Particle Film Research Articles

Practical model for improved classification of trace chemical residues on surfaces in active spectroscopic measurements

Trace chemical detection and classification in stand-off reflection-based spectroscopic data is challenging due to the variability of measured data and the lack of physics-based models that can accurately predict spectra. Most available models assume that the chemical takes the form of spherical particles or uniform thin films. A more realistic chemical presentation that could be encountered is that of a nonuniform chemical film that is deposited after evaporation of the solvent that contained the chemical. We present an improved signature model for this type of solid film. The proposed model, called sparse transfer matrix, includes a log-normal distribution of film thicknesses and is found to reduce the root mean square error between simulated and measured data by about 25% when compared with either the particle or uniform thin film models. When applied to measured data, the sparse transfer matrix model provides a 10% to 28% increase in classification accuracy over traditional models.

SCHOTTKY DIODE FABRICATION VIA COLD SUBSTRATE EVAPORATED Ag ON SOL-GEL DERIVED ZnO ULTRA-THIN FILMS FOR SEMICONDUCTOR DEVICES

ZnO thin films were grown on glass and SnO2 substrate by using Sol-gel method with a simple, low cost-temperature and high controlled away. ZnO thin films were contacted with Ag in two different temperatures at 200K (cold substrate) and 300K (room temperature) by PVD Cold Substrate Method. Characterization of the obtained films and Schottky diodes studied by XRD, SEM, Optical and Electrical measurements. The average particle size and film thickness of the films were calculated as ~25 and ~300nm. Bandgap of the ZnO films coated on different substrates was calculated to be around 3.29-3.31 eV. Peaks of various types of defects were observed in different wavelengths from photoluminescence measurements. The barrier height and ideal factor values of Ag/ZnO Schottky diodes at 200K and 300K were (0.48-0.43eV; 15.60) and (0.66-0.15eV; 8.6- 7.41), respectively. The series resistance values (4.46Ω; 4.88Ω) at 200K and (3.65Ω; 4.78Ω) at 300K were obtained from two different methods, respectively. Diodes made at 200K temperature were found to have a higher ideality factor. However, while 75% of all produced Schottky diodes at 200K substrate temperature show rectifying feature, this rate is only 25% in contacts made at 300K substrate temperature.

Particle films: chabazitic zeolites with added microorganisms in the protection and growth of tomato plants (Lycopersicon esculentum L.)

In this experiment, given the excellent premises for the use of zeolites in agriculture, the biostimulation and protection capacity of a new chabazite zeolite enriched with microorganisms on tomato plants was evaluated, in order to introduce sustainable innovations on the market that can facilitate the reduction of plant protection products and synthetic fertilizers. The experimentation was divided into two parallel trials, one concerning the growth and biostimulation of tomato plants by mixing appropriate amounts of zeolite enriched with microorganisms (diameter of zeolite 3-6 mm) to the growing medium. The second experiment, instead, concerned the use of micronized chabazite zeolites (D 10 µm) enriched with microorganisms in the protection from pathogenic fungi (Phytophthora infestans, Leivellula taurica). The test showed a significant improvement in agronomic parameters analysed in tomato plants treated with granular chabazite (3-6 mm) enriched with microorganisms and an improvement in protection against Phytophthora infestans and Leivellula taurica with the use of micronized zeolite also enriched with microorganisms. Zeolites and more specifically chabazite once added into the growing medium can improve the absorption of water and fertilisers and also increase the quality of cultivated plants. The presence of beneficial microorganisms added to chabazite, further improves these aspects and provides the plant with greater protection from biotic and abiotic stress.

Particle films: chabazitic zeolites with added microorganisms in the protection and growth of tomato plants (Lycopersicon esculentum L.)

Particle films: chabazitic zeolites with added microorganisms in the protection and growth of tomato plants (Lycopersicon esculentum L.)

On the Effect of Modified Carbohydrates on the Size and Shape of Gold and Silver Nanostructures.

