Absorbent Substrate Research Articles

Properties and interaction of layers in board-biodegradable primer-printing ink screen-printed system

Surface interactions of the materials during and after the printing process are extremely important for understanding and optimizing the process of graphic reproduction. In screen printing on porous and absorbent substrates, mesh type and ink composition significantly influence the properties of the printed product. To protect the absorbent printing substrates such as board from moisture penetration and to ensure the optimal interaction of the printed ink layer and the substrate, board substrates can be coated with protective primers before printing. In this research, biodegradable primers made of poly(ɛ‐caprolactone) and poly(lactic acid) were applied on the board substrate which was then screen‐printed using two screen rulings of the mesh and two different types of water‐based printing inks on unprimed and primed board substrates. Printed ink layer thickness, surface roughness, water vapor transmission rate, surface free energy and adhesion parameters were measured/calculated on all produced samples. Microscopy of the printed elements was performed to visualize the influence of the primers on the printed line edge. Results of the research have shown that the primers influence the roughness reduction of the printed ink layer. Furthermore, thickness of the printed ink layers increased when the primers were applied on the substrate, pointing to the decreased permeability of the board, which was confirmed by the reduced water vapor transmission rate of the primed and printed substrates. The surface free energies of the tested surfaces and the adhesion parameters between biodegradable primers and prepared printing inks differed depending on the type of the ink and primer, pointing to the optimal combination of the primer and ink for the favorable acceptance of printing ink on the substrate. Results of this research have enabled the optimization of the quality of screen‐printed board product.

Urinating in transponder-controlled feeding stations – Analysis of an undesirable behaviour in horses

Urination in transponder-controlled roughage feeding stations is a widespread undesirable behaviour of group-housed horses. Urination on hard surfaces, such as the floor of the stations, is contrary to the natural elimination behaviour of horses because they prefer to urinate on soft, absorbent surfaces, and it increases ammonia emissions around the stations. The following aspects were analysed: a) urination as potential displacement activity during feed anticipation, b) absence of appropriate elimination areas in the stable and c) ammonia odour as a trigger stimulus. We observed a group of 33 horses in three different situations: 1) baseline situation, 2) provision of elimination areas containing an absorbent substrate in front of the feeding stations and 3) neutralisation of ammonia odour in the feeding stations. In the baseline situation all horses were observed, regardless whether they urinated in the feeding station or not. In the other two situations, only the urinating-horses were observed. We analysed 5 h of video per day, recorded on 4 days from seven feeding stations in each situation. We used an information theory approach, calculating three different (generalized) linear mixed effects models and all according sub-models. In the baseline situation, the horses showed that the horses urinated often after ‘ground exploration’, and there was more ground exploration in the urinating-horses than in the non-urinating-horses. In addition, a higher percentage of the mares than of the geldings urinated during at least one station visit, and mares urinated more often per visit than geldings. Before urination, the horses in most cases lowered the head toward the hay container to trigger the sensor and cause the station to open the partition and make the hay accessible. The time span between lowering the head and access to feed could be perceived as too long by the horses (maximum duration: 30 s) and lead to urination as a displacement activity. In addition, urination never occurred when the hay was accessible, only when the hay was inaccessible, closed, opening or closing. This leads us to conclude that urination is related to feed anticipation. The frequency of urination bouts was not reduced by installing additional elimination areas or neutralising the urine odour, so additional elimination areas and urine odour do not seem to have a role in the undesirable behaviour. Further research is needed to investigate a displacement activity or a classical conditioning in more detail to prevent urination by horses in automated feeding stations.

Multifunctional bacterial cellulose photothermal aerogels with multi-bonded network assisted by carbon nanotube

As one of the important ways to utilize solar energy, it is of great significance to construct composite photothermal materials with high photothermal conversion and multifunctionality for in-depth investigation of their application performance. The nanofiber network and the reactivity of a large number of hydroxyl groups on the surface of environmentally friendly bacterial cellulose (BC) provide a prerequisite for its use as an excellent matrix material. Here, we use bacterial cellulose nanofibers (BCNFs) as the matrix, methyltrimethoxysilane (MTMS) as the crosslinking agent and hydroxylated multi-walled carbon nanotubes (MCNT − OH) as the photothermal absorber and conductive substrate to construct a multifunctional BC photothermal aerogel with multi-bonded network structure. Multiple chemical bond and physical bond interactions are formed between BCNF, MTMS and CNT, and fiber entanglement is combined to make CNT uniformly dispersed. This optimal photothermal aerogel has rich network structure with high hydrophobicity of 147°, compressive strength of 17.62 kPa and high elasticity. It also shows high light absorption of 93.5%, eminent photothermal conversion of 80.4 °C and photothermal stability under 1 kW m−2 irradiation with a low CNT content of 27.1%. Therefore, the photothermal aerogel shows potential of multi-scenario applications in the field of solar-driven high-viscosity crude oil recovery and piezoresistive strain sensors.

