Nanotube Layers Research Articles

Effect of the Current-Collecting Carbon Nanotubes Layer on the Properties of the Lead Zirconate Titanate Film for Vibration Sensors.

One of the challenging problems in the research and development of vibration sensors relates to the formation of Ohmic contacts for the removal of an electrical signal. In some cases, it is proposed to use arrays of carbon nanotubes (CNTs), which can serve as highly elastic electrode materials for vibration sensors. The purpose of this work is to study the effect of a current-collecting layer of CNTs grown over silicon on the properties of a lead zirconate titanate (PZT) film, which is frequently employed in mechanical vibration sensors or energy harvesters. For the experiments, a vibration sensor mock-up was created with the PZT-CNT-Ni-V-SiO2-Si and PZT-CNT-Ni-V-Si structures where an array of vertically oriented CNTs was grown over an oxidized or high-alloyed silicon substrates by plasma chemical deposition from a gas phase. Then, a thin film of PZT was applied to the CNT layer with a high-frequency reactive plasma spraying. For comparison, the PZT film was applied to silicon without a CNT layer (PZT-Si structure). The calculated average value of the piezoelectric module is 112 pm/V for the Ni-PZT-PT-Ni-Si-SiO2 sample, and 35 pm/V for PZT-Ni-SiO2-Si. It can be seen that the contact realized with the help of CNT ensures more than three times the best efficiency in terms of the piezoelectric module. The value of the piezoelectric module of the vibration sensor with the PZT-CNT-Ni-V-Si structure was 186 pm/V, and the value of the residual polarization was 23.2 µC/cm2, which is more than eight and three times, respectively, higher than the values of these properties for the vibration sensor with the PZT-Si structure. It is shown that the vibration sensor can operate in the frequency range of 0.1-10 kHz.

Enhancing Alkaline Hydrogen Evolution Reaction on Ru‐Decorated TiO2 Nanotube Layers: Synergistic Role of Ti3+, Ru Single Atoms, and Ru Nanoparticles

Synergistic interplays involving multiple active centers originating from TiO2 nanotube layers (TNT) and ruthenium (Ru) species comprising of both single atoms (SAs) and nanoparticles (NPs) augment the alkaline hydrogen evolution reaction (HER) by enhancing Volmer kinetics from rapid water dissociation and improving Tafel kinetics from efficient H* desorption. Atomic layer deposition of Ru with 50 process cycles results in a mixture of Ru SAs and 2.8 ± 0.4 nm NPs present on TNT layers, and it emerges with the highest HER activity among all the electrodes synthesized. A detailed study of the Ti and Ru species using different high‐resolution techniques confirmed the presence of Ti3+ states and the coexistence of Ru SAs and NPs. With insights from literature, the role of Ti3+, appropriate work functions of TNT layers and Ru, and the synergistic effect of Ru SAs and Ru NPs in improving the performance of alkaline HER were elaborated and justified. The aforementioned characteristics led to a remarkable performance by having 9 mV onset potentials and 33 mV dec−1 of Tafel slopes and a higher turnover frequency of 1.72 H2 s−1 at 30 mV. Besides, a notable stability from 28 h staircase chronopotentiometric measurements for TNT@Ru surpasses TNT@Pt in comparison.

Ultrathin ALD Coatings of Zr and V Oxides on Anodic TiO2 Nanotube Layers: Comparison of the Osteoblast Cell Growth.

The current study investigates and compares the biological effects of ultrathin conformal coatings of zirconium dioxide (ZrO2) and vanadium pentoxide (V2O5) on osteoblastic MG-63 cells grown on TiO2 nanotube layers (TNTs). Coatings were achieved by the atomic layer deposition (ALD) technique. TNTs with average tube diameters of 15, 30, and 100 nm were fabricated on Ti substrates (via electrochemical anodization) and were used as primary substrates for the study. The MG-63 cell growth and proliferation after 48 h of incubation on hybrid TNTs/ZrO2 and TNTs/V2O5 surfaces was evaluated in comparison to the uncoated TNTs of each diameter. The density of viable MG-63 cells was assessed for all the TNT surfaces, along with the cell morphology and the spreading behavior (i.e., the cell length). The ultrathin coatings retained the original morphology of the TNTs but changed the surface chemical composition, wettability, and cell behavior, whose interplay is the subject of the present investigation. These findings offer interesting views on the influence of the composition of biomedical implant surfaces, triggered by ALD ultrathin coatings on them. The outcomes of this work shed light on the assessment of the biocompatibility of the two different ALD coatings.

