Solid Support Material Research Articles

Capillary forces drive buckling, plastic deformation, and break-up of 3D printed beams.

Capillary forces acting at the interfaces of soft materials lead to deformations over the scale of the elastocapillary length. When surface stresses exceed a material's yield stress, a plastocapillary effect is expected to arise, resulting in yielding and plastic deformation. Here, we explore the interfacial instabilities of 3D-printed fluid and elastic beams embedded within viscoelastic fluids and elastic solid support materials. Interfacial instabilities are driven by the immiscibility between the paired phases or their solvents. We find that the stability of an embedded structure is predicted from the balance between the yield stress of the elastic solid, τy, the apparent interfacial tension between the materials, γ', and the radius of the beam, r, such that τy > γ'/r. When the capillary forces are sufficiently large, we observe yielding and failure of the 3D printed beams. Furthermore, we observe new coiling and buckling instabilities emerging when elastic beams are embedded within viscous fluid support materials. The coiling behavior appear analogous to elastic rope coiling whereas the buckling instability follows the scaling behavior predicted from Euler-Bernoulli beam theory.

Scalable 3D printing method for the manufacture of single-material fluidic devices with integrated filter for point of collection colourimetric analysis

Assembly and bonding are major obstacles in manufacturing of functionally integrated fluidic devices. Here we demonstrate a single-material 3D printed device with an integrated porous structure capable of filtering particulate matter for the colourimetric detection of iron from soil and natural waters. Selecting a PolyJet 3D printer for its throughput, integrated filters were created exploiting a phenomenon occurring at the interface between the commercially available build material (Veroclear-RGD810) and water-soluble support material (SUP707). The porous properties were tuneable by varying the orientation of the print head relative to the channel and by varying the width of the build material. Porous structures ranging from 100 to 200 μm in thickness separated the sample and reagent chambers, filtering particles larger than 15 μm in diameter. Maintaining the manufacturing throughput of the Polyjet printer, 221 devices could be printed in 1.5 h (∼25 s per device). Including the 12 h post-processing soak in sodium hydroxide to remove the solid support material, the total time to print and process 221 devices was 13.5 h (3.6 min per device), with a material cost of $2.50 each. The applicability of the fluidic device for point of collection analysis was evaluated using colourimetric determination of iron from soil slurry and environmental samples. Following the reduction of Fe3+ to Fe2+ using hydroxylammonium chloride, samples were introduced to the fluidic device where particulate matter was retained by the filter, allowing for particulate-free imaging of the red complex formed with 1,10-phenanthroline using a smartphone camera. The calibration curve ranged from of 1–100 mg L−1 Fe2+ and good agreement (95%) was obtained between the point of collection device and Sector Field ICP-MS.

Versatile Process for the Preparation of Nanocomposite Sorbents: Phosphorus and Arsenic Removal.

Nanomaterials are being increasingly utilized for environmental remediation. The use of these materials, however, is greatly hindered due to challenges in material handling and deployment. Here we present a novel nanocomposite synthesis method based on the direct growth of nanoparticles on and within solid support materials, referred to as Crescoating. In this work, iron and copper nanoparticles have been grown on polyurethane support materials using this process and applied as sorbents for dissolved phosphorus and arsenic in water, respectively. These nanocomposite sorbents exhibit rapid sorption with saturation occurring in less than 5 min. The loading capacity is 104.8 mg PO43- g-1 and 254.4 mg As(III) g-1 for the iron and copper nanocomposite sorbents respectively, which is up to four times higher than commercially available alternatives. In addition, phosphorus can be recovered from the iron nanocomposite sorbent. This coating by growth process produces nanocomposites that do not emit particles and has the capability to be scaled and applied to other nanoparticles for diverse pollutant sorption applications.

