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1.
Langmuir ; 39(34): 12270-12282, 2023 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-37586045

RESUMO

Amphiphilic copolymers comprising hydrophilic segments of poly(ethylene glycol) and hydrophobic domains that are able to adhere to solid/liquid interfaces have proven to be versatile ingredients in formulated products for various types of applications. Recently, we have reported the successful synthesis of a copolymer designed for modifying the surface properties of polyesters as mimics for synthetic textiles. Using sum frequency generation (SFG) spectroscopy, it was shown that the newly developed copolymer adsorbs effectively on the targeted substrates even in the presence of surfactants as supplied by common detergents. In the present work, these studies were extended to evaluate the ability of the formed copolymer adlayers to passivate polyester surfaces against undesired deposition of bio(macro)molecules, as represented by fibrinogen as model protein foulants. In addition, SFG spectroscopy was used to elucidate the structure of fibrinogen at the interface between polyester and water. To complement the obtained data with an independent technique, analogous experiments were performed using quartz-crystal microbalance with dissipation monitoring for the detection of the relevant interfacial processes. Both methods give consistent results and deliver a holistic picture of brush copolymer adsorption on polyester surfaces and subsequent antiadhesive effects against proteins under different conditions representing the targeted application in home care products.


Assuntos
Polímeros , Quartzo , Adsorção , Análise Espectral/métodos , Propriedades de Superfície , Poliésteres , Fibrinogênio/química
2.
Langmuir ; 39(13): 4557-4570, 2023 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-36947877

RESUMO

Polymers containing poly(ethylene glycol) (PEG) units can exhibit excellent antifouling properties, which have been proposed/used for coating of biomedical implants, separation membranes, and structures in marine environments, as well as active ingredients in detergent formulations to avoid soil redepositioning in textile laundry. This study aimed to elucidate the molecular behavior of a copolymer poly(MMA-co-MPEGMA) containing antiadhesive PEG side chains and a backbone of poly(methyl methacrylate), at a buried polymer/solution interface. Polyethylene terephthalate (PET) was used as a substrate to model polyester textile surfaces. Sum frequency generation (SFG) vibrational spectroscopy was applied to examine the interfacial behavior of the copolymer at PET/solution interfaces in situ and in real time. Complementarily, copolymer adsorption on PET and subsequent antiadhesion against protein foulants were probed by quartz-crystal microbalance experiments with dissipation monitoring (QCM-D). Both applied techniques show that poly(MMA-co-MPEGMA) adsorbs significantly to the PET/solution interface at bulk polymer solution concentrations as low as 2 ppm, while saturation of the surface was reached at 20 ppm. The hydrophobic MMA segments provide an anchor for the copolymer to bind onto PET in an ordered way, while the pendant PEG segments are more disordered but contain ordered interfacial water. In the presence of considerable amounts of dissolved surfactants, poly(MMA-co-MPEGMA) could still effectively adsorb on the PET surface and remained stable at the surface upon washing with hot and cold water or surfactant solution. In addition, it was found that adsorbed poly(MMA-co-MPEGMA) provided the PET surface with antiadhesive properties and could prevent protein deposition, highlighting the superior surface affinity and antifouling performance of the copolymer. The results obtained in this work demonstrate that amphiphilic copolymers containing PMMA anchors and PEG side chains can be used in detergent formulations to modify polyester surfaces during laundry and reduce deposition of proteins (and likely also other soils) on the textile.

