Layer Of Nanoparticles Research Articles

Uniform lithium deposition guided by Au nanoparticles in vertical-graphene/carbon-cloth skeleton for dendrite-free and stable lithium metal anode

Owing to the high electrochemical reactivity and infinite volume expansion of lithium metal anode, the uncontrollable lithium dendrite growth drags the lithium metal anode out of the real application for a long time. Herein, a heterogeneous seed layer of Au nanoparticles (NPs) is uniformly deposited on the 3D porous vertical graphene nanosheets on carbon cloth (Au-VG/CC) to construct a lithiophilic surface, achieving a smooth and dendrite-free morphology. As a result, Au-VG/CC electrode delivers a small voltage hysteresis of 67.2 mV and a long cycling life of more than 500 h at a high current density of 5 mA cm−2 with 5 mAh cm−2. Results of XRD and in-situ transmission electron microscopy indicate that the formed lithiophilic layer is Li3Au which can guide the lithium deposition. Moreover, a full battery assembled with Li@Au-VG/CC as the anode and LiFePO4 as the cathode delivers 77.3 mAh g−1 at 100 mA g−1 after 200 cycles.

Photocatalytic degradation of gaseous pollutants on nanostructured TiO2 films of various thickness and surface area

This work deals with the preparation of TiO2 nanoparticulate layers of various mass (0.05 mg/cm2 to 2 mg/cm2) from three commercial nanopowder materials, P90, P25 and CG 300, their characterisation (profilometry, BET and SEM) and evaluation of their photocatalytic activity in the gaseous phase in a flow-through photoreactor according to the ISO standard (ISO 22197-2). Hexane was chosen as a single model pollutant and a mixture of four compounds, namely acetaldehyde, acetone, heptane and toluene was used for the evaluation of the efficiency of simultaneous removal of several pollutants. A linear dependence between the layer mass and the layer thickness for all materials was found. Up to a layer mass 0.5 mg/cm2, the immobilisation P90 and P25 powder did not result in a decrease in BET surface area, whereas with an increase in layer mass to 1 mg/cm2, a decrease of the BET surface was observed, being more significant in the case of P90. The photocatalytic conversion of hexane was comparable for all immobilised powders up to a layer mass of 0.5 mg/cm2. For higher layer mass, the photocatalytic conversion of hexane on P25 and P90 differ; the latter achieved about 30% higher conversion. In the case of the simultaneous degradation of four compounds, acetaldehyde was degraded best, followed by acetone and toluene; the least degraded compound was heptane. The measurement of released CO2 revealed that 90% of degraded hexane was mineralised to CO2 and water while for a mixture of 4 VOCs, the level of mineralisation was 83%.Graphical abstract

Acetic acid‐assisted mild dealloying of fine CuPd nanoalloys achieving compressive strain toward high‐efficiency oxygen reduction and ethanol oxidation electrocatalysis

AbstractDealloying by which the transition metal is partially or completely leached from an alloy precursor is an effective way to optimize the fundamental effects for further enhancing the electrocatalysis of a catalyst. Herein, to address the deficiencies associated with the commonly used dealloying methods, for example, electrochemical and sulfuric acid/nitric acid treatment, we report an acetic acid‐assisted mild strategy to dealloy Cu atoms from the outer surface layers of CuPd alloy nanoparticles to achieve high‐efficiency electrocatalysis for oxygen reduction and ethanol oxidation in an alkaline electrolyte. The leaching of Cu atoms by acetic acid exerts an additional compressive strain effect on the surface layers and exposes more active Pd atoms, which is beneficial for boosting the catalytic performance of a dealloyed catalyst for the oxygen reduction reaction (ORR) and the ethanol oxidation reaction (EOR). In particular, for ORR, the CuPd nanoparticles with a Pd/Cu molar ratio of 2:1 after acetic dealloying show a half‐wave potential of 0.912 V (vs. RHE) and a mass activity of 0.213 A mgPd−1 at 0.9 V, respectively, while for EOR, the same dealloyed sample has a mass activity and a specific activity of 8.4 A mg−1 and 8.23 mA cm−2, respectively, much better than their dealloyed counterparts at other temperatures and commercial Pd/C as well as a Pt/C catalyst.