Biofilm reactors for value-added products production: An in-depth review

Biofilms in the environment can both detrimental and beneficial effects. On the other hand, biofilms can be useful for wastewater treatment, bioremediation, and removal of toxic pollutants. Furthermore, biofilms can be used for the productions of value-added products (VAPs) such as biofuels, polysaccharides, antibiotics, organic acids, vitamins, and enzymes. To establish biofilms in the reactors, solid support materials (SSMs) made of inorganic compounds and various agricultural by-products. For these, several types biofilm reactors (BRs) have been utilized such as stirred tank biofilm (bio)reactor (STBR), fluidized-bed biofilm (bio)reactor (FBR), fixed/packed-bed biofilm (bio)reactor (PBR), rotary disc biofilm (bio)reactor (RDR)/rotating biological contactor (RBC), membrane biofilm (bio)reactor (MBR), moving bed biofilm (bio)reactor (MBBR) and trickling filter biofilm (bio)reactor (TBR). The benefits of BRs: increase product yield, provide logarithmic phase growth, reduce lag phase and fermentation time for repeated fermentations, increase biomass population, provide resistance toward toxic compounds, and improve product recovery. This review paper will summarize the literature for biofilm formation and structure, BR types, biofilm support materials, and various VAPs-produced by using BRs. • Biofilm reactors are effective tools for the production of added-value products. • Support materials are used to form biofilm in the biofilm reactors. • Biofilm support materials can be of organic and inorganic structure. • They increase product yield and biomass population and improve product recovery. • Modeling provides information about kinetic-metabolic nature of the fermentations.

3D-Printed Labware for High-Throughput Immobilization of Enzymes.

In continuous flow biocatalysis, chemical transformations can occur under milder, greener, more scalable, and safer conditions than conventional organic synthesis. However, the method typically involves extensive screening to optimize each enzyme's immobilization on its solid support material. The task of weighing solids for large numbers of experiments poses a bottleneck for screening enzyme immobilization conditions. For example, screening conditions often require multiple replicates exploring different support chemistries, buffer compositions, and temperatures. Thus, we report 3D-printed labware designed to measure and handle solids in multichannel format and expedite screening of enzyme immobilization conditions. To demonstrate the generality of these advances, alkaline phosphatase, glucose dehydrogenase, and laccase were screened for immobilization efficiency on seven resins. The results illustrate the requirements for optimization of each enzyme's loading and resin choice for optimal catalytic performance. Here, 3D-printed labware can decrease the requirements for an experimentalist's time by >95%. The approach to rapid optimization of enzyme immobilization is applicable to any enzyme and many solid support resins. Furthermore, the reported devices deliver precise and accurate aliquots of essentially any granular solid material.

Optimization Strategies for Purification of Mycophenolic Acid Produced by Penicillium brevicompactum.

The microbial fermentation of Penicillium brevicompactum produces secondary metabolite mycophenolic acid (MPA), which exhibits antifungal, antiviral, antibacterial, and antitumor activity. It is also a potent, selective, non-competitive, and reversible inhibitor of the human inosine monophosphate dehydrogenase (IMPDH). This study is an attempt to optimize the MPA production through a fermentation process using Penicillium brevicompactum and its further purification process optimization. In the batch fermentation process, the maximum concentration of MPA (1.84g/L) was attained in a 3.7L stirred tank reactor. Response surface methodology (RSM) using central composite design (CCD) was employed as a statistical tool to investigate the effect of pH, the volume of eluent and flow rate of the mobile phase on MPA purification process. Under optimum conditions, the experimental yield was observed to be 84.12%, which matched well with the predictive yield of 84.42%. High-performance liquid chromatography (HPLC) and Fourier-transform infrared spectroscopy (FTIR) analysis of the fermented product was carried out to confirm the presence of mycophenolic acid. The MPA purification was done by using column chromatography technique. The purification of broth involved mycophenolic acid extraction by selecting different solvents on the basis of polarity and the extraction efficiency of solvent. Various solid support materials were used for MPA purification in column chromatography. The MPA recovery through alumina column was observed to be 84.12% under the optimum conditions, which was maximum elution as compared with other support materials. The optimized purification process yielded pure MPA crystals.

Buckypaper Thickness Dependent Bilirubin Oxidase Electrochemistry

Among various electrode materials, freestanding buckypapers made from carbon nanotubes have gained significance as they do not require a solid support material and thus facilitate miniaturization. We present the effect of buckypaper (BP) thickness on the electrocatalytic properties of bilirubin oxidase (BOD) enzyme. In this study, we prepared BPs of varying thicknesses ranging from 87 micron, the minimum thickness for suitable handling with good stability in aqueous experiments, to 380 micron. BOD was adsorbed overnight onto the BPs. We determined that the lower range BP thickness (< 220 micron) exhibited better sigmoidal shaped electrocatalytic currents than the higher BP thickness based BOD biofilms with larger capacitive currents. Oxygen reduction current density of up to 3 mA cm–2 is achieved without use of any redox mediators or tedious electrode modifications. Using the 87 micron thick BP as the representative case, we were able to obtain distinguishable peaks for all Cu sites of BOD, and assigned their types, T1, T2, and T3, based on peak-width at half-maximum in anaerobic cyclic voltammograms. Our peak assignment is further supported by the appearance of dual electrocatalytic reduction waves at higher scan rate region (> 10 mV s-1) in oxygen-saturated buffer, which is identified to be driven by an ~ 3.5-times faster electron transfer rate from the buckypaper to the T2/T3 center than the T1 Cu site. Findings from this study are significant for designing new enzyme electrocatalytic systems and biosensors. In addition, accessing electrochemical and catalytic properties of often-buried inaccessible redox centers of many important metalloenzymes can be achieved by the freestanding BP design of optimal thickness.

