Publications

We present the use of an ultraporous permanently polarized hydroxyapatite (upp-HAp) catalyst for continuous and highly efficient production of formic acid (predominant) and acetic acid using wet CO2 (i.e. CO2 bubbled into liquid water) as a reagent. In all cases, reactions were conducted at temperatures ranging from 95 to 150 degrees C, using a CO2 constant flow of 100 mL s(-1), and without applying any external electric field and/or UV radiation. Herein, we study how to transfer such a catalytic system from batch to continuous reactions, focusing on the water supply (proton source): (1) wet CO2 or (2) liquid water in small amounts is introduced in the reactor. In general, the reduction of CO2 to formic acid predominates over the C-C bond formation reaction. On the other hand, when liquid water is added, two interesting outcomes are observed: (1) the yield of products is higher than in the first scenario (>2 mmol g(c)(-1)min(-1)) while the initial liquid water remains largely available due to the mild reaction temperature (95 degrees C); and (2) a high yield of ethanol (>0.5 mmol g(c)(-1)min(-1)) is observed at 120 degrees C, as a result of the increased efficiency of the C-C bond formation. Analysis of kinetic studies through temporal and temperature dependence shows that CO2 fixation is the rate limiting step, ruling out the competing effect of proton adsorption on the binding sites and confirming the crucial role of water. The activation energy for the CO2 fixation reaction has been determined to be 66 +/- 1 kJ mol(-1), which is within the range of conventional electro-assisted catalysts. Finally, mechanistic insights on the CO2 activation and role of the binding sites of upp-HAp are provided through isotopic-labeling ((CO2)-C-13) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) studies.

JTD Keywords: Butano, Challenges, Co2 reduction, Fuels, Hydrogenation, Mechanism, Nanomaterials, Noble-metal

This paper is aimed to develop ultrananoporous polarized hydroxyapatite (HAp) catalyst and evaluate its per-formance in transforming CO2 into useable ethanol considering three different scenarios: 1) a batch reaction using a mixture of CO2 and CH4 as feeding gas; 2) a batch reaction using as reactant exhaust gases captured from the fumes of diesel vehicles; and 3) a continuous flow reaction using pure CO2 as feeding gas. Ultrananoporous HAp scaffolds were prepared using a four-step process: 1) as prepared HAp powder was mixed with 60% wt. of a commercial hydrogel at low-temperature; 2) the resulting paste was shaped at low temperature to reduce the adhesion between the metallic tools and the mixture, enhancing the homogeneity of the sample; 3) the shaped paste was calcined in air by applying 1000 oC during 2 h to eliminate the hydrogel; and 4) an external DC electric field of 3 kV/cm was imposed at 1000 oC during 1 h to the calcined scaffold. The resulting polarized scaffolds both ultrananoporosity and catalytic activation. Thus, the mass: volume ratio of the ultrananoporous catalyst was much lower than that of conventional HAp catalyst (718 vs 5093 g/L. Furthermore, the ethanol yield was much higher (up to a factor of x21.4) for the ultrananoporous catalyst than for the compact one, allowing us to conclude that ultrananoporous polarized HAp catalyst is a promising technology for transforming CO2 into valuable chemical products from highly polluted gases, especially those coming from road, sea and air transport.

JTD Keywords: A: ceramics, Air pollution, Automotives, Batch reactions, Calcination, Carbon, Carbon dioxide, Co2 fixation, Co2 reduction, Desig, Electric fields, Environmental process, Ethanol, Exhaust gases, Feeding gas, Fumes, Hydrogels, Hydroxyapatite, Lows-temperatures, Nano-catalyst, Nanocatalysts, Polarized catalys, Polarized catalyst, Scaffolds, Temperature, ]+ catalyst

