The frenetic global development is improving the average quality of life in an unprecedented way, but at the expense of increasing pressure on natural resources, environmental pollution and energy ...demand, which are being exacerbated by population growth and industrialization in developing countries. The energy demand probably is the one contributing the most to such a situation, thus urging the development of clean and renewable alternative energy sources in order to avoid an imminent energy crisis in the near future. A possible solution is a society in which most energy needs are fulfilled by photoinduced or electrochemical water-splitting, storing solar energy as hydrogen and dioxygen gas, and releasing the chemical energy in fuel cells while regenerating water. However, the oxygen evolution reaction (OER) and the oxygen reduction reaction taking place respectively in water-splitting and fuel cells are quite sluggish because of their multielectronic and multiprotonic nature. Catalysts such as IrO
2
and RuO
2
are being successfully used as state-of-the-art OER electrocatalysts but such noble metal-based materials are severely limited by their scarcity and high cost. Thus, noble metal free electro/photocatalysts are being eagerly pursued to provide more sustainable alternatives. In this context, vanadium-based and vanadium-containing electro and photocatalysts based on hydroxides/oxyhydroxides/oxides, vanadates, chalcogenides and nitrides stand out among the most promising alternatives, and recent advances have demonstrated their key role in enhancing the catalytic activity by strong synergic electronic and structural effects. In fact, such high-performance materials have potential in the fabrication of fuel cells and photosynthetic devices competitive enough in converting chemical energy into electricity and solar energy into solar fuel, enabling large-scale production, storage and usage of the infinite energy of the sun in a more convenient and safe manner. Perspectives are also provided on the preparation, evaluation of synergic effects in OER electro/photocatalytic activity, and their correlation with the electronic and crystalline structure of the materials, as well as on the electrode material design.
This review summarizes the recent progress in vanadium-containing catalysts, including the synthesis strategies and performance in electrocatalytic and photocatalytic oxygen evolution.
Environmentally friendly energy sources such as solar and wind power as alternatives to fossil fuels are strategic for meeting the energy needs of an increasingly demanding population, but they are ...periodic or intermittent in nature, making energy storage devices fundamental for the realization of a sustainable society. Thus, the quest for much higher power and energy dense devices, especially hybrid supercapacitors, as alternatives to lithium-ion batteries, has been scaling up since the combining of the outstanding power density of supercapacitive materials with the high energy density of battery-type materials into a single device. Despite their high resistance, transition metal oxides are promising electrode materials for use in devices, since their rich electrochemistry can be activated by three main strategies to boost the specific charge capacity, charge-discharge and ion diffusion kinetics, and cyclability of devices
via
: (a) the incorporation of hetero-atoms that generate trimetallic oxides, (b) nanostructuration
via
hierarchical core@shell furry and mesoporous systems, and (c) combination with other materials to generate nanocomposites. These strategies, especially those leading to highly porous 3D core@shell architecture nanomaterials, are very successful, where trimetallic oxides, and ternary
T
LDHs and multicomponent systems, realized
via
the combination of mono- and/or bimetallic oxides and hydroxides, have demonstrated exceptionally good performances as electrode materials, presenting bright new perspectives for the future of hybrid energy storage devices.
The main strategies to impart synergistic catalytic effects to trimetallic oxide/layered double hydroxide materials are discussed: (a) heteroatom incorporation, (b) the formation of nanocomposites, and (c) hierarchical core@shell nanostructuration.
The high demand for energy by our society, and consequent large consumption of fossil fuel, is leading not only to its depletion but also to increasing environmental pollution, thus urging the ...development of clean and renewable energy sources such as based in solar energy and water in a cyclic way, by photoinduced water-splitting and regeneration in fuel cells. This means being in command of the tetra-protonic and tetra-electronic reaction mechanism of the oxygen evolution reaction, a formidable challenge that is starting to be overcome using catalysts based on more abundant and inexpensive elements. Interestingly, the most promising ones in this context are low-cost materials based on NiFe, NiCo and NiV-LDH precursors, highly flexible and tunable materials that would enable large-scale production, storage and utilization in a more convenient and safe manner. In fact, the vast majority of high performance electrocatalysts based on ternary LDHs are being produced by doping of that matrix with Co
2+/3+
and V
2+/3+/4+
ions to modulate the electronic and structural properties of NiFe-LDH metal sites, thus reducing the OER overpotentials while activating and increasing the concentration of active sites and improving the OER rate. On the other hand, the V ion coordination geometry can be distorted from octahedral to tetrahedral and used to induce very strong electronic effects to the neighboring transition metal ions to adjust the metal-oxygen bond energy in the transition state to the expected optimal value, and optimize the O
2
release in the OER process. Finally, nanostructuration and deposition on suitable conducting materials generating nanocomposites can be used as additional strategies to enhance further the conductivity as well as the concentration and number of available active sites, while facilitating the electrolyte diffusion, thus improving their electrocatalytic performances. In short, catalysts for oxygen evolution reaction based on ternary LDHs were reviewed considering their key role in the way to a more sustainable society.