Gold (Au) and silver (Ag) nanostructures have widespread utilization from biomedicine to materials science. Therefore, their synthesis with control of their morphology and surface chemistry have been among the hot topics over the last decades. Here, we introduce a new approach relying on sugar derivatives that work as reducing, stabilizing, and capping agents in the synthesis of Au and Ag nanostructures. These sugar derivatives are utilized alone and as mixture, resulting in spherical, spheroid, trigonal, polygonic, and star-like morphologies. The synthesis approach was further tested in the presence of acetate and dimethylamine as size- and shape-directing agents. With the use of transmission electron microscopy (TEM), selected area electron diffraction (SAED), x-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) absorption spectroscopy techniques, the particle size, shape, assembly, aggregation, and film formation characteristics were evaluated. NPs’ attributes were shown to be tunable by manipulating the sugar ligand selection and sugar ligand/metal-ion ratio. For instance, with an imine side group and changing the sugar moiety from cellobiose to lactose, the morphology of the Ag nanoparticles (NPs) transformed from well dispersed cubic to rough and aggregated. The introduction of acetate and dimethylamine further extended the growth pattern and morphological properties of these NPs. As examples, L5 AS, G5AS, and S5AS ligands formed spherical or sheet-like structures when used alone, which upon the use of these additives transformed into larger multicore and rough NPs, revealing their significant effect on the NP morphology. Selected samples were tested for their stability against protein corona formation and ionic strength, where a high chemical stability and resistance to protein coating were observed. The findings show a promising, benign approach for the synthesis of shape- and size-directed Au and Ag nanostructures, along with a selection of the chemistry of carbohydrate-derivatives that can open new windows for their applications.

Kaolin Reduces ABA Biosynthesis Through the Inhibition of Neoxanthin Synthesis in Grapevines Under Water Deficit.

In many viticulture regions, multiple summer stresses are occurring with increased frequency and severity because of warming trends. Kaolin-based particle film technology is a technique that can mitigate the negative effects of intense and/or prolonged drought on grapevine physiology. Although a primary mechanism of action of kaolin is the increase of radiation reflection, some indirect effects are the protection of canopy functionality and faster stress recovery by abscisic acid (ABA) regulation. The physiological mechanism underlying the kaolin regulation of canopy functionality under water deficit is still poorly understood. In a dry-down experiment carried out on grapevines, at the peak of stress and when control vines zeroed whole-canopy net CO2 exchange rates/leaf area (NCER/LA), kaolin-treated vines maintained positive NCER/LA (~2 µmol m−2 s−1) and canopy transpiration (E) (0.57 µmol m−2 s−1). Kaolin-coated leaves had a higher violaxanthin (Vx) + antheraxanthin (Ax) + zeaxanthin (Zx) pool and a significantly lower neoxanthin (Nx) content (VAZ) when water deficit became severe. At the peak of water shortage, leaf ABA suddenly increased by 4-fold in control vines, whereas in kaolin-coated leaves the variation of ABA content was limited. Overall, kaolin prevented the biosynthesis of ABA by avoiding the deviation of the VAZ epoxidation/de-epoxidation cycle into the ABA precursor (i.e., Nx) biosynthetic direction. The preservation of the active VAZ cycle and transpiration led to an improved dissipation of exceeding electrons, explaining the higher resilience of canopy functionality expressed by canopies sprayed by kaolin. These results point out the interaction of kaolin with the regulation of the VAZ cycle and the active mechanism of stomatal conductance regulation.

Assessment of the efficiency of different control programs to reduce Trioza apicalis Först. (Triozidae: Hemiptera) feeding damage and the spread of “Candidatus Liberibacter solanacearum” on carrots (Daucus carota ssp. sativus L.)

