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Here, the authors report on the manufacturing and in vivo assessment of a bioresorbable nanostructured pH sensor. The sensor consists of a micrometer‐thick porous silica membrane conformably coated layer‐by‐layer with a nanometer‐thick multilayer stack of two polyelectrolytes labeled with a pH‐insensitive fluorophore. The sensor fluorescence changes linearly with the pH value in the range 4 to 7.5 upon swelling/shrinking of the polymer multilayer and enables performing real‐time measurements of the pH level with high stability, reproducibility, and accuracy, over 100 h of continuous operation. In vivo studies carried out implanting the sensor in the subcutis on the back of mice confirm real‐time monitoring of the local pH level through skin. Full degradation of the pH sensor occurs in one week from implant in the animal model, and its biocompatibility after 2 months is confirmed by histological and fluorescence analyses. The proposed approach can be extended to the detection of other (bio)markers in vivo by engineering the functionality of one (at least) of the polyelectrolytes with suitable receptors, thus paving the way to implantable bioresorbable chemical sensors. In this work in vivo operation, biocompatibility, and full degradation of a nanostructured pH sensor are demonstrated. The sensor leverages a nanometer‐thick multilayer stack of polyelectrolytes labelled with a pH‐insensitive fluorophore conformably coated within a porous silica membrane—thickness of a few micrometers—to boost fluorescence up to 600 times and enable reliable measurements through skin.

The importance of early cancer diagnosis has been recognized for decades, driving the demand for technological advancements and novel strategies for cancer detection. The conventional detection of circulating tumor cells (CTCs) often relies on size-based separation to distinguish CTCs from other blood cells. However, this method frequently leads to significant cell congestion and poorly recognizable fluorescent images, which inevitably reduces the sensitivity and specificity of CTC detection. Most CTC current separation devices with a cell filtration process have a cell capture efficiency ranging from 50% to 80% in clinical application. We constructed a flexible antibody network on the surface of gold-plated iron meshes with a pore size of 20 μm using the layer-by-layer (LbL) assembly technique. These meshes were then used to enrich MCF7 cells and CTCs in 10 clinical blood samples from breast cancer patients. This antibody network reduced the effective pore size, thereby improving both capture efficiency and specificity for CTCs. In a cell line separation study, meshes with a trilayered antibody network demonstrated a capture efficiency of 65% compared to 26% for those with a single layer. In tests using clinical samples, the trilayered antibody network achieved 100% accuracy, whereas the single-layer configuration only reached 40%. The multilayered antibody network shows strong potential for enhancing widely used immunosensors.

Layer-by-layer (LbL) strategy has been developed to form bulk heterojunction (BHJ) structure for processing efficient organic solar cells (OSCs). Herein, LbL slot-die coating with twin boiling point solvents (TBPS) strategy was developed to fabricate highly efficient OSCs, which matches with large-scale, high throughput roll-to-roll (R2R) industrialized mass process. The TBPS strategy could produce high-quality thin film without any additive, leading to the optimized vertical phase separation with interpenetrating nanostructures, as well as the enhanced charge transport and extraction. Thus, the power conversion efficiency up to 14.42% was achieved for [(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo [1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione)]:2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2″,3″:4″,5″]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene)) bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (PM6:Y6) OSCs fabricated via sequentially LbL slot-die coating using the TBPS strategy under ambient condition. The research provides a potential route for industrialized production of high-efficiency and large-area OSC devices.

The development of functional materials and the use of nanotechnology are ongoing projects. These fields are closely linked, but there is a need to combine them more actively. Nanoarchitectonics, a concept that comes after nanotechnology, is ready to do this. Among the related research efforts, research into creating functional materials through the formation of thin layers on surfaces, molecular membranes, and multilayer structures of these materials have a lot of implications. Layered structures are especially important as a key part of nanoarchitectonics. The diversity of the components and materials used in layer-by-layer (LbL) assemblies is a notable feature. Examples of LbL assemblies introduced in this review article include quantum dots, nanoparticles, nanocrystals, nanowires, nanotubes, g-C3N4, graphene oxide, MXene, nanosheets, zeolites, nanoporous materials, sol–gel materials, layered double hydroxides, metal–organic frameworks, covalent organic frameworks, conducting polymers, dyes, DNAs, polysaccharides, nanocelluloses, peptides, proteins, lipid bilayers, photosystems, viruses, living cells, and tissues. These examples of LbL assembly show how useful and versatile it is. Finally, this review will consider future challenges in layer-by-layer nanoarchitectonics.

