Strong Trapping Effect Research Articles

Construction and photothermal properties of Ag nanoparticles modified multilevel porous CuO film with ultra-wide infrared spectrum absorption

Based on lattice vibration and energy band theory, narrow bandgap inorganic semiconductor materials have become a new type of photothermal material, but it is difficult to achieve absorption for long wavelength infrared radiation to meet the application requirements of ultra-wide spectrum (2.5–20 μm) infrared detectors. From the perspective of structural optics, this paper constructed a multilevel porous CuO film with both coral-like micro-porous and flower-like nano-porous structures based on chemical bath deposition technique, and the Ag nanoparticles were uniformly embedded in the "petal" gaps of flower-like nano-porous CuO by optimizing the dosages of PVP. Benefiting from the synergistic effect of multilevel porous structure and loaded Ag nanoparticles, the Ag nanoparticles modified multilevel porous CuO (CuO@Ag-PVP 0.05) film had an average absorption of 94.17 % over the wavelength range of 2.5–20 μm. The photothermal conversion efficiency of CuO@Ag-PVP 0.05 film can reach up to 81.12 % and 86.96 % over near-infrared and far-infrared light ranges, respectively. The various material characterizations and simulations analysis showed that the multilevel porous structure containing coral-like and flower-like multi-scale pores can form two guiding modes for light, and based on the synergistic effect of the two guiding modes, the CuO film can form a strong trapping effect for light over ultra-wide spectral range, broaden its absorption range, and enhance its absorption characteristics. The loaded Ag nanoparticles contain a large number of free electrons, which can capture light energy and convert it into heat energy through local surface plasmon resonance (LSPR) effect, further enhancing the light absorption and photothermal conversion efficiency.

Characterization and source apportionment of pharmaceuticals in surface water of the Yangtze Estuary and adjacent sea.

Pharmaceuticals, which are closely linked to human activities, have attracted global attention. This study investigated the occurrence characteristics of 20 pharmaceuticals in surface water of the Yangtze Estuary and adjacent sea. A total of 14 targeted pharmaceuticals were detected in both spring and summer sampling campaigns. The mean concentrations of sulfonamides and non-sulfonamides were 36.60 ± 19.43ng·L-1 and 50.02 ± 41.07ng·L-1, respectively. As for non-antibiotics, their concentrations were in the range of 24.34 ± 916.8ng·L-1 with caffeine accounting for 6.17 ~ 86.70% (average percentage of 42.22%). Meanwhile, spatial distribution patterns showed similarities between antibiotics and non-antibiotics, with high levels occurring near the upper estuary, aquaculture areas, wastewater treatment plants, and the maximum turbidity zone. This phenomenon could be related to the sources of pharmaceuticals and the physicochemical properties of water bodies. Obviously, the first three areas are highly impacted by human activities or serve as important sources of terrestrial contaminants entering the East China Sea. The last area retains high amounts of suspended particles which may exert strong trapping effects on hydrophobic chemicals. Principal component analysis revealed the presence of three potential sources for pharmaceuticals in the Yangtze Estuary, with a relatively high percentage originating from incompletely treated municipal sewage. As for the temporal trend, pharmaceutical contamination was found to be higher in spring compared to summer, potentially due to variations in pharmaceutical consumption patterns, local rainfalls, and water temperatures. These findings provide fundamental data support for implementing appropriate local management strategies for pharmaceutical usages.

Construction of carbon coated spherical Zn0.71Mn0.29Se@C for high-performance aluminum ion batteries

As a high energy density material, selenides have shown highly competitive initial capacity when applied to the positive electrode of aluminum ion batteries. However, in acidic electrolytes, the volume effect of selenides during electrochemical reactions can cause damage to the material structure. In long-term cycling tests, the performance of selenide cathode materials deteriorates rapidly, which greatly limits the application of this high-performance material in aluminum ion batteries. Here, Zn0.71Mn0.29Se@C material was synthesized for the cathode of aluminum ion batteries, which is covered by a carbon layer on the sphere shells and has good crystallinity. Zn0.71Mn0.29Se@C showed excellent performance: the capacity was maintained at 102.79 mAh/g after 2000 cycles. Attributed to the supporting effect of the carbon material, Zn0.71Mn0.29Se@C exhibits excellent structural stability. During charging and discharging, the carbon layer of the sphere shell effectively limits the volume expansion and improves the cycling performance of the battery. Meanwhile, the simulation results show that the Zn0.71Mn0.29Se@C material has a strong trapping effect for AlCl4− ions. As the main ion involved in the reaction, this strong interaction can greatly improve the reaction kinetics. On the other hand, the charge accumulation caused by the embedding of potential ions enhances the charge transfer. In conclusion, the carbon layer in the outer layer of Zn0.71Mn0.29Se@C not only supports the sphere structure, but also enhances the trapping effect for potential ions, and this novel electrode material is expected to improve the application prospect of aluminum ion batteries.

