Al Nanoparticles Research Articles

Aluminum/Graphene Thermal Interface Materials with Positive Temperature Dependence.

Graphene is widely used in excellent thermal interface materials (TIMs), thanks to its remarkably high in-plane thermal conductivity (k∥). However, the poor through-plane thermal conductivity (k⊥) limits its further application. Here, we developed a simple in situ growth method to prepare graphene-based thermal interface composites with positively temperature-dependent thermal conductivity, which loaded aluminum (Al) nanoparticles onto graphene nanoplatelets (GNPs). To evaluate the variations in thermal performance, we determined the thermal diffusivity and specific heat capacity of the composites using a laser-flash analyzer and a differential scanning calorimeter, respectively. The Al nanoparticles act as bridges between the nanoplatelets, enhancing the k⊥ of the 1.3-Al/GNPs composite to 11.70 W·m-1·K-1 at 25 °C. Even more remarkably, those nanoparticles led to a unique increase in k⊥ with temperature, reaching 20.93 W·m-1·K-1 at 100 °C. Additionally, we conducted an in-depth investigation of the thermal conductivity mechanism of the Al/GNPs composites. The exceptional heat transport property enabled the composites to exhibit a superior heat dissipation performance in simulated practical applications. This work provides valuable insights into utilizing graphene in composites with Al nanoparticles, which have special thermal conductivity properties, and offers a promising pathway to enhance the k⊥ of graphene-based TIMs.

Activation and reaction mechanism of nano‐aluminized explosives under shock wave

AbstractTo investigate the effect of aluminum (Al) nanoparticles on the energy release mechanism of high explosives, a comprehensive analysis was conducted on the mechanical response and chemical reaction mechanism of pure 1,3,5‐Trinitro‐1,3,5‐triazinane (RDX) and nano‐aluminized RDX across varying particle velocities using molecular dynamics simulation. The simulation results show that the velocity of the shock wave which is formed in the explosive increases as the velocity of the particle increases. Notably, detonation was absent when the particle velocity was below 3 km/s, but prominently observed beyond this threshold, accompanied by a diminishing delay in reaction time for aluminum particles as particle velocity increased. After detonation, a localized pressure reduction behind aluminum particles was observed, elucidating the diminished detonation efficacy of aluminized explosives. Furthermore, the introduction of aluminum particles led to a deceleration in the RDX reaction rate, with the emergence of aluminum atomic clusters highlighting previously overlooked gas‐phase reactions that necessitate inclusion in detonation modeling for aluminized explosives.

Room-Temperature Polariton Lasing from CdSe Core-Only Nanoplatelets.

This paper reports how CdSe core-only nanoplatelets (NPLs) coupled with plasmonic Al nanoparticle lattices can exhibit exciton-polariton lasing. By improving a procedure to synthesize monodisperse 4-monolayer CdSe NPLs, we could resolve polariton decay dynamics and pathways. Experiment and theory confirmed that the system is in the strong coupling regime based on anticrossings in the dispersion diagrams and magnitude of the Rabi-splitting values. Notably, polariton lasing is observed only for cavity lattice periodicities that exhibit specific dispersive characteristics that enable polariton accumulation. The threshold of polariton lasing is 25-fold lower than the reported photon lasing values from CdSe NPLs in similar cavity designs. This open-cavity platform offers a simple approach to control exciton polaritons anticipated to benefit quantum information processing, optoelectronics, and chemical reactions.

Enhancing the performance of optoelectronic potential of CuO/Al nanoplats in a PVC for medium voltage cables applications

This study investigates the potential of incorporating CuO and Al nanoplates into a polyvinyl chloride (PVC) matrix to enhance the performance of medium voltage cables. The incorporation of nanoparticles into the PVC insulation material aims to improve the electrical, dielectric, and optical properties of the cable. The nanocomposite films were synthesized by dissolving PVC in tetrahydrofuran (THF) solvent and adding a mixture of 5 wt% CuO and Al nanoparticles. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the successful incorporation of the nanoparticles into the PVC matrix. The optical properties of the PVC/AlNPs and PVC/CuONPs + AlNPs nanocomposite films were characterized, revealing a decrease in band gap energy (4.35 eV) and Urbach tail energy (0.3702 eV) for the PVC/CuONPs + AlNPs film compared to the PVC/AlNPs film (4.5 eV and 0.41816 eV, respectively). Additionally, the PVC/CuONPs + AlNPs film exhibited higher absorption coefficients and increased electron delocalization and conjugation (carbon cluster value of 62.53). The dielectric properties of the CuONPs + AlNPs nanocomposites were investigated, with the sample containing 1.5% AlNPs demonstrating the highest AC conductivity (2.029 × 10−3 S/m), dielectric constant, and dielectric loss across the frequency range. Simulations of electric field distribution revealed that the PVC/CuONPs+1.5% AlNPs nanocomposite cable exhibited a more uniform electric field distribution compared to the PVC market cable, contributing to a reduction in electrostatic tension and a relative permittivity increase from 2.25 to 2.35. The electric potential distribution along the cable radius remained similar for both cable samples. These findings demonstrate the potential of nanocomposite insulation materials in enhancing the performance of medium voltage cables, paving the way for improved reliability, longevity, and efficiency.