Evaluation of Aging Methods on the Surface Characteristics of Hydrochar and Germination Indices for Kale Seeds

Hydrochar derived from hydrothermal carbonization (HTC) has been recognized as a potential absorbent and horticultural substrate. However, its practical application has been limited due to its low adsorption capacity and negative effects on plant growth. To address these issues, three pre-treatment methods (water washing, microbial aging, and freezing-thawing aging) were employed to further improve the physical structure and chemical properties of hydrochar. A seed germination test with kale (Brassica oleracea var. acephala D.C) was conducted to evaluate the phytotoxicity of modified hydrochars. The results showed that microbial aging considerably enhanced the physicochemical properties of the hydrochar. Specifically, under microbial aging, the bulk density of microbial-aged hydrochar (MHC) decreased by 8.1%, the porosity increased by 24.8%, and the water-holding capacity increased by 36.54% compared to fresh hydrochar (FHC). Moreover, the surfaces of MHC and freezing-thawing aged hydrochar (FTHC) were observed with rough and cracked surfaces and macro pore structures. Fourier transform infrared (FTIR) spectroscopy revealed that the functional group’s intensities of the four hydrochar materials varied, and that MHC and FTHC had more oxygen-containing groups than the others. Additionally, the surface areas of MHC and FTHC increased by 318.64% and 238.98% compared to FHC, respectively. The seed germination test indicated the strong inhibitory effect of FHC, while MHC significantly (p < 0.05) improved the seed germination rate and root development. These findings suggest that among the different pre-treatment methods, microbial aging demonstrated the greatest potential for practical application in improving the physicochemical properties of hydrochar and promoting seed germination. This study opens up new avenues for further research on improving hydrochar and suggests that future studies should focus on optimizing the aging process.

Compact and efficient wire grid reflecting polarizersat 121.6 nm

In this work, two structures of wire grid reflecting polarizers have been proposed and optimized through simulation at the target wavelength of 121.6 nm (H Lyman-α), which aims to realize compact and efficient polarizers for measuring the magnetic field vector of the solar corona. Both structures are based on a high reflective patterned Al/MgF2 bi-layer on top of an absorbent substrate, and a layer of MgF2 is sandwiched in the Al gaps to prevent it from being oxidized. Two promising solutions were selected, exhibiting a polarization degree of more than 99.99% and a TE-reflectance over 0.3. Their sensitivity to nanowire parameters has been carried out to evaluate manufacturing feasibility. The angular and spectral performance demonstrated that such polarizers have the large potential to significantly contribute to the future far-ultraviolet (FUV) instruments.

Research and Application of Compact Air-Coupled Ground Penetrating Radar in Thin-Layer Asphalt Thickness Testing and Vibration Resistant Calibration Method

For high-precision continuous thickness measurement of thin-layer asphalt loose paving, the paper proposes a compact ground penetrating radar (GPR) solution with smaller volume than the conventional air-coupled antenna. It takes into account the minimum identifiable thickness of the GPR tailing characteristics of radar signals, the common thickness range of thin-layer asphalt, and the vibration of construction machinery. In general, the overlap between bottom reflection and surface reflection of thin-layer asphalt can be solved by subtracting the reflection of the asphalt surface from the calibration waveform file of a metal plate. However, because the operating environment of asphalt paving is not suitable to realize the frequent static calibration of metal plates, the paper designs a bow-tie antenna loaded with high loss absorbent material substrate, which significantly improves the signal tailing phenomenon and greatly reduces the size of the air-coupled antenna. At the same time, in view of dynamic change of paver vibration and the requirements of the construction site, less calibration is more advantageous. Based on the full-amplitude reflection method, a fitting formula for the dielectric constant of asphalt suitable for mechanical vibration is proposed in this paper, to further improve the engineering applicability of the detection system. Finally, static calibration asphalt thickness, dynamic measured dielectric constant asphalt thickness, and manual sampling thickness under three construction conditions are compared, and the capability of the compact air-coupled GPR detection system proposed in this paper is comprehensively verified.