Enhancement of biocompatibility of anodic nanotube structures on biomedical Ti-6Al-4V alloy via ultrathin TiO2 coatings.

This work aims to describe the effect of the surface modification of TiO2 nanotube (TNT) layers on Ti-6Al-4V (TiAlV) alloy by ultrathin TiO2 coatings prepared via Atomic Layer Deposition (ALD) on the growth of MG-63 osteoblastic cells. The TNT layers with two distinctly different inner diameters, namely ∼15nm and ∼50nm, were prepared via anodic oxidation of the TiAlV alloy. Flat, i.e., non-anodized, TiAlV alloy foils were used as reference substrates. Additionally, a part of the TNT layers and alloy foils was coated with ultrathin coatings of TiO2 by ALD. The number of TiO2 ALD cycles used was 1 and 5 leading to a nominal TiO2 thickness of ∼0.055 and ∼0.3nm, respectively. The ultrathin TiO2 coating by ALD enabled to optimize the surface hydrophilicity for optimal cell growth. In addition, coatings shaded impurities of V- and F-based species (stemming from the alloy and the anodization electrolyte) that affect the biocompatibility of the tested materials while preserving the original structure and morphology. The evaluation of the biocompatibility before and after TiO2 ALD coating on TiAlV flat surfaces and TNT layers was carried out using MG-63 osteoblastic cells and compared after incubation for up to 96h. The cell growth, adhesion, and proliferation of the MG-63 on TiAlV foils and TNT layers showed significant enhancement after the surface modification by TiO2 ALD.

(Invited) Titania Nanotube Layers as Anodes for Li-Ion Microbatteries

With many advantages such as high surface area and improved charge transport, self-supported 3-D nanostructured metal oxides such as titania nanotubes (TNT) layers are promising electrode materials for Li-ion microbatteries.This presentation will review the fabrication of Li-ion microbatteries using as-formed and chemically modified TNTs as negative electrodes [1-9]. Effects of material selection and processing on the performance and reliability are presented as a means to develop conceptual guidelines to understand and improve microbattery designs. Different chemical modifications of nanotubes by ALD technique [10-13] and by the conformal electrodeposition of polymer electrolytes [14] for enhanced electrochemical performance will be presented. Fabrication of full 3D microcells showing high electrochemical performance will be shown and the development of the next generation of 3D flexible microbatteries will be also introduced. REFERENCES [1] V. Galstyan, J. Macak, T. Djenizian, App. Mater. Today, 29, 101613 (2022).[2] N. Plylahan, M. Letiche, M. Barr, and T. Djenizian, Electrochem. Commun., 43, 121 (2014).[3] N. Plylahan, A. Demoulin, C. Lebouin, P. Knauth, T. Djenizian, RSC Adv., 5, 28474 (2015).[4] N. Plylahan, M. Letiche, M. Barr, B. Ellis, S. Maria, T. N. T. Phan, E. Bloch, P. Knauth, and T. Djenizian, J. Power Sources, 273, 1182 (2015).[5] G. Salian, C. Lebouin, A. Demoulin, S. Maria, P. Knauth, M. Lepihin, A. Galeyeva, A. Kurbatov, and T. Djenizian, Power Sources, 340, 242 (2017). [6] I. V. Ferrari, M. Braglia, T. Djenizian, and P. Knauth, J. Power Sources, 353, 95 (2017).[7] G. Salian, B. M. Koo, C. Lefevre, T. Cottineau, C. Lebouin, A. T. Tesfaye, P. Knauth, V. Keller, T. Djenizian, Adv. Mater. Technol., 3, 1700274 (2018).[8] Fraoucene, V. A. Sugiawati, D. Hatem, M. S. Belkaid, F. Vacandio, M. Eyraud, M. Pasquinelli, T. Djenizian, Front. Chem., 7, 66 (2019).[9] G. D. Salian, C. Lebouin, M. Galeyeva, A. P. Kurbatov, T. Djenizian, Front. Chem., 7, 675 (2019).[10] H. Sopha, et al, Materials Chemistry and Physics, 276, 125307 (2022).[11] H. Sopha, et al, Flat. Chem., 17, 100130 (2019).[12] A. T. Tesfaye, et al, Nanomaterials, 10, 953 (2020).[13] H. Sopha, et al, ACS Omega, 2, 2749 (2017).[14] V. A. Sugiawati, F. Vacandio, T. Djenizian, Molecules, 25, 2121 (2020).