3.
Langmuir ; 38(34): 10392-10399, 2022 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-35976253

RESUMO

Chemical gardens are self-assembled structures with intricate plant-like morphologies and consist of mineralized membranes, which form spontaneously at interfaces between compartments with dissimilar chemical composition, most typically acidic metal salt and alkaline sodium silicate solutions. While this phenomenon is thought to occur in a number of practical settings, it has also proven to be valuable for investigating transport characteristics in distinct applied systems. For example, coupled diffusion and precipitation processes were monitored in silica gardens based on calcium and iron salts, considered to be models for cement hydration and steel corrosion, respectively. Here we extend these studies to the case of aluminum-based silica gardens, one of the so far less frequently investigated examples of silica gardens. To this end, single macroscopic tubes were prepared in a reproducible way by the controlled addition of sodium silicate solution to a pellet of pressed aluminum nitrate. Continued sampling of the volumes enclosed by and surrounding the formed membraneous structure allowed the time-dependent development of ion concentration gradients to be tracked over extended periods of time, while both the pH and electrochemical potential differences across the membrane were recorded online by immersed probes. The dynamic behavior revealed in this way was finally complemented by ex-situ analyses of the composition of the formed tubes. The collected data shows that the as-prepared tubular structures consist of sodium aluminosilicate phases with certain similarities to zeolites and geopolymers. The emerging tube wall was further found to be permeable to all ionic species present in the system, allowing significant electrochemical potential to be sustained over tens of hours until diffusion had eventually diminished the initially generated gradients. The findings of this work may have important implications for the geochemical fate of natural aluminosilicate sources, the use of such geopolymers in construction applications, and the synthesis and properties of zeolites.

4.
Phys Chem Chem Phys ; 24(17): 9978-9989, 2022 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-35319032

RESUMO

Potentiometric titrations are a powerful tool to study the early stages of the precipitation of minerals such as calcium carbonate and were used among others for the discovery and characterisation of key precursors like prenucleation clusters. Here we present a modified procedure for conducting such titration experiments, in which the reactants (i.e. calcium and (bi)carbonate ions) are added simultaneously in stoichiometric amounts, while both the amount of free calcium and the optical transmission of the solution are monitored online. Complementarily, the species occurring at distinct stages of the crystallisation process were studied using cryogenic transmission electron microscopy. This novel routine was applied to investigate CaCO3 nucleation in the absence and presence of polymeric additives with different chemical functionalities. The obtained results provide new insights into the critical steps underlying nucleation and subsequent ripening, such as the role of liquid mineral-rich phases and their transformation into solid particles. The studied polymers proved to interfere at multiple stages along the complex mineralisation pathway of calcium carbonate, with both the degree and mode of interaction depending on the chosen polymer chemistry. In this way, the methodology developed in this work allows the mechanisms of antiscalants - or crystallisation modifiers in general - to be elucidated at an advanced level of detail.

5.
Chemistry ; 27(65): 16135-16144, 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34590745

RESUMO

Chemical gardens are self-assembled tubular precipitates formed by a combination of osmosis, buoyancy, and chemical reaction, and thought to be capable of catalyzing prebiotic condensation reactions. In many cases, the tube wall is a bilayer structure with the properties of a diaphragm and/or a membrane. The interest in silica gardens as microreactors for materials science has increased over the past decade because of their ability to create long-lasting electrochemical potential. In this study, we have grown single macroscopic tubes based on calcium carbonate and monitored their time-dependent behavior by in situ measurements of pH, ionic concentrations inside and outside the tubular membranes, and electrochemical potential differences. Furthermore, we have characterized the composition and structure of the tubular membranes by using ex situ X-ray diffraction, infrared and Raman spectroscopy, as well as scanning electron microscopy. Based on the collected data, we propose a physicochemical mechanism for the formation and ripening of these peculiar CaCO3 structures and compare the results to those of other chemical garden systems. We find that the wall of the macroscopic calcium carbonate tubes is a bilayer of texturally distinct but compositionally similar calcite showing high crystallinity. The resulting high density of the material prevents macroscopic calcium carbonate gardens from developing significant electrochemical potential differences. In the light of these observations, possible implications in materials science and prebiotic (geo)chemistry are discussed.


Assuntos
Carbonato de Cálcio , Minerais , Microscopia Eletrônica de Varredura , Análise Espectral Raman , Difração de Raios X
6.
Phys Chem Chem Phys ; 23(2): 1381-1391, 2021 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-33393569

RESUMO

Amphiphilic molecules (e.g. hydrotropes) that enhance the solubility of hydrophobic compounds in water are often charged. As a result, such compounds also show specific ion effects. These effects can either strengthen or weaken the solubilisation power of amphiphilic molecules, depending on their degree of ion hydration. They can even prevail and transform an apparent solubilizer into an "anti-hydrotrope", i.e. a salting-out agent. In the present paper, we discuss this subtle balance between specific (Hofmeister) effects exerted by ionic headgroups and the hydrophobicity of the residual compound structure, including the size of the molecule and the presence of electron-withdrawing groups.

