| 1. |
- Selegård, Linnéa, et al.
(författare)
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Step by step rare-earth catalyzed SiOx annealing and simultaneous formation of Europium- silicide by low coverage of Eu doped Gd2O3 nanoparticles
- 2021
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 704
-
Tidskriftsartikel (refereegranskat)abstract
- We report the formation of silicide by annealing of a SiOx surface, with low coverage of Eu doped Gd2O3 nanoparticles. The annealing temperature required for removal of native oxide from the Si substrate decreases with close to 200 °C in presence of the nanoparticles. X-ray photoemission electron microscopy, low-energy electron microscopy and mirror electron microscopy are used to monitor the silicide formation and SiOx removal. Fragmentation of the nanoparticles is observed, and the SiOx layer is gradually removed. Eu migrates to clean Si areas during the annealing process, while Gd is found in areas where oxide is still present. This annealing process is clearly facilitated in the presence of rare-earth based nanoparticles, where nanoparticles are suggested to function as reaction sites to catalyze the oxygen removal and simultaneously form Eu based silicide. Reduction of the annealing temperature of SiOx substrates is also observed in presence of pure Eu3+ and Gd3+ ions. Simultaneous oxygen removal and EuSi formation enable this new rare-earth catalyzed annealing and silicide formation to find applications both within optoelectronics and processing microelectronic industry.
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| 2. |
- Ahrén, Maria, et al.
(författare)
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A simple polyol-free synthesis route to Gd 2O 3 nanoparticles for MRI applications : An experimental and theoretical study
- 2012
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Ingår i: Journal of nanoparticle research. - : Springer. - 1388-0764 .- 1572-896X. ; 14:8
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Tidskriftsartikel (refereegranskat)abstract
- Chelated gadolinium ions, e.g., Gd-DTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd 2O 3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r 1 and r 2 values almost as high as those for free Gd 3+ ions in water. The Gd 2O 3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI.
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| 3. |
- Ahrén, Maria, et al.
(författare)
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Synthesis and Characterization of PEGylated Gd2O3 Nanoparticles for MRI Contrast Enhancement
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:8, s. 5753-5762
-
Tidskriftsartikel (refereegranskat)abstract
- Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study. We report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in NI RI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3-5 nm) gadolinium oxide (DEG-Gd2O3) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd2O3 nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd2O3 nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r(1) and r(2) values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd2O3. Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is. an extremely high MR signal at the cellular and molecular level.
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| 4. |
- Björk, Linnea, et al.
(författare)
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Amino-Acid Side-Chain Nanoarchitectonics for Tuning the Chiroptical Properties and Supramolecular Structure of Pentameric Oligothiophenes
- 2024
-
Ingår i: ChemPhotoChem. - : WILEY-V C H VERLAG GMBH. - 2367-0932.
-
Tidskriftsartikel (refereegranskat)abstract
- Oligothiophenes with specific photophysical properties and molecular organization are of great interest, since this class of materials are used in organic electronics and bioelectronics, as well as biosensing. Herein, 8 different pentameric oligothiophenes, denoted proteophenes, with different amino acid substitution patterns at distinct positions along the thiophene backbone were investigated. Spectroscopic and microscopic studies of the ligands revealed the formation of optically active self-assembled materials under acidic or basic conditions. The distinct photophysical characteristics, including induced circular dichroism, as well as the supramolecular structures of the assemblies deduced from light scattering and transmission electron microscopy, were highly influenced by the positioning of distinct amino acid moieties along the thiophene backbone. Proteophenes functionalized with only glutamate residues or these functionalities in combination with hydrophobic valine moieties formed fibrillar structures with excellent chiroptical properties under acidic conditions. In addition, the amino acid functionality at the beta-position of distinct thiophene moieties influenced the induced circular dichroism pattern observed from the proteophenes. Overall, the obtained results demonstrate how changes in the position of various amino acid functionalities, as well as the chemical nature of the amino acid side chain functionality greatly affect the optical properties as well as the architecture of the self-assembled materials. Self-assembled Proteophenes. Oligothiophenes with distinct amino acid side-chain functionalities along the conjugated backbone displayed distinct chiroptical and structural properties in acidic or alkaline solutions. The distinct photophysical characteristics, as well as the supramolecular structures of the assemblies were highly influenced by the chemical nature of the amino acid, as well as the positioning of distinct amino acid moieties along the thiophene backbone.image
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| 5. |
- Chen, Zhiwen, et al.
