Nanoparticle Thin Films Research Articles

Emissive Platforms Employing NaYF4‐based Upconverting Nanoparticles and Mesoporous Metal Oxide Thin Films

AbstractWe present the design and synthesis of a novel optically transparent platform based on the combination of NaYF4: Er3+, Yb3+ upconverting nanoparticles (UCNPs) and mesoporous metal oxide thin films (MOTFs). The UCNP were obtained by the thermolysis method and were deposited onto a glass substrate by spin coating. The MOTFs (TiO2, ZrO2 and SiO2), prepared by the combination of the sol‐gel approach and the self‐assembly of surfactants, were subsequently deposited on top of the particles giving rise to an ultrathin composite. The characterization of the obtained composite films indicates that they blend the properties of both starting materials: they exhibit upconverting properties, as they are capable of emitting visible light when irradiated in the NIR region, and the MOTFs deposited on top provide an ordered array of mesopores with highly accessible porosity. As the UCNPs emission properties depend on their surrounding temperature, the composite films were tested for temperature sensing applications, using both emission intensity and lifetimes of different signals, with promising results.

Structural and optical properties of TiO2:NiO nanoparticles thin films prepare by chemical spray pyrolysis

The properties of structural and optical of pure and doped nano titanium dioxide (TiO2) films, prepared using chemical spray pyrolysis (CPS) technique, with different nanosize nickel oxide (NiO) concentrations in the range (3-9)wt% have been studied. X-Ray diffraction (XRD) technique where using to analysis the structure properties of the prepared thin films. The results revealed that the structure properties of TiO2 have polycrystalline structure with anatase phase. The parameters, energy gap, extinction coefficient, refractive index, real and imaginary parts were studied using absorbance and transmittance measurements from a computerized ultraviolet visible spectrophotometer (Shimadzu UV-1601 PC) in the wavelengths range (300-800)nm. Optical properties of TiO2 affected by the adding of NiO impurity where the transmittance increased as NiO concentration increased but with more adding the transmittance returned to decrease again. It was found the extinction coefficient, refractive index, real and imaginary parts values decreased with increasing doping percentage up to 7% and then increases occur one more again at 9%. Energy gap values increased after doping with NiO where the values lies in the range was 3.31 to 3.51 eV .

Mechanistic Insights into Interactions at Urea-Hydroxyapatite Nanoparticle Interface.

Development of controlled release biomolecules by surface modification of hydroxyapatite nanoparticles has recently gained popularity in the areas of bionanotechnology and nanomedicine. However, optimization of these biomolecules for applications such as drug delivery, nutrient delivery requires a systematic understanding of binding mechanisms and interfacial kinetics at the molecular level between the nanomatrix and the active compound. In this research, urea is used as a model molecule to investigate its interactions with two morphologically different thin films of hydroxyapatite nanoparticles. These thin films were fabricated on quartz crystal piezoelectric sensors to selectively expose Ca2+ and PO43- sites of hydroxyapatite. Respective urea adsorption and desorption on both of these sites were monitored in situ and in real time in the phosphate buffer solution that mimics body fluids. The measured kinetic parameters, which corroborate structural predisposition for controlled release, show desorption rates that are one-tenth of the adsorption rates on both surfaces. Furthermore, the rate of desorption from the PO43- site is one-half the rate of desorption from the Ca2+ site. The Hill kinetic model was found to satisfactorily fit data, which explains cooperative binding between the hydroxyapatite nanoparticle thin film and urea. Fourier transform infrared spectra and X-ray photoemission spectra of the urea adsorbed on the above surfaces confirm the cooperative binding. It also elucidates the different binding mechanisms between urea and hydroxyapatite that contribute to the changes in the interfacial kinetics. These findings provide valuable information for structurally optimizing hydroxyapatite nanoparticle surfaces to control interfacial kinetics for applications in bionanotechnology and nanomedicine.