The recent advances in ternary layered double hydroxide electrocatalysts, including the strategies used for the design, synthesis, and evaluation of their performance for oxygen evolution reaction are reviewed in this account.
Porphyrins and analogous macrocycles exhibit interesting photochemical, catalytic, and luminescence properties demonstrating high potential in the treatment of several diseases. Among them can be ...highlighted the possibility of application in photodynamic therapy and antimicrobial/antiparasitic PDT, for example, of malaria parasite. However, the low efficiency generally associated with their low solubility in water and bioavailability have precluded biomedical applications. Nanotechnology can provide efficient strategies to enhance bioavailability and incorporate targeted delivery properties to conventional pharmaceuticals, enhancing the effectiveness and reducing the toxicity, thus improving the adhesion to the treatment. In this way, those limitations can be overcome by using two main strategies: (1) Incorporation of hydrophilic substituents into the macrocycle ring while controlling the interaction with biological systems and (2) by including them in nanocarriers and delivery nanosystems. This review will focus on antiparasitic drugs based on porphyrin derivatives developed according to these two strategies, considering their vast and increasing applications befitting the multiple roles of these compounds in nature.
To evaluate the antibacterial effects, cytotoxicity and microtensile bond strength of an adhesive containing low concentrations of silver nanoparticles (NAg).
Various concentrations of NAg (50, 100, ...150, 200 and 250 ppm) were incorporated into the primer of the Scotchbond Multi-Purpose adhesive system (SBMP). Antibacterial activity was examined using a broth microdilution assay to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), agar diffusion assay and the MTT assay was used to examine the biofilm metabolic activity (S. mutans). The Microtensile Bond Test (μTBS) was performed after 24 h, followed by 6-months storage in distilled water. Cytotoxicity was assessed with an MTT reduction assay in human dental pulp stem cells viability after exposure to Nag-conditioned culture media during 0, 24, 48, and 72 h. The results were statistically analyzed (α ≤ 0.05).
MIC was found between NAg 25 and 50 ppm MBC was determined at 50 ppm of NAg. Bacterial activity inhibition was higher than control in all NAg groups compared to control in agar diffusion assay. Biofilm inhibition was statistically higher in 250 ppm NAg than control. All NAg groups and SBMP presented similar cytotoxicity in each period. Adhesives with NAg 200 and 250 ppm and SBMP (control) presented the highest μTBS values, similar to that of SBMP control, in both instances (24 h and 6 months) (p > 0.05).
The commercial primer containing NAg 250 ppm showed both antibacterial effect and reliable bond strength with no cytotoxicity increase. The addition of NAg to primers seems promising for the improvement of conventional dental adhesives efficacy.
Clinical Significance: The addition of low concentrations of NAg (250 ppm) to primers were effective to improve antibacterial effect preserving the bond strength and the biocompatibility of the commercial product. NAg/primer association could protect the tooth-adhesive interface increasing dental restoration longevity.
Gas sensors are fundamental for continuous online monitoring of volatile organic compounds. Gas sensors based on semiconductor materials have demonstrated to be highly competitive, but are generally ...made of expensive materials and operate at high temperatures, which are drawbacks of these technologies. Herein is described a novel ethanol sensor for room temperature (25 °C) measurements based on hematite (α‑Fe
O
)/silver nanoparticles. The AgNPs were shown to increase the oxide semiconductor charge carrier density, but especially to enhance the ethanol adsorption rate boosting the selectivity and sensitivity, thus allowing quantification of ethanol vapor in 2-35 mg L
range with an excellent linear relationship. In addition, the α-Fe
O
/Ag 3.0 wt% nanocomposite is cheap, and easy to make and process, imparting high perspectives for real applications in breath analyzers and/or sensors in food and beverage industries. This work contributes to the advance of gas sensing at ambient temperature as a competitive alternative for quantification of conventional volatile organic compounds.
Abstract This study aimed to evaluate the antibacterial effect, cytotoxicity, and microtensile bond strength of an adhesive system containing silver nanoparticles (NAg). NAg was synthesized and ...incorporated (500 and 1000 ppm) into Scotchbond Multi-Purpose (SBMP) primer and bond. A microtensile bond test (μTBS) was performed after 24 h and 1 year. The adhesive interface was characterized using a confocal Raman microscope. The antibacterial activity was assessed using agar diffusion and biofilm inhibition assays (S. mutans). MTT assay was used to assess the cytotoxicity of NAg-conditioned culture media on human dental pulp stem cells (hDPSCs). The results were statistically analyzed using analysis of variance and Tukey's tests (α = .01). Incorporating 500 and 1000 ppm of NAg in the SBMP did not affect the μTBS after 24 h (p > 0.05). However, in the 1 year evaluation, 500 ppm presented the highest μTBS values (p < 0.05). The addition of NAg at 500 and 1000 ppm in the primer and bond led to larger inhibition halos and colony-forming units than the control (p < 0.05). For the unpolymerized and polymerized groups, the combination of primer and bond presented the highest cytotoxic effects on hDPSCs (p < 0.05). In conclusion, incorporating 500 or 1000 ppm of NAg into an etch-and-rinse adhesive system led to an antibacterial effect without altering the cytotoxicity. SBMP at 500 ppm presented a higher μTBS at 1 year.