(författare)
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Integrated Design of Hierarchical CoSnO3@NC@MnO@NC Nanobox as Anode Material for Enhanced Lithium Storage Performance
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 12:17, s. 19768-19777
-
Tidskriftsartikel (refereegranskat)abstract
- Transition-metal oxides (TMOs) are potential candidates for anode materials of lithium-ion batteries (LIBs) due to their high theoretical capacity (similar to 1000 mA h/g) and enhanced safety from suppressing the formation of lithium dendrites. However, the poor electron conductivity and the large volume expansion during lithiation/delithiation processes are still the main hurdles for the practical usage of TMOs as anode materials. In this work, the CoSnO3@NC@ MnO@NC hierarchical nanobox (CNMN) is then proposed and fabricated to solve those issues. The as-prepared nanobox contains hollow cubic CoSnO3 as a core and dual N-doped carbon-"sandwiched" MnO particles as a shell. As anode materials of LIBs, the hollow and carbon interlayer structures effectively accommodate the volume expansion while dual active TMOs of CoSnO3 and Notably, the dual-layer structure of N-doped carbons plays a critical functional role MnO efficiently increase the specific capacity. in the incorporated composites, where the inner layer serves as a reaction substrate and a spatial barrier and the outer layer offers electron conductivity, enabling more effective involvement of active anode materials in lithium storage, as well as maintaining their high activity during lithium cycling. Subsequently, the as-prepared CNMN exhibits a high specific capacity of 1195 mA h/g after the 200th cycle at 0.1C and an excellent stable reversible capacity of about 876 mA h/g after the 300th cycle at 0.5C with only 0.07 mA h/g fade per cycle after 300 cycles. Even after a 250 times fast charging/discharging cycle both at SC, it still retains a reversible capacity of 422.6 mA h/g. We ascribe the enhanced lithium storage performances to the novel hierarchical architectures achieved from the rational design.
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| 6. |
- de Oliveira, Sergio, et al.
(författare)
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Failure prediction in fiber-reinforced composites based on continuum damage mechanics
- 2019
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Ingår i: Proceedings - 7th ECCOMAS THEMATIC CONFERENCE ON THE MECHANICAL RESPONSE OF COMPOSITES.
-
Konferensbidrag (refereegranskat)abstract
- The paper presents an approach to intra/inter-laminar failure modeling of fiber reinforced composites using continuum damage. The intra-laminar damage model is based on elastic damage, focusing propagation of damage for compression dominated loadings. A special feature is the study on ply elasticity, induced by graphene enhancement of the polymer matrix linked to the damage evolution. The results shows that the considered intra-laminar composite response is only slight affected by the graphene. The open hole compression test involves mechanisms of both intra- and interlaminar failure. The results show a fairly good correlation between the experiments and the proposed model.
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| 7. |
- Enander, Karin, 1972-, et al.
(författare)
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A peptide-based, ratiometric biosensor construct for direct fluorescence detection of a protein analyte
- 2008
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Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 19:9, s. 1864-1870
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Tidskriftsartikel (refereegranskat)abstract
- We present the design, synthesis, and functional evaluation of peptide-based fluorescent constructs for wavelength-ratiometric biosensing of a protein analyte. The concept was shown using the high-affinity model interaction between the 18 amino acid peptide pTMVP and a recombinant antibody fragment, Fab57P. pTMVP was functionalized in two different positions with 6-bromomethyl-2-(2-furanyl)-3-hydroxychromone, an environmentally sensitive fluorophore with a two-band emission. The equilibrium dissociation constant of the interaction between pTMVP and Fab57P was largely preserved upon labeling. The biosensor ability of the labeled peptide constructs was evaluated in terms of the relative intensity change of the emission bands from the normal (N*) and tautomer (T*) excited-state species of the fluorophore (IN*/IT*) upon binding of Fab57P. When the peptide was labeled in the C terminus, the IN*/I T* ratio changed by 40% upon analyte binding, while labeling close to the residues most important for binding resulted in a construct that completely lacked ratiometric biosensor ability. Integrated biosensor elements for reagentless detection, where peptides and ratiometric fluorophores are combined to ensure robustness in both recognition and signaling, are expected to become an important contribution to the design of future protein quantification assays in immobilized formats. © 2008 American Chemical Society.