Engineering Fractal Photonic Metamaterials by Stochastic Self‐Assembly of Nanoparticles

The scale‐invariant features of fractal‐structured materials offer significant opportunities for the manipulation of short‐ and long‐range light–matter interactions in a 3D space, with recent photonics applications including biomolecular sensing and visible‐blind photodetectors. The development of synthesis methods for the large‐scale fabrication of fractal metamaterials with tuneable hierarchy bears significant potential and is the focus of many research fields. Among various fabrication routes, Brownian's motion‐driven coagulation of nanomaterials, below their sintering temperature, leads to fractal‐like structures presenting self‐similar properties at different length scales. Herein, an in‐depth investigation of the properties of fractal metamaterials obtained via the scalable self‐assembly of hot aerosols of TiO2, Bi2O3, and Au‐Bi2O3 nanoparticles, chosen as representative photonic materials, is reported. The fractal properties of these aerosol‐synthesized nanoparticle powders and thin films are systematically investigated via small‐angle X‐ray scattering (SAXS), image analysis, and theoretical modeling. It is demonstrated that in the diffusion‐limited aggregation (DLA) regime the fractal dimensions are preserved and in the range of 1.75–1.83 during the formation of the nanoparticle agglomerates, independently of the material. These findings provide a flexible platform for the engineering of macroscale 3D nanomaterials with hierarchical properties with potential applications ranging from energy harvesting to photocatalysis and sensing.

Magneto-optical effects of MgFe2O4 nanoparticles in solutions and thin films of polystyrene using digital Mach-Zehnder interferometer: An optical based sensor for energy storage controller

In this work, the effects of magnetic fields on the refractive index profiles and induced birefringence of polystyrene/MgFe2O4 nanoparticles (15 nm) solutions and thin films were investigated. Both the refractive index and the induced birefringence profiles of the solutions and thin films were investigated as a function of the applied magnetic field strength using the digital two-beam Mach-Zehnder interferometric method. Image processing algorithm, based on the fast Fourier transform (FFT) analysis, was applied to extract the optical phase differences of the recorded micro-interferograms for all samples under investigation. Then the refractive index and birefringence profiles are calculated. A good correlation between the applied magnetic field and the change of refractive index (Δn) was obtained (R2~0.94). This could be useful for electric energy storage sensors based on the magneto-optical properties of polystyrene/MgFe2O4 solutions and thin films.

Influence of deposition time and applied voltage on the properties of electrophoretically deposited nickel oxide colloidal nanoparticles thin film

ABSTRACT In the present work, nickel oxide nanoparticles (NPs) have been synthesised, using the laser ablation technique in aqueous suspension. By applying the electrophoretic deposition (EPD) method with direct current (DC), the nickel oxide NPs obtained have been deposited on an aluminium substrate. During the EPD process, different films have been produced by a variety of deposition times and applied voltages. The characterisation of the samples, including nickel oxide NPs suspension and nickel oxide deposited thin films, was carried out through different methods, such as X-ray diffractometry (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy and atomic force microscopy (AFM). The crystalline structure of the samples inspected by XRD showed that nickel oxide existed in NPs suspension and all the thin films. The morphology of the deposited films and dried NPs has been obtained by SEM. By observing the SEM micrographs, it was shown that deposition time and applied voltage change the morphology of the deposited thin films. In addition, AFM results demonstrated that the electrophoretic parameters have an effect on the average particles size, thickness and roughness of the deposited films. The optical properties of the NPs and deposited films have been analysed by UV–Vis–NIR spectroscopy.

A Study on the Coating Characteristics of VO₂ Nanoparticle Thin Film with Various Conditions of Ultrasonic Spray Coater.

Research on smart windows is accelerating with a global trend that emphasizes efficient energy use. VO₂ is representativematerial for thermochromic smart windows that can reflect part of sunlight depending on the external environment. We attempted to produce thermochromic thin films by ultrasonic spray coating of VO₂ nano inks. Ultrasonic spray coating is a technique that is widely used to form thin and uniform thin films, but optimization has been required due to problems such as surface roughness and coffee-ring effect. In this study, we investigated the effects of ultrasonic spray coating process conditions on the quality of VO₂ thin films, and attempted to optimize condition.

