The impact of catalysis using transition metal nanoparticles (NPs) in promoting faster and cleaner processes is now well established. Being extracted from depletive resources, metal NPs should be recycled, particularly those from periods 5 and 6, including Pd. Heterogeneization of Pd NPs onto a support is one of the strategy allowing further recycling. However, we and others have observed that the catalytic activity of the recycled Pd NPs rapidly decreased, especially with demanding transformations, such as the Heck and the Sonogashira reactions. This unwanted behavior has been mostly attributed to the significant morphological modifications of Pd NPs at the surface of the support due to a quasi-homogeneous mechanism. We have devised novel strategy to increase the recyclability of Pd NPs on carbon-based catalysts for the Sonogashira reaction through the formation of an alloy with Au, without altering its initial shape [1]. An alternative strategy allowing the use of PdO NPs as reservoir for active Pd atoms will be also discussed [2]; REFERENCES: [1] Rossy, C.; Majimel, J.; Fouquet, E.; Delacôte, C.; Boujtita, M.; Labrugère, C.; Tréguer-Delapierre, M.; Felpin, F.-X. Chem. Eur. J. 2013, 19, 14024.; [2] Rossy, C.; Majimel, J.; Delapierre, M. T.; Fouquet, E.; Felpin, F.-X. Appl. Catal. A: Gen. 2014, 482, 157.
Catalysts are an integral part of various imperative organic transformations as they encourage the feasibility of the reaction in terms of improved yields and selectivity. In this context, heterogeneous catalysts play an important role because of easy separation from the reaction mixture but the reaction rate is constrained due to the limited accessibility to catalyst’s surface. In the present work, we choose earth-abundant iron oxides as supports (and catalyst in some cases) for immobilization of various nano-metals namely Pd, Cu, Ni, Co, and Au etc. The synthesized metal embedded nanocomposites were characterized by several techniques such as TEM, SEM-EDS, HRTEM, Mössbauer and XPS analysis and utilized for numerous organic transformations such as Suzuki reaction, Heck reaction, Ritter reaction, Ullmann-type condensation reaction, reduction-, oxidation- and multicomponent reactions under benign reaction conditions. The excellent catalytic activity, stability, ease of recovery and reusability renders these protocols economic and sustainable.
Diamond like carbon (DLC) layers based on amorphous carbon are frequently used for mechanical protection of various industrial components. However, these layers exhibit not only very high hardness, but also other interesting properties (optical, electrical, biological etc.) leading to wider range of applications. The layers in this study were prepared by Cathodic Arc Deposition method allowing rather high deposition rates, but also leading to the formation of nanoclusters. As the properties of DLC layers are closely linked to their structure, we examined them at micro- and nanoscale. In order to assess the influence of the rough substrate, we compared the DLC layers both on steel substrates and Si wafers.
DLC layers were measured by Scanning Electron Microscopy (SEM) in the range of 12x12um2 down to 0.6x0.6um2. We observed regular granular structure with clusters of 200 to 500 nm in lateral size. This observation was in good agreement with the Atomic Force Microscopy (AFM) measurements of the same range. Most interesting structures were found for 30 nm thin DLC layers at the early stages of growth, where a non-continuous isolated clusters (50-150nm in diameter and 10-30nm in height) were formed. This “combined” structure allowed us to obtain pictures with nice material contrast (specifically local friction) using the Lateral Force mode of the contact AFM. We employed Raman spectroscopy with blue excitation to detect the presence of different types of C-C bonds in the form of D/G-peaks. Finally, we correlated the Raman spectra with different test conditions having impact on layer properties.
Understanding the relationship between properties and performance of materials has always been a major challenge for Materials Science. Aldrich Materials Science develops and sells innovative materials for use in energy, electronics, and biomedical research.
More recently, we have expanded our development programs to include new materials for organic and printed electronics including novel small molecules, polymers and nanomaterials. The performance of these new materials in an application or device is a critical piece of technology development. Aldrich Materials Science collaborates with academic researchers to obtain performance data on new materials developed and synthesized in our laboratories.
