Hybrid mesoporous electrodes evidence CISS effect on water oxidation.

Controlling product selectivity is essential for improving the efficiency of multi-product reactions. Electrochemical water oxidation is a reaction of main importance in different applications, e.g., renewable energy schemes and environmental protection, where H2O2 and O2 are the two principal products. In this Communication, the product selectivity of electrochemical water oxidation was controlled by making use of the chiral induced spin selectivity (CISS) effect at mesoporous-TiO2 on the molecule-modified Au substrate. Our results show a decrease in H2O2 formation when using chiral hetero-helicene molecules adsorbed on the Au substrate. We propose a mechanism for this kinetic effect based on the onset of CISS-induced spin polarization on the Au-helicene chiral interface. We also present a new tunable substrate to investigate the CISS mechanism.

Importance of the Structural and Physicochemical Properties of Silica Nanoshells in the Photothermal Effect of Silica-Coated Au Nanoparticles Suspensions.

In this work, monodisperse silica-coated gold nanoparticles (NPs) were synthesized and used for obtaining aqueous colloidal dispersions with an optimum relationship between colloidal stability and photothermal activity. The idea behind this design was to produce systems with the advantages of the presence of a silica shell (biocompatibility, potential for surface modification, and protecting effect) with a minimal loss of optical and thermal properties. With this aim, the photothermal properties of NPs with silica shells of different thicknesses were analyzed under conditions of high radiation extinction. By using amorphous, gel-like silica coatings, thicknesses higher than 40 nm could be obtained without an important loss of the light absorption capacity of the colloids and with a significant photothermal response even at low NP concentrations. The effects produced by changes in the solvent and in the NP concentration were also analyzed. The results show that the characteristics of the shell control both, the photothermal effect and the optical properties of the colloidal dispersions. As the presence of a silica shell strongly enhances the possibilities of adding cargo molecules or probes, these colloids can be considered of high interest for biomedical therapies, sensing applications, remote actuation, and other technological applications.

Light-Induced Polymer Response through Thermoplasmonics Transduction in Highly Monodisperse Core-Shell-Brush Nanosystems.

Smart nanosystems that transduce external stimuli to physical changes are an inspiring challenge in current materials chemistry. Hybrid organic-inorganic materials attract great attention due to the combination of building blocks responsive to specific external solicitations. In this work, we present a sequential method for obtaining an integrated core-shell-brush nanosystem that transduces light irradiation into a particle size change through a thermoplasmonic effect. We first synthesize hybrid monodisperse systems made up of functionalized silica colloids covered with controllable thermoresponsive poly(N-isopropylacrylamide), PNIPAm, brushes, produced through radical photopolymerization. This methodology was successfully transferred to Au@SiO2 nanoparticles, leading to a core-shell-brush architecture, in which the Au core acts as a nanosource of heat; the silica layer, in turn, adapts the metal and polymer interfacial chemistries and can also host a fluorescent dye for bioimaging. Upon green LED irradiation, a light-to-heat conversion process leads to the shrinkage of the external polymer layer, as proven by in situ DLS. Our results demonstrate that modular hybrid nanosystems can be designed and produced with photothermo-physical transduction. These remote-controlled nanosystems present prospective applications in smart carriers, responsive bioscaffolds, or soft robotics.

Chemical Stability of Mesoporous Oxide Thin Film Electrodes under Electrochemical Cycling: from Dissolution to Stabilization.

Mesoporous oxide thin films (MOTF) present very high surface areas and highly controlled monodisperse pores in the nanometer range. These features spurred their possible applications in separation membranes and permselective electrodes. However, their performance in real applications is limited by their reactivity. Here, we perform a basic study of the stability of MOTF toward dissolution in aqueous media using a variety of characterization techniques. In particular, we focus in their stability behavior under the influence of ionic strength, adsorption of electrochemical probes, and applied electrode potential. Mesoporous silica thin films present a limited chemical stability after electrochemical cycling, particularly under high ionic strength, due to their high specific surface area and the interactions between the electrochemical probes and the surface. In contrast, TiO2 or Si0.9Zr0.1O2 matrices present higher stability; thus, they are an adequate alternative to produce accessible, sensitive, and robust permselective electrodes or membranes that perform under a wide variety of conditions.