Ultrastretchable Triboelectric Nanogenerators Based on Ecoflex/Porous Carbon for Self‐Powered Gesture Recognition (Adv. Mater. Technol. 9/2023)

Triboelectric Nanogenerators In article number 2201769, Huamin Chen and co-workers present an ecoflex/porous carbon-based triboelectric nanogenerator (TENG) that exhibits ultrahigh stretchability and high performance due to the appropriate conductive networks and strong trapping effect. Its performance just degrades about 30% at a stretching strain of 177%. The stretchable TENG array can recognize gesture signal of the finger to control mechanical hand, which demonstrates a promising potential in human-machine interaction.

Ultrastretchable Triboelectric Nanogenerators Based on Ecoflex/Porous Carbon for Self‐Powered Gesture Recognition

AbstractStretchable triboelectric nanogenerator (STENG) has become the research hotspots in flexible power supply, which is indispensable in intelligent wearable electronics. In this work, an ultrastretchable Ecoflex/porous carbon‐based STENG (EP‐STENG) is presented for gesture recognition application. Due to the ultrahigh stretchability of Ecoflex (570%) and high conductivity of porous carbon, the EP thin film acts as an excellent stretchable electrode under various deformations. In addition, the output performance of the EP‐STENG can be enhanced by adjusting the concentration of porous carbon. At a mass fraction of 0.28 wt%, the EP‐STENG reaches the optimal output performance. This is due to the appropriate conductive networks and strong trapping effect. Surprisingly, the performance of the EP‐STENG still remains 70% at a stretching strain of 177%, which makes it a promising wearable sensor for human–machine interaction. Finally, the EP‐STENG‐based stretchable sensor array can acquire gesture signal of the fingers, which can control the mechanical hand to make corresponding actions. The proposed ultrastretchable EP‐STENG can promote the development of intelligent wearable system and flexible electronics.

The irradiation effects on the nanoindentation hardness and helium bubbles evolution mechanism of Ni-based alloy

High-dose neutron irradiation could produce various kinds of microstructural defects, and the radiation resistance of nickel alloy is put forward for higher requirements under the high temperature. To simulate the (n, α) reaction, helium ions with an energy of 540 keV were implanted into nickel-based alloy 617 at 700 °C. The microstructure and mechanical properties were established by comparing the nanoindentation hardness before and after irradiation. For the low dose irradiation, the microstrain induced by vacancy-type defects like He-vacancy clusters and helium bubbles is slight, which would not result in a large increase of hardness. The hardening effect of high-temperature irradiation was much lower than that of room-temperature irradiation due to the recovery of matrix defects. The actual distribution of helium bubbles observed by Transmission Electron Microscope (TEM) was comparable to the SRIM simulation result. The helium bubbles were spherical near the surface of the alloy and polyhedral deeper in the matrix. Moreover, chromium carbide had a strong trapping effect on helium bubbles. The shapes and distribution of the helium bubbles were analyzed to evaluate irradiation effects on nickel-based alloys.