Because of its remarkable electronic, mechanical, and optical properties, graphene has generated a significant research interest and attracted a lot of investments in such areas as advanced electronic sensors, displays, transistors, batteries, supercapacitors, fuel cells, as well as photovoltaic (solar) systems for energy generation. Low toxicity is a prerequisite for the successful use of graphene-based systems in medicine as well; this topic is currently subject to numerous ongoing studies.
In order to unravel graphene’s performance details and to determine its behavior in real applications, researchers require high-quality materials with reproducible performance characteristics on the scale, which exceeds capabilities of a conventional research laboratory. In general, an efficient transfer of novel technologies from a small research scale to a much large prototype scale and beyond proceeds through intermediate steps, which include an initial scale up, validation, reproducibility studies and final scale up to the manufacturing scale available at Sigma-Aldrich.
This talk will highlight the results of both our recent internal development and that of our collaborations, as well as describe our recent strategy for further increasing interaction with university researchers in order to accelerate the availability of validated new materials worldwide. It will discuss the current product portfolio focusing on materials for electronic, energy and biomedical applications.
Electrospinning as preparation method of ultrathin fibers is widely used in nowa-days laboratories due to its versatility and low cost of devices. Range of possible prepared materials is tremendous and counts in organic and inorganic materials [1]. Electrospinning method was successfully introduced to industrial scale under the commercial name Nanospider technology [2].
We have prepared and characterized for the first time scaled up nanofibrous LiFePO4 (Figure 1). Used precursors (iron nitrate, phosphorous pentoxide, lithium, polyvinyl alcohol) and aqueous solvent were focused to achieve the most envi-ronmentally and industrially suitable process.
Prepared solution was characterized (conductivity, viscosity, surface tension) and electrospun on pilot plant scale needleless electrospinning machine (Nanospider).
Process was optimized to obtain continuous nanofibrous layer of polyvinyl aldo-hol/inorganic precursors composite with stable quality. Through high tempera-ture calcination in hydrogen/nitrogen atmosphere of prepared composite we have obtained wanted nanofibrous product which was characterized by SEM, STEM, PXRD, BET and other methods. Prepared nanofibrous LifePO4 will be test-ed as cathodic material.
REFERENCES: [1] Greiner, A; Wendorff, JH Angew. Int. Ed. 2007, 46, 5670; [2] Jirsák O; Sanetrník F; Lukáš D; Kotek V; Martinová L; Chaloupek J (2005), CZ Patent, CZ294274 (B6), A, Method of nanofibers production from polymer solution using electrostatic spinning and a device for carrying out the method
Wastewater treatment is one of the urgent needs by reason of increasing water pollution. Polymeric nanofibrous composite membranes have been developed for the purpose of wastewater filtration due to small pore size and highly porous structure. In this work, various nanofibrous composite membranes were prepared and flux performance was compared using a custom-built cross-flow unit. Various membranes were prepared according to area weight of electrospun nanofiber mat, supporting layers and lamination methods.
A new wet milling procedure for a cost-effective production of nZVI focused on groundwater remediation is presented. The conventional ball milling of iron in an organic solvent as Mono Ethylene Glycol produces flattened iron particles (flakes) that are unlikely to break even after very long milling times. This improved method is based on the addition of alumina during the milling which has a positive effect on particle reduction by breaking iron flakes down and also producing nZVI particles from the direct abrasion of the iron from the grinding media. The first experiments were aimed to assess the importance of the grinding media size, while maintaining a constant alumina concentration. Once the best grinding media size was determined (0.5 mm Ø), the following research was focused on finding the best alumina concentration for this specific media. Finally, the optimal alumina concentration for the selected media was 80.4g·l-1 leading particles to a 100% fraction under 1µm and a mean diameter of 520nm (by lased diffraction) and 200nm (by SEM).
To assess the reactivity of the new particles, these were tested on Cr(VI) reduction and the elimination of Chlorinated Aliphatic Hydrocarbons (CAHs), and compared to available commercial ones. These new particles showed a very good Cr(VI) and CAHs removal efficiency compared with other commercial available products. It is believed that the high reactivity shown is produced by the combination of two phenomena observed by TEM images. First, the absence of an oxide layer thanks to the abrasion action of alumina and secondly, the fine nanostructure inside the iron produced by the mechanical milling.