AbstractThe control of carrot psyllid Trioza apicalis Förster largely relies on chemical measures, and the current integrated pest management (IPM) strategy is based on pest scouting. The number of active ingredients available for psyllid control will further decline in the coming years. The need for alternative control measures is therefore urgent. In this work the efficiency of different control programs including a kaolin particle film and plant‐derived, crude saponin extract, chemical control, insect net and IPM (kaolin in combination with insecticides) programs to reduce psyllid feeding damage, reproduction and the spread of “Candidatus Liberibacter solanacearum” (CLso) in carrots was studied. Each year in 2016–2018, four replicates of each treatment were randomised in a row‐column design on a commercial carrot farm. After the treatments were executed, the psyllid nymphs and eggs were counted. At the harvest, the carrot roots and shoots were weighed, damages assessed, and samples were taken for CLso detection from 50 plants at each replicate. Kaolin treatment alone and in combination with insecticides effectively reduced the number of psyllid nymphs and eggs in all the years studied. Saponin was applied only on the first year, since it significantly increased the number of T. apicalis eggs compared to other treatments. The insect net was superior to other treatments in all the studied aspects in all the years. Under normal weather conditions, the highest root weight was harvested under the insect net, followed by the chemical control program consisting of pyrethroids, kaolin treatment, untreated control and saponin treatment. During extreme weather conditions, chemical control programs were not effective at protecting the carrots from psyllid feeding, which was reflected as low root yield. In all years, the carrot leaf damage percent negatively correlated with the root weight. Similarly, the shoot:root ratio increased as the leaf‐curling percentage rose, which was even pronounced under drought stress. The effect of climatic stress should be considered when developing IPM strategies.

Effects of kaolin-based particle film on physiological, nutritional, nutraceuticals parameters and Ceratitis capitata infestations in peach fruit at harvest and after storage

The Mediterranean fruit fly (Ceratitis capitata Wiedemann) is a worldwide pest of economi importance because attacks a large number of agricultural crops and for the extent of the damage it causes. Among the alternative control strategies to the use of sprays with synthetic insecticides, a very important role can be played by powders obtained from rocks whose activity arise from the ability to form a film of white powder, which acts as a repellent and irritant to insects. This film can also interfere with plants’ physiology and affect quality of fruit. In this study the efficacy of a commercial kaolin-based formulation to control medfly infestations was compared to synthetic insecticides commonly used against this pest (phosmet, alfa-cypermethrin, deltamethrin). The results showed a significant reduction of medfly attacks in fruits treated with insecticides (1.5% damaged fruit) or with kaolin (0.5% damaged fruits) compared to the untreated sample (10% damaged fruits), while physiological and quality parameters ded not show relevant differences between treatments and control fruit. Overall results highlight how the use of kaolin represents a valid alternative to treatments with synthetic insecticides to control C. Capitata attacks on peaches, while not affecting fruits’ quality.

Zinc chloride–activated glycerine pitch distillate for methylene blue removal—isotherm, kinetics and thermodynamics

This work was aimed at evaluating the adsorptive properties of glycerine pitch distillate-based activated carbons by zinc chloride activation. A commercial activated carbon derived from petroleum pitch distillate was employed for comparison. Activated carbons were characterized for elemental composition, textural characteristics, and surface chemistry. The adsorption data were analyzed using isotherm and kinetic models, and thermodynamic parameters. The specific surface area of activated carbons is between 50.4 and 804 m2/g. The maximum methylene blue capacity of 368 mg/g is comparable with that of commercial activated carbon. The fitting of adsorption data suggests a monolayer coverage of dye molecules onto activated carbon via chemisorption where a cooperative mechanism of particle diffusion and film diffusion may be the controlling mechanism. The adsorption is spontaneous for potential applications in dye wastewater treatment.

Light–Matter Interactions in Films of Randomly Distributed Unidirectionally Scattering Dielectric Nanoparticles

We theoretically investigate the light scattering characteristics of monolayer films composed of randomly positioned unidirectionally scattering dielectric nanoparticles that support overlapping electric and magnetic dipole modes. We show using generalized Mie theory that the optical response of both sparse and dense nanoparticle films can be understood from the scattering properties of the individual dielectric nanoparticles, despite random particle-particle coupling effects, and validate these results with full wave electromagnetic simulations. The spectral, angular, and polarization dependent reflection and transmission scattering characteristics of these random particle films are also shown to be strikingly different from those of homogeneous dense solid thin films of equivalent dielectric permittivity.