Polarized hydroxyapatite (p-HAp) has been used as a catalyst for the synthesis of urea coupling N-2, CO2 and water under mild reaction conditions when compared to classical nitrogen fixation reactions, such as the Haber-Bosch process. The reaction of 3 bar of N-2 and 3 bar of CO2 under UV illumination at 120 degrees C (for 48 h) results in a urea yield of 1.5 +/- 0.1 mmol per gram of catalyst (g(c)) with a selectivity close to 80%, whereas the reaction is not successful without UV irradiation. However, the addition of small amounts of NO (314 ppm) produces 15.2 +/- 0.6 and 4.6 +/- 0.4 mmol g(c)(-1) with and without UV illumination, respectively, with the selectivity in both cases being close to 100%. As nitrogen fixation without UV irradiation using p-HAp as a catalyst is a challenge, studies with NO have been conducted varying the reaction conditions (time, pressure and temperature). The results suggest a mechanism based on the production of NH4+ through the oxidation of N-2.

JTD Keywords: Carbon dioxide, Carbon,dinitrogen,reduction,nitrogen,ammonia,dioxid, Catalyst selectivity, Condition, Haber-bosch process, Hydroxyapatite, Irradiation, Metabolism, Mild reaction conditions, Nitrogen fixation, Pressure and temperature, Reaction conditions, Time pressures, Time-temperature, Urea, Uv illuminations, Without uv irradiations, ]+ catalyst

Charge exchange is the fundamental process that sustains cellular respiration and photosynthesis by shuttling electrons in a cascade of electron transfer (ET) steps between redox cofactors. While intraprotein charge exchange is well characterized in protein complexes bearing multiple redox sites, interprotein processes are less understood due to the lack of suitable experimental approaches and the dynamic nature of the interactions. Proteins constrained between electrodes are known to support electron transport (ETp) through the protein matrix even without redox cofactors, as the charges housed by the redox sites in ET are furnished by the electrodes. However, it is unknown whether protein ETp mechanisms apply to the interprotein medium present under physiological conditions. We study interprotein charge exchange between plant photosystem I (PSI) and its soluble redox partner plastocyanin (Pc) and address the role of the Pc copper center. Using electrochemical scanning tunneling spectroscopy (ECSTS) current-distance and blinking measurements, we quantify the spatial span of charge exchange between individual Pc/PSI pairs and ETp through transient Pc/PSI complexes. Pc devoid of the redox center (Pcapo) can exchange charge with PSI at longer distances than with the copper ion (Pcholo). Conductance bursts associated with Pcapo/PSI complex formation are higher than in Pcholo/PSI. Thus, copper ions are not required for long-distance Pc/PSI ETp but regulate its spatial span and conductance. Our results suggest that the redox center that carries the charge in Pc is not necessary to exchange it in interprotein ET through the aqueous solution and question the canonical view of tight complex binding between redox protein partners.

JTD Keywords: azurin, binding, blinking, crystal-structure, cupredoxin, current distance spectroscopy, electrochemical tunneling microscopy, proteinconductance, reduction, single metalloprotein, single molecule measurements, site, spectroscopy, Blinking, Cupredoxin, Current distance spectroscopy, Electrochemical tunneling microscopy, Interprotein electron transfer, Protein conductance, Single molecule measurements, State electron-transport

Alzheimer's disease is characterized by a combination of several neuropathological hallmarks, such as extracellular aggregates of beta amyloid (Aβ). Numerous alternatives have been studied for inhibiting Aβ aggregation but, at this time, there are no effective treatments available. Here, we developed the tri-component nanohybrid system AuNPs@POM@PEG based on gold nanoparticles (AuNPs) covered with polyoxometalates (POMs) and polyethylene glycol (PEG). In this work, AuNPs@POM@PEG demonstrated the inhibition of the formation of amyloid fibrils, showing a 75% decrease in Aβ aggregation in vitro. As it is a potential candidate for the treatment of Alzheimer's disease, we evaluated the cytotoxicity of AuNPs@POM@PEG and its ability to cross the blood-brain barrier (BBB). We achieved a stable nanosystem that is non-cytotoxic below 2.5 nM to human neurovascular cells. The brain permeability of AuNPs@POM@PEG was analyzed in an in vitro microphysiological model of the BBB (BBB-on-a-chip), containing 3D human neurovascular cell co-cultures and microfluidics. The results show that AuNPs@POM@PEG was able to cross the brain endothelial barrier in the chip and demonstrated that POM does not affect the barrier integrity, giving the green light to further studies into this system as a nanotherapeutic.