To assess the reactivity of the new particles, these were tested on Cr(VI) reduction and the elimination of Chlorinated Aliphatic Hydrocarbons (CAHs), and compared to available commercial ones. These new particles showed a very good Cr(VI) and CAHs removal efficiency compared with other commercial available products. It is believed that the high reactivity shown is produced by the combination of two phenomena observed by TEM images. First, the absence of an oxide layer thanks to the abrasion action of alumina and secondly, the fine nanostructure inside the iron produced by the mechanical milling.
Nanoscale zero-valent iron (nZVI) is the most commonly used nanoremediation material. While there has been a reasonable level of application of nZVI technologies for in situ remediation in the United States, its utilization across Europe has been much more limited. There has been significant uncertainty about the balance between deployment risks and benefits for nanoparticles (NPs), which has affected the regulatory position in several countries. Some member states of the European Union (EU) take a strong precautionary view of the risks from the deployment of NPs into the subsurface, preventing the adoption of the technology. This article provides a risk–benefit assessment for nZVI based on published information and describes the steps that will be taken by a major European research project (NanoRem), as part of its work to provide a basis for better informed decision making in European environmental restoration markets. A key part of this process is dialogue between practitioners and researchers. NanoRem therefore has an active process of communication with different stakeholder networks (regulators, service providers, and site owners). NanoRem hopes to stimulate a consensus on appropriate use of nanoremediation and thereby stimulate effective technology transfer to the European remediation market.
Novel types of magnetic biochar composites have been tested in recent years as promising materials for environmental applications. Modified biochar containing iron oxides (IOX) can be used as a magnetically responsible sorbent. In case of nano zero valent iron (nZVI) modification it can be applied as a reactive sorbent with reducing properties. Several methods for the preparation of various types of iron modified pyrolyzed biomass have been utilized. The first one employs modification of non-magnetic biochar by IOX or ZVI particles. The second procedure is based on pyrolysis of biomass pretreated with iron precursors or synthesis of ZVI or IOX on already prepared biochar. All types of materials can be easily and rapidly separated using magnetic separator.
In our research, both types of biochars have been studied, especially optimization of synthetic procedures using various iron precursors, physicochemical properties and morphology characterization. Selected materials have been tested as (reactive) sorbents for chlorinated hydrocarbons, organic dyes, nitro compounds, phosphates or endocrine disruptors removal.
Large scale production and application of biochar-based materials prepared from cheap waste biomaterials and ZVI can offer interesting properties and reduction of financial costs.
Development of Mid-IR sensors is a challenge of great importance for the detection of biochemical molecules. Mid-infrared range (4000-400 cm-1) contains the absorption bands related to the vibrations of organic molecules. Chalcogenide glasses are an important class of amorphous materials appropriate for sensing applications. Indeed, they are mainly studied and used for their wide transparency in the infrared range (2-15 mum for selenide glasses) and their high refractive index (between 2 and 3). The aims of this study are to synthetize and characterize chalcogenide thin films for developing mid-IR optical waveguides.
For this study, chalcogenide glasses with composition (GeSe2)100-x(Sb2Se3)x, where x=5, 10, 20, 30, 40, 50, 60 and 70, were prepared. Among these compositions, two bulk glasses were chosen for their mid-IR transparency, stability against crystallization, and refractive index contrast suitable for mid-IR optical wave-guiding. The two compositions were used for radiofrequency magnetron sputtering deposition. The study of the influence of different sputtering parameters (time deposition, power and Ar pressure) on thin films characteristics (chemical composition, deposition rate, surface roughness, refractive index in near-IR and mid-IR and band gap energy) allows controlling the structure of the optical waveguide. Light injection efficiency experiments in near-IR and mid-IR were performed. Finally, optical waveguide surface was functionalized by deposition of a hydrophobic polymer, which enables detection of organic molecules in water.
ACKNOWLEDGEMENTS: Authors are thankful to Region Bretagne, IFREMER, BRGM, Czech Science Foundation (Project No. 16-17921S) and CONACYT for PhD funding.
