating with the inclination change of the cumulative mass gain line. It was observed that the PVG/5CeO2@3TiO2 system presents an absorption edge around 3.23 eV. This shows qualitative evidence about the PVG/5CeO2@3TiO2 CSN formation. Therefore, if the PVG/5CeO2 core is not covered, it will show an absorption edge around 3.17 eV. The PVG/xCeO2@yTiO2 (x = 3, 5 e 7 e y = 3, 5 e 7) system was studied by Raman spectroscopy. The results showed systematic shifts in TiO2 A Eg band dependent for the TiO2 shell thickness and the CeO2 T2g band stabilization related to the CeO2 covered in the core. Raman spectra on the PVG/xTiO2@yCeO2 (x = 3, 5 e 7 e y = 3, 5 e 7) system showed a big band shift when CeO2 was in the shell / Mestrado / Quimica Inorganica / Mestre em Química

Through enrichment of the elastic potential by the second-order gradient of deformation, gradient elasticity formulations are capable of taking nonlocal effects into account. Moreover, geometry-induced singularities, which may appear when using classical elasticity formulations, disappear due to the higher regularity of the solution. In this contribution, a mixed finite element discretization for finite strain gradient elasticity is investigated, in which instead of the displacements, the first-order gradient of the displacements is the solution variable. Thus, the C1 continuity condition of displacement-based finite elements for gradient elasticity is relaxed to C0. Contrary to existing mixed approaches, the proposed approach incorporates a rot-free constraint, through which the displacements are decoupled from the problem. This has the advantage of a reduction of the number of solution variables. Furthermore, the fulfillment of mathematical stability conditions is shown for the corresponding small strain setting. Numerical examples verify convergence in two and three dimensions and reveal a reduced computing cost compared to competitive formulations. Additionally, the gradient elasticity features of avoiding singularities and modeling size effects are demonstrated.