7.
Phys Chem Chem Phys ; 22(33): 18631-18638, 2020 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-32789345

RESUMO

Hydrogels consisting of poly(acrylic acid) (PAA) and calcium ions are a promising class of materials with shapeable, stretchable and self-healing behaviour originating from the reversible and dynamic nature of the electrostatic and hydrogen bonds in the structure. In the dry state, such materials - referred to as "mineral plastics"- can be transparent, hard and flame-resistant, while addition of water will result in rehydration and complete recoverage of the initial gel-like state. These desirable characteristics strongly depend on the molar mass of the used type of PAA and the experimental conditions at which the hydrogels are prepared. In this work, we show how the macroscopic properties of the materials can be adjusted by controlling the initial concentration of dissolved PAA and/or its molecular weight, and how rheological measurements can be used to monitor the resulting physical properties. Furthermore, we have employed isothermal titration calorimetry (ITC) to investigate thermodynamic aspects of the hydrogel formation to gain a better understanding of the underlying mechanism(s). Our results reveal that, and explain why, PAA molar masses between 50 and 100 kDa are particulary suitable for the formation of hydrogels with optimized properties, thus establishing a rational basis for targeted design of such materials with tailor-made characteristics.

8.
Chemphyschem ; 18(4): 338-345, 2017 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-28001337

RESUMO

Silica gardens are extraordinary plant-like structures resulting from the complex interplay of relatively simple inorganic components. Recent work has highlighted that macroscopic self-assembly is accompanied by the spontaneous formation of considerable chemical gradients, which induce a cascade of coupled dissolution, diffusion, and precipitation processes occurring over timescales as long as several days. In the present study, this dynamic behavior was investigated for silica gardens based on iron and cobalt chloride by means of two synchrotron-based techniques, which allow the determination of concentration profiles and time-resolved monitoring of diffraction patterns, thus giving direct insight into the progress of dissolution and crystallization phenomena in the system. On the basis of the collected data, a kinetic model is proposed to describe the relevant reactions on a fundamental physicochemical level. The results show that the choice of the metal cations (as well as their counterions) is crucial for the development of silica gardens in both the short and long term (i.e. during tube formation and upon subsequent slow equilibration), and provide important clues for understanding the properties of related structures in geochemical and industrial environments.

9.
Chemphyschem ; 17(21): 3535-3541, 2016 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-27540706

RESUMO

The understanding of the molecular mechanisms underlying the early stages of crystallisation is still incomplete. In the case of calcium carbonate, experimental and computational evidence suggests that phase separation relies on so-called pre-nucleation clusters (PNCs). A thorough thermodynamic analysis of the enthalpic and entropic contributions to the overall free energy of PNC formation derived from three independent methods demonstrates that solute clustering is driven by entropy. This can be quantitatively rationalised by the release of water molecules from ion hydration layers, explaining why ion association is not limited to simple ion pairing. The key role of water release in this process suggests that PNC formation should be a common phenomenon in aqueous solutions.

10.
Chem Soc Rev ; 43(7): 2348-71, 2014 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-24457316

RESUMO

Crystallisation is at the heart of various scientific disciplines, but still the understanding of the molecular mechanisms underlying phase separation and the formation of the first solid particles in aqueous solution is rather limited. In this review, classical nucleation theory, as well as established concepts of spinodal decomposition and liquid-liquid demixing, is introduced together with a description of the recently proposed pre-nucleation cluster pathway. The features of pre-nucleation clusters are presented and discussed in relation to recent modifications of the classical and established models for phase separation, together with a review of experimental work and computer simulations on the characteristics of pre-nucleation clusters of calcium phosphate, calcium carbonate, iron(oxy)(hydr)oxide, silica, and also amino acids as an example of small organic molecules. The role of pre-nucleation clusters as solute precursors in the emergence of a new phase is summarized, and the link between the chemical speciation of homogeneous solutions and the process of phase separation via pre-nucleation clusters is highlighted.