Charge percolation in redox-active thin membrane hybrids of mesoporous silica and poly(viologens).

This work reports the fabrication of redox-active films of oligomeric and molecular viologens and mesoporous silica via the infiltration method. Pore-ellipsometry and UV-vis confirm that low-molecular-weight poly(viologens) in solution are able to enter the mesoporous structure, in contrast to high-molecular weight polymers that adsorb only on top of the film. Cyclic voltammetry shows that viologens are able to reach the bottom of the pores and access the electrode/film interface. However, the number of viologen sites that can be accessed by cyclic voltammetry at 50 mV s-1 is only a tenth of the total viologen population determined by UV-vis and pore-ellipsometry. The effect is ascribed to the very small apparent diffusion coefficient for charge transport within the film (Dapp < 10-12 cm2 s-1). A theoretical model is put forward to describe charge transport via the electron-hopping mechanism for redox sites randomly adsorbed on the inner walls of the pores. Our model predicts that the threshold of charge percolation occurs for viologen surface coverages close to those observed in our experiments; therefore, the low fraction of electrochemically addressable viologens is ascribed to inefficient charge percolation via the electron-hopping mechanism.

TiO2 mesoporous thin film architecture as a tool to control Au nanoparticles growth and sensing capabilities.

In this paper, a systematic study regarding the effect of the mesoporous structure over Au nanoparticles (NPs) growth inside and through the pores of mesoporous TiO2 thin films (MTTFs) is presented, and the effect of such characteristics over the composites' sensing capabilities is evaluated. Highly stable MTTFs with different pore diameters (range: 4-8 nm) and pore arrangements (body- and face-centered cubic) were synthesized and characterized. Au NPs were grown inside the pores, and it was demonstrated-through a careful physicochemical characterization-that the amount of incorporated Au and NP size depends on the pore array; being higher for bigger pore diameters and face-centered cubic structures. The same structure allows the growth of more and longer tips over Au NPs deposited at the thin film-substrate interface. Finally, to confirm the effect of the structural characteristics of the composites over their possible applications, the materials were tested as surface-enhanced Raman scattering (SERS)-based substrates. The composites with a higher amount of Au and more ramified NPs were the ones that presented better sensitivity in the detection of a probe molecule (4-nitrothiophenol). Overall, this work demonstrates that the pore size and ordering in MTTFs determine the materials' accessibility and connectivity, and therefore, have a clear impact on their potential applications.

iRGD-guided tamoxifen polymersomes inhibit estrogen receptor transcriptional activity and decrease the number of breast cancer cells with self-renewing capacity.

BACKGROUND: Tamoxifen (Tam) is the most frequent treatment for estrogen receptor (ER) positive breast cancer. We recently showed that fibronectin (FN) leads to Tam resistance and selection of breast cancer stem cells. With the aim of developing a nanoformulation that would simultaneously tackle ER and FN/ß1 integrin interactions, we designed polyethylene glycol-polycaprolactone polymersomes polymersomes (PS) that carry Tam and are functionalized with the tumor-penetrating iRGD peptide (iRGD-PS-Tam). RESULTS: Polyethylene glycol-polycaprolactone PS were assembled and loaded with Tam using the hydration film method. The loading of encapsulated Tam, measured by UPLC, was 2.4 ± 0.5 mol Tam/mol polymer. Physicochemical characterization of the PS demonstrated that iRGD functionalization had no effect on morphology, and a minimal effect on the PS size and polydispersity (176 nm and Pdi 0.37 for iRGD-TAM-PS and 171 nm and Pdi 0.36 for TAM-PS). iRGD-PS-Tam were taken up by ER+ breast carcinoma cells in 2D-culture and exhibited increased penetration of 3D-spheroids. Treatment with iRGD-PS-Tam inhibited proliferation and sensitized cells cultured on FN to Tam. Mechanistically, treatment with iRGD-PS-Tam resulted in inhibition ER transcriptional activity as evaluated by a luciferase reporter assay. iRGD-PS-Tam reduced the number of cells with self-renewing capacity, a characteristic of breast cancer stem cells. In vivo, systemic iRGD-PS-Tam showed selective accumulation at the tumor site. CONCLUSIONS: Our study suggests iRGD-guided delivery of PS-Tam as a potential novel therapeutic strategy for the management of breast tumors that express high levels of FN. Future studies in pre-clinical in vivo models are warranted.