Nanoscale Al precipitation in the Si phase in AlSi10Mg alloy during electron beam powder bed fusion

Additive manufacturing of Al alloys has garnered attention in the aerospace and automobile industries. This is the first study on the formation of nanoscale Al precipitates in the Si phase of an AlSi10Mg alloy during electron beam powder bed fusion (EB-PBF). Spherical Si particles were homogeneously dispersed in the Al matrix, highlighting the difference from the laser beam PBF (LB-PBF) microstructures. Nanoscale Al phase was formed with a crystallographic orientation relationship with the surrounding Si phase: (111)Si//(111)Al and [11¯0]Si//[11¯0]Al. The formation of Al nanoprecipitates was attributed to an interplay between non-equilibrium solidification, wherein excess Al was dissolved in the Si particles, and the subsequent decomposition of the supersaturated Si phase during high-temperature exposure owing to the preheating procedure. To the best of our knowledge, such formation of Al nanoparticles has not been reported in AlSi10Mg produced through conventional processing or LB-PBF. Thus, the unique thermal history of EB-PBF provides novel opportunities for microstructural evolution, which may be beneficial for the development of novel Al-based alloys.

Accelerating Surface Reaction Kinetics and Enhancing Bulk as well as Surface Charge Carrier Dynamics in Al/ Al2O3‐Coated BiVO4Photoanode

AbstractPhotoelectrochemical (PEC) hydrogen evolution from water splitting of semiconductor photoanodes is intricately linked to their light‐absorbing capacity, surface reaction kinetics, bulk charge carrier separation efficiency, and surface charge carrier injection efficiency. Harnessing the surface plasmon resonance effect of metals emerges as a promising approach to enhance PEC performance of semiconductor photoanodes. This work presents the first application of non‐noble metal Al nanoparticles to sensitize a BiVO4nanoporous film (NPF) photoanode. This process significantly expedites the surface kinetics of water oxidation, and improves both bulk charge carrier separation and surface carrier injection efficiencies of BiVO4NPF photoanode. Additionally, the surface‐formed Al2O3film effectively preserves the stability of photoanode, leading to a substantial improvement in PEC hydrogen evolution of BiVO4NPF photoanode in a three‐electrode PEC cell with sulfite scavenger. The constructed BiVO4/Al NPF heterojunction photoanode exhibits a hydrogen evolution rate of 73.9 µmol cm⁻2h⁻¹ at 1.23 V versus reversible hydrogen electrode, 1.68 times of BiVO4photoanode. Additionally, BiVO4/Al NPF photoanode exhibits excellent stability under long‐time light irradiation of 8 h. This study provides valuable insights into the design of nonnoble‐metal‐based plasmonic photoanodes for efficient hydrogen generation through PEC cell from the perspectives of surface reaction kinetics, charge carrier injection, and separation.

Secondary Atomization and Micro-Explosion Effect Induced by Surfactant and Nanoparticles on Enhancing the Combustion Performance of Al/JP-10/OA Nanofluid Fuel.