A multi-scale aqueous dispersion coating technique for manufacturing carbon fiber reinforced PEEK composite

Carbon fiber (CF)/ PEEK composites were manufactured using towpregs impregnated with PEEK microparticles via an in-house developed dispersion coating method. The PEEK microparticles were dispersed in a self-stabilized aqueous solution of Polyimide (PI) precursor polyamic acid ammonium salt solution (PAAS). The dispersion coating produced a uniform coating of PEEK microparticles on the surface and along the cross-section of CF tow to overcome the low melt flow of PEEK, a high-performance thermoplastic. The PAAS formed a layer of PI nanoparticles on CF acting as an interface between CF and PEEK in the composite. The composites yielded a flexural strength of ∼1160 MPa; tensile strength of ∼1900 MPa; compressive strength of ∼600 MPa; interlaminar shear strength of ∼70 MPa and free of void evident from micro-CT and microstructure evaluations. A detailed physiochemical study of the dispersion, coated tow and composite are provided to understand the mechanism of the dispersion coating process.

Incorporation of ZnO/Ag-ZnO nanoparticles into a cotton fiber by the LbL method for Self-Cleaning applications

This paper reports the ZnO particles synthesis and characterization stabilized in poly-(diallyldimethylammonium chloride) polymer (ZnO-PDDA). By means of the TEM images, ZnO nanoparticles showed ellipsoid-shaped particles, with diameters ranging from 100–500 nm. The LbL method was utilized for the cotton fibers functionalization, using Ag and ZnO nanoparticles. The nano-hybrids incorporation through this method was carried out after a chemical modification in the cotton fabric surface. The functionalized cotton fibers characterization was performed and showed an excellent photocatalytic activity, degrading about 75 % of methylene blue (MB) in 8 h of sun exposure. The presence of one layer of Ag nanoparticles improved photocatalytic efficiency reasonably, completely degrading the MB dye in 4 h. Fabric washing tests showed that even after 15 consecutive-cycle washes, the particle detachment is minimal (about 0.1 ppm), so the LbL technique is a good alternative for the functionalization of new materials, including textile materials.

Stabilizing nucleation seeds in Li metal anode via ion-selective graphene oxide interfaces

Inhomogeneous lithium deposition is an intractable issue that would cause the uncontrollable formation of lithium dendrites, triggering the cycle-life and safety concern of lithium-metal batteries. Constructing lithiophilic sites is considered as an effective approach to modify the lithiophobic Cu current collector. However, whether the lithiophilic site is stable or can sustainably regulate the lithium deposition in the long-term cycling still keeps unknown. Herein, we conceive a unique “sandwich” anode composed of nanoscale Zn metals uniformly confined between GO and Cu foil. In such a unique structure the middle layer of lithiophilic Zn nanoparticles as a nucleation seed facilitates the deposition of lithium to form a zinc-lithium alloy, while the GO layer at the interface not only provides a channel for the rapid transport of lithium ions, but also has strong adsorption properties with Zn to ensure the stability of the nucleation seed during long-term cycling. As a result, the GO-protected alloy composite anode has a smaller overpotential and more stable cycling than the pure alloy anode and the graphene-protected unalloyed anode. Consequently, a high Coulombic efficiency above 98% for 200 cycles at 1 ​mA ​cm-2 and a prolonged lifespan of symmetrical cells for 600 ​h ​at 1 ​mA ​cm-2 with lower polarization are achieved, which further renders the commercial LiFePO4 (LFP) based full cell cathode (11.5 mg cm-2) with high rate capacity of 90 mAh g-1 at 5 C) and high capacity retention of 81.1% at 1 C after 100 cycles. This work provides a new insight into high-efficiency Li storage by sustainable alloy sites.