Luminescent Lanthanide Metal Organic Frameworks as Chemosensing Platforms towards Agrochemicals and Cations.

Since the first studies of luminescent sensors based on metal organic frameworks (MOFs) about ten years ago, there has been an increased interest in the development of specific sensors towards cations, anions, explosives, small molecules, solvents, etc. However, the detection of toxic compounds related to agro-industry and nuclear activity is noticeably scarce or even non-existent. In this work, we report the synthesis and characterization of luminescent lanthanide-based MOFs (Ln-MOFs) with diverse crystalline architectures obtained by solvothermal methods. The luminescent properties of the lanthanides, and the hypersensitive transitions of Eu3+ (5D0→7F2) and Tb3+ (5D4→7F5) intrinsically found in the obtained MOFs in particular, were evaluated and employed as chemical sensors for agrochemical and cationic species. The limit of detection (LOD) of Tb-PSA MOFs (PSA = 2-phenylsuccinate) was 2.9 ppm for [UO22+] and 5.6 ppm for [Cu2+]. The variations of the 4f⁻4f spectral lines and the quenching/enhancement effects of the Ln-MOFs in the presence of the analytes were fully analyzed and discussed in terms of a combinatorial "host⁻guest" vibrational and "in-silico" interaction studies.

Novel Electrochemical Paper-Based Immunocapture Assay for the Quantitative Determination of Ethinylestradiol in Water Samples.

We report a novel and innovative electrochemical paper-based immunocapture assay (EPIA) to address the need for ultrasensitive detection of emerging pollutants without regulatory status and whose effects on environment and human health are not completely yet understood. In particular, we present the application of this system toward highly sensitive detection of the emerging pollutant ethinyl estradiol (EE2). The EPIA approach is based on the use of paper microzones modified with silica nanoparticles (SNs) and anti-EE2 specific antibodies for capture and preconcentration of EE2 from river water samples. After the preconcentration procedure, the paper microzones are placed onto a screen-printed carbon electrode modified with electrochemically reduced graphene (RG). The bound EE2 is subsequently desorbed adding a diluted solution of sulfuric acid on the paper microzones. Finally, recovered EE2 is electrochemically detected by OSWV. The proposed novel methodology showed an appropriate LOD and linear range for the quantification of EE2 for water samples with different origins. The nonsophisticated equipment required, the adequate recovery values obtained (from 97% to 104%, with a RSD less than 4.9%), and the appropriate LOD and linear range value (0.1 ng L-1 and 0.5-120 ng L-1, respectively) achieved by our immunocapture sensor present significant analytical figures of merit, particularly when the routine quantification of EE2 is considered. In addition, our system was based on electrochemical paper-based technology, which allows obtainment of portable, easy-to-use, inexpensive, and disposable devices. The EPIA can also serve as a general-purpose immunoassay platform applicable to quantitation of other drugs and emerging pollutants in environmental samples.

Tethering Luminescent Thermometry and Plasmonics: Light Manipulation to Assess Real-Time Thermal Flow in Nanoarchitectures.

The past decade has seen significant progresses in the ability to fabricate new mesoporous thin films with highly controlled pore systems and emerging applications in sensing, electrical and thermal isolation, microfluidics, solar cells engineering, energy storage, and catalysis. Heat management at the micro- and nanoscale is a key issue in most of these applications, requiring a complete thermal characterization of the films that is commonly performed using electrical methods. Here, plasmonic-induced heating (through Au NPs) is combined with Tb3+/Eu3+ luminescence thermometry to measure the thermal conductivity of silica and titania mesoporous nanolayers. This innovative method yields values in accord with those measured by the evasive and destructive conventional 3ω-electrical method, simultaneously overcoming their main limitations, for example, a mandatory deposition of additional isolating and metal layers over the films and the previous knowledge of the thermal contact resistance between the heating and the mesoporous layers.

