Active Metal Nanoparticles Research Articles

New active meso-porous titania foam as size limiter for metal nanoparticles

We present here a new sustainable method to fabricate peculiar titania mesofoam (mF), showing open cells with homogeneous size and shape for applications in heterogeneous catalysis. The mF was fabricated from an aqueous suspension of monodisperse polystyrene beads in diluted titanium acetylacetonate. The acetylacetonate group is proposed to be the driving force for the adsorption of the metal complex on the polystyrene beads. On top of the obtained anatase foam, we deposited gold nano-particles as an example of catalytically active metal nanoparticles, where the size of the metal nanoparticles was very sensitive to the temperature of catalytic tests. The resulting catalyst was fully characterized for application in the catalytic oxidation of CO and C3H6. The catalytic activity is strongly influenced by thermal treatments which increase the mean Au particle size distribution of the catalyst. Nevertheless, the proposed method for mF fabrication is able to generate mesopores that delimit the size of the gold nanoparticles to the mesopore size of the foam (i.e at average size below 10 nm) even in severe reaction conditions. This unusual attitude of the mF to delimit the gold nanoparticle size might also be effective for other metal nanoparticles. Consequently, we foresee that the proposed method could open a new route foractive inorganic mF, as support for metal nanoparticles.

Efficient and Environmentally Friendly Microwave-Assisted Synthesis of Catalytically Active Magnetic Metallic Ni Nanoparticles

Pure magnetic metallic nickel was synthesized by a simple and fast microwave-assisted method using a monomode microwave reactor. Nickel chloride was employed as metal precursor, while an environmental-friendly mixture of ethylene glycol and ethanol was simultaneously used as solvent and reducing agent. The parameters combination, for the occurrence of the reaction, of the mixture molar fraction and the metal precursor concentration was developed. The influence of the temperature and the time of the irradiation was investigated. The best performance (71% yield) was achieved at 250°C in 5 minutes of microwave irradiation. The phase and the morphology of the metal were analyzed by X-ray diffraction (XRD), scanning emission microscopy (SEM) and transmission electron microscopy (TEM) while the surface area was determined by nitrogen physisorption. The material exhibited a strong magnetic behavior. The metallic Nickel showed high catalytic activity for the hydrogenolysis of benzyl phenyl ether, a lignin model c...

Lanthanum and cerium co-modified Ni/SiO2 catalyst for CO methanation from syngas

Sintering of active metal nanoparticles (NPs) and carbon deposition is critical problems for many metal catalysts, such as nickel based catalysts for generating methane from syngas. To improve the resistance to the sintering and carbon deposition, a new scheme was proposed in this work. Lanthanum and cerium co-modified Ni/SiO2 catalysts were synthesized by using perovskite type oxide of La1-xCexNiO3 loaded on SiO2 as the precursor. In a nanocrystallite of La1-xCexNiO3, ions of nickel, lanthanum and cerium are evenly mixed at atomic level and confined in the nanocrystallite, therefore, Ni NPs and the two promoters of La2O3 and CeO2 should be in close contact and highly dispersed on SiO2 after reduction. The catalysts were characterized by using XRD, TEM, BET, H2-TPD, XPS, TG and Raman techniques. Compared with the mono-promoted catalysts, the bi-promoted La0.75Ce0.25NiO3/SiO2 showed much better resistance to carbon deposition, higher resistance to sintering and higher activity for CO methanation, which are attributed to co-eliminating effect of the two promoters for the deposited carbon, confinement of the interacted two promoters for Ni NPs and the higher dispersion of Ni NPs derived from the smaller size of La0.75Ce0.25NiO3.

Durabilty of Pt-Based Alloy Nanoparticles Supported on Functionalized Carbon Materials for the ORR – Tuning the Interaction between Particles and Support Material