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| 8. |
- Hu, Zhangjun, et al.
(författare)
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Highly Water-Dispersible Surface-Modified Gd2O3 Nanoparticles for Potential Dual-Modal Bioimaging
- 2013
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Ingår i: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 19:38, s. 12658-12667
-
Tidskriftsartikel (refereegranskat)abstract
- Water-dispersible and luminescent gadolinium oxide (GO) nanoparticles (NPs) were designed and synthesized for potential dual-modal biological imaging. They were obtained by capping gadolinium oxide nanoparticles with a fluorescent glycol-based conjugated carboxylate (HL). The obtained nanoparticles (GO-L) show long-term colloidal stability and intense blue fluorescence. In addition, L can sensitize the luminescence of europium(III) through the so-called antenna effect. Thus, to extend the spectral ranges of emission, europium was introduced into L-modified gadolinium oxide nanoparticles. The obtained Eu-III-doped particles (Eu:GO-L) can provide visible red emission, which is more intensive than that without L capping. The average diameter of the monodisperse modified oxide cores is about 4nm. The average hydrodynamic diameter of the L-modified nanoparticles was estimated to be about 13nm. The nanoparticles show effective longitudinal water proton relaxivity. The relaxivity values obtained for GO-L and Eu:GO-L were r(1)=6.4 and 6.3s(-1)mM(-1) with r(2)/r(1) ratios close to unity at 1.4T. Longitudinal proton relaxivities of these nanoparticles are higher than those of positive contrast agents based on gadolinium complexes such as Gd-DOTA, which are commonly used for clinical magnetic resonance imaging. Moreover, these particles are suitable for cellular imaging and show good biocompatibility.
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| 9. |
- Huang, Shoushuang, et al.
(författare)
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Fabrication of multi-layer CoSnO3@carbon-caged NiCo2O4 nanobox for enhanced lithium storage performance
- 2021
-
Ingår i: Chemical Engineering Journal. - : Elsevier Science SA. - 1385-8947 .- 1873-3212. ; 410
-
Tidskriftsartikel (refereegranskat)abstract
- Mixed transition metal oxides (MTMOs) are deemed as promising anode materials for lithium-ion batteries (LIBs) because of the high theoretical capacity and low cost. However, the low electrical conductivity, agglomeration effects, and huge volume variation during discharging/charging still seriously restrict the actual applications of MTMOs as anode materials. Herein, a novel core-shell structure of CoSnO3@carbon-caged NiCo2O4 nanobox (CNC) is rationally designed. It starts from the preparation of CoSnO3@ZIF-67 core-shell nanocubes, followed by chemical etching/anion exchange, dopamine coating and carbonization at high temperature in sequence. It is shown that the CNC achieves high activities from the applied MTMOs components, excellent relief of volume variation from the unique double hollow structure, improved conductivity and inhabited aggregations from the uniform-coated outmost carbon shell, and effective ion/electron transfer rates from the synergetic effects. As a result, the CNC exhibits a discharge capacity of 1548 mA h g(-1) at the first cycle and a retention capacity of 992 mA h g(-1) after 100 cycles at 0.1 A g(-1). In addition, it exhibits a high reversible capacity of about 670 mA h g(-1) after 500 cycles at a current density of 1 A g(-1). The improved Li+ storage performances of CNC demonstrates that such rational design of double hollow structure could be a novel strategy to apply MTMOs as anode materials of LIBs.
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| 10. |
- Kanungo, J, et al.
(författare)
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XPS study of palladium sensitized nano porous silicon thin film
- 2010
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Ingår i: BULLETIN OF MATERIALS SCIENCE. - : Indian Academy of Sciences; 1999 / Indian Academy of Sciences, Springer. - 0250-4707 .- 0973-7669. ; 33:6, s. 647-651
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Tidskriftsartikel (refereegranskat)abstract
- Nano porous silicon (PS) was formed on p-type monocrystalline silicon of 2-5 Omega cm resistivity and (100) orientation by electrochemical anodization method using HF and ethanol as the electrolytes. High density of surface states, arising due to its nano structure, is responsible for the uncontrolled oxidation in air and for the deterioration of the PS surface with time. To stabilize the material PS surface was modified by a simple and low cost chemical method using PdCl2 solution at room temperature. X-ray photoelectron spectroscopy (XPS) was performed to reveal the chemical composition and the relative concentration of palladium on the nanoporous silicon thin films. An increase of SiO2 formation was observed after PdCl2 treatment and presence of palladium was also detected on the modified surface. I-V characteristics of Al/PS junction were studied using two lateral Al contacts and a linear relationship was obtained for Pd modified PS surface. Stability of the contact was studied for a time period of around 30 days and no significant ageing effect could be observed.