Thermosensitive Cation-Selective Mesochannels: PNIPAM-Capped Mesoporous Thin Films as Bioinspired Interfacial Architectures with Concerted Functions.

Rational design and elaborate modular construction of interfacial architectures in which molecular transport is mediated by responsive/adaptive nanostructures has become a growing and fertile field of research in supramolecular materials chemistry. This work presents, for the first time, the use of PNIPAM-capped mesoporous silica thin films as thermosensitive cation-selective mesochannels. Thus far, this feature has only been observed in thermosensitive biological channels. The interfacial architecture created here accomplishes its specific functions through the concerted or simultaneous action of spatially addressed subunits with temperature response and ion exclusion capabilities. The thermo-perm-selectivity effect stems from the synergistic interplay between the pH-dependent electrostatic characteristics of the silica scaffold and the thermo-controlled steric effects introduced by the capping brush layer. It is hoped that the "nanoarchitectonic" approach presented here will provide new routes toward the generation of heterosupramolecular nanosystems displaying addressable transport properties similar to those encountered in biological ion channels.

Formation of ordered mesostructured TiO2 thin films: a soft coarse-grained simulation study.

Ordered mesostructured TiO2 thin films are employed in diverse applications ranging from catalysis and sensing, to photovoltaic and lithium-ion batteries. Experimentally these mesostructured thin films are fabricated via a sol-gel process coupled with evaporation-induced self-assembly of a supramolecular template, where the concentration of hydrogen chloride (HCl) and water play vital roles. We employ a soft, coarse-grained model of the amphiphilic template Brij58 and spherical particles, representing titanium-oxo clusters, to study the role of HCl and water in the formation of mesostructured TiO2 thin films. The template-cluster and cluster-cluster interactions are reflected in the interaction terms δNBP and εPP, respectively. The results show that a decrease in HCl (increase in εPP) leads to the formation of large mesopores due to the strong attraction between particles, giving rise to a high dispersity index (low order) of the thin films. However, a decrease in water (increase in δNBP) will compensate for the entropic attraction between particles, resulting in thin films with low dispersity index (high order). The variation of the dispersity index in the δNBP-εPP plane provides an intuitive understanding that the slow evaporation of HCl could drive the film towards a uniform mesoporous state, whereas fast evaporation pushes the film through a non-uniform phase. These results indicate that even if the mass proportion of the surfactants Brij58 and titanium precursors is the same in the initial solution, the final mesoporous structures could be diverse, which was confirmed by the controlled experiments. We also confirm the post-processing-towards-order strategy by making the particle rearrangement available by weakening the εPP. The outlined procedure paves the way for soft, coarse-grained models to understand the complex co-assembly of transition metal clusters and amphiphilic surfactants towards the rational design of highly ordered mesoporous structures.

Glyco-nano-oncology: Novel therapeutic opportunities by combining small and sweet.

Recent efforts toward defining the molecular features of the tumor microenvironment have revealed dramatic changes in the expression of glycan-related genes including glycosyltransferases and glycosidases. These changes affect glycosylation of proteins and lipids not only in cancer cells themselves, but also in cancer associated-stromal, endothelial and immune cells. These glycan alterations including increased frequency of ß1,6-branched N-glycans and bisecting N-glycans, overexpression of tumor-associated mucins, preferred expression of T, Tn and sialyl-Tn antigen and altered surface sialylation, may contribute to tumor progression by masking or unmasking specific ligands for endogenous lectins, including members of the C-type lectin, siglec and galectin families. Differential expression of glycans or glycan-binding proteins could be capitalized for the identification of novel biomarkers and might provide novel opportunities for therapeutic intervention. This review focuses on the biological relevance of lectin-glycan interactions in the tumor microenvironment (mainly illustrated by the immunosuppressive and pro-angiogenic activities of galectin-1) and the design of functionalized nanoparticles for pharmacological delivery of multimeric glycans, lectins or selective inhibitors of lectin-glycan interactions with antitumor activity.