Research progress of silicon nanowires array photodetectors

As one of the most important semiconductor materials, silicon (Si) is widely used in optoelectronic devices such as solar cells and photodetectors. Owing to the difference in refractive index between silicon and air, a large amount of incident light is reflected back into the air from the silicon surface. In order to suppress the loss caused by this reflection, a variety of silicon nanostructures with strong trapping effect have been developed. Most of the dry-etching schemes encounter the problems of high cost and complex preparation, while the silicon nanowires array prepared by the wet-etching schemes has the problems of low controllability of some parameters such as the spacing between two adjacent nanowires, and the small effective area of heterojunction. The method of using polystyrene microsphere as the mask can integrate the advantages of dry-etching method and wet-etching method, and it is easy to obtain periodic silicon nanowires (pillars) array. In this paper, first, we summarize the properties and preparation methods for silicon nanowires structure, the strategies to effectively improve the performance of silicon nanowires (pillars) array photodetectors, Then we analyze the existing problems. Further, the latest developments of silicon nanowires (pillars) array photodetector are discussed, and the structure, morphology of photosensitive layer and methods to improve the performance parameters of silicon nanowires (pillars) array photodetector are analyzed. Among them, we focus on the ultraviolet light sensitive silicon based photodetector and its method to show tunable and selective resonance absorption through leaky mode resonance, the silicon nanowires array photodetector modified with metal nanoparticles and the method of improving performance through surface plasmon effect, and plasmon hot electrons. Heterojunction photodetectors composed of various low-dimensional materials and silicon nanowires (pillars) array, and methods to improve the collection efficiency of photogenerated charge carriers through the “core/shell” structure, methods to expand the detection band range of silicon-based photodetectors by integrating down-conversion light-emitting materials and silicon nanowires (pillars) array, flexible silicon nanowires array photodetectors and their various preparation methods, are all introduced. Then, the main problems that a large number of defect states will be generated on the silicon nanostructure surface in the MACE process are briefly introduced, and several possible solutions for defect passivation are also presented. Finally, the future development for silicon nanowires (pillars) array photodetectors is prospected.

Electronic properties and photo-gain of UV-C photodetectors based on high-resistivity orthorhombic κ-Ga2O3 epilayers

Electrical and optical properties of nominally-undoped high-resistivity κ -Ga2O3 epitaxial films are presented, along with the ultraviolet detection performance of solar-blind photodetectors fabricated from these epilayers. The photodetectors exhibited a solar-blind rejection ratio higher than 104, reproducible on–off switching times and a remarkable photo-gain (up to 103). The latter can be ascribed to either a strong trapping effect of free holes by deep levels inducing a majority carrier excess Δn with respect to the minority carriers Δp, or to a hole mobility several orders of magnitude lower than the electron mobility, both the hypothesis being consistent with literature data. A saturation of the gain, dependent on detector size, was observed beyond a certain applied voltage, that is consistent with a minority carrier diffusion length of a few 10-5 cm.Non-critical growth conditions, reproducibility and intrinsic spectral selectivity together with good UV-detection performance make κ-Ga2O3 a suitable material for solar-blind ultraviolet photodetectors.

Behavioral Responses of Bemisia tabaci Mediterranean Cryptic Species to Three Host Plants and Their Volatiles.

Simple SummaryBemisia tabaci Gennadius (Hemiptera: Aleyrodidae) was first observed in tobacco in Greece in 1889. In China, since the introduction of Euphorbia pulcherrima (Euphorbiales: Euphorbiaceae, native to Central America) at the end of the previous century, B. tabaci has gradually become an increasingly significant agricultural pest. In recent years, the push–pull strategy has been widely applied to the control of the pest. The distinct volatiles are emitted of plants directly affect the efficiency of pushing and pulling; hence, we aimed to study the behavioral responses of B. tabaci to three plants (Gossypium hirsutum, Abutilon theophrasti, and Ricinus communis) during various growth phases (pre-flowering, fluorescence, and fruiting) and analyzed the quality and quantity of volatiles from of three growth stage, as well as identified few compounds that attract or repel the B. tabaci. The results demonstrated that the distinct volatiles are emitted by pre-flowering, flowering, and fruiting plants with varying effects on B. tabaci preference. Three volatile compounds (linalool, (Z)-3-hexenyl acetate, and nonanal) analyzed in this study had trapping/repellent effects on B. tabaci. Therefore, these compounds can be adopted as potential attractants or repellents to control B. tabaci.Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a worldwide pest that damages over 900 host plant species. The volatile organic compounds (volatiles) of contrasting plants, as well as their growth stage, influence this pest’s infestation behavior. The chemical contents of volatiles isolated from three plants (Gossypium hirsutum, Abutilon theophrasti, and Ricinus communis) during various growth phases (pre-flowering, fluorescence, and fruiting) were examined, as well as their influence on the behavior of adult B. tabaci. The olfactometer studies demonstrated that growth periods of the three plants affected the preference of B. tabaci. Volatiles of piemarker and cotton plants had dissimilar levels of attraction to adults during all stages. Volatile substances released by the castor at the stage of flowering had repellent effect on B. tabaci. In the plant versus plant combination, piemarker volatiles before and during anthesis were most preferred by adults, followed by cotton and then castor. A total of 24, 24, and 20 compounds were detected from volatiles of piemarker, cotton, and castor, respectively, and proportions among the compounds changed during different stages of plant development. The olfactory responses of B. tabaci to volatile compounds presented that linalool and high concentration of (Z)-3-hexenyl acetate had a strong trapping effect on this pest, while nonanal had a significant repellent effect at high concentration. This study indicates that distinct plants and their growth stage affect their attractiveness or repellency to B. tabaci adults, which are mediated by changing plant volatiles. These compounds obtained by analysis screening can be adopted as potential attractants or repellents to control Mediterranean (MED) B. tabaci.