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| 11. |
- Larsson, Ragnar, 1960, et al.
(författare)
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Carbon-fibre composites with graphene filler for enhanced properties
- 2019
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Ingår i: Proceedings of XVIII Brazil MRS Meeting. - 9788563273406 ; , s. 558-
-
Konferensbidrag (refereegranskat)abstract
- Carbon fibre reinforced polymer (CFRP) is often used in applications where lightweight design is essential. The material however suffers from inherent drawbacks such as high brittleness, low electrical conductivity. This Swedish-Brazilian collaboration combines experimental studies with modelling and simulation to investigate the improvement of the CFRP material properties after addition of graphene. Graphene exhibits excellent electrical and thermal conductivity, barrier properties, unique strength which makes it an optimal additive. In this industrial-driven project, the electrical percolation threshold is studied and the strength of the reinforced polymer around the threshold value is investigated. The improvement is dependent on dispersion techniques and the grade of exfoliation of graphene. This has been shown both experimentally and from the modeling.
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| 12. |
- Larsson, Ragnar, 1960, et al.
(författare)
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Elastic surrogate modeling of graphene nanoplatelet-reinforced epoxy using computational homogenization
- 2024
-
Ingår i: Composites Science and Technology. - 0266-3538. ; 256
-
Tidskriftsartikel (refereegranskat)abstract
- 2D nanoparticles, such as graphene or graphite nanoplatelets, are used as additives in polymer matrices to improve their stiffness and electrical conductivity. In this paper, a finite element-based model for homogenized macrolevel stiffness is developed to understand the increase in stiffness of the epoxy matrix induced by graphene nanoplatelets. The model uses image segmentation of regular SEM micrographs to account for the morphology of the graphene platelet network. Here, it is essential to include a fluctuation field in computational homogenization to describe microstructural relaxation. Platelets of the microstructure are modeled as embedded membranes, assuming perfect bonding to the polymer. To estimate the stiffness of the membrane, we used molecular dynamics simulations from a related paper on layered graphene platelets. A novel feature is the identified anisotropic and isotropic elastic surrogate models obtained by least-squares fits of homogenized microstructural responses. Surrogate models serve as a basis for the evaluation of the stiffness of the nanocomposites, and these models are validated through the Halpin–Tsai and Mori–Tanaka models. According to the experimental investigation, the results show that the samples exhibit an increase in stiffness of up to 10 % to 30 % for GNP contents ranging from 1 to 5 wt. %, respectively, obtained from the morphological properties and the weight fraction of the carbon filler.
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| 13. |
- Lenz, Annika, et al.
(författare)
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ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:40, s. 17332-17341
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical synthesis and physical characterization of ZnO nanoparticles functionalized with four different organic acids, three aromatic (benzoic, nicotinic, and trans-cinnamic acid) and one nonaromatic (formic acid), are reported. The functionalized nanoparticles have been characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV−vis, and photoluminescence spectroscopy. The adsorption of the organic acids at ZnO nanoparticles was further analyzed and interpreted using quantum-chemical density-functional theory computations. Successful functionalization of the nanoparticles was confirmed experimentally by the measured splitting of the carboxylic group stretching vibrations as well as by the N(1s) and C(1s) peaks from XPS. From a comparison between computed and experimental IR spectra, a bridging mode adsorption geometry was inferred. PL spectra exhibited a remarkably stronger near band edge emission for nanoparticles functionalized with formic acid as compared to the larger aromatic acids. From the quantum-chemical computations, this was interpreted to be due to the absence of aromatic adsorbate or surface states in the band gap of ZnO, caused by the formation of a complete monolayer of HCOOH. In the UV−vis spectra, strong charge-transfer transitions were observed.