Enhancement of photoelectrochemical activity of TiO2 electrode by particulate/dense double-layer formation.

Photoelectrochemical water splitting has attracted significant attention as an environment-friendly method to generate H2 and O2. Electrodes composed of powders exhibit a large surface area and are favorable for surface reactions; however, their high resistance prevents charge transportation. In contrast, photoelectrodes composed of a dense film exhibit high conductivity; however, they constitute a small surface area. Therefore, a combination of these two films can lead to higher photoelectrochemical activities. Herein, a particulate/dense TiO2 hybrid electrode exhibited eightfold and twofold higher activities for water oxidation at sufficiently positive potentials as compared to those of the single particulate and dense film electrodes, respectively. Electrochemical impedance measurements and the light intensity dependence of the photocurrent suggest that the activity enhancement is responsible for the synergistic effects of effective charge separation in the highly conductive dense TiO2 film and effective hole-consuming reaction at the particulate TiO2 layer. However, the activity rather decreased near the onset potential of water oxidation (<0.3 V) under the illumination of light near the bandgap energy (375 nm). Such an activity decrease was not observed for the 340 nm illumination; hence, the recombination of charge carriers generated in dense and particulate layers is responsible: the charge transfer resistance at the particulate/dense interface prevents the effective charge separation. These results demonstrate that the combination of particulate matter and dense films can produce a synergistic effect; however, the resistance at the junction remains a significant bottleneck, rendering resistance reduction necessary to maximize the advantages of hybrid electrodes, especially under the illumination of longer wavelength light.

Room temperature self-assembled Ag nanoparticles/Mo-37.5% Ag film as efficient flexible SERS substrate

Mo-Ag films with different thicknesses were deposited on flexible polyimide (PI) substrate by DC magnetron sputtering. The phase, surface morphology, composition and thickness of the Mo-Ag films were characterized by XRD, FESEM, EDS and TEM, respectively. The most outstanding result indicates that many monodisperse single crystal Ag nanoparticles are spontaneously formed on the surface of the deposited Mo-Ag films at room temperature. The Ag nanoparticles/Mo-37.5% Ag film has rich active “hot spots”, which can be used as an effective surface-enhanced Raman scatting (SERS) substrate by covering a thin layer of silver on the surface, and the detection limit of Rhodamine 6G solution can reach 10-12 mol/L. The Ag nanoparticles/Mo-Ag films prepared at room temperature provided a new idea for the preparation of novel particle films and high-sensitivity flexible SERS substrates.

Production and quality of eucalyptus mini-cuttings using kaolin-based particle films

Considering the expansion of forest plantations over the Brazilian territory and the imminent increase in air temperatures due to global warming, the search for technologies that ensure high levels of productivity and high quality plants in clonal nurseries is essential. Applying kaolin-based particle films (KBPF) has been used as a physical barrier to reduce the negative effects of excessive solar radiation and adverse temperatures. The effects of KBPF on production and physiological quality of eucalyptus mini-cuttings were evaluated during two different seasons. A randomized block design was used, consisting of five treatments and four replications. Five concentrations (0, 3%, 5%, 7%, and 10%) were tested here and six weekly replicates of each concentration was applied. The different kaolin concentrations and seasonal variations resulted in a quadratic response of the leaf SPAD reading during both daily evaluation periods. KBPF applications resulted in a quadratic response of photochemical efficiency in the morning period, and an increasing specific leaf weight linear response, and during the dry season, the different kaolin concentrations resulted in a bud length quadratic response. The results indicated that the kaolin application maintained the production and yield index statistically equal between weekly KBPF applications, improving photochemical efficiency, leaf thickness, SPAD reading, and bud length. The use of KBPF could reduce the intervals between collections of mini-cuttings and increase nursery yields in environments that present high temperatures.