A Comparison of Electrical Breakdown Models for Polyethylene Nanocomposites

The development of direct current high-voltage power cables requires insulating materials having excellent electrically insulation properties. Experiments show that appropriate nanodoping can improve the breakdown strength of polyethylene (PE) nanocomposites. Research indicates that traps, free volumes, and molecular displacement are key factors affecting the breakdown strength. This study comprehensively considered the space charge transport, electron energy gain, and molecular chain long-distance movement during the electrical breakdown process. In addition, we established three simulation models focusing on the electric field distortion due to space charges captured by traps, the energy gain of mobile electrons in free volumes, the free volume expansion caused by long-distance movement of molecular chains under the Coulomb force, and the energy gained by the electrons moving in the enlarged free volumes. The three simulation models considered the electrical breakdown modulated by space charges, with a maximum electric field criterion and a maximum electron energy criterion, and the electrical breakdown modulated by the molecular displacement (EBMD), with a maximum electron energy criterion. These three models were utilized to simulate the breakdown strength dependent on the nanofiller content of PE nanocomposites. The simulation results of the EBMD model coincided best with the experimental results. It was revealed that the breakdown electric field of PE nanodielectrics is improved synergistically by both the strong trapping effect of traps and the strong binding effect of molecular chains in the interfacial regions.

Graphene/Ge microcrystal photodetectors with enhanced infrared responsivity

We report on the electrical and optical properties of microcrystal arrays obtained by depositing Ge on a deeply patterned Si substrate. Finite difference time domain simulations indicate that the faceted morphology and high refractive index of Ge microcrystals lead to strong light trapping effects, enhancing infrared light absorption in the spectral window between the direct and indirect absorption edge of Ge (≈1550–1800 nm). This is experimentally confirmed by fabricating microcrystal-based Ge-on-Si photodiodes employing graphene as a top transparent contact. In these devices, the ratio between the responsivities at 1550 and 1700 nm is more than ten times larger than that of photodiodes based on conventional Ge-on-Si epilayers.

How charge trapping affects the conductivity of electrochemically doped poly(3-hexylthiophene) films

Electrochemical doping is an elegant method of controlling the doping level and charge carrier densities of conjugated polymer films and enhancing their thermoelectric figure of merit. Applying this doping technique to films of poly(3-hexylthiophene) (P3HT) results in conductivities with values as high as 200 S/cm. The stability of the doped films in the solid state can be probed by UV-vis-NIR spectroscopy. We found that the choice of the conducting salt in the liquid electrolyte exerts a strong influence over the conductivity. Using TBAPF6 and LiClO4 provides highest conductivities for P3HT films, while LiTFSI and TBABF4 show overall lower performance. This effect is also reflected in cyclic voltammetry measurements coupled with in situ spectroscopy. Overall lower reversibility upon multiplex cycling in LiTFSI and TBABF4 electrolytes suggests strong charge trapping effects, which one might attribute to a considerable fraction of charges (holes/ions) remaining in the films after charge/discharge cycles. The salts with stronger charge irreversibility in the electrochemistry experiments show the poorer solid state conductivities. Our conclusion is that one should carefully choose the electrolyte to ensure good percolation pathways and delocalized charge transport throughout doped films.