JTD Keywords: beta-amyloid, blood-brain barrier organ-on-a-chip, cellular uptake, citrate, cytotoxicity, electrocatalytic reduction, gold nanoparticles, hypothesis, nanorods, polyoxometalates, size, stability, surface, Alzheimers-disease, Blood–brain barrier organ-on-a-chip, Gold nanoparticles, Nanovehicle, Polyoxometalates, Β-amyloid

Permanently polarized hydroxyapatite (p-HAp) has been reported as a feasible green alternative to conventional catalysts for the selective conversion of CO2 into highly valuable chemical products. However, structural control and enhanced electrical properties achieved on p-HAp clearly contrast with other reported catalytic systems, where hydroxyapatite mainly acts as a support receiving much less attention. In this work we take advantage of the knowledge obtained on p-HAp to develop an HAp-based catalytic system composed of TiO2 nanoparticles deposited on p-HAp. It is important to stress that p-HAp is not only considered as a mechanical support but has been put in the spotlight for catalyst preparation and as an active catalytic part. Therefore, the use of p-HAp in this system has unveiled exceptional synergies with TiO2 attributed to the enhanced electrical properties of p-HAp, capable of attracting the photo-electrons generated in TiO2 nanoparticles avoiding electron-hole recombination. CO2 fixation reactions carried out under mild conditions (120 degrees C, 6 bar and under UV exposure) result in complete selectivity control of the C2 products, shifting from ethanol (201 mu mol g(catalyst)(-1)) for p-HAp alone to acetic acid (381 mu mol g(catalyst)(-1)) when TiO2 nanoparticles are loaded in the system. Considering the challenging CO2 activation energy and the high control of the selectivity achieved, we do believe that this novel approach can be considered as a starting point to explore other systems and reactions where control of the crystal structure and the enhanced electrical properties of HAp can play a crucial role in the final products, reaction conditions, yields and selectivities.

JTD Keywords: Behavior, Cobalt, Conversion, Methane, Ni, Oxidation, Performance, Reduction, Syngas production, Tio2

JTD Keywords: copper, emissions, ethanol productions, greenhouse gases, solar energy, sustainable catalysts, Environmental pollution, Reduction

Polarized hydroxyapatite (p-HAp), a calcium phosphate catalyst obtained at high temperature under intense electric field, has been used for the synthesis of ammonium starting from N2 and liquid water at low pressure (<6 bar) and temperatures below 120 C. The success of the nitrogen fixation process has been demonstrated by isotope labelling experiments using 15N2. Considering the optimal reaction conditions for the production of ammonium, the yield is as high as 154.6 +/- 25.8 mu mol/g of catalyst. The proposed synthesis exhibits three important advantages for its utilization in green chemistry environmental processes related to the recycling of polluted air. These are: i) the catalysts converts CO2 into valuable chemical products in addition of transforming N2 in ammonium; ii) the final energy balance is very favorable since no external electrical field is necessary to promote nitrogen and carbon fixation reactions; and iii) products are easily transferred to water favoring their extraction and avoiding the saturation of the catalyst.