Ligand Exchange Reaction Enables Digital‐To‐Analog Resistive Switching and Artificial Synapse within Metal Nanoparticles

AbstractThe transition between digital and analog resistive switching in a single memristive device is beneficial for the reduction in power consumption and circuit complexity, the development of in‐memory neuromorphic computing, and the discovery of new switching mechanisms. However, achieving such transition is a challenge due to the complex switching mechanisms and device designs. Here, it is shown that the digital‐to‐analog resistive switching can be realized by the ligand exchange reaction of metal nanoparticles. The field‐injected copper cations migrate within carboxyl‐functionalized gold nanoparticle (AuNP) layer that are subsequently reduced into metallic filaments, enabling an abrupt resistive switching. Importantly, when the carboxyl groups on the gold nanoparticle are replaced by amino‐carboxyl ligands, the copper cations coordinate with the new ligands and create the conductance bridges to reduce the electron tunneling/hopping energy barriers, leading to continuous modulation in conductivity. This analog resistive switching allows to implement several important synaptic functions such as potentiation/depression, paired‐pulse facilitation, learning behaviors including forgetting curves and spaced learning effect. In the end, due to the non‐volatile characteristics, the gold nanoparticle synapse is used to build single layer perceptron for pattern classification with 100% accuracy.

Wearable Localized Surface Plasmon Resonance-Based Biosensor with Highly Sensitive and Direct Detection of Cortisol in Human Sweat

Wearable biosensors have the potential for developing individualized health evaluation and detection systems owing to their ability to provide continuous real-time physiological data. Among various wearable biosensors, localized surface plasmon resonance (LSPR)-based wearable sensors can be versatile in various practical applications owing to their sensitive interactions with specific analytes. Understanding and analyzing endocrine responses to stress is particularly crucial for evaluating human performance, diagnosing stress-related diseases, and monitoring mental health, as stress takes a serious toll on physiological health and psychological well-being. Cortisol is an essential biomarker of stress because of the close relationship between cortisol concentration in the human body and stress level. In this study, a flexible LSPR biosensor was manufactured to detect cortisol levels in the human body by depositing gold nanoparticle (AuNP) layers on a 3-aminopropyltriethoxysilane (APTES)-functionalized poly (dimethylsiloxane) (PDMS) substrate. Subsequently, an aptamer was immobilized on the surface of the LSPR substrate, enabling highly sensitive and selective cortisol capture owing to its specific cortisol recognition. The biosensor exhibited excellent detection ability in cortisol solutions of various concentrations ranging from 0.1 to 1000 nM with a detection limit of 0.1 nM. The flexible LSPR biosensor also demonstrated good stability under various mechanical deformations. Furthermore, the cortisol levels of the flexible LSPR biosensor were also measured in the human epidermis before and after exercise as well as in the morning and afternoon. Our biosensors, which combine easily manufactured flexible sensors with sensitive cortisol-detecting molecules to measure human stress levels, could be versatile candidates for human-friendly products.

A Facile Candle-Soot Nanoparticle Decoration Enables Dendrite-Free Zn Anodes for Long-Cycling Aqueous Batteries

The practical application of aqueous Zn-metal batteries (ZMBs) is largely hampered by awful parasitic reactions and notorious dendrite growth occurring on Zn anodes. Herein, we directly form a uniform candle-soot (CS) carbon nanoparticle layer on the Zn anode (denoted as CS-Zn) using a facile flame vapor deposition method. The CS layer tightly covers the Zn surface and thus mitigates electrolyte corrosion products. In addition, it balances the electric field and induces fast and even Zn nucleation, promoting interfacial reaction kinetics and suppressing dendrite growth. Benefiting from this synergy effect, CS-Zn allows a low voltage overpotential of 28 mV and a good cyclability (256 h) under an aggressive 5 mA cm–2/5 mAh cm–2 cycling in symmetric cells. Furthermore, the CS-Zn||NaV3O8·1.5H2O (NVO) full cell delivers a high initial capacity of 123.9 mAh g–1 and a capacity retention of 77.2% after over 1000 cycles at 2 A g–1, significantly surpassing those of the Zn||NVO cells (93.9 mAh g–1, 50.3%). The present work offers a simple and cost-efficient strategy to stabilize metallic Zn anodes in progressive aqueous batteries.

High response plasma-enhanced graphene/GaAs near-infrared photodetector

In this paper, a graphene/GaAs near-infrared photodetector with Ag nanoparticles (NPs) is fabricated and the photoelectric characteristics of the device under near-infrared light is investigated. By spin-coating a 30 nm Ag NPs layer on the surface of the device, the local surface plasmon resonance (LSPR) of the Ag NPs can enhance the absorption of near-infrared light, thereby improving the sensitivity of the device. Compared with the device without Ag NPs, the responsivity of the device is significantly increased to 96 mA/W (increased by 1.6 times) under zero bias voltage at 808 nm near infrared light, the maximum detectivity of the device can be up to 4.72 × 1011cmHz1/2W−1. In addition, the response time (τr) and recovery time (τf) of the device are 28.21 μs/68.11 μs. The quantum efficiency of the detector is increased from 37% to 84% compared with the device without Ag NPs. This result shows the graphene/GaAs photodetectors have a broad application prospect in the field of near-infrared detection.