In the last decades, proton exchange membrane fuel cells (PEMFC) have attracted large attention as promising renewable and clean technology for energy conversion. Designing nanomaterials with the aim to improve their electrocatalytic performance and long-term durability is still a critical challenge. Today´s PEMFC research has focused on Pt-based alloy nanoparticles combined with high surface area carbon materials due to its improved activity and stability for the ORR compared to pure Pt/C.[1,2,3] Although many studies have focused on the relations between the structural and chemical properties of the catalytically active metal nanoparticles and their catalytic ORR performance, the interactions of these nanoparticles with the carbon substrate have been rarely investigated up to date. In particular, the immobilization and stabilization of the nanoparticles on the support material have a strong influence on the long-term durability of the ORR catalysts. Therefore, one crucial point is the functionalization of the carbon support with hydroxide and carboxylate groups which seems to improve nucleation and dispersion of the Pt alloy nanoparticles; on the other hand, these oxygen-containing surface groups can accelerate the carbon corrosion associated with particle detachment during the potential cycling. Therefore, another strategy is the introduction of hetero-atoms as N-C-, C-B, C-F and C-S-bonds into the carbon framework improving their electrochemical oxidation resistance.[4,5,6,7]One target of this work is the stabilization of the carbon support material by functionalization to prevent carbon corrosion under the operating fuel cell conditions. We modified the morphology, structure and chemical properties of the porous carbon materials by using different methods such as acid treatment or thermal treatment in a reactive gas atmosphere. On the other hand, we optimized the design of Pt-based alloy (Pt-Ni, Pt-Co) nanoparticles supported on these functionalized porous carbon support materials. The properties and behavior of these materials are monitored by using high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and X-ray absorption spectroscopy (XAS). The electrochemical stability and durability of the catalysts were also investigated by applying various accelerated test protocols such as potential cycling between 0.5 - 1.0 (10.000 cycles), 0.5 - 1.5 (2000 cycles) and 1.0 - 1.5 V vs. RHE (2000 cycles). We monitored the electrochemically active surface area (ECSA) of the Pt and Pt alloy nanoparticles supported on these functionalized carbon materials during the runs to correlate its loss to the number of cycles, scan rate and potential range. Based on these results we evaluate the relationship between the carbon modification, size and chemical composition of the bimetallic nanoparticles, electrocatalytic properties and durability.Based on this study, we developed a model, describing the critical parameters to improve the interaction between the particles and the support material. This approach serves to enhance the catalytic properties and long-term durability of the ORR electrocatalysts for PEMFC applications.

Carbon Nanofibers Functionalized with Active Screen Plasma-Deposited Metal Nanoparticles for Electrical Energy Storage Devices.

Supercapacitors are energy storage devices with higher energy densities than conventional capacitors but lower than batteries or fuel cells. There is a strong interest in increasing the volumetric and gravimetric capacitance of these devices to meet the growing demands of the electrical and electronic sectors. The capacitance depends largely on the electrode material, and carbon nanofibers (CNFs) have attracted much attention because of their relatively low cost, large surface area, and good electrical conductivity as well as chemical and thermal stability. The deposition of metal nanoparticles on CNFs is a promising way to increase their surface properties and, ultimately, the capacitance of the devices. In this study, nickel and silver nanoparticles were deposited on CNFs using the active screen plasma technology. The CNFs were characterized, and their electrochemical performance was assessed in a three-electrode cell. The results show significant improvements over the untreated CNFs, particularly after functionalization with silver nanoparticles.

Palladium(0) Nanoparticles Embedded in Core–shell Nanogels as Recoverable Catalysts for the Mizoroki–Heck Reaction

AbstractCore–shell nanogels are attractive stabilizers and supports for catalytically active metallic nanoparticles. Herein, we present the synthesis and the characterization of a nanostructured well‐defined core–shell nanogel with the ability to stabilize Pd0 nanoparticles in its core. This hybrid nanogel displays a remarkable stability in both the solid state and in solution. This feature allowed its successful application as a catalyst for the Mizoroki–Heck reaction between n‐butyl acrylate and a series of bromo‐ and iodoarenes. The yields spanned from good to excellent, and catalyst recycling could be achieved up to three times without a significant activity loss. Three‐phase tests indicated that the hybrid nanogel acts as a Pd0 nanoreservoir. The catalysis proceeds in a quasihomogeneous fashion as part of the catalytic activity occurs outside the nanogel, which explains the observed limited recyclability.