Effect of deposition time on the structure, direct and indirect energy gap of nanoparticles CdO thin films deposited by chemical bath deposition technique

In this research, cadmium oxide (CdO) nanoparticle thin films have been prepared at room temperature using a chemical bath deposition (CBD) technique, and the effect of the deposition time were studied. CdO thin films have been deposited on glass substrate from cadmium chloride (CdCl2) as cd +2 ions source and sodium hydroxide NaOH as O −2 ions source. The pH value (acidity level) of the chemical bath was fixed at about 11. The CdO thin films structures were analyzed by X-ray diffraction. It shows that all the prepared thin films have a cubic polycrystalline structure with a preferential orientation along (111) plane. All structural parameters were calculated. Particle size for the preferential orientation is calculated between (19.1-35.5 nm). It is found that the grain size increased with increasing the deposition time. UV-Vis spectrophotometer was used to study the optical properties, and a blue shift in the absorption peaks was noticed. The energy gap values (direct transition and indirect) calculated from the absorption spectrum located between (3.026-3.409 eV) for direct transitions and (2.197-2.917 eV) for indirect transitions, and this indicates that all CdO thin films prepared nanoparticles. We found that the energy gap decreased with increasing the deposition time.

DLP fabrication of TiO2 nanoparticle thin films

3D printing technology has become a valuable and successful tool for many areas, including materials sciences. Nanoparticle thin film fabrication commonly requires expensive, highly specialized equipment not available in basic sciences laboratories. A simple, inexpensive, and straightforward methodology for the deposition of thin films composed of semiconductor TiO2 nanoparticles using a DLP (Digital Light Processing) 3D printer is presented in this work. X-ray diffraction (XRD), Raman, Ultraviolet–visible (UV–Vis), and Photoluminescence (PL) spectroscopies were used to study the film's structural and optical properties. By analyzing Scanning Electron Microscopy (SEM) micrographs, particle size distribution and film thickness were studied. Single-layer TiO2 (anatase) thin films with thickness around 114.3 ± 39.5 nm were successfully deposited through DLP 3D printing. The deposited films can be used in sensors, energy harvesting, catalysis, hydrogen production, and other UV light applications.

Flexible NO gas sensor fabricated using graphene/silver nanoparticles stacked electrode structures

The study presents micro- and nano-structures forming a flexible gas sensor based on combinative coating and ultrashort-pulse laser techniques in graphene/silver nanoparticles (G-Ag) thin film electrodes on polyimide (PI) substrate. The prepared silver nanoparticles (AgNPs) revealed the nano-microstructures retain the characteristics of graphene (G). The irregularly distributed AgNPs were deposited on the surface of G sheets, promoting the formation of stacked porous structures with high specific surface area between the AgNPs and G sheets. Under temperature-assisted control, G-Ag composite structures with high sensitivity (response) and selectivity increase gas detection of nitric oxide (NO). This is due to the high adsorption capacity and stability of AgNPs for NO gas molecules, and therefore G-Ag thin film on flexible substrate is a potential sensor for gas detection.

Synthesis, Optical, Chemical and Thermal Characterizations of PMMA-PS/CeO2 Nanoparticles Thin Film.