High nitrate concentrations in water present serious risks to human health. This study evaluates two removal strategies: layered double hydroxide (LDH) nanoparticles (NPs) and LDH-incorporated thin‐film composite nanofiltration (TFC-NF) membranes to reduce nitrate concentration. First, Mg–Al, Ni–Fe, and Mn-impregnated Zn–Al LDH NPs were co-precipitated, characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, field emission scanning electron microscopy (FESEM), and zeta potential measurement, and tested in batch adsorption experiments (20 mg/L nitrate solution, 1 g/L adsorbent dosage). Among the LDH NPs tested, Ni–Fe LDH demonstrated the highest nitrate rejection, achieving 13–14% at this concentration, with no significant change with further calcination. Next, the TFC-NF membranes were fabricated by embedding LDH NPs into the support layer; one variant received additional layer-by-layer (LBL) surface modification. The membranes were also characterized using FESEM and then evaluated using a 50 mg/L nitrate solution at 6 bar pressure and 25 °C. The TFC-NF membrane containing 0.25 wt% Mn-impregnated Zn–Al LDH achieved nitrate rejection of 43% with pure water flux (PWF) of 4.5 L/m 2 h bar −1 . Under the same conditions, the LBL-TFC NF membrane showed lower nitrate rejection of 17% but higher PWF of 7.7 L/m 2 h bar −1 .

Biofouling proceeds in successive steps where the primary colonizers affect the phylogenetic and functional structure of a future microbial consortium. Using microbiologically influenced corrosion (MIC) as a study case, a novel approach for material surface protection is described, which does not prevent biofouling, but rather shapes the process of natural biofilm development to exclude MIC‐related microorganisms. This approach interferes with the early steps of natural biofilm formation affecting how the community is finally developed. It is based on a multilayer artificial biofilm, composed of electrostatically modified bacterial cells, producing antimicrobial compounds, extracellular antimicrobial polyelectrolyte matrix, and a water‐proof rubber elastomer barrier. The artificial biofilm is constructed layer‐by‐layer (LBL) by manipulating the electrostatic interactions between microbial cells and material surfaces. Field testing on standard steel coupons exposed in the sea for more than 30 days followed by laboratory analyses using molecular‐biology tools demonstrate that the preapplied artificial biofilm affects the phylogenetic structure of the developing natural biofilm, reducing phylogenetic diversity and excluding MIC‐related bacteria. This sustainable solution for material protection showcases the usefulness of artificially guiding microbial evolutionary processes via the electrostatic modification and controlled delivery of bacterial cells and extracellular matrix to the exposed material surfaces. The artificial biofilm is a multilayered structure composed of the selected bacterial cells, extracellular polyelectrolyte matrix, and rubber elastomer. It is constructed on the surface of materials layer‐by‐layer conditioning it physically, chemically, and biologically. Its application manipulates the processes of biofouling and the development of natural microbial communities by excluding corrosion causing microorganisms.