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| 14. |
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| 15. |
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| 16. |
- Poot, Thirza
(författare)
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Sustainable Surface Functionalization of Lightweight Materials : Cerium Oxide Nanoparticles Replacing Chromium in Anodic Coatings and Carbon Nanomaterials for Lightning Strike Protection
- 2022
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aviation accounts for 2-3% of the carbon dioxide emitted globally. One way to reduce emissions is to develop and introduce sustainable, functional, lightweight materials and coatings that increase the lifetime and fuel efficiency of aircraft. The main lightweight materials used in the aerospace industry today are aluminum alloys and carbon fiber reinforced plastic composites. In the work presented in this licentiate thesis, a new sustainable alternative for the replacement of toxic hexavalent chromium in a low energy and chemical consumption sealing procedure of anodized aluminum alloys is suggested (paper I and II). An alternative to the conventional metal mesh used as lightning strike protection for composite structures used today is also presented. The proposed solution adds considerably less weight and has a possibility to reduce the CO2 emission from aviation (paper III). Aluminum alloys as well as composites both exhibit high strength-to-weight ratios but come with individual drawbacks. Fiber reinforced plastics exhibit limited electrical conductivity, which is why additional protection is needed to avoid severe damage following a lightning strike. Aluminum alloys have instead the disadvantage of being susceptible to corrosion and surface protection is required to prolong the materials lifetime and to avoid devastating failures. Anodization, formation of a porous aluminum oxide coating, is the most common choice of surface treatment. This is often followed by closure of the pores through a sealing procedure. Both processes have up until recently been performed in large, energy consuming tanks with highly toxic solutions containing hexavalent chromium which must be replaced to reduce the environmental impact. In paper I, the environmentally friendly tartaric sulfuric acid has been used as anodization electrolyte and cerium oxide nanoparticles have been investigated as a promising alternative for sealing. Cerium-based and hydrothermal sealing (immersion in hot water), individually and combined, were investigated. The morphological and chemical composition were studied by means of scanning electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The investigation confirmed the growth of cerium oxide nanoparticles throughout the coating and closing of the pores by hydrothermal sealing. A corrosion immersion test revealed a superior corrosion resistance of surfaces treated with the two-step sealing process compared to plain anodized, cerium or hydrothermally sealed surfaces. In paper II, the potential use of an aerosol-based wet thin film coating technique called nFOG for cerium sealing as a low chemical and energy consumption alternative to traditional bath-type sealing was investigated. Characterizations of the morphology and composition reveal cerium oxide nanoparticles evenly distributed within the porous coating by the nFOG technique. The new application of the nFOG method was also shown to provide anti-corrosion properties comparable to bath-type sealing. This wet coating technique has the potential to replace chromium and reduce the environmental impact in the treatment process. Furthermore, the limited electrical conductivity of carbon fiber reinforced plastics can be circumvented by loading the polymer matrix of the composite structure (commonly epoxy) with highly conductive carbon nanomaterials. In paper III, graphene nanoplatelets and carbon nanotubes were loaded into the epoxy. Simulated lightning strike tests showed an improved damage tolerance for the loaded composites compared to composites prepared with plain epoxy. The results suggest that a combination of graphene nanoplatelets and carbon nanotubes increases the damage tolerance by carrying the resulting high electric current from a lightning strike. In conclusion, the application of cerium oxide nanoparticles and carbon nanomaterials moves the aerospace industry towards a sustainable fuel efficiency using functional, lightweight materials and coatings.
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| 17. |
- Selegård, Linnéa, et al.
(författare)
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Bifunctional gadolinium decorated ZnO nanocrystals integrating both enhanced MR signal and bright fluorescence
- 2013
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Gadolinium decorated ZnO nanoparticles simultaneously possess both fluorescent and MR enhancement properties. These ZnO nanoparticles are crystalline and shielded by an amorphous gadolinium acetate matrix. Interestingly, the Gd-acetate decoration enhances the fluorescence emission of the ZnO nanoparticles. The quantum yield does increase for samples with high Gd/Zn relative ratios and these samples do also show a higher colloidal stability.In addition, these nanoparticles show an enhanced relaxivity value per Gd atom (r119.9mM1s-1) compared to results earlier reported both on Gd alloyed ZnO nanoparticles and pure Gd2O3 nanoparticles. This improvement is considered to be due to the close proximity of Gd atoms and surrounding water molecules. A comprehensive study of the quantum yield and the relaxivity, as a function of composition, enable us to identify the ultimate design/composition of gadolinium decorated ZnO nanoparticles for optimum fluorescence and MR enhancement properties.