Pd Nanoparticles/Au@SiO2 Core–Shell Nanostructures for Hydrogen Sensing

Herein, a multistep synthesis method was implemented to prepare nanoscale core@shell spherical heterostructures for H2 optical detection. The resulting nanoheterostructures are built with gold cores and silica shells further coated by a thin layer of spherical palladium nanoparticles. Samples with various thicknesses of silica and densities of palladium nanoparticles were synthesized and characterized by transmission electron microscopy. In particular, the three-dimensional core@shell configuration was confirmed by electron tomography. The optical properties of the obtained nanostructures were first analyzed by optical absorbance measurements, and their potential use for H2 detection was evaluated by simulations based on the discrete dipole approximation method. Thus, the optical response of the studied nanostructures is investigated theoretically when the Pd layer is hydrogenated, showing the great sensitivity achievable with these nanostructures.

Optical constants of multilayered colloidal ZnSe nanoparticles

The purpose of this study was to prepare multilayered films of colloidal ZnSe nanoparticles (NPs) and investigate their optical constants. Thin films comprising multilayered ZnSe–NPs were prepared on a SiO2 substrate using the layer-by-layer (LbL) method. The samples were studied using spectroscopic ellipsometry in the range of 0.75–3.20 eV. The film thickness increased linearly with the number of layers of colloidal NPs, and the prepared films were optically homogeneous. Furthermore, the refractive index of the ZnSe–NP films varied depending on the NP size owing to the quantum-confinement size effect. Multilayered ZnSe–NP films deposited using the LbL method are particularly useful as optical thin films because they can help control the film thickness and refractive index. It is expected that thin films with various refractive indices and corresponding dispersions can be produced using other semiconductor NPs and combinations thereof.

Ti3C2@Bi2O3 nanoaccordion for electrochemical determination of miRNA-21.

Based on a dual signal amplification strategy of novel accordion-like Bi2O3-decorated Ti3C2 (Ti3C2@Bi2O3) nanocomposites and hybridization chain reaction (HCR), an ultra-sensitive electrochemical biosensor was constructed for miRNA-21 detection. By etching Ti3AlC2 with HF, Ti3C2 with an accordion-like structure was first obtained and subsequently covered by Bi2O3 nanoparticles (NPs), forming Ti3C2@Bi2O3. A layer of Au NPs was electrodeposited on the glassy carbon electrode coated with Ti3C2@Bi2O3, which not only significantly improved the electron transport capacity of the electrode but also greatly increased its surface active area. Upon the immobilization of the thiolated capture probe (SH-CP) on the electrode, the target miRNA-21 specifically hybridized with SH-CP and thus opened its hairpin structure, triggering HCR to form a long double strand with the primers H1 and H2. A large number of the electrochemical indicator molecules were thus embedded inside the long double strands to produce the desirable electrochemical signal at a potential of - 0.19V (vs. Ag/AgCl). Such dual signal amplification strategy successfully endowed the biosensor with ultra-highsensitivity for miRNA-21 detection in a wide linear range from 1fM to 100pM with adetection limit as low as 0.16fM. The excellent detection of miRNA-21 in human blood plasma displayed a broad prospect in clinical diagnosis. An ultra-sensitive electrochemical biosensor was successfully constructed for miRNA-21 detection in human blood plasma based on the dual signal amplification strategy of novel accordion-like Bi2O3 decorated Ti3C2 (Ti3C2@Bi2O3) nanocomposites and hybridization chain reaction.