(Invited) One Dimensional Anodic TiO2 Nanotubes for Energy and Catalytic Applications

Self-organized TiO2 nanotube (TNT) layers, prepared by anodization of Ti have in suitable electrolytes, attracted considerable scientific and technological interest, especially due to their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2].The advantages of anodic TNT layers compared to TiO2 nanotubes prepared by other methods (e.g. hydrothermal) are the tunability of dimensions, their directionality, the ability to absorb significant amount of incident light, and the possibility to utilize nanotube interiors and exteriors for decoration or coating with secondary materials [2].The presentation will review the recent advancements in TNT layer synthesis for their use for the photocatalytic degradation of pollutants in the liquid and in the gas phase. This will include the upscaling of TNT layers from the laboratory scale to several dozens of cm2 [3-6], with a strong focus on the anodization of 3D Ti substrates by bipolar electrochemistry, which cannot be directly connected to the potentiostat (such as Ti meshes) [5-6]. The application of these large scale TiO2 nanotube layers in flow-through photocatalytic reactors will be discussed [3-6]. Additionally, the selective etching of double wall TiO2 nanotube layers towards single wall TiO2 nanotube layers [7] and single nanotube powders [8, 9] will be presented, showing the possibility of preparing magnetically guidable single nanotube photocatalysts by a decoration with Fe3O4.The presentation will also summarize recent advancements in the utilization of TNT layers in energy conversion and energy storage applications [10], in particular Li-ion microbatteries. Experimental details and photocatalytic and battery results will be presented and discussed.

Fabrication of Patterned TiO2 Nanotube Layers Utilizing 3D Printer Platform and Their Electrochromic Properties

An anodization method can easily fabricate nanostructured oxide layers by controlling electrochemical parameters such as the types of electrolyte solutions, the electrolyte composition, applied voltage/current, temperature and pH. In the anodization process, it is common to form an oxide on the surface of a metal substrate with an area of several to several hundred cm2. However, several approaches have been attempted to form oxide layers on a local area or manufacture a certain oxide layer pattern using the anodization process. For this purpose, partial oxidation can be achieved through the masks and patterned metal substrates can be employed for local anodization. However, these methods are disadvantageous in process-complexity and time-consumption. Therefore, this study realizes complicated patterns composed of anodized TiO2 nanostructures using a 3D printer and apply them to the electrochromic displays. A commercial 3D printer was modified to enable a direct anodization and TiO2 nanotube was anodized on the Ti substrate with the desired pattern designed by a digital code (G-code). High speed anodization was performed at a speed of 1 mm/s. Furthermore, the surface of the patterned TiO2 nanotube was modified by adsorption of the viologen molecules and the electrochromic properties of the viologen-anchored TiO2 (V-TiO2) nanotube layers were investigated.