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| 18. |
- Selegård, Linnéa, et al.
(författare)
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Biotinylation of ZnO Nanoparticles and Thin Films: A Two-Step Surface Functionalization Study
- 2010
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Ingår i: ACS APPLIED MATERIALS and INTERFACES. - : AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA. - 1944-8244 .- 1944-8252. ; 2:7, s. 2128-2135
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Tidskriftsartikel (refereegranskat)abstract
- This study reports ZnO nanoparticles and thin film surface modification using a two-step functionalization strategy. A small silane molecule was used to build up a stabilizing layer and for conjugation of biotin (vitamin B7), as a specific tag. Biotin was chosen because it is a well-studied bioactive molecule with high affinity for avidin. ZnO nanoparticles were synthesized by electrochemical deposition under oxidizing condition, and ZnO films were prepared by plasma-enhanced metal organic chemical vapor deposition. Both ZnO nanoparticles and ZnO thin films were surface modified by forming a (3-mercaptopropyl)trimethoxysilane (MPTS) layer followed by attachment of a biotin derivate. lodoacetyl-PEG2-biotin molecule was coupled to the thiol unit in MPTS through a substitution reaction. Powder X-ray diffraction, transmission electron microscopy, X-ray photoemission electron microscopy, atomic force microscopy. X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy were used to investigate the as-synthesized and functionalized ZnO materials. The measurements showed highly crystalline materials in both cases with a ZnO nanoparticle diameter of about 5 nm and a grain size of about 45 nm for the as-grown ZnO thin films. The surface modification process resulted in coupling of silanes and biotin to both the ZnO nanoparticles and ZnO thin films. The two-step functionalization strategy has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications.
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| 19. |
- Selegård, Linnéa, et al.
(författare)
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In-situ growth of cerium nanoparticles for chrome-free, corrosion resistant anodic coatings
- 2021
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Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 410
-
Tidskriftsartikel (refereegranskat)abstract
- Chrome-based anodization and sealing combined is a cost-effective solution for developing good corrosion protective coatings on aluminum (Al) and its alloys. The toxicity of hexavalent chromium, however, requires new, sustainable, environmentally friendly, and efficient chromate-free sealing procedures. Herein, a combination of cerium (Ce) sealing and hydrothermal sealing (HTS) is employed to improve the corrosion resistance of the commonly used alloy AA2024-T3 anodized by tartaric sulfuric acid (TSA). The morphologies and components of the resulting surfaces are systematically studied. Characterization technologies such as SEM, TEM, EDX, XRD, and XPS demonstrate the in-situ growth of Ce oxide nanoparticles all through the porous structures of the anodic coating and closing of the pores by additional HTS treatment. The results from the standardized corrosion test (ASTM B895) demonstrate an improved corrosion resistance obtained by the utilized chrome-free process.
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| 20. |
- Selegård, Linnéa, et al.
(författare)
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PEEM, LEED and PES temperature study of Eu doped Gd2O3 nanoparticles and their interactions with silicon
- 2013
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We report the formation of silicate and silicide by annealing of a SiOx surface, with low coverage of Eu doped Gd2O3 nanoparticles. Interestingly, the annealing temperature required for removal of native oxide from the Si substrate decreases with as much as 200 degrees in presence of the nanoparticles. XPEEM, LEEM and MEM are used to monitor the silicide/silicate formation and SiOx removal. Fragmentation of the nanoparticles is observed, and the SiOx layer is gradually removed. Eu is migrating to clean Si areas during the annealing process, while Gd is found in areas where oxide is still present. This annealing process is clearly facilitated in the presence of rare-earth based nanoparticles, where nanoparticles are suggested to function as reaction sites. Reduction of the annealing temperature of SiOx substrates is also observed in presence of pure Eu3+ and Gd3+ ions, but to lesser extent. The significant reduction of the annealing temperature of SiO by several hundred degrees, in presence of Eu doped Gd2O3 nanoparticles, is remarkable. This type of material may find applications both within optoelectronics and processing microelectronic industry.
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| 21. |
- Selegård, Linnéa, et al.