Stable Quantum Dot Light-Emitting Diodes Employing TiO2 Nanoparticles as a Mixed Emission Layer

Colloidal quantum dots (QDs) have attractive optical and electrical characteristics for various applications in the display industry. They have superb properties including color tunability, which is achieved by controlling the particle size and solution processes used for quantum dot light-emitting diodes (QLEDs). Here we demonstrate high efficiency QLEDs that consist of a mixed layer of TiO2 nanoparticles (NPs) and QDs. ZnO is the key material responsible for the promising results of the electroluminescence devices, which exhibited well-matched energy levels and robustness. In this report, Li-doped TiO2 NPs were synthesized under ambient conditions as an alternative electron transport layer (ETL) for QLEDs. A stable mixture of TiO2 NPs and QDs was prepared in chlorobenzene and then applied to QLEDs without a conventional ETL. QLEDs with such a simplified structure produce a maximum luminance of 123,311 cd/m<sup>2</sup> with a current efficiency of 40.5 cd/A. These results are comparable to those of conventional QLEDs. Additionally, the predicted T50 at 100 cd/m<sup>2</sup> was 1,420 h, based on the T50 at 1,600 cd/m<sup>2</sup>. These clearly indicate not only the promising results of the TiO2 NPs as an inorganic ETL, but also the remarkable performance of the simplified device with less layers. The reduction in fabrication steps using this solution-based process is also advantageous for next-generation display technology.

Poly(Glycerol)-Based Biomedical Nanodevices Constructed by Functional Programming on Inorganic Nanoparticles for Cancer Nanomedicine

Nanomedicine is promising to improve conventional cancer medicine by making diagnosis and therapy more accurate and more effective in a more personalized manner. A key of the cancer nanomedicine is construction of medical nanodevices by programming various requisite functions to nanoparticles (NPs). As compared to that of soft NPs, including organic micelles and polymers, fabrication of an inorganic NP based nanodevice is still challenging; the approved nanoformulations have been confined to the limited number of superparamagnetic iron oxide NPs (SPIONs). The major challenges lie in how to program the requisite functions to inorganic NPs. In spite the much denser and less hydrophilic properties of inorganic NPs, most of the following functions have to be programmed for their in vivo applications: (A) high dispersibility in a physiological environment, (B) high stealth efficiency to slip through the trap by liver and spleen, (C) high targeting efficiency to cancer tissue, (D) clear visualization of cancer for diagnosis, and (E) high anticancer activity for treatment.In our approach, poly(glycerol) (PG), containing a hydroxy group at every monomer unit, was found as a better alternative to poly(ethylene glycol) (PEG), the most commonly used hydrophilic polymer, giving (A) high dispersibility to inorganic NPs. Although most of the inorganic NPs are not dense in functional groups, the hyperbranched structure with many hydroxy groups in PG turns the less functional surface into highly functional one, imparting not only good hydrophilicity but also (B) high stealth efficiency as we reported recently. In addition, a number of hydroxy groups in PG afford the structural or functional extensibility to introduce the additional layer or function. This enables us to design and construct a three-layer architecture consisting of a core inorganic NP, a hydrophilic and stealthy PG layer, and a functional molecule layer, where their interfaces are connected firmly by covalent bonds. The three-layered nanodevice is very flexible in its design for the following reasons: The PG coating can be applied to a wide variety of inorganic NPs with various functions, and various functional moieties can be introduced on the PG layer as a functional molecule layer. Owing to the versatility of the three-layer model, the rest of the above functions (C)-(E) can be programed in the NP core and/or the outmost layer in nanodevices.In this Account, the author described first the methodology for precise construction and quantitative characterization of various biomedical nanodevices. This fundamental aspect of this research has been achieved by "applying organic chemistry to nanomaterials" which is the concept of our research. That is, the rich chemistry in synthesis and characterization of organic compounds has been applied to the nanodevice fabrication and characterization. Second, evaluation of the functions programmed in the nanodevices is described in terms of stealth and targeting efficiencies, cancer diagnosis and therapy, and biomedical sensing. This stage in our research made us more interdisciplinary from chemistry and nanoscience to biology and medicine. The following research spiral has been established in our group to strongly promote the improvement of our biomedical nanodevices; nanodevice design → precise construction → quantitative characterization → functional evaluation.