Assuntos
Aminoácidos/química , Carbonato de Cálcio/química , Fosfatos de Cálcio/química , Compostos Férricos/química , Dióxido de Silício/química , Cristalização
11.
Angew Chem Int Ed Engl ; 54(13): 4083-6, 2015 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-25650565

RESUMO

Calcium sulfate is a naturally abundant and technologically important mineral with a broad scope of applications. However, controlling CaSO4 polymorphism and, with it, its final material properties still represents a major challenge, and to date there is no universal method for the selective production of the different hydrated and anhydrous forms under mild conditions. Herein we report the first successful synthesis of pure anhydrite from solution at room temperature. We precipitated calcium sulfate in alcoholic media at low water contents. Moreover, by adjusting the amount of water in the syntheses, we can switch between the distinct polymorphs and fine-tune the outcome of the reaction, yielding either any desired CaSO4 phase in pure state or binary mixtures with predefined compositions. This concept provides full control over phase selection in CaSO4 mineralization and may allow for the targeted fabrication of corresponding materials for use in various areas.

12.
Angew Chem Int Ed Engl ; 53(46): 12380-96, 2014 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-25156760

RESUMO

Nanotechnology enables the design of materials with outstanding performance. A key element of nanotechnology is the ability to manipulate and control matter on the nanoscale to achieve a certain desired set of specific properties. Here, we discuss recent insight into the formation mechanisms of inorganic nanoparticles during precipitation reactions. We focus on calcium carbonate, and describe the various transient stages potentially occurring on the way from the dissolved constituent ions to finally stable macrocrystals-including solute ion clusters, dense liquid phases, amorphous intermediates, and nanoparticles. The role of polymers in nucleating, templating, stabilizing, and/or preventing these structures is outlined. As a specific example for applied nanotechnology, the properties of cement are shown to be determined by the formation and interlocking of calcium-silicate-hydrate nanoplatelets. The aggregation of these platelets into mesoscale architectures can be controlled with polymers.

13.
Chem Commun (Camb) ; 60(5): 610-613, 2024 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-38099963

RESUMO

Calcium sulfate hemihydrate, also known as bassanite or Plaster of Paris, is one of the most extensively produced inorganic materials worldwide. Nowadays, bassanite is mainly obtained by thermal dehydration of calcium sulfate dihydrate (gypsum) - a process that consumes considerable amounts of energy and thus leaves a significant carbon footprint. Towards a more sustainable future, alternative technologies for bassanite production at low temperatures are therefore urgently required. While successful approaches involving organic solvents have been reported, we chose precipitation from aqueous solutions as a potentially even "greener" way of synthesis. In a previous work, we have shown that spontaneous formation of bassanite in water (in competition with thermodynamically favoured gypsum) can be achieved at 40 °C by the use of additives that maintain specific interactions with calcium sulfate precursors and modulate the local hydration household during crystallisation. The results of the present study demonstrate that bassanite can be obtained via simple precipitation from aqueous solutions at room temperature by the combination of additives acting through orthogonal mechanisms.

14.
Microorganisms ; 11(4)2023 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-37110314

RESUMO

Biofilms are often tolerant towards routine cleaning and disinfection processes. As they can grow on fabrics in household or healthcare settings, resulting in odors and serious health problems, it is necessary to contain biofilms through eradication strategies. The current study proposes a novel test model for the growth and removal of biofilms on textiles with Pseudomonas fluorescens and the opportunistic nosocomial pathogen Pseudomonas aeruginosa as model organisms. To assess the biofilm removal on fabrics, (1) a detergent-based, (2) enzyme-based, and (3) combined formulation of both detergent and enzymes (F1/2) were applied. Biofilms were analyzed microscopically (FE-SEM, SEM, 3D laser scanning- and epifluorescence microscopy), via a quartz crystal microbalance with mass dissipation monitoring (QCM-D) as well as plate counting of colonies. This study indicated that Pseudomonas spp. form robust biofilms on woven cellulose that can be efficiently removed via F1/2, proven by a significant reduction (p < 0.001) of viable bacteria in biofilms. Moreover, microscopic analysis indicated a disruption and almost complete removal of the biofilms after F1/2 treatment. QCM-D measurements further confirmed a maximal mass dissipation change after applying F1/2. The combination strategy applying both enzymes and detergent is a promising antibiofilm approach to remove bacteria from fabrics.