Aluminum/tetrahydrodicyclopentadiene/oleic acid (Al/JP-10/OA) nanofluid fuel is considered a potential fuel for aircraft powered by aviation turbine engines. However, an optimized formula for an Al/JP-10/OA system inducing a secondary atomization and micro-explosion effect and improving the burning performance needs to be developed. With this aim, in this work, the combustion characteristics of pure JP-10, JP-10/OA, JP-10/Al, and Al/JP-10/OA were experimentally tested, and a comparative analysis was conducted. Specifically, the influence of the surfactant and nanoparticle concentrations on the combustion characteristics of Al/JP-10/OA nanofluid fuel, including the flame structure, the flame temperature, the burning rate, the secondary atomization and micro-explosion effect, etc., were evaluated in detail. The results demonstrate that the addition of OA surfactant and Al nanoparticles had a significant effect on the burning rate of fuel droplets. The OA had an inhibition effect, while the Al nanoparticles had a promotion effect. As both OA and Al nanoparticles were added to the JP-10, the synergetic effect had to be considered. At the optimum ratio of OA to Al for the best suspension stability, there is a critical Al concentration of 1.0 wt.% from promotion to inhibition with increases in the Al concentration. The addition of OA and Al nanoparticles induced the secondary atomization and micro-explosion, resulting in an unsteady combustion and chaotic flame structure. The transient flame temperature of hundreds of Kelvins increased, the high-temperature flame zone widened, and thus, the energy release was elevated. Therefore, the combustion performance and energy release of Al/JP-10/OA nanofluid fuel can be improved through the secondary atomization and micro-explosion effect induced by the surfactant and nanoparticles.

Atomistic Insights into the Influence of High Concentration H2O2/H2O on Al Nanoparticles Combustion: ReaxFF Molecules Dynamics Simulation.

The combination of Al nanoparticles (ANPs) as fuel and H2O2 as oxidizer is a potential green space propellant. In this research, reactive force field molecular dynamics (ReaxFF-MD) simulations were used to study the influence of water addition on the combustion of Al/H2O2. The MD results showed that as the percentage of H2O increased from 0 to 30%, the number of Al-O bonds on the ANPs decreased, the number of Al-H bonds increased, and the adiabatic flame temperature of the system decreased from 4612 K to 4380 K. Since the Al-O bond is more stable, as the simulation proceeds, the number of Al-O bonds will be significantly higher than that of Al-H and Al-OH bonds, and the Al oxides (Al[O]x) will be transformed from low to high coordination. Subsequently, the combustion mechanism of the Al/H2O2/H2O system was elaborated from an atomic perspective. Both H2O2 and H2O were adsorbed and chemically activated on the surface of ANPs, resulting in molecular decomposition into free radicals, which were then captured by ANPs. H2 molecules could be released from the ANPs, while O2 could not be released through this pathway. Finally, it was found that the coverage of the oxide layer reduced the rate of H2O2 consumption and H2 production significantly, simultaneously preventing the deformation of the Al clusters' morphology.

An innovative aluminium foil electrode modified with Al nanoparticles and EDTA for lead detection in biological samples

This study presents a novel Aluminium foil-based electrode characterized by its affordability, flexibility, and ease of modification with carboxylic moiety-containing organic molecules. Upon foil modification with Aluminium nanoparticles and EDTA (AlNP-EDTA/AlE), the modified electrode exhibits remarkable activity in the oxidation of lead at potentials around −0.4 V. The lead signal is derived from the oxidation of lead deposited on the electrode surface using anodic stripping voltammetry (ASV). The addition of EDTA to AlNP/AlE increased the anodic peak current of lead by more than 500 %. The surface characterization of the electrode was performed by scanning electron microscopy (SEM) and infrared spectroscopy (IR), while its electroactive properties were evaluated by cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS). Optimal operating parameters include pH 2.1, square-wave voltammetry (SWV) with an accumulation time of 60 s and an accumulation potential of −0.8 V. A low detection limit of 0.20 µmol/L and a relative standard deviation (RSD) of 3.0 % were achieved using five different electrodes. The effectiveness of AlNP-EDTA/AlE was further demonstrated with consistent results in biological samples spiked with Pb.

Biodegradable Monometallic Aluminum as a Biotuner for Tumor Pyroptosis

AbstractPyroptosis is an effective anti‐tumor strategy. However, monometallic pyroptosis biotuners have not been explored until now. Here, we discover for the first time that biodegradable monometallic Al can act as a pyroptosis biotuner for tumor therapy. pH‐sensitive Al nanoparticles (Al@P) are obtained by equipping polyethylene glycol‐b‐(poly(methyl methacrylate)‐co‐poly(4‐vinylpyridine), which can exert their effect at the tumor site without affecting normal cells. The H2 and Al3+ release by Al@P in the acidic environment of tumors disrupts the redox balance and ionic homeostasis in tumor cells, thus generating large amounts of reactive oxygen species (ROS), leading to caspase‐1 activation, gasdermin D cleavage, and IL‐1β/LDH release, which induces canonical pyroptotic death. Meanwhile, the prodrug Doxorubicin (Pro‐DOX) is successfully loaded onto Al@P (Al@P‐P) and can be activated by ROS to release DOX in the tumor cells, thus further improving the tumor‐killing efficiency. Ultimately, Al@P‐P is degradable and exhibits efficient tumor inhibition.