Role of Cobalt Oxide-Based Catalysts for Styrene Production: A Review on Significance of Various Promoters, Calcination Temperature, Chemical Behavior of Support Materials and Synthesis Procedure

The direct CO2 oxidative dehydrogenation of ethyl benzene (ODH-EB) is a great potential for the production of valuable styrene monomer. In contrast, past/present styrene (ST) synthesis is mainly obtained from oxidative dehydrogenation of ethyl benzene (EB) and being transformed into pilot scale under CO2 atmosphere. It was due to few unresolved restrictions existed in the synthesis of styrene monomer using the steam assisted process and commercial ST production technology. These problems are being rectified by ODH-EB process using CO2 as a soft oxidant. Therefore, ODH of EB is well-known high temperature process to convert the EB (petroleum by product) into valuable ST monomer through the utilizing of CO2. Present study clearly explains the concise history of dehydrogenation process used to convert EB to ST monomer, which is essential feedstock in the wide range of industrial commodities production. In this discussion we majorly devoted to design, development and synthesis of different Co based catalysts by applying different support materials such as SiO2, MgO, MgAl2O4 and γ-Al2O3 respectively. Moreover, this study extensively deals with chemical behavior of oxidants, utilization of viable active promoters and its characteristics features in the oxidative dehydrogenation process. Different reaction mechanisms in the ODH of EB process to describe CO2 utilization as well as surface styrene monomer formation and evaluation of other by products were discussed widely in this review paper. The surface acidic and basic chemistry of various support materials, its preparation, utilization and its catalytic activity applications have been discussed. Acidic–basic textural properties of different solid oxide support materials have been extensively illustrated through incorporation of variety active metallic oxide and promoters. The catalyst activity evaluation in ODH of EB process as well as plausible reaction mechanism of styrene monomer formation has been explained.

Cucurbit[6]uril Glued Magnetic Clay Hybrid as a Catalyst for Nitrophenol Reduction

Cucurbit[6]uril (CB6) was used as a molecular glue for preparation of a new hybrid material using exfoliated montmorillonite clay and copper ferrite magnetic nanoparticles. Hybrid material was prepared by ultra-sonication method and characterised by FTIR, DR UV–Vis, XRD, FE-SEM, TEM, TGA and BET surface area measurements. The catalytic activity of the hybrid was examined for reduction of a potential industrial pollutant, 4-nitrophenol. The hybrid exhibited good catalytic activity (kapp 0.026 s−1) with low catalyst loading (∼0.05 mg/ml) and was found suitable for large scale application. The hybrid catalyst was successfully recycled and reused up to eight reaction cycles without any loss in catalytic activity. Here, CB6 acted like a molecular glue stabilising the hybrid catalyst. This greatly improved reusability in comparison with bare nanoparticles and clay composite. This approach where CB6 was used as a molecular glue can be conveniently utilised for stabilising nanoparticles on various solid support materials to develop better quality catalysts, composites and hybrid materials.

Buckypaper-Bilirubin Oxidase Biointerface for Electrocatalytic Applications: Buckypaper Thickness.