Photoelectrochemical properties of Single walled and Double walled TiO2 nanotubes

Titanium dioxide (TiO2) is one of the most studied materials to be applied in various filed due to its high environmental compatibility and corrosion resistance [1-2]. Among the nanostructures of TiO2 is including nanoparticles, nanorods, nanoplates, and nanotubes, nanotubular TiO2 acquires not only a high surface area but also rapid charge carrier transfer, providing higher efficiency for photocatalytic application such as, the degradation of organic contaminants and hydrogen production. Although various methods have been investigated to fabricate TiO2 nanotubes, the anodization technique is favored with its straightforward control over structure and direct growth on Ti substrates[3]. However, conventional anodic TiO2 nanotubes exhibit surface irregularities and double-walled structure consisting of carbon-rich inner and TiO2 out layer[4]. The inner layer of TiO2 nanotubes diminishes the photoelectrochemical efficiency owing to the carbon contamination.In this study, double walled TiO2 nanotubes were synthesized by anodization with an applied voltage of 60 V for various periods. A piranha solution was utilized to eliminate the inner layer for double walled TiO2 nanotubes, achieving a single-walled TiO2 nanotube configuration. The morphological properties, crystallinity, and surface resistance of both single and double-walled TiO2 nanotubes were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Electrochemical Impedance Spectroscopy (EIS). In addition, the photoelectrochemical efficiencies of all TiO2 nanotubes were evaluated employing linear sweep voltammetry (LSV) and Incident photon-to-current efficiency (IPCE) measurements. As a result, the single-walled TiO2 nanotubes, produced under the specific conditions of 60 V for 7 min, showed the highest photoelectrochemical efficiencies at LSV and IPCE. The higher photoelectrochemical properties of the single walled nanotube are attributed to the enhancenment of surfave chage dynamics and environmental reactions as eliminating the inner layer.[1] Fujishima A, Honda K, Electrochemical photolysis of water at semiconductor electrode. Nature 238 (1972) 37-38[2]Lee K, Mazare A, Schmuki P, One-dimensional titanium dioxide nanomaterials: nanotubes, Chem. Rev, 114 (2014) 9385–9454,[3] Yoo JE, Lee K, Altomare M, Selli E, Schmuki P, Self-organized arrays of single-metal catalyst particles in TiO2 cavities: a highly efficient photocatalytic system, Angew. Chem., Int. Ed, 52 (2013) 1002[4] Liu N, Mirabolghasemia H, Lee K, Albua SP, Tighineanua A, Altomareab M, Schmuki P, Anodic TiO2 nanotubes: double walled vs. single walled. Faraday Discuss, 164 (2013) 107-116.

Anodic TiO2 Single Nanotubes with Fe3O4 Nanoparticles: Advanced Photocatalytical Applications

Self-organized TiO2 nanotube (TNT) layers, formed by electrochemical anodization of Ti foils, have attracted tremendous scientific and technological attention, due to their remarkable properties such as the tunability of dimensions, their directionality, high surface area, high stability, and the ability to absorb a significant amount of incident light [1,2].The most widely used electrolyte to develop TNT layers is based on ethylene glycol containing small amounts of water and fluoride ions. However, TNT layers prepared in these electrolytes present a double-walled structure. The outer wall consists of almost pure TiO2, and the inner wall consists of TiO2 contaminated with carbon and fluoride species [3,4]. In recent years, the selective etching of the inner nanotube wall of the TNT layer enabled the synthesis of single-wall nanotubes that showed superior photo-electrochemical performance compared to their double-walled counterparts [5,6]. Modification of the etching process by prolonging and optimizing the etching conditions also enabled the synthesis of single-tube TiO2 powders, which offer various new prospects compared to the TNT layers. At first glance, these powders can be effectively decorated with Fe3O4 nanoparticles to act as magnetically guidable photocatalysts, which is exactly what we recently exploited [7,8,9].The presentation will discuss the synthesis of these TiO2 nanotube morphologies and their performance in the photocatalytic degradation of model dye in the liquid phase and model drugs that are unwanted in wastewater. We will demonstrate how photocatalytic performance is influenced by single nanotubes and single nanotubes decorated with Fe3O4 magnetic particles. Experimental details and photocatalytic results will be presented and discussed.