Biodegradable Monometallic Aluminum as a Biotuner for Tumor Pyroptosis.

Pyroptosis is an effective anti-tumor strategy. However, monometallic pyroptosis biotuners have not been explored until now. Here, we discover for the first time that biodegradable monometallic Al can act as a pyroptosis biotuner for tumor therapy. pH-sensitive Al nanoparticles (Al@P) are obtained by equipping polyethylene glycol-b-(poly(methyl methacrylate)-co-poly(4-vinylpyridine), which can exert their effect at the tumor site without affecting normal cells. The H2 and Al3+ release by Al@P in the acidic environment of tumors disrupts the redox balance and ionic homeostasis in tumor cells, thus generating large amounts of reactive oxygen species (ROS), leading to caspase-1 activation, gasdermin D cleavage, and IL-1β/LDH release, which induces canonical pyroptotic death. Meanwhile, the prodrug Doxorubicin (Pro-DOX) is successfully loaded onto Al@P (Al@P-P) and can be activated by ROS to release DOX in the tumor cells, thus further improving the tumor-killing efficiency. Ultimately, Al@P-P is degradable and exhibits efficient tumor inhibition.

G-C3N4 modified with non-precious metal Al with LSPR as an efficient visible light catalyst.

The issue of water pollution has emerged as a formidable challenge, prompting a pressing need for solutions. The utilization of metal nanoparticles with surface plasmon resonance and semiconductor composite photocatalysts is regarded as a highly effective approach to solve this problem. g-C3N4 is an effective catalyst for the degradation of organic pollutants. Its photocatalytic performance is usually enhanced by the use of the noble metal Au Ag. However, the high cost of these materials limits their application. In this study, we present the synthesis of Al NPs/g-C3N4 nanocomposites using the bridging effect of ligands. The characterized of transmission electron microscopy (TEM), X-ray diffractometer (XRD) and ultraviolet-visible spectroscopy (UV-Vis) proved that Al NPs/g-C3N4 with a wider light absorption range were successfully synthesized. The effects of ligands, (glutathione (GSH), glutamic acid (GAG), and cysteine (CYS)), Al diameter (40 to 200 nm) and the ratio of Al to g-C3N4 (1:1 to 5:1) on the photocatalytic degradation of methylene blue (MB) by Al NPs/g-C3N4 were also evaluated. The results showed that the optimum degradation efficiency of Al NPs/g-C3N4 for MB at 5 mg/L reached 100% within 60 min, which was 11 times higher than that of pure g-C3N4. The principal analysis of Al enhancing the photocatalytic performance of g-C3N4 was studied through transient photocurrent spectroscopy (TPC), electrochemical impedance spectroscopy (EIS), and steady-state transient fluorescence spectroscopy (PL). The results confirmed that hot carriers generated by localized surface plasmon resonance (LSPR) of Al nanoparticles increase the carrier concentration. In addition, the Schottky barrier generated by Al and g-C3N4 could also improve the carrier separation rate and increase the carrier lifetime. This work is expected to solve the problem of organic wastewater treatment and lay the foundation for subsequent research on photocatalysis.

Enhancing Silicon Solar Cell Performance Using a Thin-Film-like Aluminum Nanoparticle Surface Layer.

Solar cells play an increasing role in global electricity production, and it is critical to maximize their conversion efficiency to ensure the highest possible production. The number of photons entering the absorbing layer of the solar cell plays an important role in achieving a high conversion efficiency. Metal nanoparticles supporting localized surface plasmon resonances (LSPRs) have for years been suggested for increasing light in-coupling for solar cell applications. However, most studies have focused on materials exhibiting strong LSPRs, which often come with the drawback of considerable light absorption within the solar spectrum, limiting their applications and widespread use. Recently, aluminum (Al) nanoparticles have gained increasing interest due to their tuneable LSPRs in the ultraviolet and visible regions of the spectrum. In this study, we present an ideal configuration for maximizing light in-coupling into a standard textured crystalline silicon (c-Si) solar cell by determining the optimal Al nanoparticle and anti-reflection coating (ARC) parameters. The best-case parameters increase the number of photons absorbed by up to 3.3%. We give a complete description of the dominating light-matter interaction mechanisms leading to the enhancement and reveal that the increase is due to the nanoparticles optically exhibiting both particle- and thin-film characteristics, which has not been demonstrated in earlier works.