15.
Adv Mater ; 35(20): e2210015, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-36861429

RESUMO

The design of additives showing strong and selective interactions with certain target surfaces is key to crystallization control in applied reactive multicomponent systems. While suitable chemical motifs can be found through semi-empirical trial-and-error procedures, bioinspired selection techniques offer a more rationally driven approach and explore a much larger space of possible combinations in a single assay. Here, phage display screening is used to characterize the surfaces of crystalline gypsum, a mineral of broad relevance for construction applications. Based on next-generation sequencing of phages enriched during the screening process, a triplet of amino acids, DYH, is identified as the main driver for adsorption on the mineral substrate. Furthermore, oligopeptides containing this motif prove to exert their influence in a strictly selective manner during the hydration of cement, where the sulfate reaction (initial setting) is strongly retarded while the silicate reaction (final hardening) remains unaffected. In the final step, these desired additive characteristics are successfully translated from the level of peptides to that of scalable synthetic copolymers. The approach described in this work demonstrates how modern biotechnological methods can be leveraged for the systematic development of efficient crystallization additives for materials science.

16.
Chemistry ; 18(8): 2272-82, 2012 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-22259042

RESUMO

Upon slow crystallization from silica-containing solutions or gels at elevated pH, alkaline-earth carbonates spontaneously self-assemble into remarkable nanocrystalline ultrastructures. These so-called silica biomorphs exhibit curved morphologies beyond crystallographic symmetry and ordered textures reminiscent of the hierarchical design found in many biominerals. The formation of these fascinating materials is thought to be driven by a dynamic coupling of the components' speciations in solution, which causes concerted autocatalytic mineralization of silica-stabilized nanocrystals over hours. In the present work, we have studied the precipitation kinetics of this unique system by determining growth rates of individual aggregates using video microscopy, and correlated the results with time-dependent data on the concentration of metal ions and pH acquired online during crystallization. In this manner, insight to the evolution of chemical conditions during growth was gained. It is shown that crystallization proceeds linearly with time and is essentially reaction controlled, which fits well in the proposed morphogenetic scenario, and thus, indirectly supports it. Measurements of the silica concentration in solution, combined with analyses of crystal aggregates isolated at distinct stages of morphogenesis, further demonstrate that the fraction of silica coprecipitated with carbonate during active growth is rather small. We discuss our findings with respect to the role of silica in the formation of biomorphs, and moreover, prove that the external silica skins that occasionally sheath the aggregates--previously supposed to be involved in the growth mechanism--originate from secondary precipitation after growth is already terminated.


Assuntos
Carbonatos/química , Nanopartículas/química , Dióxido de Silício/química , Cristalização , Concentração de Íons de Hidrogênio , Cinética , Soluções/química
17.
ACS Omega ; 7(13): 10910-10920, 2022 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-35415322

RESUMO

In the light of clean beauty and sustainability requirements emerging in the personal care market, the urgent need for the replacement of silicones in hair conditioners-with comparable performance and customer experience-has been highlighted in the industry. In this context, the goal of the present study was to investigate the physical effects of different silicone-free conditioner formulations on Mongolian hair after damage due to bleaching and compare the results to property changes induced by a classical silicone-containing formulation. To that end, the morphology, structure, and composition of strands and individual fibers of this hair type were characterized before and after bleaching by means of optical microscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). It is shown that oxidative bleaching causes significant damage to the native hair surface, leading to local depletion or even large-area removal of the outer hydrophobic lipid layer. This results in enhanced wettability of the bleached hair by water (as confirmed by contact angle measurements) and is accompanied by an undesired loss of hair gloss and softness. Upon treatment with suitable cosmetic emulsions, the natural hydrophobicity of intact Mongolian hair can be partially or fully restored, with silicone-free formulations having effects similar to those of established silicone-containing products. The successive influence of bleaching and conditioning was further monitored using inverse gas chromatography (iGC), a technique that probes changes in surface energetics and polarity over an ensemble of an entire hair strand through interactions with specific molecules at the solid/gas interface. The resulting data mirror the macroscopic behavior of the bleached/conditioned hair and provide a quantitative scale for measuring damage and repair effects. Most notably, the effect of bleaching and subsequent conditioning on the haptic perception of hair strands could also be quantified with the aid of a biomimetic measurement system, which identifies increased friction (both tactile and sliding) as the major cause for the strawy feel of bleached hair and indicates successful relubrication after treatment with suitable conditioner formulations. Finally, the different physical properties determined for native, bleached, and reconditioned Mongolian hair are found to be reflected in application-oriented tests, namely in vitro measurements of wet and dry combing work. Overall, the data collected in this work shed novel light on the surface properties of Mongolian hair and highlight that effective hair conditioning after damage can be achieved without silicones in advanced cosmetic emulsions based on octyldodecyl myristate and glyceryl oleate.