Zinc-induced changes on structural pathways, optical parameters, optical constants extracted by Kramers-Kronig Formulas, Photoluminescence Spectra and photovoltaic characteristics of n-Cd50-xZnxS50/i-AgSe/p-Si solar cells

In highlighted our study's scenarios, the importance of using a buffer layer of AgSe between an absorbent silicon substrate and a Cd50-xZnxS50 window layer with different Zn content with (x = 0, 10, 20, 30, 40, and 50 wt%) was discussed. The significant influence of the window layer on the properties of fabricated designs: (front electrode) Nickel (Ni)/n-Cd50-xZnxS50/i-AgSe/p-Si/(pt), platinum (back electrode) was also studied. This work devoted a large portion of its parts to investigate the structural, optical, photoluminesce, and thermopower properties of the CdZnS window layer to highlight the rationale for its application in the solar cells fabricated in this study. Pure phases of CdS and ZnS were confirmed through XRD and SEM analysis for the CdZnS window layers. Based on Tauc and Urbach's relationships, the optical parameters (bandgap energy Eg, tail energy Ee) were extracted. The optical constants (refractive index n, absorption index k) were calculated via the Kramers-Kronig formulas. In the visible region at 300–800 nm, the CdZnS thin layers showed a sharp peak in photoluminescence PL study results. The current density-voltage (J-V) characteristics in dark and illumination conditions were discussed. The highest power conversion efficiency (PCE) was for the last window layer. Thus, this layer was appropriate for the fabricated solar cells to obtain good photovoltaic properties.

Low-voltage electron scattering in advanced extreme ultraviolet masks

To limit the shadowing effect, improve the process stability, and enhance the optical performance of extreme ultraviolet (EUV) masks, several absorbers have been proposed in previous studies. We investigated the effects of some of these absorbers on electron scattering events through Monte Carlo simulations in which the mask throughput was considered at 5 keV. A two-layer structure consisting of a resist and an absorber substrate, rather than a full-mask structure, was used to eliminate the influence of electron scattering on the resist. The effects of electron interaction volume, ray tracing, and scattering dependency on penetration depth, backscattering coefficient, lateral radius, and absorbed energy distribution were analyzed for absorber materials of conventional argon fluoride and advanced EUV masks. The results of the proposed method for electron scattering analysis and prediction exhibited greater agreement with the simulation results than those of relevant conventional methods.

The long-term engineering properties and sustainability indices of dewatering hydrated lime mortars through Jacaranda seed pods

The progressive increase in the industrialisation, consequently the energy consumption and carbon footprint reacquaint the sustainable and environmental credentials of hydrated lime mortars and re-congregate the implications of such binders in masonry construction. The low water retaining characteristics of hydrated lime mortars that often results in insufficient bond development with the subsequent substrate, were manipulated through the incorporation of powdered Jacaranda seed pods and silica fume to establish mortar-masonry optimisation in practice. Although there are numerous studies addressing the agricultural waste incorporation in cement-based materials, the incorporation of Jacaranda seed pods on construction materials have not been reported in the literature. Characterisation study comprising the elemental composition and physical properties of Jacaranda seed pods were essential in assessing the compatibility of pods utilisation in hydrated lime mortars. The paper reports authentic experimental research results on the utilisation of Jacaranda seed pods as a binder substitute in hydrated lime mortars concerning the effect of dewatering on the long-term engineering properties and sustainability indices. The utilisation of powdered Jacaranda seed pods and silica fume demonstrated the eligibility of manipulating the strong water retaining characteristics of hydrated lime mortars to attain improved mortar-substrate optimisation in masonry construction. It is essentially shown in the paper that the degree of dewatering, governed by the incorporation of powdered Jacaranda seed pods and silica fume herein, could not be underestimated as this phenomenon yields approximately 18% increase in the compressive strength of hydrated lime mortars comprising both at short- and long-terms. Although the incorporation of both the powdered Jacaranda seed pods and silica fume decreased the water penetration depth and porosity of mortars by ~11% and 17% respectively, dewatering, an inevitable incident that occurs as soon as the freshly mixed mortars are placed on dry absorbent substrates, further yields a greater decrease in these physical measurements at 1 year. Incorporation of powdered Jacaranda seed pods and silica fume generated a crucial improvement on cost efficiency and eco-strength efficiency of mortars both at 91 days and 1 year. The results have shown that more than 30% reduction on the carbon footprint could be established through this practice. It is essentially established in the paper that the degree of dewatering, experienced at freshly-mixed stage, determines the authentic performance of hydrated lime mortars in masonry construction and governs the veritable sustainability analysis to be performed. The results reported in this paper does not only encourage the re-introduction of the hydrated lime binder in construction practice but also assert a cleaner alternative waste management route for the agricultural wastes.