Study on the Size Dependence of the Shell-Breaking Response of Micro/Nano Al Particles at High Temperature

The reactivity of Al nanoparticles is significantly higher than that of micron Al particles, and the thermal reaction properties exhibit notable distinctions. Following the previous studies on micron Al particles, the shell-breaking response of Al nanoparticles under vacuum conditions was analyzed using COMSOL simulation. Relationships between thermal stabilization time, shell-breaking cause, shell-breaking response time, and particle size were obtained, and a systematic analysis of the differences between micrometer and nanometer-sized particles was conducted. The results indicate that the thermal stabilization time of both micrometer and nanometer particles increases with the enlargement of particle size. The stress generated by heating Al nanoparticles with sizes ranging from 25–100 nm is insufficient to rupture the outer shell. For particles within the size range of 200 nm to 70 μm, the primary cause of shell-breaking is compressive stress overload, while particles in the range of 80–100 μm experience shell rupture primarily due to tensile stress overload. These results provide an important basis for understanding the shell-breaking mechanism of microns and nanoparticles of Al and studying the oxidation mechanism.

An Application of Polymer Nanocomposites Based On Carboxymethylcellulose along with Aluminium (Al) and Copper (Cu) Nanoparticles for Increasing Oil Production

As an agent for displacing residual and hard-to-recover oil reserves, polymer nanocomposites based on sodium salts of carboxymethylcellulose (CMC) and aluminium (Al) and copper (Cu) nanoparticles were investigated. It has been shown that polymer nanocomposites are more effective as oil displacement agents than the sodium salt of carboxymethylcellulose itself. Increasing the viscosity of an oil displacement solution can be achieved by varying the concentrations of CMC and nanoparticles. This study thoroughly examined the dynamic viscosities of carboxymethylcellulose (CMC) and polymer nanocomposites that contain CMC and metal nanoparticles (Al and Cu) across various concentrations. The results obtained are robust and reliable. It has been shown that, among polymer nanocomposites containing Al nanoparticles, there is a higher dynamic viscosity compared to its Cu nanoparticle counterpart at equivalent concentrations. This work proposes a simulation reservoir model to enhance oil recovery from hard-to-recovery reserves. Through this reservoir model simulation, the oil recovery factor was calculated using filler sand and oil extracted from a hydrocarbon field. The experimental data revealed the most effective concentration of CMC and nanoparticles for oil displacement. The results suggest that polymer nano composites composed of different metal nano powders have varying impacts on oil displacement efficiency. In this experiment, a composition consisting of Al nanoparticles with a size range of 50-70 manometers (nm) proved to be more successful as an oil displacement agent than a polymer nanocomposite made of Cu nanoparticles and CMC. At these concentrations and combinations, the highest oil recovery factors were achieved.

Perfluorotetradecanoic acid-directed precipitation of P(VDF-HFP) around nano-Al for the improved ignition and combustion characteristics

In this study, the self-assembly method is used to modify Al nanoparticles (Al NPs) with perfluorotetradecanoic acid (PFTD) to obtain Al@PFTD. Based on the C–F…F–C interaction and the hydrogen bond between –CF and –CH, the adsorbed PFTD is used to direct the precipitation of P(VDF-HFP) around modified Al NPs to obtain Al@PFTD@P(VDF-HFP) composite energetic materials. Scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy are used to characterize the prepared samples, which prove a successful preparation process. The prepared Al@PFTD@P(VDF-HFP) is compared with physically mixed Al/P(VDF-HFP) counterparts by thermal analysis, electric ignition and constant-volume combustion tests. Thermal analysis results show that the reaction onset temperature of Al@PFTD@P(VDF-HFP) is 20 °C lower while its heat release is 135% higher. Electric ignition and constant-volume combustion tests show that the ignition delay, combustion time and pressurization rate are 50% shorter, 50% shorter and 40% faster, respectively. The improved energetic performance is mainly due to PFTD-directed precipitation of P(VDF-HFP) around Al NPs. Moreover, the fluorine-containing PFTD also contributes positively to energy density and reactivity through the pre-ignition reaction.