Atomic Layer Deposition of Noble Metal Single Atoms and Nanoparticles for Electrocatalytic Applications

Platinum group metals such as Pt, Ru, Pd, Ir, etc., have superior performance for various catalytic applications [1]. Due to their scarcity, efforts were being made to reduce the mass/loading or replace these noble metals. Atomic Layer Deposition (ALD) is one among the best technique to facilitate lowering of loading mass on a support of interest [2,3]. Due to the governing surface energy variations between noble metals and support surfaces, the growth initiates as nanoparticles (NP) and with a further increase in ALD cycles the agglomeration among NP’s dominates over the individual NP size increase, thus developing thin films of relatively higher thickness.For electrocatalytic applications, it is important to choose the right substrates. Among available substrates, carbon papers and titania nanotube layers are best choices considering their physio-chemical properties, availability and low costs incurred.The uniform decoration of these substrates by NPs of catalysts proved to be highly efficient in electrocatalysis, as shown in our recent papers [3-6].The presentation will introduce and describe the synthesis of different noble metal NPs by ALD on important substrates. It will also include the corresponding physical and electrochemical characterization and encouraging results obtained in electrocatalysis.

Anodic TiO2 Films for Water Purification in Solar Evaporators

The interest in titanium and its oxides keeps growing on account of their peculiar engineered properties, which find applications in several fields, from architecture to bioengineering, from automotive to photovoltaic cells and photocatalytic devices. There are several methods that allow to grow titanium oxides, among which anodic oxidation has the nice advantage of growing TiO2 nanostructures directly immobilized on a substrate, avoiding the issue of nanostructure recovery from the medium [1]. Yet, these systems also present a drawback, i.e., the immobilization on a metallic, non-transparente and non-permeable substrate. For this reason, different methods have been developed to detach the nanotubes layer and use it as a self-standing membrane [2].In this work, we address this specific challenge and present the obtaining and characterization of self-standing TiO2 nanotubes membranes. The application envisioned requires their mandatory detachment, as the membranes will be used inside a solar evaporator device to improve the quality of evaporating water, by removing also volatile compounds that may evaporate together with water, reducing the purification extent.Membranes are produced by anodizing commercially pure titanium sheets in ethylene glycol solutions containing different amounts of water, ammonium fluoride and lactic acid. Anodizing time was varied between 30 min and 90 min, and voltage was varied between 30 V and 60 V. Double anodizing was performed to ensure better nanotubes uniformity; then annealing was performed at 500°C for 2 h to allow for oxide crystallization to anatase form. Afterwards, a third, brief anodizing step (10 min) was needed to facilitate nanotubes detachment, which then was carried out chemically, by immersion in HCl. An example of SEM image of detached membrane is shown in Figure 1, indicating that membranes can indeed be obtained and have sufficient mechanical stability to allow for handling and testing. SEM and XRD results indicate a thickness ranging from few micrometers to tens of micrometers, and their crystal structure is mainly anatase, although small quantities of rutile may form in the base of the oxide.Preliminary photocatalysis tests were conducted on the degradation of organic dyes, showing promising photoactivity. Several decoration methods were also considered, with different aims: silver nanoparticles for antifouling, and quantum dots for improved photoactivity. Silver nanoparticles did not enhance photoactivity, and in some cases decreased it slightly; yet, their scope was different, i.e., exploiting the antibacterial and antifouling characteristics of silver on the membrane layer, therefore the formulation leading to unaltered photocatalytic activity was selected for the prosecution of this work, which envisions antibacterial and antifouling testing procedures. Acknowledgements: We acknowledge financial support under the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, Call for tender No. 1409 published on 14.9.2022 by the Italian Ministry of University and Research (MUR), funded by the European Union – NextGenerationEU– Project Title COPE - COmposite nanomaterials coupling Photothermal Evaporation and photocatalysis for durable water purification systems – CUP G53D23006660001 - Grant Assignment Decree No. 1384 adopted on 01.09.2023 by the Italian Ministry of Ministry of University and Research (MUR). References Lee, K.; Mazare, A.; Schmuki, P. (2014) One-dimensional titanium dioxide nanomaterials: Nanotubes. Chem. Rev., 114, 9385–9454.So, S.; Hwang, I.; Riboni, F.; Yoo, J.; Schmuki, P. (2016) Robust free standing flow-through TiO2 nanotube membranes of pure anatase. Electrochem. Commun., 71, 73–78. Figure 1: Morphology of nanotubular membrane. Figure 1

Fabrication of patterned TiO2 nanotube layers utilizing a 3D printer platform and their electrochromic properties