The presence of mercury ions in environmental water sources has become a serious environmental and public threat around the world. Therefore, there is a growing need for development of highly efficient mercury remediation techniques. The formation of insoluble mercury amalgams from aqueous solution through the reaction with noble metals is a promising method for environmental clean-up. This work reports a promising avenue whereby mercury (II) ions are removed from aqueous solution using silver nanoparticles immobilized on the surface of modified silica. Commercially available fumed silica was treated with triethoxysilane in order to form silicon hydride groups on the surface. The reducing properties of silicon hydride functional groups towards precious metal ions promotes the formation of silver nanoparticles from aqueous solution of silver salt. Therefore, the modified silica was subsequently used in generation of silver nanoparticles on the surface of silica substrate. It was determined that the synthesized silver nanoparticles are of high purity and stably immobilized on the silica support; the concentration of silver nitrate solution and contact time between silicon hydride groups and silver ions linearly affect the size of generated metal nanoparticles.
Silver nanoparticles on the silica support were tested in the process of mercury (II) ions removal. In order to verify the mercury uptake a Zeeman furnace atomic-absorption spectrometer (RA-950, Lumex) was used.
There is a wide variety of printed large area flexible electronic devices and at the same time a number of different visions and estimates for this the development of this new emerging industry and market. But as every new industry or technology printed electronics has to overcome technology challenges and drawbacks against existing technologies like silicon technologies.
The talk wants to give a definition of common characteristics for printed electronics and the potential of not only single printed devices, but for integrated products. Additionally a broad picture on these new products and a potential market outlook is presented.
Out of the broad picture the talk focuses then on how to scale up processes from lab to fab, from the view of an equipment maker being in high tech developing markets like printed electronics, fuel cells, lithium ion batteries, nanostructured surfaces and so-lar for more than fifteen years.
From this overview the talk then gets more detailed into needed processes, parameters, printing systems, laser scribing, nano-imprint and coating systems. A special focus is dedicated to the challenges encountered for the optimal choice of substrates, chemicals and nanoinks for real applications and products.
Nitrogen-doped porous carbons are of special interest, because their unique physical properties such as high surface area, multidimensional electron transport pathways and good mechanical strength, and are thus very important for applications in the fields of catalysis, environment techniques and energy generation and storage.1 Moreover, nitrogen-doping can be further amplified in a porous structure that bears a high surface area to increases their materials performance in electrochemical devices, such as double layer capacitors and lithium-ion batteries.2 In addition, nitrogen-doping can enhance the lithium insertion, between the nitrogen-doped carbon material and lithium.3 And it can create a large number of defects in the porous configuration and offer more active sites for lithium insertion.4.
Toward this goal, a hierarchically structured macro- and mesoporous N-doped carbon with dispersed Fe2O3 nanoparticles (NDC@Fe2O3) is prepared by thermal treatment of a novel composite composed by PMMA particles decorated by graphene oxide (GO), PPy and iron salts. The NDC@Fe2O3 composite exhibited high surface area with a hierarchical pores structure. Integrated as a lithium ion battery anode, NDC@Fe2O3 exhibited high reversible capacity of 930 mA h/g over 200 cycles. The combination of Fe2O3 nanoparticles with nitrogen-doped porous carbons to form hybrid anode has been an efficient way to maintain the electronic integrity of the whole electrode since the carbon acts as a buffer layer to accommodate the volume variation and to provide multidimensional electron transport pathways during the charge/discharge process. REFERENCES: [1] Z. S. Wu, W. C. Ren, L. Xu, F. Li and H. M. Cheng, ACS Nano, 2011, 5, 5463-5471.; [2] J. P. Paraknowitsch, A. Thomas and M. Antonietti, J. Mater. Chem., 2010, 20, 6746.; [3] Z. Zhong, G. I. Lee, C. B. Mo, S. H. Hong and J. K. Kang, Chem. Mater., 2007, 19, 2918.; [4] C. C. Ma, X. H. Shao and D. P. Cao, J. Mater. Chem., 2012, 22, 8911-8915.