A highly sensitive sensor for quantification of uric acid (UA) directly in body fluids (saliva and sweat) is reported, working at a potential as low as 0.0 V vs Ag/AgCl. New mixed hydroxide materials ...exhibiting stable electrocatalytic responses from alkaline to acidic media were prepared, their structure was thoroughly characterized, and the electrochemical properties of the modified FTO (fluorine-doped tin oxide) electrodes were evaluated for UA determination by cyclic voltammetry, chronoamperometry
,
and batch injection analysis. A very low limit of detection (2.3 × 10
−8
mol L
−1
) with good repeatability (RSD = 3.2% for 30 successive analyses
)
was achieved based on a fast and simple BIA procedure. Finally, α-Ni
0.75
Zn
0.25
(OH)
2
screen-printed electrodes (SPE) were developed for the measurement of UA directly in real saliva and sweat samples, without interference of ascorbic acid, acetaminophen, lactate
,
and glucose at their typical concentrations present in those body fluids, revealing high potential for application as disposable sensors in biological systems.
Graphical abstract
A new supramolecular electrocatalyst for Oxygen Evolution Reaction (OER) was synthesized from a central multibridging cobalt tetrapyridylporphyrazine (CoTPyPz) species by attaching four Ru(bpy)2Cl+ ...groups. Both CoTPyPz and the tetraruthenated cobalt porphyrazine species, TRuCoTPyPz, form very homogenous molecular films just by dropcasting their methanol solutions onto GCE electrodes. Such films exhibited low overpotentials for O2 evolution, e.g., 560 e 340 mV, respectively, displaying high stability, typically exceeding 15 h. The kinetic parameters obtained from the Tafel plots showed that the peripheral complexes are very important for the electrocatalytic activity. Hyperspectral Raman images taken along the electrochemical process demonstrated that the cobalt center is the primary active catalyst site, but its performance is enhanced by the ruthenium complexes, which act as electron-donating groups, in the supramolecular system.
Omega 3 fatty acids, such as docosahexaenoic acid (DHA) have been widely consumed as supplements to control chronic inflammation. Nanocapsules containing DHA (MLNC-DHA-a1) were developed and showed ...excellent stability. Thus, our objective was to evaluate the effect of MLNC-DHA-a1 nanocapsules on biomarkers of chronic inflammation.
Cells viability was determined by flow cytometry. The uptake of MLNC-DHA-a1 nanocapsules by macrophages and their polarization were determined. In vivo, LDLr(-,-) mice were fed a Western diet to promote chronic inflammation and were treated with MLNC-DHA-a1 nanocapsules, intravenously injected via the caudal vein once a week for 8 weeks.
MLNC-DHA-a1 nanocapsules decreased the concentration of TNFα (p = 0.02) in RAW 264.7 cells compared to the non-treated group (NT), with no changes in IL-10 (p = 0.29). The nanocapsules also exhibited an increase in the M2 (F4/80+ CD206) phenotype (p < 0.01) in BMDM cells. In vivo, no difference in body weight was observed among the groups, suggesting that the intervention was well tolerated. However, compared to the CONT group, MLNC-DHA-a1 nanocapsules led to an increase in IL-6 (90.45 ×13.31 pg/mL), IL-1β (2.76 ×1.34 pg/mL) and IL-10 (149.88 ×2.51 pg/mL) levels in plasma.
MLNC-DHA-a1 nanocapsules showed the potential to promote in vitro macrophage polarization and were well-tolerated in vivo. However, they also increased systemic pro-inflammatory cytokines. Therefore, considering that this immune response presents a limitation for clinical trials, further studies are needed to identify the specific compound in MLNC-DHA-a1 that triggered the immune response. Addressing this issue is essential, as MLNC-DHA-a1 tissue target nanocapsules could contribute to reducing chronic inflammation.
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•Docosahexaenoic acid has been consumed as supplement to control chronic inflammation.•Nanocapsules containing docosahexaenoic acid increased M2 phenotype in BMDM cells.•Mice were treated with nanocapsules, intravenously injected once a week for 8 weeks.•While the intervention was well tolerated it increased cytokines levels in the plasma.•This immune response must be investigated to improve the nanocapsules effectiveness.
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