We report the synthesis of hybrid thin films based on polymethyl methacrylate) (PMMA) and polystyrene (PS) doped with 1%, 3%, 5%, and 7% of cerium dioxide nanoparticles (CeO2 NPs). The As-prepared thin films of (PMMA-PS) incorporated with CeO2 NPs are deposited on a glass substrate. The transmittance T% (λ) and reflectance R% (λ) of PMMA-PS/CeO2 NPs thin films are measured at room temperature in the spectral range (250–700) nm. High transmittance of 87% is observed in the low-energy regions. However, transmittance decreases sharply to a vanishing value in the high-energy region. In addition, as the CeO2 NPs concentration is increased, a red shift of the absorption edge is clearly observed suggesting a considerable decrease in the band gap energy of PMMA-PS/CeO2 NPs thin film. The optical constants (n and k) and related key optical and optoelectronic parameters of PMMA-PS/Ce NPs thin films are reported and interpreted. Furthermore, Tauc and Urbach models are employed to elucidate optical behavior and calculate the band gaps of the as-synthesized nanocomposite thin films. The optical band gap energy of PMMA-PS thin film is found to be 4.03 eV. Optical band gap engineering is found to be possible upon introducing CeO2 NPs into PMMA-PS polymeric thin films as demonstrated clearly by the continuous decrease of optical band gap upon increasing CeO2 content. Fourier-transform infrared spectroscopy (FTIR) analysis is conducted to identify the major vibrational modes of the nanocomposite. The peak at 541.42 cm−1 is assigned to Ce–O and indicates the incorporation of CeO2 NPs into the copolymers matrices. There were drastic changes to the width and intensity of the vibrational bands of PMMA-PS upon addition of CeO2 NPs. To examine the chemical and thermal stability, thermogravimetric (TGA) thermograms are measured. We found that (PMMA-PVA)/CeO2 NPs nanocomposite thin films are thermally stable below 110 °C. Therefore, they could be key candidate materials for a wide range of scaled multifunctional smart optical and optoelectronic devices.

Manipulating SnO2 Growth for Efficient Electron Transport in Perovskite Solar Cells

AbstractSolution‐processed tin oxide (SnO2) is ubiquitously used as the electron transport layer (ETL) in perovskite solar cells, while the main concerns related to the application of SnO2 nanoparticles are the self‐aggregation potential and infeasible energy level adjustment, leading to inhomogeneous thin films and mismatched energy alignment with perovskite. Herein, a novel route is developed by adding a functional titanium diisopropoxide bis(acetylacetonate) (TiAcAc) molecule, comprising TiO44– core, functional CO, and long alkene groups, into the SnO2 nanoparticle solution, to optimize the electronic transfer property of SnO2 for efficient perovskite solar cells. It is found that the TiO44– can be used to tune the electronic property of the SnO2 layer, and the long alkenes can act as a stabilizer to avoid the nanoparticle aggregation and electronic glue among the SnO2 nanoparticles in the eventual nanoparticulate thin film, enhancing its homogeneity and conductivity. Furthermore, the residual CO groups on the ETL surface can strongly associate with the Pb2+ and improve the interface intimacy between the ETL and perovskite. As a result, the efficiency of perovskite solar cells can be boosted from 18% to above 20% with significantly reduced hysteresis by employing SnO2‐TiAcAc as electron transport layer, indicating a great potential for efficient perovskite solar cells.

Molecular Dynamics study on size dependencies of melting dynamics in Gold thin film

We explore the size dependencies of melting dynamics of Gold in the form of thin film. The sizes are 4.896 nm, 7.344 nm and 9.792 nm which is comparable between nanoparticle diameter and thin film thickness. The systems are treated by increasing temperature from 300 K to 1400 K. Molecular Dynamics (MD) scheme is employed to follow the trajectories of the systems up to 20 ps. Structure factor analysis indicated that the melting is suppressed by the increasing size.

Impact on Development of ZnS Nanoparticles Thin Film Deposited by Chemical Bath Deposition and Spin Coating

Research comparing the advantages of spin coating and chemical bath deposition is going, and there are varied views on these methods. Here, we used spin coating and chemical bath deposition to prepare thin films of ZnS nanoparticles. The film was analysed by photoluminescence (PL) spectrophotometry, field emission scanning electron microscopy (FE-SEM), ultraviolet spectroscopy (UV-Vis), and energy-dispersive X-ray (EDX) spectroscopy. The UV-Vis spectra revealed that the wavelength of ZnS is between 220 nm - 320 nm while the PL spectra showed a peak centred in the blue region. Both spin coating and chemical bath deposition rendered spherical nanoparticles but of different sizes 17.9 nm and 21.2 -25.7 nm, respectively. It was concluded that each method has its potential. This work can help researchers choose a suitable method for fabricating thin films, depending on the aims and objectives of their work.