Nano-designed enzyme-functionalized hierarchical metal-oxide mesoporous thin films: en route to versatile biofuel cells.

A versatile bioelectronic system is presented, based on Ag nanoparticle assemblies embedded into hierarchically mesoporous titania thin films on which electroactive enzymes are simply immobilized by a fast adsorption process. This strategy enables straightforward, cost effective, high-performance, thin-film enzymatic fuel cell technology with foreseeable applications in self-powered microfluidic and electronic devices.

Ion-Fluid Transport-Control Feedback along Nanopore Networks.

Biological signaling correlates with the interrelation between ion and nanofluidic transportation pathways. However, artificial embodies with reconfigurable ion-fluid transport interaction aspects remain largely elusive. Herein, we unveiled an intimate interplay between nanopore-driven advancing flow and ion carriage for the spontaneous imbibition of aqueous solutions at the nanoporous thin film level. Ionic factors dominate transport phenomena processing and integration (ions influence fluid motion, which in turn governs the self-regulated ion traveling). We show an ion-induced translation effect that finely converts a chemical input, the nature of ions, into a related fluidic output: modulation of the extent of imbibition. We further find complex imbibition dynamics induced by the ion type and population. We peculiarly pinpoint a stop-and-go effective transport process with a programmable delay time triggered by selective guest-host interactions. The ion-fluid transport interplay is captured by a simple model that considers the counterbalance between the capillary infiltration and solution concentration, owing to water loss at the nanoporous film-air interface. Our results demonstrate that nanopore networks present fresh scenarios for understanding and controlling autonomous macroscopic liquid locomotion and offer a distinctive working principle for smart ion operation.

Enhancement of electrocatalysis through magnetic field effects on mass transport.

Magnetic field effects on electrocatalysis have recently gained attention due to the substantial enhancement of the oxygen evolution reaction (OER) on ferromagnetic catalysts. When detecting an enhanced catalytic activity, the effect of magnetic fields on mass transport must be assessed. In this study, we employ a specifically designed magneto-electrochemical system and non-magnetic electrodes to quantify magnetic field effects. Our findings reveal a marginal enhancement in reactions with high reactant availability, such as the OER, whereas substantial boosts exceeding 50% are observed in diffusion limited reactions, exemplified by the oxygen reduction reaction (ORR). Direct visualization and quantification of the whirling motion of ions under a magnetic field underscore the importance of Lorentz forces acting on the electrolyte ions, and demonstrate that bubbles' movement is a secondary phenomenon. Our results advance the fundamental understanding of magnetic fields in electrocatalysis and unveil new prospects for developing more efficient and sustainable energy conversion technologies.

Fe-Ni porphyrin/mesoporous titania thin film electrodes: a bioinspired nanoarchitecture for photoelectrocatalysis.

Porphyrin and porphyrinoid derivatives have been extensively studied in the assembly of catalysts and sensors, seeking biomimetic and bioinspired activity. In particular, Fe and Ni porphyrins can be used for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by immobilization of these molecular catalysts on semiconductor materials. In this study, we designed a hybrid material containing a crystalline mesoporous TiO2 thin film in which the catalytic centres are Ni-porphyrin (NiP), Fe-porphyrin (FeP), and a NiP/FeP bimetallic system to assess whether the coexistence of both metalloporphyrins improves the OER activity. The obtained photoelectrodes were physicochemically and morphologically characterized through high-resolution FE-SEM images, UV-vis and Raman spectroscopies, cyclic voltammetry, and impedance measurements. The results show a differential behavior of the mono- and bimetallic porphyrin systems, where the Fe(iii) centre in FeP may increase the acidity and lower the reduction potential of the Ni2+/3+ couple when co-deposited with NiP leading to an improved photoelectrochemical water-oxidation performance. We have validated the cooperative effect of both metal complexes within this novel system, where the µ-peroxo-bridged interaction between Fe and Ni is integrated into a supramolecular heterometallic structure of porphyrins.