Large-Scale Production of Electrocatalyst Micro- and Nanoparticles By Photonic Curing of Inkjet Printed Metal and Metal Alloy Precursor Inks

Catalytically active metal and metal-alloy nanoparticles, such as Pt and PtxNiy, play an important role inside the catalyst layers of various energy conversion devices, for instance polymer electrolyte membrane fuel cells (PEMFCs) and PEM electrolyzers. The catalytic activity and stability depend on various factors, such as the material properties, particle size and shape, and also the catalyst support. Various routes have been developed to fabricate such electrocatalyst nanoparticles mainly based on thermal, chemical and electrochemical approaches. In the thermal approach, catalyst precursor salts are thermally decomposed at several hundred degrees Celsius in a furnace, often under inert or reducing atmosphere. One promising alternative is the use of photonic curing (also known as flash light irradiation) where a Xe flash lamp provides under ambient conditions high energy light pulses with an emission spectrum ranging from around 300 nm up to 1000 nm. Depending on the light absorbing properties of the irradiated material, a thin film can be heated up to several hundred degrees Celsius on the millisecond scale [1]. This technique is usually applied to sinter metal nanoparticle deposits for flexible electronics. Metal and metal alloy nanoparticles can be made by the photonic curing of the corresponding precursor salts in an indirect as well as direct way [2-4]. On the direct route, the absorption of the flash lamp light is only realized by a light absorbing support material while the coated precursor is not directly affected. The thermal decomposition of the precursor is then initiated by the heat transfer from the support material to the precursor. On the second route, the metal precursors absorb the light directly. We made a detailed analysis of the photonic curing process for the direct formation of Pt and Pt alloy nano- and microparticles in terms of light absorbing properties of the precursor and support material, and we analyzed the influence of the precursor film thickness, wetness and spreading. Various light absorbing (e.g., carbon nanotubes) and non-absorbing (quartz glass) substrate materials have successfully been tested. In order to deposit well defined metal and metal alloy precursor layers, a state-of-the art inkjet printer platform with three parallel printheads and integrated photonic curing has been used. Dispensing metal precursor inks by using inkjet printing has already demonstrated its huge potential for printing of electrocatalyst materials [5]. We obtained combinatorial libraries of Pt and Pt alloy nano- and microparticles on a large scale within few minutes. The catalyst particles where then characterized using spectroscopic and electrochemical methods. Soft probe scanning electrochemical microscopy (SECM) [6] with arrays of contact mode microelectrodes was used for the rapid screening of the catalyst libraries in constant distance mode. [1] K.A. Schroder, S.C. McCool, W.F. Furlan, NSTI Nanotech 2006 Technical Proceedings 2006, 3, 198 - 201. [2] S. H. Park, H. S. Kim, J. Electrochem. Soc. 2015, 162, F204-F210. [3] K. Jang, S. Yu, S. H. Park, H. S. Kim, H. Ahn, J. Alloys Compd. 2014, 618, 227-232. [4] A. Lesch, V. Costa Bassetto, H. H. Girault, in preparation. [5] E. Reddington, A. Sapienza, B. Gurau, R. Viswanathan, S. Sarangapani, E. S. Smotkin, T. E. Mallouk, Science 1998, 280, 1735-1737. [6] A. Lesch, B. Vaske, F. Meiners, D. Momotenko, F. Cortés-Salazar, H. H. Girault, G. Wittstock; Angew. Chem. Int. Ed. 2012, 51, 10413-10416. Figure 1

Highly Selective Hydrogenation of R-(+)-Limonene to (+)-p-1-Menthene in Batch and Continuous Flow Reactors

In our study, heterogeneous catalysts based on different active metal nanoparticles (Pt, Pd, and Ru) and supports (carbon, silica, and alumina) were systematically tested in hydrogenation of limonene under mild reaction conditions (room temperature, 3 bar H2). The heterogeneous catalyst Pt/C was found highly active and selective for the reduction of limonene into the partial hydrogenation product (+)-p-1-menthene. Pt/C and Pt/Al2O3 are the most active systems among the series of commercially available catalysts that have been investigated. The catalytic activity and stability of Pt/C remained high throughout the recycling tests under batch conditions and thus allowed for the implementation of this catalytic system into continuous flow operations. The selective hydrogenation of the terminal over the internal C═C bond of limonene was rationalized by detailed kinetic studies which revealed an 8-fold difference in reaction rate between the two reactions.

A Novel Magnetically Recoverable Ni-CeO2-x/Pd Nanocatalyst with Superior Catalytic Performance for Hydrogenation of Styrene and 4-Nitrophenol.