Soft-Microstructured Transparent Electrodes for Photonic-Enhanced Flexible Solar Cells

Microstructured transparent conductive oxides (TCOs) have shown great potential as photonic electrodes in photovoltaic (PV) applications, providing both optical and electrical improvements in the solar cells’ performance due to: (1) strong light trapping effects that enhance broadband light absorption in PV material and (2) the reduced sheet resistance of the front illuminated contact. This work developed a method for the fabrication and optimization of wavelength-sized indium zinc oxide (IZO) microstructures, which were soft-patterned on flexible indium tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) substrates via a simple, low-cost, versatile, and highly scalable colloidal lithography process. Using this method, the ITO-coated PET substrates patterned with IZO micro-meshes provided improved transparent electrodes endowed with strong light interaction effects—namely, a pronounced light scattering performance (diffuse transmittance up to ~50%). In addition, the photonic-structured IZO mesh allowed a higher volume of TCO material in the electrode while maintaining the desired transparency, which led to a sheet resistance reduction (by ~30%), thereby providing further electrical benefits due to the improvement of the contact conductance. The results reported herein pave the way for a new class of photonic transparent electrodes endowed with mechanical flexibility that offer strong potential not only as advanced front contacts for thin-film bendable solar cells but also for a much broader range of optoelectronic applications.

Molecular dynamics studies of the grain-size dependent hydrogen diffusion coefficient of nanograined Fe

Nanograined materials have much denser grain boundary (GB) networks than their coarse-grained counterparts, thereby the hydrogen (H) diffusion and trapping behaviors in nanograined materials, which are strongly influenced by GBs, may differ greatly from those in coarse-grained materials. In the present research, the grain-size dependent hydrogen diffusion coefficient in nanograined Fe is studied by theoretical analysis and molecular dynamics (MD) simulations. A theoretical model based on thermodynamics is developed. The GB-related material parameters required by the model are then obtained by fitting the MD simulation results. Finally, the grain-size dependent diffusion coefficients are compared with model predictions to evaluate the validity of the model. It is found that the trapping effect of triple junctions that usually ignored in coarse-grained materials becomes increasing important as grain size and temperature decrease. Due to the strong trapping effect of GBs in nanograined Fe, H diffusion is slowed down by the GBs.

Effects of yttrium doping on helium behavior in zirconium hydride films

The zirconium hydride alloy films with different yttrium concentration were prepared by magnetron sputtering and studied using ion beam analysis (IBA), X-ray diffraction (XRD), thermal desorption spectrometry (TDS), positron annihilation spectroscopy (PAS) and nanoindentation. It was found that the yttrium atom, which is originally insoluble in zirconium metal, can largely dissolve in the zirconium hydride matrix through the introduction of hydrogen. The helium thermal desorption experiment shows that as the doped amount of yttrium atoms increases, a large number of helium atoms will be released in the form of helium bubbles at the grain boundaries in the matrix at ca. 900K. Combined with XRD results, it is concluded that as the yttrium atoms are introduced, more grain boundaries will form in the zirconium hydride matrix. These grain boundaries act as crystal defects, which have a strong trapping effect on helium atoms, causing a large number of helium bubbles to aggregate at the grain boundaries in the matrix. In addition, it is noteworthy that yttrium doping can increase the hardness and elastic modulus of zirconium hydride.

Supersonic antigravity aerodynamic atomization dusting nozzle based on the Laval nozzle and probe jet

To improve the trapping efficiency of respiratory dust by aerodynamic atomization and to maintain the health and safety of workers, a numerical simulation (droplet fragmentation and particle tracking in a high Mach number flow) and an aerodynamic atomization experiment were adopted on the basis of the existing supersonic aerodynamic atomization nozzles that utilize the Laval nozzle as the core. A new type of this kind of nozzle based on a probe structure was designed and optimized. Both the simulation and experimental results have shown that the probe injection method is more suitable for the progress of supersonic aerodynamic atomization. The new nozzle inherits the characteristics of fast droplet speed, conservation of water and pressure, long-range and slow attenuation. The atomization performance of the new nozzle is better than that of traditional nozzles at the same power, and the new nozzle has a larger atomization angle, smaller atomization granularity, lower noise and a more stable atomization output. For the first time, the process of breaking particles by using supersonic gas in the field of dust removal is truly realized. When the pressure is more than 0.1 MPa, antigravity water absorption can be realized. The dust removal rate can be approximately twice as high as that of the traditional ultrasonic atomization method. Compared with the traditional ultrasonic atomization method (84.75%), the dust isolation efficiency can reach 94.07%. The droplets of ultra-fine size with high-speed produced by the new nozzle will have a strong trapping effect on respiratory dust and will save more energy by the vacuum force siphon than currently used nozzles (the amount of gas saved by the same efficiency is 40% and the amount of water saved is 45%).