(författare)
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Residual Stresses in Dengeling-Treated Aluminum Alloy AA 7050
- 2017
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Ingår i: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2017). - : Materials Research Foum. - 9781945291166 - 9781945291173 ; , s. 425-430
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Konferensbidrag (refereegranskat)abstract
- Dengeling is a new method for mechanical surface treatment of metallic parts to enhance fatigue properties. The treatment produces consecutive lines of indents by a spherical indenter, resulting in compressive residual stresses in a surface layer. This paper investigated residual stresses, surface roughness and near surface deformation, in specimens of AA 7050 T7451 after different dengeling treatments. The effect of indent overlap (0%, 25% and 50%) and indenter size (∅3 and ∅8 mm) were studied. X-Ray diffraction measurements revealed that plastic deformation and compressive residual stresses were generated in a surface layer of about 1 mm by treatments using the ∅3 mm indenter and about 1.2 mm by treatment using the ∅8 mm indenter. Anisotropic residual stress fields were observed with higher compressive residual stresses (-360 MPa for 50% indent overlap, independent of indenter size) perpendicular to indent lines and lower (max -270 MPa for all the treatments) parallel to indent lines. Increasing the overlap between indents gave higher subsurface compressive residual stresses only in the transverse direction of indent lines. It also reduced the surface roughness. Best surface finish (Ra below 1 μm) was obtained when using the ∅8 mm indenter and 50% indent overlap.
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| 22. |
- Selegård, Linnéa, 1983-
(författare)
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Synthesis, Surface Modification, and Characterization of Metal Oxide Nanoparticles : Nanoprobes for Signal Enhancement in Biomedical Imaging
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we investigate crystalline metal oxide nanoparticles of our own design to obtain nanoprobes for signal enhancement and bioimaging purposes. We report fabrication, surface modification and characterization of nanoparticles based on zinc (Zn), and rare earths (i.e. gadolinium (Gd) and europium (Eu)) singly and in combination. Our ZnO nanoparticles show high potential as fluorescent probes and Gd2O3 nanoparticles are promising as nanoprobes for MR signal enhancement. A combined Zn, Gd material is investigated as a potential dual probe. Interestingly, this nanoprobe shows, compared to the pure oxides, both increased fluorescent quantum yield and do induce improved relaxivity and by that enhanced MR signal. Nanoparticles composed of Eu doped Gd2O3 are also investigated in terms of their ability to interact with silicon surfaces. The presence of nanoparticles shows a catalytic effect on the annealing procedure of SiOx.Surface modification of Gd and Zn based nanoparticles is performed, in a first step to improve stabilization of the nanoparticle core. Both carboxylic acids (paper I) and a thiol terminated silane (paper II and III) are used for this purpose. In a second step, a polyethylene glycol (PEG) is used for surface modification, to increase the biocompatibility of the nanoparticles. The Mal PEG NHS is chemically linked to thiol terminated silane groups via a maleimide coupling (Paper II). The presence of free NHS functional groups is intended to enable further linking of specific molecules for targeting purposes. The fluorescent dye rhodamine was, as a proof of concept, linked via the NHS functional group to the PEGylated Gd2O3 nanoparticles (Paper II). In Paper III, an alternative linking strategy is investigated, using iodized PEG2-Biotin for coupling via the iodide unit to the thiol terminated silane on ZnO nanoparticles. The resulting surface modified nanoparticles are investigated by means of coordination chemistry and coupling efficiency using X-ray photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy and infrared spectroscopy.
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- Yakimova, Rositza, et al.
(författare)
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ZnO materials and surface tailoring for biosensing
- 2012
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Ingår i: Frontiers in bioscience (Elite edition). - Albertson, NY, United States : Frontiers in Bioscience. - 1945-0508 .- 1945-0494. ; 4:1, s. 254-278
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Tidskriftsartikel (refereegranskat)abstract
- ZnO nanostructured materials, such as films and nanoparticles, could provide a suitable platform for development of high performance biosensors due to their unique fundamental material properties. This paper reviews different preparation techniques of ZnO nanocrystals and material issues like wettability, biocompatibility and toxicity, which have an important relevance to biosensor functionality. Efforts are made to summarize and analyze existing results regarding surface modification and molecular attachments for successful biofunctionalization and understanding of the mechanisms involved. A section is devoted to implementations of tailored surfaces in biosensors. We end with conclusions on the feasibility of using ZnO nanocrystals for biosensing.
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