Anodization enables nano-structure fabrication through electrochemical parameter control. While various approaches exist for creating localized or patterned oxide layers, many are complex and time-consuming. This study adopted a commercial 3D printer for high-speed (1 mm/s) anodization, forming TiO2 nanotube layers on Ti substrates in G-code-designed patterns. Comprehensive characterization using XRD, SEM, XPS, and simulated electric field distribution analysis revealed well-defined nanostructures and provided insights into the formation mechanism. Furthermore, viologen-anchored TiO2 showed significantly improved electrochromic performance compared to pristine TiO2, with a higher reflectance difference (46.2% vs. 6.85%). This 3D printing-anodization hybrid method offers a rapid approach to fabricating patterned TiO2 nanostructures, showing promise for electrochromic devices with enhanced optical modulation capabilities.

A novel photocurable polymeric solid–solid phase change material for intelligent temperature regulators

The advancement of solid–solid phase change materials (SSPCMs) with crystalline segments embedded onto crosslinked polymer backbones offers a promising solution to the leakage problems associated with traditional phase change materials. Despite its potential, this technology faces challenges, including energy-intensive synthesis processes of SSPCMs and difficulties in custom designing materials for confined spaces. Herein, we introduce a novel strategy for the rapid preparation of polyurethane acrylate-based SSPCMs via UV-initiated polymerization. By leveraging crystalline segments from polyethylene glycol, the resulting SSPCM exhibits an impressive enthalpy of 110.4 J⋅g−1, enabling seamless transitions from rigid to soft states during solid–solid phase changes. When applied in portable electronic devices, this SSPCM can be synthesized in-situ to meet various size requirements, demonstrating exceptional temperature regulation performance based on latent thermal energy storage mechanisms. Furthermore, by integrating thin layers of carbon nanotubes (CNTs) onto the rough surfaces of SSPCM films and employing a face-to-face configuration to convert temperature-sensitive mechanical changes into electric resistance variations, we have engineered high-temperature alarms for SSPCM-based temperature regulators. The advantages of this preparation strategy, combined with the thermal regulation capabilities and innovative temperature alarm design, underscore the significant potential for intelligent and adaptive applications of SSPCMs in advanced technological landscapes.

Flexible antibacterial strain sensor with low electrical hysteresis, ultralow detection limit, and wide linear sensing range for human motion monitoring and human–machine interaction

Achieving low electrical hysteresis, an ultralow detection limit, and a wide linear sensing range is critical for the practical application of flexible strain sensors. However, the intrinsic viscoelasticity of the elastomer macromolecules can adversely affect the behavior of the conductive sensing network during stretching and relaxation, rending it challenging to simultaneously achieve these properties. Herein, a novel strategy is proposed to design a hybrid covalent-ionic crosslinking network within the elastomer and to construct a robust conductive carbon nanotube (CNT) layer on the elastomer surface using a swelling-driven penetration method. The hybrid crosslinking network gives the elastomer enhanced mechanical strength and exceptional stretchability, while reducing the dynamic losses of the macromolecules. It also reduces the impact of the elastomer macromolecules on the conductive layer during stretching. Even minimal strains are sufficient to induce slippage of the CNTs, leading to changes in resistance. As the strain increases, further disentanglement and slippage of the CNTs results in crack formation, which enables greater resistance variation and dominates the sensing mechanism. As a result, the as-prepared conductive elastomer-based strain sensors exhibit exceptional sensing performance, including low electrical hysteresis (2.3 %), ultralow detection limit (0.1 %), wide linear working range (690 %), and excellent durability (>10,000 cycles). The strain sensors have been successfully employed in human motion monitoring, human–machine interaction, and angle measurement. In addition, the incorporation of the ionic crosslinking network endows the sensor with excellent antibacterial properties. Consequently, the developed conductive elastomers hold significant promise for applications in smart wearable electronics.

Exploiting the Bragg Mirror Effect of TiO2 Nanotube Photonic Crystals for Promoting Photoelectrochemical Water Splitting.