Metal/support nanocatalysts consisting of various metals and metal oxides not only retain the basic properties of each component but also exhibit higher catalytic activity due to their synergistic effects. Herein, we report the creation of a highly efficient, long-lasting, and magnetic recyclable catalyst, composed of magnetic nickel (Ni) nanoparticles (NPs), active Pd NPs, and oxygen-deficient CeO2-x support. These hybrid nanostructures composed of oxygen deficient CeO2-x and active metal nanoparticles could effectively facilitate diffusion of reactant molecules and active site exposure that can dramatically accelerate the reaction rate. Impressively, the rate constant k and k/m of 4-nitrophenol reduction over 61 wt % Ni-CeO2-x/0.1 wt % Pd catalyst are 0.0479 s-1 and 2.1 × 104 min-1 g-1, respectively, and the reaction conversion shows negligible decline even after 20 cycles. Meanwhile, the optimal 61 wt % Ni-CeO2-x/3 wt % Pd catalyst manifests remarkable catalytic activity toward styrene hydrogenation with a high TOF of 6827 molstyrene molPd-1 h-1 and a selective conversion of 100% to ethylbenzene even after eight cycles. The strong metal-support interaction (SMSI) between Ni NPs, Pd NPs, and oxygen-deficient CeO2-x support is beneficial for superior catalytic efficiency and stability toward hydrogenation of styrene and 4-nitrophenol. Moreover, Ni species could boost the catalytic activity of Pd due to their synergistic effect and strengthen the interaction between reactant and catalyst, which seems responsible for the great enhancement of catalytic activity. Our findings provide a new perspective to develop other high-performance and magnetically recoverable nanocatalysts, which would be widely applied to a variety of catalytic reactions.

Ceria-supported small Pt and Pt3Sn nanoparticles for NOx-assisted soot oxidation

Introduced herein are small Pt and Pt3Sn nanoparticles, stabilized with organosilane or organostannane and impregnated on ceria support, as active sites for NOx-assisted soot oxidation reaction. The catalysts have been tested with four reactions: CO oxidation, NO oxidation, NOx-free soot oxidation and finally NOx-assisted soot oxidation. Our Pt nanoparticles reportedly possess remarkable catalytic activities in CO oxidation, as they actively convert CO at 50°C, while the alloy Pt3Sn nanoparticles are active at higher temperature. The Pt nanoparticles also mediate more actively NO oxidation than their alloy counterpart, leading to more NO2 production beneficial for soot oxidation. The influence of Pt and Pt3Sn active sites on the catalytic activity during NOx-free soot oxidation becomes less prominent than the morphology, due to the high dependency of the reaction on catalyst structure. The presence of Sn, nevertheless, induces lower oxidation reaction temperature. Finally, in the presence of NOx, the metal active sites undoubtedly boost the catalytic activity of soot oxidation. Pt/CeO2-NC (NC stands for “nanocubes”), reported herein as our most achieving catalyst, demonstrates a remarkable activity, lowering the oxidation temperature at about 80°C, thanks to the synergy of the active metal nanoparticles and reactive ceria nanocubes. Surprisingly, the catalytic activity of the alloy counterpart (Pt3Sn/CeO2-NC) is close to Pt/CeO2-NC, indicating the potential of the catalyst as an alternative to reducing the employment of precious metal in automotive catalysis. The thermally aged Pt catalysts have demonstrated good resistance to sintering, thanks to the outer protection by silica patches. However, the catalytic activities of the aged Pt3Sn catalysts rely heavily on support morphology.

Bismuth Oxyhalide Induced Growth of Pt Nanoparticles within Mesoporous Alumina Films and their Use as Reusable Catalyst for Chromium(VI) Reduction

AbstractGreen and efficient immobilization of catalytically active metal nanoparticles into porous supporting materials and their successful application in environmental remediation is of important scientific interest in practice. Herein, we established a new role of bismuth oxyhalides (BiOX) to produce Pt NPs inside mesoporous alumina to develop the nanocomposite film (Pt‐ BiOCl0.8Br0.2/Al2O3) using ethanol as reducing agent. Those films were applied as reusable catalysts for the reduction of highly toxic CrVI ions into CrIII by formic acid at room temperature. Different amounts of bismuth oxyhalides were loaded with alumina to generate Pt NPs and found 2 mol% BiOCl0.8Br0.2 loaded film showed optimum activity towards Pt generation and highest catalytic conversion of CrVI with the rate constant 0.177 min−1 which is very high considering any thin film as catalyst.

Robust, non-fouling liters-per-day flow synthesis of ultra-small catalytically active metal nanoparticles in a single-channel reactor

Robust, non-fouling, litres-per-day continuous synthesis of catalytically active palladium nanoparticles using triphasic segmented flow in a hybrid milli-meso flow reactor.

Visualizing the Cu/Cu2(O) Interface Transition in Nanoparticles with Environmental Scanning Transmission Electron Microscopy.