18.
J Colloid Interface Sci ; 618: 206-218, 2022 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-35338927

RESUMO

HYPOTHESIS: Chemical gardens are tubular inorganic structures exhibiting complex morphologies and interesting dynamic properties upon ageing, with coupled diffusion and precipitation processes keeping the systems out of equilibrium for extended periods of time. Calcium-based silica gardens should comprise membranes that mimic the microstructures occurring in ordinary Portland cement and/or silicate gel layers observed around highly reactive siliceous aggregates in concrete. EXPERIMENTS: Single macroscopic silica garden tubes were prepared using pellets of calcium chloride and sodium silicate solution. The composition of the mineralized tubes was characterized by means of various ex-situ techniques, while time-dependent monitoring of the solutions enclosed by and surrounding the membrane gives insight into the spatiotemporal distribution of the different ionic species. The latter data reflect transport properties and precipitation reactions in the system, thus allowing its complex dynamic behavior to be resolved. FINDINGS: The results show that in contrast to the previously studied cases of iron- and cobalt-based silica gardens, the formed calcium silicate membrane is homogeneous and ultimately becomes impermeable to all species except water, hydroxide and sodium ions, resulting in the permanent conservation of considerable concentration gradients across the membrane. The insights gained in this work may help elucidate the nature and mechanisms of ion diffusion in Portland cements and concrete, especially those occurring during initial hydration of calcium silicates and the so-called alkali-silica reaction (ASR), one of the major concrete deterioration mechanisms causing serious problems with respect to the durability of concrete and the restricted use of many potential sources of raw materials.


Assuntos
Compostos de Cálcio , Cálcio , Cálcio/química , Compostos de Cálcio/química , Teste de Materiais , Microscopia Eletrônica de Varredura , Silicatos/química , Espectrometria por Raios X , Difração de Raios X
19.
J Am Chem Soc ; 132(50): 17859-66, 2010 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-21117693

RESUMO

In biomineralization, living organisms carefully control the crystallization of calcium carbonate to create functional materials and thereby often take advantage of polymorphism by stabilizing a specific phase that is most suitable for a given demand. In particular, the lifetime of usually transient amorphous calcium carbonate (ACC) seems to be thoroughly regulated by the organic matrix, so as to use it either as an intermediate storage depot or directly as a structural element in a permanently stable state. In the present study, we show that the temporal stability of ACC can be influenced in a deliberate manner also in much simpler purely abiotic systems. To illustrate this, we have monitored the progress of calcium carbonate precipitation at high pH from solutions containing different amounts of sodium silicate. It was found that growing ACC particles provoke spontaneous polymerization of silica in their vicinity, which is proposed to result from a local decrease of pH nearby the surface. This leads to the deposition of hydrated amorphous silica layers on the ACC grains, which arrest growth and alter the size of the particles. Depending on the silica concentration, these skins have different thicknesses and exhibit distinct degrees of porosity, therefore impeding to varying extents the dissolution of ACC and energetically favored transformation to calcite. Under the given conditions, crystallization of calcium carbonate was slowed down over tunable periods or completely prevented on time scales of years, even when ACC coexisted side by side with calcite in solution.


Assuntos
Carbonato de Cálcio/química , Dióxido de Silício/química , Concentração de Íons de Hidrogênio , Nanopartículas/química , Tamanho da Partícula , Pós , Dióxido de Silício/farmacologia , Água/química
20.
J Mater Chem B ; 8(22): 4831-4835, 2020 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-32432609

RESUMO

Microcarriers with the ability to release and catch substances are highly desired metamaterials and difficult to obtain. Herein, we report a straightforward strategy to synthesize these materials by combining silica-biomorphs with mesocrystals. An easy access to microcarrier hulls with covalently bound spiropyrans as light-switchable anchor points is presented.


Assuntos
Materiais Biomiméticos/química , Luz , Piranos/química , Dióxido de Silício/química , Compostos de Espiro/química , Materiais Biomiméticos/síntese química , Fenômenos Magnéticos , Estrutura Molecular , Tamanho da Partícula , Propriedades de Superfície
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