Evaluation of Ni-Based Flexible Resistance Temperature Detectors Fabricated by Laser Digital Pattering.

Temperature sensors are ubiquitous in every field of engineering application since temperature control is vital in operating, testing and monitoring various equipment systems. Herein, we introduce a facile and rapid laser digital patterning (LDP) process to fabricate low-cost, Ni-based flexible resistance temperature detectors (RTDs). Ni-based RTDs are directly generated on a thin flexible polyimide substrate (thickness: 50 µm) by laser-induced reductive sintering of a solution-processed nonstoichiometric nickel oxide (NiOx) nanoparticle thin film under ambient conditions. The shape of RTDs can be easily adjusted by controlling computer-aided design (CAD) data without using the physical patterning mask while the sensitivity (temperature coefficient of resistance (α) ~ 3.52 × 10−3 °C−1) of the sensors can be maintained regardless of shape and size of the sensor electrodes. The flexible Ni-based RTDs can operate over a wide temperature range up to 200 °C with excellent repeatability. Additionally, the Ni-based RTDs respond quickly to the temperature change and can operate in corrosive environments including water and seawater. Moreover, the Ni-based RTDs show a superior mechanical and electrical stability with a negligible resistance change up to a radius of curvature of 1.75 mm. Finally, a tape-pull test demonstrates the robust adhesion of Ni-based RTDs on the substrate.

Ag modified bathocuproine:ZnO nanoparticles electron buffer layer based bifacial inverted-type perovskite solar cells

An Ag modified bathocuproine:ZnO nanoparticles (BCP:ZnO NPs) thin film was used as the buffer layer of inverted-type perovskite solar cells, which increased the bifacial power conversion efficiency from 6.82% to 15.50%. The surface-enhanced Raman scattering and absorbance spectra show that the Ag modified BCP small molecules can effectively passivate the surface oxygen defects of ZnO NPs and thereby increasing the crystallinity, which simultaneously increases the short-circuit current density (J SC ) and fill factor. It is noted that a high incident photon-to-electron conversion efficiency (IPCE) of 92% is achieved at the wavelength of 587 nm due to the constructive interference effect in the multilayer structure, which can be used to explain the high photocurrent generation in a semi-transparent solar cell. In addition, the light intensity-dependent experimental results of the bifacial perovskite solar demonstrates that the hole transportation is better than the electron transportation in the perovskite thin film. This concept can be readily used in the optimization of high-efficiency bifacial perovskite solar cells. • A bifacial PCE of 15.50% is achieved in the bifacial inverted-type MAPbI 3 solar cells. • Ag modified BCP:ZnO NPs thin film is used as the electron buffer layer of MAPbI3 solar cells. • The higher deposition rate of Ag results in the higher FF and PCE. • The asymmetric FF implies that the hole mobility is higher than electron mobility in MAPbI 3 thin films.

Laser-induced shock wave sintering of silver nanoparticles on flexible substrates

With the ever-increasing demand for lightweight, small, flexible, and portable devices, solving problems such as film cracking, delamination, and substrate damage has become a key issue in the direct fabrication of metal nanoparticle thin films on flexible substrates. In this work, we propose a method to sinter silver nanoparticles mechanically on heat-sensitive polymer substrates using a laser-induced shock wave generated by pulsed-laser ablation of a sacrificial layer. Physical mechanisms involved in silver nanoparticle sintering and properties of the sintered film were experimentally analyzed. Sintering of silver nanoparticles occurred predominantly by surface necking through solid-state atomic diffusion. In terms of density and electrical conductivity of the sintered films, the method shows substantially better sintering performance than typical sintering methods. Under optimal condition, near-full-density silver films were produced with an electrical resistivity as low as ~2.7 μΩ·cm. Consequently, this work demonstrates that the proposed laser-induced shock pressing technique has good potential for the fabrication of high-density metal films and patterns on heat-sensitive flexible substrates with exceptional film properties.