Understanding the oxidation and reduction mechanisms of catalytically active transition metal nanoparticles is important to improve their application in a variety of chemical processes. In nanocatalysis the nanoparticles can undergo oxidation or reduction in situ, and thus the redox species are not what are observed before and after reactions. We have used the novel environmental scanning transmission electron microscope (ESTEM) with 0.1 nm resolution in systematic studies of complex dynamic oxidation and reduction mechanisms of copper nanoparticles. The oxidation of copper has previously been reported to be dependent on its crystallography and its interaction with the substrate. By following the dynamic oxidation process in situ in real time with high-angle annular dark-field imaging in the ESTEM, we use conditions ideal to track the oxidation front as it progresses across a copper nanoparticle by following the changes in the atomic number (Z) contrast with time. The oxidation occurs via the nucleation of the oxide phase (Cu2O) from one area of the nanoparticle which then progresses unidirectionally across the particle, with the Cu-to-Cu2O interface having a relationship of Cu{111}//Cu2O{111}. The oxidation kinetics are related to the temperature and oxygen pressure. When the process is reversed in hydrogen, the reduction process is observed to be similar to the oxidation, with the same crystallographic relationship between the two phases. The dynamic observations provide unique insights into redox mechanisms which are important to understanding and controlling the oxidation and reduction of copper-based nanoparticles.

Water-dispersible Hollow Microporous Organic Network Spheres as Substrate for Electroless Deposition of Ultrafine Pd Nanoparticles with High Catalytic Activity and Recyclability.

Microporous organic networks (MONs) have been considered as an ideal substrate to stabilize active metal nanoparticles. However, the development of highly water-dispersible hollow MONs nanostructures which can serve as both the reducing agent and stabilizer is highly desirable but still challenging. Here we report a template-assisted method to synthesize hollow microporous organic network (H-MON) spheres using silica spheres as hard template and 1,3,5-triethynylbenzene as the building blocks through a Glaser coupling reaction. The obtained water-dispersible H-MON spheres bearing sp- and sp2 -hybridized carbon atoms possess a highly conjugated electronic structure and show low reduction potential; thus, they can serve as a reducing agent and stabilizer for electroless deposition of highly dispersed Pd clusters to form a Pd/H-MON spherical hollow nanocomposite. Benefitting from their high porosity, large surface area, and excellent solution dispersibility, the as-prepared Pd/H-MON hollow nanocomposite exhibits a high catalytic performance and recyclability toward the reduction of 4-nitrophenol.

Use of Monosaccharides in Metal-Catalyzed Coupling Reactions

The addition of monosaccharides to metal-catalyzed coupling reactions can be beneficial in terms of decreasing the time required, chemical waste products and overall cost of the process. Monosaccharides are used in a number of different ways, including (a) acting as a ligand for the metal, (b) providing the appropriate reduction potential for a chemical process and (c) acting as a reducing agent for the formation and stabilization of catalytically active metal nanoparticles. Recently, there has been a significant amount of research in this growing field and there is thus the potential for the addition of monosaccharides to coupling reactions to have a significant impact on the synthesis of the important small molecules on which we have all come to rely. This Perspectives Article will cover recent developments in the addition of monosaccharides to metal-catalyzed coupling reactions with an emphasis on their utility and limitations in order to facilitate the further development of this exciting area of rese...

From material design to mechanism study: Nanoscale Ni exsolution on a highly active A-site deficient anode material for solid oxide fuel cells

Nonstoichiometric perovskites with active metal nanoparticles exsolved on the surface have shown promising potential in energy and environmental applications ranging from catalysis to power generation. In this work, a novel Sc-based A-site deficient perovskite material La0.4Sr0.4Sc0.9Ni0.1O3−δ (LSSN) is reported as a highly active anode for intermediate-temperature solid oxide fuel cells. The material is designed using both thermodynamical analysis and ab-initio simulations. The drop in Gibbs free energy for Ni in H2 is substantial in comparison to the other elements, and density functional theory simulations indicate that the segregation of Ni towards the surface is energetically favored. Spherical Ni nanoparticles with well-defined boundaries are exsolved on the surface of LSSN after reduction in hydrogen, and the reduced samples show a high electrochemical catalytic activity in symmetric-cell measurements with an area specific resistance as low as 0.055Ωcm2 at 800°C in humid H2. Insights into the exsolution mechanism are also derived from both experiments and analytical modeling. Experimental observations show a patterned particle distribution, which is consistent with heterogeneous nucleation. The particle size evolution is investigated using the strain, reactant, and diffusion limited analytical models. The mechanistic insights gained here can be broadly applied to design more efficient materials capable of exsolution and to control the nanoparticle growth and coverage.