Electrode materials play an important role on the electrocatalytic properties of immobilized biocatalysts. In this regard, achieving direct electronic communication between the electrode and redox sites of biocatalysts eliminates the need for additional electron transfer mediators for biocatalytic applications in fuel cells and other electrochemical energy devices. In order to increase electrocatalytic currents and power in fuel cells and metal-air batteries, conductive carbon-nanostructure-modified large surface area electrodes are quite useful. Among various electrode materials, freestanding buckypapers made from carbon nanotubes have gained significance as they do not require a solid support material and thus facilitate miniaturization. In this article, we present the effect of buckypaper (BP) thickness on the electrocatalytic properties of a bilirubin oxidase (BOD) enzyme. In this study, we prepared BPs of varying thicknesses ranging from 87 μm, the minimum thickness for suitable handling with a good stability in aqueous experiments, to 380 μm. BOD was adsorbed overnight onto the BPs, mostly via hydrophobic and π-π interactions since the nanotubes used were not chemically functionalized. Furthermore, intercalation of the BOD molecules onto the nanotubes' multicylindrical network is feasible. We determined that the lower range BP thickness (<220 μm) exhibited better sigmoidal shaped electrocatalytic currents than the higher BP-thickness-based BOD biofilms with larger capacitive currents. An oxygen reduction current density of up to 3 mA cm-2 is achieved without the use of any redox mediators or tedious electrode modifications. Using the 87 μm thick BP as the representative case, we were able to obtain distinguishable peaks for all Cu sites of BOD and assign their types, T1, T2, and T3, based on the peak-width at half-maximum in anaerobic cyclic voltammograms. Our peak assignment is further supported by the appearance of dual electrocatalytic oxygen reduction waves at a higher scan rate region (>10 mV s-1) in oxygen-saturated buffer, which is identified to be driven by an ∼3.5 times faster electron transfer rate from the buckypaper to the T2/T3 center than the T1 Cu site. Findings from this study are significant for designing enzyme electrocatalytic systems and biosensors in general and fuel cells and aerobic energy storage devices in particular, where the cathodic oxygen reduction current is often inadequate.

Admicelles in open-tube capillaries for chromatography and electrochromatography

Surfactant bilayers or admicelles at the solid surface-liquid interface inside 50–200 μm inner diameter (i.d.) open-tube fused-silica capillaries were developed as ‘soft’ stationary pseudophases for the liquid chromatographic (LC) separations of neutral and charged analytes. Admicelles were formed in-situ from buffered aqueous mobile phases with cetytrimethylammonium bromide at concentrations between the critical surface aggregation concentration and critical micelle concentration, which were determined by electroosmotic flow measurements using capillary electrophoresis. There were no micelles in the mobile phase solution. Also, there was no solid phase that is classically required in LC. Pressure and voltage driven modes or open-tubular admicellar liquid chromatography (OT-AMLC) and electrochromatography, respectively were proposed based on the separation of neutral analytes. The parameters (i.e., pH, concentration of surfactant, salt, and methanol in the mobile phase and capillary i.d.) that affected the surprising chromatographic effect of admicelles at the interface were investigated. The analytical performance of OT-AMLC for small molecules were found acceptable. Applications to environmental water and biological (HepG cell line metabolism media) samples analysis with appropriate sample preparation procedures were also conducted. The use of pseudophases at the solid surface-liquid interface could be a viable solution to problems associated with the use of solid stationary or support materials in nano- and micro-liquid chromatography and electrochromatography.

Influence of silica architecture on the catalytic activity of immobilized glucose oxidase

Immobilizing enzymes on solid support materials is of great interest for many applications as it improves enzyme lifetime and enables its recycling. Synthetic mesoporous silica materials are widely used as supports for enzyme immobilization due to their high enzyme-loading capacity and their excellent mass transport properties through interconnected channels of mesopores. Much less is known about the enzyme support properties of naturally occurring mesoporous silica materials. These are readily available through the growth of diatoms, which biosynthesize hierarchically porous silica microshells with pore diameters ranging from 10 to 1000 nm. Here the authors investigated the performance as enzyme support materials of biosilica from three diatom species in comparison to synthetic silica materials. Using glucose oxidase (GOx) as a model enzyme, the authors determined the enzyme-loading capacities and the specific catalytic activities of the GOx-bearing (bio)silicas both under suspension conditions and in a flow-through setting. Remarkably, the specific activity of GOx was strongly dependent on the type of diatom biosilica material and in the best case was as high as on synthetic mesoporous silica. Porosity analysis of the materials points to an important role of large mesopores (diameters &gt;20 nm) for supporting a high specific activity of (bio)silica-immobilized GOx.