Highly sensitive surface plasmon resonance sensor for refractive index detection of Helicobacter Pylori

Helicobacter Pylori (H-Pylori) is gram-negative and spiral micro-organism that is responsible for its colonization in gastric microniche. The outcome of recent studies indicates that the development of H-Pylori in human bodies results in peptic ulcers, gastric mucosa, and gastric cancer. Therefore, on-time diagnosis of H-Pylori infection is very important to overcome its adverse effects. In this work, we have adopted the surface plasmon resonance (SPR) sensor for the detection of H-Pylori infection in human bodies. The SPR phenomenon is initiated by placing a 40–50 nm thick layer of gold nanoparticles on the flat surface of the glass prism. Four different configurations are designed by immobilizing a layer of biocompatible materials. Probe 1, 2, 3, and 4 are designed by immobilizing the layers of silicon oxynitride (SiON), molybdenum oxide (MoS2), graphene oxide (GO), and graphene, respectively. Added to this, the specificity of all the sensor structures is attained by functionalizing them with a 0.11 nm thick layer of urease enzyme, which oxidizes only in the presence of H-Pylori. Thereafter, the sensing analysis of all the sensor probes is done in a wide range of refractive index (RI) from 1.3227 to 1.3382 which corresponds to the RI of human urine in presence of H-Pylori. The performance analysis of the sensor is done in the terms of sensitivity, detection accuracy (DA), quality factor (QF), the figure of merit (FoM), and dip of a figure of Merit (DFoM). Added to this, the signal propagation through all the sensor structure is analyzed by using two-dimensional finite-difference-time-domain (FDTD) method-based tool.

Dynamics of Citrate Coordination on Gold Nanoparticles Under Low Specific Power Laser-Induced Heating.

SERS evolution recorded over a drop-coated coffee-ring pattern of citrate-capped gold colloids was investigated as a function of time under low-specific laser power. Spectral changes caused by plasmon-induced reaction could not be detected, but a long-term transient original spectral profile showing additional lines was observed. We performed deep qualitative and quantitative SERS intensity variation analysis based on the complementary use of extreme deviation and cross-correlation statistics, which provided further insights on the behavior of citrate-capping layers of gold nanoparticles upon laser illumination. More precisely, the cross-correlation analysis made possible to follow the so-called individual events denoting particular resonance structures, in which groups of modes were assigned to an evolution of citrate coordination on gold surface driven by photo-activation. As a consequence, the detection limit was increased and new lines were related to the presence of a very low amount of dicarboxy-acetone (DCA), which was already present in the system.

Assessment of back-side activation of titania thin film using a fixed-bed photocatalytic-reactor: Kinetic study, operating cost and ANN modeling

This work is concerned with construction, application and modeling of a thin-film fixed photocatalytic bed multi lamp photo-reactor as an organic pollutant treatment system. Five photocatalytic units were located in a cylindrical vessel with a recycling current. In each unit, a thin layer of titania nanoparticles was coated on the outer surface of a quartz tube which a UV lamp was installed inside it. By this configuration, the UV lamps irradiation can approach directly to the photocatalyst particles before penetration into the reaction media. The effect of initial pH, initial DR16 (as model pollutant) dosage, H2O2 (as auxiliary oxidant) concentration and number of applied activated photocatalytic units were studied. The process was monitored via the kinetic rate constant and operating cost factors. The photocatalytic degradation of DR16 molecules in the constructed multi lamp photo-reactor followed a pseudo-first-order kinetic, and well described by the Langmuir-Hinshelwood equation. Under the initial pH of 3, 150 mg/L of H2O2 and illumination of the five lamps, complete degradation of the target pollutant was achieved after 60 min. Under these conditions, the rate constant and operating cost were 0.078 min−1 and 1.13 US$/m3 respectively. The real photon flux inside the reactor and quantum efficiency of the photocatalytic degradation of DR16, using five turned on lamps, were evaluated as 10.84 × 10−6 (einstein.s−1) and 0.009 respectively Also, the photocatalytic process was well modeled (with mean square error of 16.81 ×10−5) by a three layered feed forward back propagation artificial neural network consists of trainlm as training function, 7 hidden neurons and tansig-tansig as transfer functions calibrated at 156th epoch.

Influence of filling rate and working fluid on thermal performance of heat pipes using nanoparticle layer as wick

Influence of filling rate and working fluid on thermal performance of heat pipes using nanoparticle layer as wick

Investigation of Dielectric Functions of a Layer of Ag Nanoparticles on Silicon Using Spectro-Ellipsometry and Spectrophotometry

Investigation of Dielectric Functions of a Layer of Ag Nanoparticles on Silicon Using Spectro-Ellipsometry and Spectrophotometry