Nanoparticles of Ni-Co Alloy Derived from Layered Double Hydroxides and Their Catalytic Performance for CO Methanation

Sintering of the active metallic nanoparticles and carbon deposition are the key problems faced for CO methanation catalysts. For overcoming those problems, bimetallic nanocatalyst is a promising route. In this work, a series of Al2O3 supported Ni-Co alloy catalysts were prepared by reducing NiCoAl layered double hydrotalcite (LDHs), and characterized with X-ray diffraction (XRD), temperature programmed reduction TPR, N2 adsorption-desorption, transmission electron microscopy (TEM) and temperature programed oxidation (TPO) techniques. The resultant catalysts were mesoporous with nanoparticles of Ni-Co alloy ranging from 7.9[Formula: see text]nm to 9.2[Formula: see text]nm which were highly dispersed in alumina matrix. The sample Ni7Co3-Al2O3 catalysts showed very good catalytic performance during the stability test at 500/600[Formula: see text]C for 300[Formula: see text]h, meanwhile exhibited excellent anti-sintering ability and anti-carbon deposition ability, owing to the formation of Ni-Co alloy and the feature of LDHs. This strategy for improving anti-sintering and anti-carbon deposition should be extendable for catalysts of other reactions.

Robust Polymer-Coated Diamond Supports for Noble-Metal Nanoparticle Catalysts

Much research has been done using polymer and silica particles as support materials for catalytically active noble metal nanoparticles, but these materials have limited stability in organic solvents or under extreme reaction conditions such as high pH. Here we present a robust and versatile composite polymer-diamond support for ultrasmall noble metal nanoparticles combining chemical and mechanical stability of diamond with the chemical versatility of a polymer. By exploiting the rich surface chemistry of nanodiamond and incorporating a reactive thiol–ene polymer, a thinly coated polymer-diamond composite was formed. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) confirmed the presence of the polymer. High resolution scanning transmission electron microscopy (S/TEM) analysis showed that in situ growth of gold, platinum and palladium nanoparticles produced high density coverage at the polymer-diamond support surface. Energy dispers...

Toward Self-Assembled Plasmonic Devices: High-Yield Arrangement of Gold Nanoparticles on DNA Origami Templates

Plasmonic structures allow the manipulation of light with materials that are smaller than the optical wavelength. Such structures can consist of plasmonically active metal nanoparticles and can be fabricated through scalable bottom-up self-assembly on DNA origami templates. To produce functional devices, the precise and high-yield arrangement of each of the nanoparticles on a structure is of vital importance as the absence of a single particle can destroy the functionality of the entire device. Nevertheless, the parameters influencing the yield of the multistep assembly process are still poorly understood. To overcome this deficiency, we employed a test system consisting of a tubular six-helix bundle DNA origami with binding sites for eight oligonucleotide-functionalized gold nanoparticles. We systematically studied the assembly yield as a function of a wide range of parameters such as ionic strength, stoichiometric ratio, oligonucleotide linker chemistry, and assembly kinetics by an automated high-throughput analysis of electron micrographs of the formed heterocomplexes. Our optimized protocols enable particle placement yields up to 98.7% and promise the reliable production of sophisticated DNA-based multiparticle plasmonic devices for applications in photonics, optoelectronics, and nanomedicine.

Plasmonic Nanospectroscopy of Platinum Catalyst Nanoparticle Sintering in a Mesoporous Alumina Support

In situ plasmonic nanospectroscopy has proven useful to bridge the pressure gap in heterogeneous catalysis. The method has, however, so far been used only for idealized two-dimensional systems without the structural complexity of realistic three-dimensional porous oxides, which generally are used as supports for the catalytically active metal nanoparticles. Here, we report a generic method that addresses this structural gap by demonstrating the possibility to use nanoplasmonic sensing to monitor surface processes in a traditional three-dimensional mesoporous alumina matrix, wet-impregnated with Pt nanoparticles. The capability of the experimental platform is illustrated by measuring sintering kinetics of the Pt nanoparticles inside the mesoporous matrix under oxidizing conditions at atmospheric pressure and at temperatures up to 625 °C. The study thus demonstrates in operando plasmonic nanospectroscopy of realistic, commercial catalyst systems.