Realizing high color-stability in tetra-chromatic white organic light-emitting diodes by strict manipulation of red emissive layer

Tetra-chromatic (Blue–Green–Red–Orange) white organic light-emitting diodes (WOLEDs) with superior color stability was demonstrated. Strong carrier trapping effects of red dyes cause significant color shift in multi-color WOLEDs. The high color stability here is attributed to the decrease of red dye trapping sites and enhancement of effective energy transfer to red dye while maintaining appropriate exciton concentration near red dye. As luminance increased from 1000 to 10 000 cd m−2, variations in Commission Internationale de L’Eclairage are merely (0.007, 0.007). Furthermore, this color-stable WOLED achieved a color rendering index close to 90 simultaneously. Our work shows the manipulation of red dye is crucial for achieving superior color stability in multi-color WOLEDs.

Enlarged responsivity-ZnO honeycomb nanomaterials UV photodetectors with light trapping effect

The ability of ZnO photodetectors to absorb UV light plays a key role in enhancing responsivity and performance in electronic, optical, and photonic devices. Herein, the light trapping effect of ZnO is used to design and fabricate a novel honeycomb-like ZnO nanomaterial-based UV photodetector with an excellent photoelectric performance. Compared with the traditional ZnO film UV photodetector, the photoresponsivity of the film with honeycomb nanomaterials can reach up to 4.79 A W−1, which is an improvement of about 300 times. In addition, the honeycomb ZnO nanomaterials UV photodetectors exhibit an improved light absorption, a very photo-to-dark current ratio (2.46 × 103), and an excellent detectivity (4.61 × 1012 Jones). The ZnO honeycomb nanostructure synthesized in this work exhibits a strong trapping effect, providing new insights into the research of nanomaterials used for UV photodetectors.

Towards understanding the strong trapping effects of noble gas elements on hydrogen in tungsten

We have investigated the effects of noble gas elements (helium, neon, argon and krypton) on the dissolution and accumulation behavior of hydrogen (H) in tungsten (W) using a first-principles method, as well as the behaviors of themselves. Noble gas atoms energetically prefer to occupy the tetrahedral interstitial site (TIS) in W, as the same of H. The TIS → TIS is their optimal diffusion path, and the diffusion energies increase with the increasing of atomic radius. All of them are energetically favorable clustering by self-trapping. It is found that the presence of the noble gas elements have significant effect on H behavior in W. Both interstitial noble gas atoms and their complex with vacancy can serve as strong trapping centers of H, which can be attributed to the redistribution of electron density and lattice distortion induced by noble gas. Most importantly, we have demonstrated that H trapping capability of noble gas clusters will increase with the increasing of the number of noble gas atoms in both interstitial and vacancy-complex cases. The H trapping energy surrounding the noble gas clusters with four atoms is comparable to that in noble gas-free vacancy. Further, the formation of noble gas clusters is much easier than that of vacancy due to the self-trapping interaction between noble gas atoms (>1 eV for interstitial case and >4 eV for vacancy-complex case), and thus the H trapping centers will rapidly increase after noble gas pre-irradiation/implantation. Consequently, the self-trapping character of noble gas induces their strong trapping effect on H.

Recombination zone of blue thermally activated delayed fluorescent devices

Recombination zone of blue thermally activated delayed fluorescent devices was identified by inserting a yellow sensitizer in the emitting layer made up of 1,3-bis(N-carbazolyl)benzene (mCP) and 4,6-di(9H-carbazol-9-yl)isophthalonitrile (DCzIPN) blue thermally activated delayed fluorescent emitter. Recombination of the mCP:DCzIPN emitting layer was mostly observed near electron transport layer at low doping concentration because of strong electron trapping effect by DCzIPN. Recombination zone of mCP:DczIPN emitting layer was broadened at high doping concentration by controlling electron density in the emitting layer.