STRUCTURAL AND DYNAMIC PROPERTIES OF ALUMINUM NANOPARTICLES DURING THE MELTING PROCESS

In recent years, nanoparticles, which play an important role in the development of nanotechnology, have been the focus of attention of many researchers. Metallic nanoparticles have many unique physical and chemical properties such as high thermal and electrical conductivity, high flexibility and strength, optical transmittance and chemical inertness compared to bulk materials due to surface effects. For the development and production of new nano-technological devices, a good understanding of the thermal, mechanical and electronic properties of nanoparticles is required. In this study, we investigated the structural and dynamic properties of metallic aluminum (Al) nanoparticles during the melting process using classical molecular dynamics (MD) simulation technique. In MD simulations, the interactions between Al atoms were described using embedded atom potentials (EAM). In order to observe how the thermal, structural and dynamic properties of Al nanoparticles change depending on the particle size and temperature, the potential energy, pairs distribution function, mean square displacement and diffusion coefficient of the system were calculated. The results obtained from MD simulations clearly showed that the melting point of nanoparticle increases as the particle size increases, and the structural and dynamic properties are directly related to the particle size and temperature.

Influence of High-frequency localized surface plasmon polariton effect of Al nanoparticles on luminescence efficiency of deep-blue BCzVBi OLED

It is difficult to enhance the blue or purple luminescence efficiency of organic light-emitting device ( OLED) for practice display applications. In this work, aluminum nano particles (Al-NPs) are inserted into the light-tight TmPyPb electron transporting layer (ETL) of ITO/PEDOT:PSS/TAPC/BCzVBi:BCPO/TmPyPb/Liq/Al OLEDs, in which BCzVBi can emit deep-blue fluorescent light, with the attempts to overcome the above deficiency through the local surface plasmon polariton(LSPP) effect excited in Al-NP at higher resonance frequencies by the luminescence radiations from BCzVBi. The distances of Al-NPs from BCzVBi:BCPO fluorescent layer are chosen as <i>x</i> = 4, 8, 12 nm. The morphologies observed by atom force microscope and scan electron microscope show that the Al film with a thickness of 1 nm, deposited at room temperature by vacuum heat evaporate, is composed of separated Al grains (therefore, called Al-NPs) with sizes on a 10 nm scale. By inserting these Al-NPs into the TmPyPb ETL, both the current density and luminance at the same voltage decrease in comparison with the counterparts of reference devices (i.e. ones without Al-NPs) due to the worsened carrier mobility. However, the current density and luminance both rebound significantly at <i>x</i> = 8 nm. This may be due to the fact that the fluorescence quenching strongly occurs at <i>x</i> < 8 nm, and on the other hand, the local surface plasmon polariton is weakened too much at <i>x</i> > 8 nm due to attenuated radiation from BCzVBi. At <i>x</i> = 8 nm, the voltage (9 V) at which the luminance reaches a maximum value is the same as that for the reference device, but the maximum luminance itself decreases from 4200 Cd/m<sup>2</sup> to 3500 Cd/m<sup>2</sup>. However, the current density also decreases from 335.19 mA/cm<sup>2</sup> to 145.71 mA/cm<sup>2</sup>. This conversely results in a promising great increase of current efficiency from 0.88 Cd·A<sup>–1</sup> to 2.36 Cd·A<sup>–1</sup>. Subsequently, the external quantum efficiency (EQE) is enhanced by 170%, while the efficiency roll-off ratio decreases from 78% to 30.5%, with a decrement of 61% . At a high current density of 270 mA/cm<sup>2</sup>, EQE enhances 66.5%. The coupling between fluorescence excitation state and local surface plasmon polariton is determined by the overlapping between fluorescence emitting peak and plasmon resonance peak. As aluminum has a number density of free electrons, 18.1×10<sup>22</sup> cm<sup>–3</sup>, much larger than those for the other normally used metals (such as gold and silver), its spectrum of local surface plasmon polariton is enough to cover the fluorescence wavelength range of BCzVBi. These research results show that the luminescence efficiency of deep-blue OLEDs can be turned better by LSPP excited in Al-NPs at higher resonance frequencies.