JTD Keywords: Adsorbed nitrogen, Air pollution, Amino-acids, Electrophotosynthesis, Environmental process, Facile synthesis, Fixation, Functionalization, Hydroxyapatite, Nitride, Nitrogen reduction, Polarized catalyst

Photosynthesis is a fundamental process that converts photons into chemical energy, driven by large protein complexes at the thylakoid membranes of plants, cyanobacteria, and algae. In plants, water-soluble plastocyanin (Pc) is responsible for shuttling electrons between cytochrome b6f complex and the photosystem I (PSI) complex in the photosynthetic electron transport chain (PETC). For an efficient turnover, a transient complex must form between PSI and Pc in the PETC, which implies a balance between specificity and binding strength. Here, we studied the binding frequency and the unbinding force between suitably oriented plant PSI and Pc under redox control using single molecule force spectroscopy (SMFS). The binding frequency (observation of binding-unbinding events) between PSI and Pc depends on their respective redox states. The interaction between PSI and Pc is independent of the redox state of PSI when Pc is reduced, and it is disfavored in the dark (reduced P700) when Pc is oxidized. The frequency of interaction between PSI and Pc is higher when at least one of the partners is in a redox state ready for electron transfer (ET), and the post-ET situation (PSIRed-PcOx) leads to lower binding. In addition, we show that the binding of ET-ready PcRed to PSI can be regulated externally by Mg2+ ions in solution.

JTD Keywords: architecture, binding-site, complexes, ferredoxin, force spectroscopy, induced structural-changes, interprotein electron transfer, light-dependent interaction, mg2+ concentration, photosystem i, plastocyanin, probe, recognition, reduction, Force spectroscopy, Interprotein electron transfer, Light-dependent interaction, Photosynthetic reaction-center, Photosystem i, Plastocyanin, Single molecule measurements

Permanently polarized hydroxyapatite is a new material with electrical enhanced properties. This review discusses the advances in this material in terms of structure, properties and catalytic activity of green processes.

JTD Keywords: ammonia, bone, copper hydroxyapatite, electrophotosynthesis, nanoparticles, oxidation, phase-transition, reduction, Amino-acids

Polypropylene (PP) surgical meshes, with different knitted architectures, were chemically functionalized with gold nanoparticles (AuNPs) and 4-mercaptothiazole (4-MB) to transform their fibers into a surface enhanced Raman scattering (SERS) detectable plastic material. The application of a thin layer of poly[N-isopropylacrylamide-co-N,N'-methylene bis(acrylamide)] (PNIPAAm-co-MBA) graft copolymer, covalently polymerized to the mesh-gold substrate, caused the conversion of the inert plastic into a thermoresponsive material, resulting in the first PP implantable mesh with both SERS and temperature stimulus responses. AuNPs were homogeneously distributed over the PP yarns, offering a clear SERS recognition together with higher PNIPAAm lower critical solution temperature (LCST ∼ 37 °C) than without the metallic particles (LCST ∼ 32 °C). An infrared thermographic camera was used to observe the polymer-hydrogel folding-unfolding process and to identify the new value of the LCST, connected with the heat generation by plasmonic-resonance gold NPs. The development of SERS PP prosthesis will be relevant for the bioimaging and biomarker detection of the implant by using the plasmonic effect and Raman vibrational spectroscopy for minimally invasive interventions (such as laparoscopy), to prevent patient inflammatory processes. Furthermore, Raman sources have been proved to not damage the cells, like happens with near-infrared irradiation, representing another advantage of moving to SERS approaches. The findings reported here offer unprecedented application possibilities in the biomedical field by extrapolating the material functionalization to other nonabsorbable polymer made devices (e.g., surgical sutures, grapes, wound dressings, among others).

JTD Keywords: gold nanoparticles, poly(n-isopropylacrylamide), polymers, polypropylene, raman-spectroscopy, reduction, resonance, sers spectroscopy, size, surface functionalization, Gold nanoparticles, Polypropylene, Surface functionalization