Analysis of rapid HIT application to touch DNA samples.

Rapid DNA technology is being utilized for reference profiles worldwide. There is also strong data in the literature to support its use for high-template DNA sources, the same is not true for low-template sources, such as touch DNA; this is a requirement before wider implementation to forensic casework is considered. We report on the Rapid HIT Intel cartridge's ability to facilitate successful amplification of touch DNA to obtain profiles from template deposited on items commonly encountered in forensic casework. Eight items were touched in ten replicates- two were tapelifted, three swabbed, and three directly inserted. Significance was observed in the alleles amplified and RFU with respect to sample type. Three samples performed well: cable tie, fabric, and matchstick. As two of these were directly inserted, this should be considered for any sample small enough. Placement of highly absorbent substrates into the cartridge is not advised as it can cause a lysate-pull error. Heterozygote loci often presented as homozygous (32%-78% loci per profile); this was influenced by substrate type and profile RFU. Loci with larger masses exhibited higher false homozygosity also. Comparison of the donor's profile analyzed was performed against previous datasets analyzing touch DNA through standard workflow, including manual DNA extraction, PCR, and CE separation. These data show that for all substrates, except for a fabric swatch, standard processing is preferential to Rapid HIT analysis. In its current form, rapid DNA technology is not fit for the routine analysis of touch DNA samples in forensic casework.

Validating a Termite-Inspired Construction Coordination Mechanism Using an Autonomous Robot.

Many species of termites build large, structurally complex mounds, and the mechanisms behind this coordinated construction have been a longstanding topic of investigation. Recent work has suggested that humidity may play a key role in the mound expansion of savannah-dwelling Macrotermes species: termites preferentially deposit soil on the mound surface at the boundary of the high-humidity region characteristic of the mound interior, implying a coordination mechanism through environmental feedback where addition of wet soil influences the humidity profile and vice versa. Here we test this potential mechanism physically using a robotic system. Local humidity measurements provide a cue for material deposition. As the analogue of the termite's deposition of wet soil and corresponding local increase in humidity, the robot drips water onto an absorbent substrate as it moves. Results show that the robot extends a semi-enclosed area outward when air is undisturbed, but closes it off when air is disturbed by an external fan, consistent with termite building activity in still vs. windy conditions. This result demonstrates an example of adaptive construction patterns arising from the proposed coordination mechanism, and supports the hypothesis that such a mechanism operates in termites.

Beneath the surface: Application of transparent super absorbent polymer substrates to track faunal activity within the sediment layer

Abstract Tracking the movement of organisms is a fundamental goal of many ecological studies. Several techniques exist in the study of terrestrial and aquatic fauna; however, to date, the ability to monitor aquatic fauna within the sediment layer efficiently and in multiple dimensions is lacking. Given the importance of subsurface sediments in supporting ecosystem functioning, this inability to observe organism behaviour represents a fundamental gap in our knowledge and limits our capability to holistically characterise the response of freshwater systems to stressors. Here we present an experimental study that employs novel transparent super absorbent polymer substrates (c. 8–12 mm in diameter) in combination with computer vision technology, which enables, for the first time, real‐time observation and tracking of organisms within the sediment layer under lotic flow conditions. Use of these substrates allowed the successful extraction of organism trajectories, which enabled the velocity and body orientation of a freshwater amphipod (Gammarus fossarum) in the sediment layer to be calculated in response to a number of vertical hydrological exchange treatments (upwelling, downwelling, and no vertical exchange). Results indicate that under vertical hydrological exchange, a higher proportion of fast velocities (both horizontal and vertical) were recorded for G. fossarum in the sediment layer compared to no vertical exchange (control) conditions. This increase was most marked for upwelling flow exchange. We also observed a change in the body orientation of individuals in the sediment layer from a vertical alignment under no vertical exchange to a more horizontal one under downwelling and more notably upwelling flow exchange. This shift in body position was exacerbated under stronger vertical exchange rates. We identified that following the flow transition of downwelling to upwelling conditions, there was an immediate shift (0–2 min) in both the orientation angle and activity level of individuals. This increased rate of activity was maintained for the individuals' velocity but not for their changing orientation angle. These trends were not apparent within the flow transition of no vertical exchange to downwelling flow. Our new methodological approach enables vital insights into the behaviour of organisms within the sediment layer. Use of super absorbent polymer substrates allows real‐time multi‐directional tracking of multiple organisms in parallel. We believe the method represents an innovative tool that can be employed to tackle a wide range of ecological questions and thereby improve our mechanistic understanding of ecological responses to biotic and abiotic processes/stressors.

