Nanoparticle Gradient Materials by Centrifugation

Spinnrock, Andreas; Schupp, David; Cölfen, Helmut

doi:10.1002/smll.201803518

Cited by 11 publications

(13 citation statements)

References 30 publications

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“…Gravitational force can be increased either by increasing the rotational speed or by using particles with a higher sedimentation coefficient. Previously, the controlled fabrication of nanoparticle gradients by sedimentation was described [24]. Superparamagnetic iron oxide nanoparticles (SPIONs) are interesting for gradient materials with specific magnetic properties for example in magnetic switches.…”

Section: Resultsmentioning

confidence: 99%

“…For example, functionally graded nanobeams for small device applications in MEMS and NEMS have been produced and their thermoelastic behavior has been modeled by stress-driven nonlocal integral modelling [15,16]. Preparation methods for polymeric gradient materials are photopolymerization [17], selective laser sintering [18,19], corona discharge [20], layer-by-layer assembly [21], 3D printing [22], centrifugal casting [23], and sedimentation in analytical ultracentrifuges [24]. Disadvantages of the established techniques are either that the gradients cannot be simulated in advance and detected in real-time during fabrication or that their upscale ability is limited due to tedious and complicated fabrication setups.…”

Section: Introductionmentioning

confidence: 99%

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Controlled Preparation of Nanoparticle Gradient Materials by Diffusion

et al. 2019

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Nanoparticle gradient materials combine a concentration gradient of nanoparticles with a macroscopic matrix. This way, specific properties of nanoscale matter can be transferred to bulk materials. These materials have great potential for applications in optics, electronics, and sensors. However, it is challenging to monitor the formation of such gradient materials and prepare them in a controlled manner. In this study, we present a novel universal approach for the preparation of this material class using diffusion in an analytical ultracentrifuge. The nanoparticles diffuse into a molten thermoreversible polymer gel and the process is observed in real-time by measuring the particle concentrations along the length of the material to establish a systematic understanding of the gradient generation process. We extract the apparent diffusion coefficients using Fick’s second law of diffusion and simulate the diffusion behavior of the particles. When the desired concentration gradient is achieved the polymer solution is cooled down to fix the concentration gradient in the formed gel phase and obtain a nanoparticle gradient material with the desired property gradient. Gradients of semiconductor nanoparticles with different sizes, fluorescent silica particles, and spherical superparamagnetic iron oxide nanoparticles are presented. This method can be used to produce tailored nanoparticle gradient materials with a broad range of physical properties in a simple and predictable way.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Controlled Preparation of Nanoparticle Gradient Materials by Diffusion

et al. 2019

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“…This approach was used to produce nanoparticle gradient materials in ultracentrifugal fields . With this method, gradient materials with the unique size‐dependent properties of nanoscale matter can be produced in a controlled way.…”

Section: Production Of Gradient Materialsmentioning

confidence: 99%

“…This approachw as used to produce nanoparticle gradient materials in ultracentrifugal fields. [36] With this method, gradient materials with the unique size-dependent properties of nanoscale matter can be produced in ac ontrolled way.I n Figure4,m aterials with defined gradients of spherical gold nanoparticles (a + c) and superparamagnetic iron oxide nanoparticles (d) in ag elatinem atrix are shown. The gradients can be simulated in good agreement with the experimental data based on the sedimentation and diffusion coefficients from previouse xperiments ( Figure 4b).…”

Section: Production Of Gradient Materialsmentioning

confidence: 99%

Putting a New Spin on It: Gradient Centrifugation for Analytical and Preparative Applications

Spinnrock

Cölfen

2019

Chemistry A European J

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Gradient centrifugation is an important technique in chemistry, biology, materials science and engineering. It has big potential beyond the well‐known centrifugation for separation of molecules and particles. Various possibilities for special analysis and separation of particles, but also preparative applications like the production of gradient materials and controlled polymerizations exist. In all examples, a gradient of physical and/or chemical properties is generated by centrifugation and used for the further application. In this Concept article, selected examples of gradient centrifugation are presented, to show important developments in the field and discuss their applications, potential, and limitations. It concludes by analysing future trends of gradient centrifugation that are relevant for academic and industrial usage.

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“…Recently, beside translational self‐diffusion and buoyancy‐driven gradient creation, analytical ultracentrifugation was presented as one of the most versatile approaches to design and create macroscale concentration gradient profiles in liquid matrices that were solidified subsequently by gelation . Depending on the relative rate of sedimentation and diffusion, different concentration gradients are generated: for example, sigmoidal profiles were obtained at high centrifugal forces where sedimentation governed the concentration profile, and exponential concentration gradients were generated when sedimentation and diffusion were in equilibrium at lower centrifugal forces …”

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confidence: 99%

Versatile Macroscale Concentration Gradients of Nanoparticles in Soft Nanocomposites

Taladriz‐Blanco

Rothen‐Rutishauser

Petri‐Fink

et al. 2020

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exponential concentration gradients were generated when sedimentation and diffusion were in equilibrium at lower centrifugal forces. [13] This is a big step in the design of soft nanocomposites for it enables that such monotonic gradient profiles can be modeled quantitatively and designed precisely before processing-owing to the availability of a mathematical framework that is able to model faithfully the related phenomena. Following this concept, i.e., that 1) the creation and fixation of macroscale gradient profiles may be decoupled and 2) may be designed and tailored accurately by mathematical means, we present an approach dedicated to creating continuous and smooth long-range longitudinal concentration gradients of NPs in macroscopic 1D soft materials, such as fibers. The available design-space is rich, and includes either symmetric or asymmetric, monotonic or nonmonotonic, linear, or nonlinear profiles, with the possibility of, e.g., periodicity, having multiple local minima and maxima with either complementary or orthogonal functionalities.The physical phenomenon our approach is based on is called Taylor dispersion, which can be accurately described by the asymptotic solution of the convective-diffusion equation [14][15][16] corresponding to the geometry of the flow channels. [17] Taylor dispersion refers to the enhanced dispersion of particles in a steady Poiseuille flow, where the linear shear stress creates a quadratic flow-velocity profile, and induces a spontaneous net transport of particles via translational self-diffusion. The rate and overall extent of spread is a function of the unidirectional velocity profile and translational self-diffusion coefficient of the particles. Taylor dispersion is characteristic to laminar flows and scalable on a wide range of dimensions. In the case of NPs, the phenomenon can be easily realized in a microcapillary laminar flow, which also provides an outstanding experimental technique to characterize the hydrodynamic radius of organic and inorganic NPs. [18][19][20][21][22][23][24][25][26] Although from the theoretical point of view, its dimensionality is scalable, Taylor dispersion is essentially a microfluidic technique, and microfluidics offer an excellent platform to create a gradient, e.g., via electrospinning. [27] Indeed, Taylor dispersion was connected to the creation of simple concentration gradients more than ten years ago, [28][29][30] yet it was shown only recently that Taylor dispersion is de facto a casual linear timeinvariant system. [31] We show here that this mathematical property has important implications for the applicability of Taylor dispersion when creating macroscale gradient profiles of NPs, because the gradient profile of NPs can be designed accurately www.advancedsciencenews.com

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Nanoparticle Gradient Materials by Centrifugation

Cited by 11 publications

References 30 publications

Controlled Preparation of Nanoparticle Gradient Materials by Diffusion

Controlled Preparation of Nanoparticle Gradient Materials by Diffusion

Putting a New Spin on It: Gradient Centrifugation for Analytical and Preparative Applications

Versatile Macroscale Concentration Gradients of Nanoparticles in Soft Nanocomposites

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