Thick Free-Standing Metallic Inverse Opals Enabled by New Insights into the Fracture of Drying Particle Films.

Metallic inverse opals are porous materials with enhanced mechanical, chemical, thermal, and photonic properties used to improve the performance of many technologies, such as battery electrodes, photonic devices, and heat exchangers. Cracking in the drying opal templates used to fabricate inverse opals, however, is a major hindrance to the use of these materials for practical and fundamental studies. In this work, we conduct desiccation experiments on polystyrene particle opals self-assembled on indium-tin oxide coated substrates to study their fracture mechanisms, which we describe using an energy-conservation fracture model. The model incorporates film yielding, particle order, and interfacial friction to explain several experimental observations, including thickness-dependent crack spacings, cracking stresses, and order-dependent crack behavior. Guided by this model, we are the first to fabricate 120 μm thick free-standing metallic inverse opals, which are 4 times thicker than previously reported non-free-standing metallic inverse opals. Moreover, by controlling cracks, we achieve a crack-free single-crystal domain up to 1.35 mm2, the largest ever reported in metallic inverse opals. This work improves our understanding of fracture mechanics in drying particle films, provides guidelines to reduce crack formation in opal templates, and enables the fabrication of free-standing large-area single-crystal inverse opals.

Reversible Conductive Inkjet Printing of Healable and Recyclable Electrodes on Cardboard and Paper.

Conductive inkjet printing with metal nanoparticles is irreversible because the particles are sintered into a continuous metal film. The resulting structures are difficult to remove or repair and prone to cracking. Here, a hybrid ink is used to obviate the sintering step and print interconnected particle networks that become highly conductive immediately after drying. It is shown that reversible conductive printing is possible on low-cost cardboard samples after applying standard paper industry coats that are adapted in terms of surface energy and porosity. The conductivity of the printed films approaches that of sintered standard inks on the same substrate, but the mobility of the hybrid particle film makes them less sensitive to cracks during bending and folding of the substrate. Damages that occur can be partially repaired by wetting the film such that particle mobility is increased and particles move to bridge insulating gaps in the film. It is demonstrated that the conductive material can be recovered from the cardboard at the end of its life time and be redispersed to recycle the particles and reuse them in conductive inks.

Room temperature multiferroicity and magnetodielectric coupling in 0–3 composite thin films

Magnetoelectric (ME) composite thin films are promising candidates for novel applications in future nanoelectronics, spintronics, memory, and other multifunctional devices as they exhibit much higher ME coupling and transition temperatures (Tc) than well-known single phase multiferroics discovered to date. Among the three types of multiferroic composite nanostructures, (2–2) layered and (1–3) vertically aligned composite nanostructures exhibit comparatively smaller ME coupling due to different shortcomings that restrict their use in many applications. Here, we study the morphological, piezoresponse force microscopic (PFM), ferroelectric, magnetic, and magnetodielectric properties of 0–3 [magnetic nanoparticles (0) homogeneously distributed in ferroelectric matrices (3)] multiferroic composite thin films. The Pb(Fe0.5Nb0.5)O3 (PFN)–Ni0.65Zn0.35Fe2O4 (NZFO) particulate composite films were synthesized by pulsed laser deposition. These particulate composite thin films are completely c-axis oriented with very low surface roughness. We observed magnetic and ferroelectric Tc above room temperature (RT) for all composite thin films. The PFN–NZFO 0–3 composites exhibit large polarization, high saturated magnetization with low coercive field, and low dielectric loss along with magnetodielectric coupling at RT. These nanocomposites might be utilized in next generation nano/microelectronics and spintronic devices.