Critical Pressure Asymmetry in the Enclosed Fluid Diode.

Joint physically and chemically pattered surfaces can provide efficient and passive manipulation of fluid flow. The ability of many of these surfaces to allow only unidirectional flow means they are often termed fluid diodes. Synthetic analogues of these are enabling technologies from sustainable water collection via fog harvesting to improved wound dressings. One key fluid diode geometry features a pore sandwiched between two absorbent substrates—an important design for applications that require liquid capture while preventing back-flow. However, the enclosed pore is particularly challenging to design as an effective fluid diode due to the need for both a low Laplace pressure for liquid entering the pore and a high Laplace pressure to liquid leaving. Here, we calculate the Laplace pressure for fluid traveling in both directions on a range of conical pore designs with a chemical gradient. We show that this chemical gradient is in general required to achieve the largest critical pressure differences between incoming and outgoing liquids. Finally, we discuss the optimization strategy to maximize this critical pressure asymmetry.

First Report of Root-Knot Nematode, Meloidogyne graminicola, on Rice in Sichuan Province, Southwest China

Root-knot nematode, Meloidogyne graminicola, is a major parasite of rice and causes substantial yield loss (Mantelin et al. 2017). In June 2018, stunned, yellowish plants were observed 30 days after transplantation in fields in Guanghan City (31°6′N, 104°13′E), Sichuan Province, Southwest China. Patches of seedlings with chlorosis were observed in source upland seedling nurseries. Galls and hooked tips were found in the roots of rice seedlings and plants. Rice plants (30) were randomly sampled from these and adjacent fields. Females and eggs were observed in galled roots and did not protrude through the root surface. Hatched second-stage juveniles (J2) were also found inside the galls. The perineal pattern of females (n = 9) was oval with low and round dorsal arches, smooth striae, sometimes with a few lines converging at either end of the vulva, and lateral lines obscure or absent. Measurements (mean ± SE, range) of J2 (n = 20): body length (446.7 ± 12.8 µm, 402.6 to 509.1µm), stylet length (12.1 ± 0.4 µm, 10.6 to 13.2 µm), tail length (70.2 ± 2.9 µm, 61.3 to 79.7 µm), and hyaline tail terminus (19.5 ± 1.0 µm, 16.5 to 22.7 µm); male (n = 10) abundant, body cylindrical and fairly long (1,270.0 ± 76.2 µm, 1,043.5 to 1,553.5 µm), stylet length (17.2 ± 0.7 µm, 15.2 to 18.9 µm), and spicule length (21.4 ± 0.4 µm, 20.1 to 22.0 µm). Morphometric analyses were consistent with M. graminicola (Golden and Birchfield 1965). Two individual females from each of 30 samples were transferred to tubes for DNA extraction. The D2 to D3 domain regions of 28S ribosomal RNA (rRNA) gene was amplified with the primers RK28SF (5′-CGGATAGAGTCGGCGTATC-3′) and MR (5′-AACCGCTTCGGACTTCCACCAG-3′) (Ye et al. 2015) and yielded a 589-bp PCR fragment. The internal transcribed spacer (ITS) region was amplified with species-specific primers Mg-F3 (5′-TTATCGCATCATTTTATTTG-3′) and Mg-R2 (5′-CGCTTTGTTAGAAAATGACCCT-3′) (Htay et al. 2016) and yielded a 338-bp PCR fragment. BLAST results of 28S rRNA gene and ITS region had 99% similarity with M. graminicola isolates available in GenBank. Sequence identities were further confirmed by Bayesian phylogeny analyses; they were nested in a well-supported clade (posterior probability = 1) together with other M. graminicola populations. The ITS and 28S rRNA sequences of the females from each of 30 samples were 99 to 100% identical. The ITS and 28S rRNA sequences of one population (GH-2) were deposited in GenBank (MK560173, 28S rRNA; MK559561, ITS). Morphological and molecular characterization confirmed this nematode as M. graminicola. To assess M. graminicola reproductive capacity, 2-week-old rice (Oryza sativa ‘Nipponbare’) seedlings were individually transplanted into a standard tube (25 × 95 mm) containing 10 ml of steam-sterilized sand and absorbent polymer substrate (Reversat et al. 1999), inoculated with 100 J2 of population GH-2 soon after transplanting, and then incubated in a growth chamber under 16/8-h light/dark at 26 to 28°C. There were 20 nematode-inoculated plants and 10 non-inoculated (tap water only) control plants. Twenty-five days after inoculation the number of egg masses and number of eggs per egg mass were determined and the multiplication factor [(number of egg masses × number of eggs per egg mass)/nematode inoculum level] calculated as 8.9 to 11.6. Hook-shaped and galled roots and stunned aboveground parts were observed on all inoculated plants; no symptoms were found on control plants. Observations confirmed the pathogenicity of the isolated M. graminicola population on rice. This is the first report of M. graminicola in Sichuan Province, a major rice-growing area. The first report of M. graminicola in China was in Fujian Province (Liu et al. 2011; Zhou et al. 2015), and it was soon found in other parts of China (Long et al. 2017; Tian et al. 2017; Wang et al. 2017). The infective J2 may be transmitted by gravity irrigation from field to field due to the topography of agricultural lands in the area. The extension of practices of upland nurseries, aerated irrigations, and direct seeding in Sichuan Province may further exacerbate the problem because such practices favor the survival and damage of M. graminicola (De Waele and Elsen 2007; Win et al. 2013). Further monitoring and research on control methods are needed.