Influence of high-frequency localized surface plasmon polariton effect of Al nanoparticles on luminescence efficiency of deep-blue BCzVBi OLED

It is difficult to enhance the blue or purple luminescence efficiency of organic light-emitting device ( OLED) for practice display applications. In this work, aluminum nano particles (Al-NPs) are inserted into the light-tight TmPyPb electron transporting layer (ETL) of ITO/PEDOT:PSS/TAPC/BCzVBi:BCPO/TmPyPb/Liq/Al OLEDs, in which BCzVBi can emit deep-blue fluorescent light, with the attempts to overcome the above deficiency through the local surface plasmon polariton (LSPP) effect excited in Al-NP at higher resonance frequencies by the luminescence radiations from BCzVBi. The distances of Al-NPs from BCzVBi:BCPO fluorescent layer are chosen as <i>x</i> = 4, 8, 12 nm. The morphologies observed by atom force microscope and scan electron microscope show that the Al film with a thickness of 1 nm, deposited at room temperature by vacuum heat evaporate, is composed of separated Al grains (therefore, called Al-NPs) with sizes on a 10 nm scale. By inserting these Al-NPs into the TmPyPb ETL, both the current density and luminance at the same voltage decrease in comparison with the counterparts of reference devices (i.e. ones without Al-NPs) due to the worsened carrier mobility. However, the current density and luminance both rebound significantly at <i>x</i> = 8 nm. This may be due to the fact that the fluorescence quenching strongly occurs at <i>x</i> < 8 nm, and on the other hand, the local surface plasmon polariton is weakened too much at <i>x</i> > 8 nm due to attenuated radiation from BCzVBi. At <i>x</i> = 8 nm, the voltage (9 V) at which the luminance reaches a maximum value is the same as that for the reference device, but the maximum luminance itself decreases from 4200 Cd/m<sup>2</sup> to 3500 Cd/m<sup>2</sup>. However, the current density also decreases from 335.19 mA/cm<sup>2</sup> to 145.71 mA/cm<sup>2</sup>. This conversely results in a promising great increase of current efficiency from 0.88 Cd·A<sup>–1</sup> to 2.36 Cd·A<sup>–1</sup>. Subsequently, the external quantum efficiency (EQE) is enhanced by 170%, while the efficiency roll-off ratio decreases from 78% to 30.5%, with a decrement of 61%. At a high current density of 270 mA/cm<sup>2</sup>, EQE enhances 66.5%. The coupling between fluorescence excitation state and local surface plasmon polariton is determined by the overlapping between fluorescence emitting peak and plasmon resonance peak. As aluminum has a number density of free electrons, 18.1×10<sup>22</sup> cm<sup>–3</sup>, much larger than those for the other normally used metals (such as gold and silver), its spectrum of local surface plasmon polariton is enough to cover the fluorescence wavelength range of BCzVBi. These research results show that the luminescence efficiency of deep-blue OLEDs can be turned better by LSPP excited in Al-NPs at higher resonance frequencies.

Memory impairment induced by aluminum nanoparticles is associated with hippocampal IL-1 and IBA-1 upregulation in mice

ABSTRACT Objectives Increasing evidence indicates a link between aluminum (Al) intake and Alzheimer’s disease (AD). The main entry of Al into the human body is through oral route, and in the digestive tract, under the influence of the pH change, Al can be transformed into Al nanoparticles (Al-NP). However, studies related to the effect of Al-NP on the brain are limited and need further investigation. Neuro-inflammation is considered as one of the principal features of AD. Microglial activation and expression of the inflammatory cytokine IL-1β (interleukin-1β) in the brain have been used as hallmarks of brain inflammation. Therefore, in the present study, the hippocampal levels of ionized calcium-binding adaptor molecule 1 (IBA-1), as the marker of microglia activation, and IL-1β were assessed. Methods Adult male NMRI mice were treated with Al-NP (5 or 10 mg/kg) for 5 days. A novel object recognition (NOR) test was used to assess memory. Following cognitive assessments, the hippocampal tissues were isolated to analyze the levels of IL-1β and IBA-1 as well as beta actin proteins using western blot technique. Results Al-NP in both doses of 5 and 10 mg/kg impaired NOR memory in mice. In addition, Al-NP increased IL-1β and IBA-1 in the hippocampus. Discussion These findings indicate that the memory impairing effect of Al-NP coincides with hippocampal inflammation. According to the proposed relationship between AD and Al toxicity, this study can increase the knowledge about the toxic effects of Al-NP and highlight the need to limit the use of this nanoparticle.