Single‐Site Molybdenum on Solid Support Materials for Catalytic Hydrogenation of N2‐into‐NH3

AbstractVery stable in operando and low‐loaded atomic molybdenum on solid‐support materials have been prepared and tested to be catalytically active for N2‐into‐NH3 hydrogenation. Ammonia synthesis is reported at atmospheric pressure and 400 °C with NH3 rates of approximately 1.3×103 μmol h−1 gMo−1 using a well‐defined Mo‐hydride grafted on silica (SiO2‐700). DFT modelling on the reaction mechanism suggests that N2 spontaneously binds on monopodal [(≡Si−O‐)MoH3]. Based on calculations, the fourth hydrogenation step involving the release of the first NH3 molecule represents the rate‐limiting step of the whole reaction. The inclusion of cobalt co‐catalyst and an alkali caesium additive impregnated on a mesoporous SBA‐15 support increases the formation of NH3 with rates of circa 3.5×103 μmol h−1 gMo−1 under similar operating conditions and maximum yield of 29×103 μmol h−1 gMo−1 when the pressure is increased to 30 atm.

Immobilized carbonic anhydrase: preparation, characteristics and biotechnological applications.

Carbonic anhydrase (CA) is an essential metalloenzyme in living systems for accelerating the hydration and dehydration of carbon dioxide. CA-catalyzed reactions can be applied in vitro for capturing industrially emitted gaseous carbon dioxide in aqueous solutions. To facilitate this type of practical application, the immobilization of CA on or inside solid or soft support materials is of great importance because the immobilization of enzymes in general offers the opportunity for enzyme recycling or long-term use in bioreactors. Moreover, the thermal/storage stability and reactivity of immobilized CA can be modulated through the physicochemical nature and structural characteristics of the support material used. This review focuses on (i) immobilization methods which have been applied so far, (ii) some of the characteristic features of immobilized forms of CA, and (iii) biotechnological applications of immobilized CA. The applications described not only include the CA-assisted capturing and sequestration of carbon dioxide, but also the CA-supported bioelectrochemical conversion of CO2 into organic molecules, and the detection of clinically important CA inhibitors. Furthermore, immobilized CA can be used in biomimetic materials synthesis involving cascade reactions, e.g. for bone regeneration based on calcium carbonate formation from urea with two consecutive reactions catalyzed by urease and CA.

Immunoassay of C-reactive protein by hot electron-induced electrochemiluminescence at polystyrene-carbon black composite electrodes

Aromatic Tb(III) chelates can be detected down to subnanomolar concentrations at polystyrene-carbon black composite electrodes on the basis of hot electron-induced electrochemiluminescence, and used as electrochemiluminescent labels in bioaffinity assays. The excitation mechanism is based on chemiluminescent reactions that are initiated by the field emission/tunnel emission of hot electrons from the composite electrode. The composition and the properties of the novel composite electrodes were studied in detail. Hot electron-induced electrochemiluminescence intensities obtainable with the present composite electrodes are comparable to the previously used metal/insulator-type electrodes without exhibiting considerable long-lived solid state electroluminescence background emission, unlike e.g. oxide-coated silicon and aluminum electrodes.C-reactive protein was finally determined in a heterogeneous sandwich-assay by using the present composite electrodes as a solid support material for the capture antibodies. The detection antibody was labeled with a commercially available Tb(II) chelate. Calibration curve for the determination of C-reactive protein was linear over two orders of magnitude and the detection limit was well below the clinical reference value, approx. 1 μg l−1. Disposable polystyrene-carbon black composite electrodes are superior alternatives for e.g. silicon-based electrodes due to the low cost, easier manufacturing process and a very good performance e.g. in immunoassays.

Macroscopic Model for Momentum Transport in Down-Flow Fluidization

Abstract Down-flow fluidization is an attractive unit operation because it allows having a smooth circulation of the fluid and the solid support material as well as an uninterrupted and controlled operation of the fluid. In addition, since the solid support material is less dense than the fluid, the pump energy consumption required for bed expansion is smaller in comparison with upward fluidization. Momentum transport in fluidized beds is usually modeled by macroscopic models, which are expressed in terms of effective-medium coefficients, by making analogies with transport in porous media. In practice, it is desirable to derive these models and to predict the involved coefficients in a reliable manner. For this reason, in this work we derive a macroscopic model for the hydrodynamics of down-flow fluidization, using the method of volume averaging obtaining a model with the form of Darcy’s law with a correction in the relative velocity of the fluid to the solid. A salient feature of the model is that it allows predicting the apparent permeability coefficient in different geometries, and under different transport conditions. Also, the average model obtained can be used for both types of fluidization, because it is not restricted by the flow direction.