Taking the ‘Secret’ out of secretions: evaluation of the ParaDNA body fluid ID system at NSWHP FASS

ABSTRACTThe ParaDNA Body Fluid ID (BFID) system has been developed for use as either a screening or confirmatory test for the simultaneous identification of six biological fluids: saliva, vaginal fluid, seminal fluid, spermatozoa, peripheral blood and menstrual blood. The ParaDNA BFID kit consists of a closed, single-tube assay, incorporating multiplexed reverse transcription of mRNA and cDNA amplification, followed by fluorescent melt curve analysis with LGC’s proprietary HyBeacon DNA Probe technology. The ParaDNA instrument and early access version of the BFID kit were evaluated in this study. The evaluation included an assessment of the system’s useability, sensitivity, substrate specificity, and performance with mixtures and mock forensic samples. The ParaDNA BFID system was user-friendly, and capable of detecting most body fluids at neat concentrations. However, the system was unable to detect diluted fluids. The system’s capacity to detect saliva was also limited. Performance of the assay with different substrates was most influenced by the effectiveness of the ParaDNA sample collection tool. The tool sampled well from dried stains on fabrics, but was less effective at sampling from rayon swabs and other absorbent substrates. The system is capable of detecting fluids in mixtures, although detection appeared dependent on the combination of fluids tested.

Analysis of the Use of Reflectors and Reflective Surfaces for Increasing the Light Efficiency of LEDs Based on AlGaInP Heterostructures

The most common technological solution for increasing the light efficiency of the LEDs based upon AlGaInP heterostructures are discussed in the paper. The creation of LEDs with the inclusion of quantum wells and quantum dots in the active region, removing the original base and placing the LED on a new substrate, the replacement of the absorbent substrate by the reflective, using light-reflective surfaces such as Bragg reflectors or a mirror base (substrate), the list of new based materials for the LEDs based upon AlGaInP heterostructures as same as sapphire, glass, gallium phosphide, silicon and silicon carbide are presented. Therefore, new advanced methods of emission power are emerging.