Exploiting the Bragg mirror effect of photonic crystal photoelectrode is desperately desired for photoelectrochemical water splitting. Herein, a novel TiO2 nanotube photonic crystal bi-layer structure consisting of a top nanotube layer and a bottom nanotube photonic crystal layer is presented. In this architecture, the photonic bandgap of bottom TiO2 nanotube photonic crystals can be precisely adjusted by modulating the anodization parameters. When the photonic bandgap of bottom TiO2 nanotube photonic crystals overlaps with the electronic bandgap of TiO2, the bottom TiO2 nanotube photonic crystal layer will act as a Bragg mirror, leading to the boosted ultraviolet light absorption of the top TiO2 nanotube layer. Benefiting from the promoted UV light absorption, the TiO2 NT-115-NTPC yields a photocurrent density of 1.4 mA/cm2 at 0.22 V vs. Ag/AgCl with a Faradic efficiency of 100%, nearly two times higher than that of conventional TiO2 nanotube arrays. Furthermore, incident photon-to-current conversion efficiency is also promoted within ultraviolet light region. This research offers an effective strategy for improving the performance of photoelectrochemical water splitting through intensifying the light-matter interaction.

Balancing stretchability and conductivity: Carbon nanotube layer-enhanced non-ionic conductive hydrogels with a sandwich structure

In non-ionic conductive hydrogels, conductivity often conflicts with mechanical properties, posing a challenge in creating hydrogels that strike a balance between conductivity and mechanical properties. Here, we addressed this issue by integrating carboxylated carbon nanotube (CNT) layers in a sandwich structure onto the surface of the cationic hydrogel (P(AM-co-DMDAAC), PAD), followed by dehydration for densification. This approach simultaneously improved the conductivity of the hydrogel while maintaining its stretchability. The stability of the composite structure was ensured through electrostatic interactions, hydrogen bonding, and physical entanglement between the PAD hydrogel and the CNT layer. Additionally, adjusting the water–solid ratio of the hydrogel allows fine-tuning of its conductivity and stretchability. Remarkably, at a 500 % water–solid ratio, the hydrogel achieved a conductivity of 2.3 S/m. By further reducing the water content, the conductivity could be increased to 25 S/m, significantly higher than similar hydrogels. The PAD-CNT hydrogel found applications in swelling response, tunable resistance wires, and as strain sensors. Notably, the sandwich structure enables the PAD-CNT hydrogel to output capacitive signals, exhibiting a more sensitive response in monitoring human movement. Overall, this study introduces a novel composite structure for conductive hydrogels, holding tremendous potential in flexible conductivity and smart response fields.

The Development of a Flexible Humidity Sensor Using MWCNT/PVA Thin Films.

The exponential demand for real-time monitoring applications has altered the course of sensor development, from sensor electronics miniaturization, e.g., resorting to printing techniques, to low-cost, flexible and functional wearable materials. Humidity sensing has been used in the prevention and diagnosis of medical conditions, as well as in the assessment of physical comfort. This paper presents a resistive flexible humidity sensor composed of silver interdigitated electrodes (IDTs) screen printed onto polyimide film and an active layer of multiwall carbon nanotubes (MWCNT) dispersed in a water-soluble polymer, polyvinyl alcohol (PVA). Different MWCNT/PVA sensor sizes and MWCNT percentages are tested to study their effect on the initial electrical resistance (Ri) values and sensor response at different humidity percentages. The results show that the Ri values decrease with the increase in % MWCNT. The sensor size did not influence the sensor response, while the % MWCNT affected the sensor behavior upon relative humidity (RH) increments. The 1% MWCNT/PVA sensor showed the best response, reaching a relative electrical resistance, ΔR/R0, of 509% at 99% RH. Comparable with other reported sensors, the produced MWCNT/PVA flexible sensor is simpler, greener and shows a good sensitivity to humidity, being easily incorporated in wearable monitoring applications, from sports to medical fields.