A bimetallic Re(I)-NCS-Pt(II) solid-support chemosensor for the selective detection of dimethyl sulfide in spoiled meat

A new bimetallic Re(I)-NCS-Pt(II) complex ([Re(bpy)(CO)3(NCS)–Pt(DMSO)(Cl)2]; bpy=2,2′-bipyridine; DMSO=dimethyl sulfoxide) was synthesized and shown to exhibit excellent sensing activity towards a volatile biogenic sulfide in solution. The complex selectively responded to dimethyl sulfide (CH3SCH3) in the presence of a mixture of other volatile organic compounds (VOCs), with a binding constant (logK) of 3.85±0.02 in CHCl3. To enhance its application potential for commercial or home use, the complex was incorporated into a solid-support material (polyacrylonitrile (PAN)), which was reformed to have a special morphology with high polarity and porosity. Scanning electron microscopy images revealed significant morphology differences for the PAN materials reformed under different solvent conditions. The isolated fine PAN powder doped with the active complex (PAN-1) was integrated into a sensing device for the fast detection of CH3SCH3 in spoiled meat samples. In the present study, a robust, easy-to-use, and naked-eye-detectable sensing device was developed and demonstrated good performance in detecting CH3SCH3 selectively. The detection ability of the solid sensing device was found to be in good agreement with GC–MS, with a recovery of more than 90% (RSD%=4.3).

Chemiluminescence biosensor for hydrogen peroxide determination by immobilizing horseradish peroxidase onto PVA-co-PE nanofiber membrane

Poly(ethylene-co-polyvinyl alcohol) (PVA-co-PE) nanofiber membrane with abundant active hydroxyl groups on the surface was modified through a solid-phase synthesis process. The PVA-co-PE nanofibers with different average diameters ranging from 200 to 500nm were modified by cyanuric chloride and 1, 3-propanediamine. The aminated PVA-co-PE nanofiber membrane was subsequently biotinylated and then horseradish peroxidase (HRP) was successfully immobilized onto it. The morphologies, hydrophilicity and chemical structures of membranes surface were investigated by SEM, water contact angle, FTIR and XPS. The HRP-immobilized PVA-co-PE nanofiber membrane revealed high activity, efficiency, sensitivity and reusability when it was used to catalyze the luminol-H2O2 reaction. The results demonstrated that the HRP-immobilized PVA-co-PE nanofiber membrane could be a promising candidate as solid support materials for catalysis of Luminol-H2O2. The relative light unit (RLU) could run up to 5×105 when the H2O2 concentration was low to 1×10−15mol/L. The HRP-immobilized PVA-co-PE nanofiber membrane was the potential chemiluminescence biosensor which could be applied in biological, medical and food fields.

Wilkinson‐Type Immobilized Catalyst on Diamond Nanoparticles for Alkene Reduction

AbstractThe immobilization of heterogeneous catalysts on solid support materials is an important task of current catalytic and materials science research. We report here the development of a diamond nanoparticles‐based Wilkinson's type catalyst for the reduction of olefins to saturated hydrocarbons. The strategy is based on the formation of rhodium(I)‐modified nanodiamonds (NDs–Rh) using a surface‐immobilized catechol phosphane ligand, to which rhodium metal centers can be coordinated. The resulting material was characterized by solid‐state NMR spectroscopy, X‐ray photoelectron spectroscopy, thermogravimetry, and TEM before testing the catalytic efficiency of the catalyst. Excellent hydrogenation efficiency with yields in the range of 85–99 % could be obtained with these new NDs–Rh catalysts, which showed in addition good recyclability without loss of activity.

Single-atom catalysts gained a toehold

Mediating chemical reactions with a single catalytically active atom on a solid surface has seemed like a good idea, albeit a fanciful one, for some time. This singular approach to catalysis gained traction this year as researchers in several countries demonstrated that such reactions are indeed feasible. Tiny particles of a catalytic material—often a noble metal such as platinum—dispersed on a metal oxide or other solid support material are workhorses for industrial-scale chemical processes, including converting crude oil to valuable products such as gasoline. Compared with these conventional multiatom catalysts, single-atom versions would greatly reduce the consumption of costly and scarce precious metals. In addition, the atomic-scale uniformity would minimize unwanted reactions and by-products and simplify researchers’ efforts to deduce reaction mechanisms, a key step in making better catalysts. In one example this year, Abhaya K. Datye of the University of New Mexico and coworkers showed that exposin...