The design of catalysts with controlled selectivity at will, also known as catalytic plasticity, is a very attractive approach for the recycling of carbon dioxide (CO2). In this work, we study how catalytically active hydroxyapatite (HAp) and brushite (Bru) interact synergistically, allowing the production of formic acid or acetic acid depending on the HAp/Bru ratio in the catalyst. Raman, wide angle X-ray scattering, X-ray photoelectron spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopy studies, combined with an exhaustive revision of the crystalline structure of the catalyst at the atomic level, allowed to discern how the Bru phase can be generated and stabilized at high temperatures. Results clearly indicate that the presence of OH– groups to maintain the crystalline structural integrity in conjunction with Ca2+ ions less bonded to the lattice fixate carbon into C1, C2 and C3 molecules from CO2 and allow the evolution from formic to acetic acid and acetone. In this way, the plasticity of the HAp-Bru system is demonstrated, representing a promising green alternative to the conventional metal-based electrocatalysts used for CO2 fixation. Thus, the fact that no electric voltage is necessary for the CO2 reduction has a very favorable impact in the final energetic net balance of the carbon fixation reaction. © 2021

JTD Keywords:

ethanol production & nbsp, brushite, co2 reduction, conversion, electrocatalytic reduction, electrode, formate, heterogeneous catalysis & nbsp, hydrogen evolution, insights, monetite, polarized hydroxyapatite,

JTD Keywords: added value chemicals, amino-acids, catalytic-hydrogenation, climate, design, electrochemical reduction, electroreduction, green co2 conversion to ethanol, nitrogen, photocatalytic reduction, polarized hydroxyapatite, recycling co2, sea-level, Acetone, Added value chemicals, Added-value chemicals, C-c coupling, Calcium apatites, Carbon dioxide, Carbon-dioxide, Co 2 reduction, Co2 reduction, Ethanol, Green co2 conversion to ethanol, Hard tissues, Hydroxyapatite, Mixtures, Morphology, Morphology and composition, Naturally occurring, Organic carbon, Phosphate minerals, Polarized hydroxyapatite, Recycling co2

A methodology to calculate analytical figures of merit is not well established for detection systems that are based on sensor arrays with low sensor selectivity. In this work, we present a practical approach to estimate the Resolving Power of a sensory system, considering non-linear sensors and heteroscedastic sensor noise. We use the definition introduced by Shannon in the field of communication theory to quantify the number of symbols in a noisy environment, and its version adapted by Gardner and Barlett for chemical sensor systems. Our method combines dimensionality reduction and the use of algorithms to compute the convex hull of the empirical data to estimate the data volume in the sensor response space. We validate our methodology with synthetic data and with actual data captured with temperature-modulated MOX gas sensors. Unlike other methodologies, our method does not require the intrinsic dimensionality of the sensor response to be smaller than the dimensionality of the input space. Moreover, our method circumvents the problem to obtain the sensitivity matrix, which usually is not known. Hence, our method is able to successfully compute the Resolving Power of actual chemical sensor arrays. We provide a relevant figure of merit, and a methodology to calculate it, that was missing in the literature to benchmark broad-response gas sensor arrays.

JTD Keywords: Gas sensor array, MOX sensors, Resolving Power, Sensor resolution, Dimensionality reduction, Machine olfaction

How do the sciences of mind and brain—neuroscience, psychology, cognitive science, and artificial intelligence (AI)—stand in relation to each other in the 21st century? This chapter proposes that despite our knowledge expanding at ever-accelerating rates, our understanding of the relationship between mind and brain is, in some important sense, becoming less and less. An increasing explanatory gap can only be bridged by a multi-tiered and integrated theoretical framework that recognizes the value of developing explanations at different levels, combining these into cross-level integrated theories, and directly contributing to new technologies that improve the human condition. Development of technologies that instantiate principles gleaned from the study of the mind and brain, or biomimetic technologies, is a key part of the validation process for scientific theories of mind and brain. We call this strategy for the integration of science and engineering a Living Machines approach. Following this path can lead not only to better science, and useful engineering, but also a richer view of human experience and of relationships between science, engineering, and art.

JTD Keywords: Convergent validation, Multi-tiered theories, Paradigms in cognitive science, Philosophy of science, Physical models, Reductionism