Active sites of two-dimensional (2D) electrocatalysts are often partially blocked owing to their inevitable stacking and hydrophobic polymeric binders in macroscale electrodes, therefore impeding their applications in efficient electrolyzers. Here, using layered double hydroxide (LDH) nanosheets as a model 2D electrocatalyst, we demonstrate that their performance toward water splitting can be boosted when they are electrostatically assembled into an organized structure pillared by hydrophilic polyelectrolytes or nanoparticles in a layer-by-layer (LbL) fashion. In particular, their mass activity on a planar electrode can be as large as 2.267 mA·µg −1 toward oxygen evolution reaction (OER), when NiFe-LDH nanosheets are electrostatically connected by poly(sodium 4-styrenesulfonate) (PSS), while drop-casted NiFe-LDH nanosheets only have a mass activity of 0.116 mA·µg −1 . In addition, these homogeneous NiFe-LDH nanofilms can be easily deposited on three-dimensional (3D) surfaces with high areas, such as carbon cloths, to serve as practical electrodes with overpotentials of 328 mV at a current density of 100 mA·cm −2 , and stability for 40 h. Furthermore, Pt nanoparticles can be LbL assembled with NiFe-LDH as bifunctional electrodes for synergistically boosted oxygen and hydrogen evolution reactions (HER), leading to successful overall water splitting powered by a 1.5 V battery. This study heralds the spatial control of 2D nanomaterials in nanoscale precision as an efficient strategy for the design of advanced electrocatalysts.

Barrier films that are used on packages play an important role, especially in the protection of food products. Research is being carried out at an accelerating pace to replace petroleum-based plastic films, which do not biodegrade and are difficult to recycle. This review article considers publications related to the use of polyelectrolyte complexes (PECs) in barrier films as a strategy to decrease the permeation of oxygen and other substances into and out from packages. Research progress has been achieved in using combinations of positively and negatively charged polymers, sometimes together with platy mineral particles, as a way to restrict diffusion through packaging materials. In principle, the ionic bonds within PECs contribute to a relatively high cohesive energy density within such a barrier film, which can resist diffusion of various gases and greasy substances. Resistance to water vapor, as well as aqueous substances, represent important challenges for barrier concepts that depend on ionic bond contributions. Factors affecting barrier performance of PEC-based films are discussed in light of research findings.

Monitoring the physiological signals of people by using wearable sensors attached to the skin while they go about their daily routine is a practical approach to prevent diseases and monitor people’s health status. However, conventional monitoring devices are bulky, their signals are corrupted by the noise generated by external sources, and they are prone to mechanical failure, which hinder their practical use. Herein, a mechanically durable biomaterial-based arterial pulse thin-film sensor is developed for real-time monitoring of cyclic physiological signals. A hierarchical layered material (rGO/SF/CNC) comprising reduced graphene oxide (rGO), silk fibroin (SF), and cellulose nanocrystals (CNCs) is fabricated using the spin-assisted layer-by-layer (SA-LbL) technique and thermal reduction. Thermal reduction is performed to tailor the defects in rGO, which significantly enhances its mechanical robustness and bending properties, as well as in-plane stress sensitivity, owing to a change in conductivity. The thin-film (thickness: 40.9 nm) sensor has a rapid response time (69 ms) and excellent durability exceeding 8000 cycles. Moreover, it is insensitive to strain in the orthogonal direction, which significantly reduces the noise level and dramatically increases its sensitivity. The sensor’s suitability for practical use as an arterial pulse sensor for monitoring physiological signals is demonstrated. The developed thin-film flexible stress sensor has the potential to contribute toward the improvement of wearable healthcare monitoring devices and human–machine interaction.

The traditional acid-based production method was often utilized to produce flame-retardant material, which is environmentally hazardous and adversely affects the intrinsic properties of the substrates. To address these critical challenges, this work was carried out to develop a pioneer flame-retardant composite material based on cotton and biocompatible hybrid cationic/anionic species deposited through the Layer-by-Layer deposition method. The FTIR results unveil the peaks reflected by coated elements, confirm the successful deposition of coating materials on the cotton substrate. The microstructure and uniform deposition of the coating were analyzed through scanning electron microscopy. The thermal stability of the composites is enhanced with higher coating layers due to the formation of a protective char layer. Flame retardancy of the investigated samples is measured through the vertical flame test and micro-combustion calorimetry method, exhibiting remarkable reduction in peak heat release rate and total heat released rate by 47.30% and 34%, respectively. The acquired results acknowledge the suitability of the production method to produce green fire-retardant materials with excellent thermal stability and flame retardancy to utilize in the fire-resistant industry.