Electrochemical characterization of TiO2 nanotubes formed on Ti6Al4V manufactured by PBF-EB or forging

AbstractThis study introduces the anisotropy effect of Ti6Al4V substrate obtained by electron beam melting (PBF-EB) on the anodizing process, revealing its capacity to induce anisotropic TiO2 nanotubes. Highly organized TiO2 nanotubes are formed on Ti6Al4V substrates produced through PBF-EB or forging, with the PBF-EB cross-orientation displaying superior nanotube growth due to enhanced catalytic activity. Morphological and electrochemical characterizations underscore the significant influence of substrate orientation and anodizing voltage on nanotube growth and corrosion resistance. PBF-EB-cross orientation at 30 V exhibits a thicker and more homogeneous nanotube layer, resulting in improved film resistance and substantially lower corrosion rates compared to forged substrates. The electrochemically calculated nanotube film thickness aligns with microscopic analyses, emphasizing the importance of a homogenous and resistive nanotube coating for effective corrosion control.

Harnessing SWCNT absorber based efficient CH3NH3PbI3 perovskite solar cells

This paper investigates the effect of incorporating a single-walled carbon nanotubes (SWCNTs) layer into the perovskite solar cell (PSC) structure as an effective technique to boost energy harvesting. The proposed PSC structure utilizes the SWCNTs layer underneath the CH3NH3PbI3 perovskite layer as an absorbing layer forming a novel design of (ITO/SnO2/CH3NH3PbI3/SWCNTs/NiOx/C) half tandem PSC structure. The suggested PSC structure is numerically analyzed using finite element method (FEM). The effects of varying thickness and doping concentration of the added layer and the material of rear electrode are investigated to maximize the power conversion efficiency (PCE) of the suggested PSC. Results of the 3D opto-electrical study and the energy bandgap analysis confirm that utilizing a 680 nm SWCNTs layer with doping concentration of 1.1 × 1020 cm-3 beneath a 150 nm perovskite layer enhances the PCE and short circuit current density (JSC) to 25.6%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$25.6\\%$$\\end{document} and 31.201mA/cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$31.201 mA/{cm}^{2}$$\\end{document}, respectively due to the improving of the PSC absorption by 27.65%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$27.65\\%$$\\end{document}. Higher performance of the proposed PSC has been achieved by using gold (Au) electrode instead of carbon (C) one, causing total enhancement of PCE and JSC of 6.185%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6.185\\%$$\\end{document} and 9.18mA/cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.18\\;mA/cm^{2}$$\\end{document}, respectively over their values for (ITO/SnO2/CH3NH3PbI3/P3HT/NiOx/C) structure reported in previously published literature. The proposed design can be considered as an efficient alternative to the conventional PSC owing to its higher performance and reduced toxicity.

Regulating Li electrodeposition by constructing Cu–Sn nanotube thin layer for reliable and robust anode‐free all‐solid‐state batteries

AbstractAnode‐free all‐solid‐state batteries (AF‐ASSBs) have received significant attention as a next‐generation battery system due to their high energy density and safety. However, this system still faces challenges, such as poor Coulombic efficiency and short‐circuiting caused by Li dendrite growth. In this study, the AF‐ASSBs are demonstrated with reliable and robust electrochemical properties by employing Cu–Sn nanotube (NT) thin layer (~1 µm) on the Cu current collector for regulating Li electrodeposition. LixSn phases with high Li‐ion diffusivity in the lithiated Cu–Sn NT layer enable facile Li diffusion along with its one‐dimensional hollow geometry. The unique structure, in which Li electrodeposition takes place between the Cu–Sn NT layer and the current collector by the Coble creep mechanism, improves cell durability by preventing solid electrolyte (SE) decomposition and Li dendrite growth. Furthermore, the large surface area of the Cu–Sn NT layer ensures close contact with the SE layer, leading to a reduced lithiation overpotential compared to that of a flat Cu–Sn layer. The Cu–Sn NT layer also maintains its structural integrity owing to its high mechanical properties and porous nature, which could further alleviate the mechanical stress. The LiNi0.8Co0.1Mn0.1O2 (NCM)|SE|Cu–Sn NT@Cu cell with a practical capacity of 2.9 mAh cm−2 exhibits 83.8% cycle retention after 150 cycles and an average Coulombic efficiency of 99.85% at room temperature. It also demonstrates a critical current density 4.5 times higher compared to the NCM|SE|Cu cell.