Advances in Nanomaterials and Composites Based on Mesoporous Materials as Antimicrobial Agents: Relevant Applications in Human Health.

Nanotechnology has emerged as a cornerstone in contemporary research, marked by the advent of advanced technologies aimed at nanoengineering materials with diverse applications, particularly to address challenges in human health. Among these challenges, antimicrobial resistance (AMR) has risen as a significant and pressing threat to public health, creating obstacles in preventing and treating persistent diseases. Despite efforts in recent decades to combat AMR, global trends indicate an ongoing and concerning increase in AMR. The primary contributors to the escalation of AMR are the misuse and overuse of various antimicrobial agents in healthcare settings. This has led to severe consequences not only in terms of compromised treatment outcomes but also in terms of substantial financial burdens. The economic impact of AMR is reflected in skyrocketing healthcare costs attributed to heightened hospital admissions and increased drug usage. To address this critical issue, it is imperative to implement effective strategies for antimicrobial therapies. This comprehensive review will explore the latest scientific breakthroughs within the metal-organic frameworks and the use of mesoporous metallic oxide derivates as antimicrobial agents. We will explore their biomedical applications in human health, shedding light on promising avenues for combating AMR. Finally, we will conclude the current state of research and offer perspectives on the future development of these nanomaterials in the ongoing battle against AMR.

Ordered Mesoporous Electrodes for Sensing Applications.

Electrochemical sensors have become increasingly relevant in fields such as medicine, environmental monitoring, and industrial process control. Selectivity, specificity, sensitivity, signal reproducibility, and robustness are among the most important challenges for their development, especially when the target compound is present in low concentrations or in complex analytical matrices. In this context, electrode modification with Mesoporous Thin Films (MTFs) has aroused great interest in the past years. MTFs present high surface area, uniform pore distribution, and tunable pore size. Furthermore, they offer a wide variety of electrochemical signal modulation possibilities through molecular sieving, electrostatic or steric exclusion, and preconcentration effects which are due to mesopore confinement and surface functionalization. In order to fully exploit these advantages, it is central to develop reproducible routes for sensitive, selective, and robust MTF-modified electrodes. In addition, it is necessary to understand the complex mass and charge transport processes that take place through the film (particularly in the mesopores, pore surfaces, and interfaces) and on the electrode in order to design future intelligent and adaptive sensors. We present here an overview of MTFs applied to electrochemical sensing, in which we address their fabrication methods and the transport processes that are critical to the electrode response. We also summarize the current applications in biosensing and electroanalysis, as well as the challenges and opportunities brought by integrating MTF synthesis with electrode microfabrication, which is critical when moving from laboratory work to in situ sensing in the field of interest.

Sunlight-Driven Photocatalysis for a Set of 3D Metal-Porphyrin Frameworks Based on a Planar Tetracarboxylic Ligand and Lanthanide Ions.

Metal-porphyrin frameworks (MPFs) with trivalent lanthanide ions are the most sought-after materials in the past decade. Their porosities are usually complemented by optical properties imparted by the metal nodes, making them attractive multifunctional materials. Here, we report a novel family of 3D MPFs obtained through solvothermal reactions between tetrakis(4-carboxyphenyl) porphyrin (H4TCPP) and different lanthanide sources, yielding an isostructural family of compounds along the lanthanide series: [Ln2(DMF)(TCPP)1.5] for Ln = La, Ce, Nd, Pr, Er, Y, Tb, Dy, Sm, Eu, Gd, and Tm. Photoluminescent properties of selected phases were explored at room temperature. Also, the photocatalytic performance exhibited by these compounds under sunlight exposure is promising for its implementation in organic pollutant degradation. In order to study the photocatalytic activity of Ln-TCPPs in an aqueous medium, methylene blue (MB) was used as a contaminant model. The efficiency for MB degradation was Sm > Y > Yb > Gd > Er > Eu > either no catalyst or no light, obtaining more than 70% degradation at 120 min with Sm-TCPP. These results open the possibility of using these compounds in optical and optoelectronic devices for water remediation and sensing.