Morphology, Photoexcitation Dynamics and Stability of Water-Dispersed Nanoparticle Films based on Semiconducting Copolymer

Water dispersed nanoparticles from the poly [2,7- (9,9-dioctyl dibenzosylole) -alt-4,7-bis (thiophen-2-yl) benzo-2,1-thiadiazole] copolymer (PSiF-DBT) were synthesized using the colloidal mini-emulsion technique. This dispersion was used to prepare thin films by spin coating making it possible to compare with similar films obtained using organic solvents. The absorption measurements pointed that the band gap of the nanoparticle thin film remain unchanged, while steady state and time resolved photoluminescent measurements presented a difference in the mechanism of relaxation processes. Through photoexcitation dynamics, it was observed that there is a difference in the electronic transition time due to the material morphology. Nanoparticles with the dimensions 50 nm were produced, and morphological analyses presented a film with good substrate coverage and nanoparticles with spherical shapes. Near edge X-ray absorption fine structure, X-ray photoemission and resonant Auger spectroscopies were employed to investigate nanoparticle films electronic structure, degree of ordering, and charge transfer dynamics.

Effect of laser power on conductivity and morphology of silver nanoparticle thin films prepared by a laser assisted electrospray deposition method

Silver nanoparticle-based electrodes were studied extensively in recent years as an electrode material for wearable and flexible electronics due to their stability and conductivity. A wet chemical deposition technique is considered as a low-cost scalable technique. The current wet chemical-based nanoparticle deposition techniques include electrospray deposition, drop casting, spin coating, and the inkjet printing process. These techniques generally require a separate postdeposition annealing step. This can be a problem for substrates with a low melting point. In addition, some of the above-mentioned methods require physical contact, which increases the probability of cross-contamination. In this research, we present a technique that combines electrospray and laser radiation to deposit and sinter nanoparticles simultaneously on a rigid or flexible substrate. In this process, the microdroplets of aqueous silver nanoparticle suspension ejected in what is known as the microdripping mode from a metallic capillary nozzle, which can be controlled by an electric potential. A conical hollow laser beam is used to vaporize the liquid and sinter the nanoparticles at desired locations on a substrate. This is a promising technique compared to the traditional methods to fabricate conductive micropatterns due to its simplified one step deposition, suppressed cross-contamination, and applicability to various surfaces. Thin-film micropatterns of silver nanoparticles were fabricated using a Nd:YAG laser with powers from 5 to 13 W. The correlation between the grain size distribution, composition, and electrical resistivity was studied using a scanning electron microscope, energy-dispersive x ray, and four-point probe analysis. The results are comparable to the conventional thermal sintering method.

Simulation of the optical properties of gold nanoparticles on sodium alginate

In this contribution, we report on the simulation of optical reflectance and transmittance (R&T) taken on a set of gold nanoparticles thin film, deposited on sodium alginate by magnetron sputtering. The gold layer is very thin, so that the films are not continuous and the material is arranged in nanostructured layers. R&T spectra are simulated using the Generalized Transfer Matrix method applied to the film-on-substrate model. The gold NP films are simulated using the Drude-Lorentz model, by taking into account that the optical function of nanostructured gold exhibits increased collision frequency and reduced relaxation time. Moreover, the signal of localized surface plasmon, evident in the spectra, is simulated by introducing a dedicated modified Lorentz oscillator. The experimental results are well reproduced by the applied model. All trends (amplitude and energy position of the plasmon oscillator, film thickness, relaxation time) are correlated with the deposition parameters. The procedure represents a useful tool in the characterisation of such nanoparticles thin films.