Indoor air partitioning of Synthetic Musk Compounds: Gas, particulate matter, house dust, and window film

Due to diversity of contaminants indoors and complexity in the physical structure of particulate matter, partition process of chemicals affects indoor concentration distribution. Synthetic Musk Compounds (SMCs) are ubiquitously found in household and personal care products, thus, in the environment. Exposure to SMCs is important for human health, therefore, their partitioning in indoor environmental media is a key issue. In this study, gas – particle, house dust, and window film partitioning of SMCs were investigated in an indoor micro-environment. In a sealed and unoccupied room, a polycyclic and nitro musk mixture was left for volatilization for an hour. Then, samples were collected using XAD-2 sandwiched between two PUF plugs, glass-fiber filter, and wipes for gas, PM10, window-film, house dust phases, respectively, for 145 h. Collected samples were analyzed using a GC–MS. Results demonstrated that SMC concentrations decreased over time, non-linearly. Six of the SMCs partitioned to PM10 with at least 10% at beginning of the experiment, whereas the number of compounds dropped to two at the end, showing that SMCs may partition well between the two phases but they tend to be in the gas phase. They were also detected in the film and dust phases but a decrease pattern similar to gas-particle was not observed. Spearman correlations indicate that the dust and film-associated concentrations were governed by similar processes but PM-associated concentrations were not. SMCs may be found in all phases, mainly in house dust in terms of mass among the studied media and unaccounted surface reservoirs. Therefore, their partitioning between indoor media has key implications for human exposure.

Robust, transparent, superhydrophobic coatings using novel hydrophobic/hydrophilic dual-sized silica particles

HypothesisThe superhydrophobic lotus leaf has dual-scale surface structures, that is, nano-bumps on micro-mountains. Large hydrophilic particles, due to its high surface energy and weight, have high affility to substrates and tend to precipitate at the bottom of coating films. Small hydrophobic particles, due to its low surface energy and weight, tends to sit on the top of coating films and form porous structures. To mimic the lotus leaf surface, it may be possible to develop dual-sized particle films, in which small particles are decorated on large particles. ExperimentsA one-step spin coating of a mixture of dual-sized silica particles (55/200 nm) was used. Epoxy resin was added to improve the adhesion of particle films. The single-sized and dual-sized particle films were compared. The mechanical robustness of particle films was tested by tape peeling and droplet impact. FindingsThe novel combination of hydrophobic silica (55 nm) and hydrophilic silica (200 nm) is essential in creating the hierarchical structures. By combining the strong adhesion of hydrophilic silica (bottom of coating film) to polymer substrates and porous structures of hydrophobic silica (top of coating film), we first time report a one-step and versatile approach to create uniform, transparent, robust, and superhydrophobic surface.

Utilization of Sunscreen Particles Film with Shading to Control Sunburn and Fruit Cracking of Wonderful Pomegranate

Utilization of Sunscreen Particles Film with Shading to Control Sunburn and Fruit Cracking of Wonderful Pomegranate

Surface treatment with silver particles isles on Titanium cp: study of antimicrobial activity

During the last decades, researchers have been growing the interest in surface treatment with an antimicrobial agent. Silver nanoparticles (AgNPs) are widely used in biomedical fields due to their potent antimicrobial activity. So, in this study was investigated silver particles (isles) coated on titanium surface for dental and orthopedic application. Silver particles coating process on titanium surface were performed via sputtering that is a plasma-assisted deposition technique with and titanium without treatment was applied as comparing standard. Plasma treatment parameters were optimized so that the result was not a thin film of Ag but dispersed particles of Ag on the Ti-cp surface. The alloy surfaces were investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). In order to investigate antibacterial potential Staphylococcus aureus and Escherichia coli have been used at Agar diffusion assay. The results were analyzed by analysis of variance (ANOVA) in order to verify significant difference antimicrobial activity between samples that have shown no difference between the surfaces studied treatments. For silver deposition scattered particles (isles) over titanium surface for a 10-minute treatment, EDS revealed by silver clusters that the particles were not properly scattered onto surface, hence, the low effectiveness in antibacterial activity.