A simple approach to analyze layer-dependent optical properties of few-layer transition metal dichalcogenide thin films

Intense interest in transition metal dichalcogenides (TMDs) is driven, among other things, by their intriguing layer-dependent optical properties down to the monolayer and strong excitonic effects. Experimental determination of optical constants such as the complex refractive index and dielectric function of large-area TMDs thin films is prone to large uncertainties at the few-layer level using a single measurement technique such as spectroscopic ellipsometry (SE). In this work, we demonstrate an approach to accurately determine the optical constants by combining transmission spectroscopy with SE. Using MoS2 as an example, the prototypical TMD material, we demonstrate our approach on transparent (Quartz, Al2O3) and absorbing (e.g. Si/SiO2) substrates. We find that pre-characterized optical properties from transmission spectroscopy significantly improve the quantitative accuracy of optical constants obtained using SE on both transparent and absorbing substrates. We show that the extracted optical constants from samples deposited on transparent substrates are highly reliable in obtaining layer-dependent optical properties of TMDs while data on absorbing Si/SiO2 substrate suffer from strong substrate contribution. Overall, we strongly conclude that SE must be combined with transmission spectroscopy to obtain optical constants with high quantitative accuracy. Our approach, though demonstrated on few-layer films, will be applicable to monolayer and bilayer TMDs.

Modification induced by laser irradiation on physical features of plastics materials filled with nanoparticles

The Thermal Laser Welding (TLW) process involves localized heating at the interface of two pieces of plastic that will be joined. Polymeric materials of Ultra High Molecular Weight Polyethylene (UHMWPE), both pure and containing nanostructures at different concentrations (titanium and silver nanoparticles), were prepared as thin foils in order to produce an interface between a substrate transparent to the infrared laser wavelength and an highly absorbent substrate, in order to be welded by the laser irradiation. The used diode laser operates at 970 nm wavelength, in continuum, with a maximum energy of 100 mJ, for times of the order of 1 -60 s, with a spot of 300 μm of diameter. The properties of the polymers and of nanocomposite sheets, before and after the laser welding process, were measured in terms of optical characteristics, wetting ability, surface roughness and surface morphology.

A “drop‐wipe‐test” SERS method for rapid detection of pesticide residues in fruits

AbstractA simple “drop‐wipe‐test” approach for rapid detection of pesticide residues in fruits was developed based on surface‐enhanced Raman spectroscopy (SERS) coupled with wiper‐type filter paper substrate. The filter paper was coated with silver nanoparticles (Ag NPs) and used as a flexible and absorbent wiper‐type SERS substrate. The first two steps “drop” and “wipe” were combined to simplify the procedures of extraction and sampling of the analyte molecules. “Test” was the last step to obtain the spectral data using a portable Raman spectrometer (Hx‐Spec) developed by our laboratory. The entire detection process was completed just in a few minutes. The optimal wipe time of ~15 s was confirmed used to ensure a thorough extraction of analyte molecules. The as‐prepared SERS substrate was used for rapid detection of pesticide residue (i.e., thiram) in apple, pear, and grape by “drop‐wipe‐test” method. Results demonstrate that the concentrations of thiram spiked on the three fruits skin show a linearly relationship with the average intensity (n = 7) of SERS spectra with R‐square values of 0.9991, 0.9872, and 0.9841, respectively. The limit of detection of thiram in apple, pear, and grape peel was 4.6261, 5.1799, and 5.7061 ng/cm2, respectively. The detection limits are all below the maximum residue limits for pesticide in food that were set by the National Food Safety Standard of China (GB). The results demonstrate that SERS method coupled with a flexible and absorbent SERS substrate can be used as a practical application for a reliable, rapid, and sensitive detection of pesticide residues.

Thermal management approaches of Cu(Inx,Ga1−x)Se2 micro-solar cells

Concentrator photovoltaics (CPV) is a cost-effective method for generating electricity in regions that have a large fraction of direct solar radiation. With the help of lenses, sunlight is concentrated onto miniature, highly efficient multi-junction solar cells with a photovoltaic performance above 40%. To ensure illumination with direct radiation, CPV modules must be installed on trackers to follow the sun’s path. However, the costs of huge concentration optics and the photovoltaic technology used, narrow the market possibilities for CPV technology. Efforts to reduce these costs are being undertaken by the promotion of Cu(Inx,Ga1−x)Se2 solar cells to take over the high cost multi-junction solar cells and implementing more compact devices by minimization of solar cell area. Micrometer-sized absorbers have the potential of low cost, high efficiencies and good thermal dissipation under concentrated illumination. Heat dissipation at low (<10×) to medium (10 × to 100×) flux density distributions is the key point of high concentration studies for macro- and micro-sized solar cells (from 1 µm2 to 1 mm2). To study this thermal process and to optimize it, critical parameters must be taken in account: absorber area, substrate area and thickness, structure design, heat transfer mechanism, concentration factor and illumination profile. A close study on them will be carried out to determine the best structure to enhance and reach the highest possible thermal management pointing to an efficiency improvement.