Highly Optically Selective and Thermally Insulating Porous Calcium Silicate Composite SiO2 Aerogel Coating for Daytime Radiative Cooling.

Daytime radiative cooling technology offers a low-carbon, environmentally friendly, and nonpower-consuming approach to realize building energy conservation. It is important to design materials with high solar reflectivity and high infrared emissivity in atmospheric windows. Herein, a porous calcium silicate composite SiO2 aerogel water-borne coating with strong passive radiative cooling and high thermal insulation properties is proposed, which shows an exceptional solar reflectance of 94%, high sky window emissivity of 96%, and 0.0854 W/m·K thermal conductivity. On the SiO2/CaSiO3 radiative cooling coating (SiO2-CS-coating), a strategy is proposed to enhance the atmospheric window emissivity by lattice resonance, which is attributed to the eight-membered ring structure of porous calcium silicate, thereby increasing the atmospheric window emissivity. In the daytime test (solar irradiance 900W/m2, ambient temperature 43 °C, wind speed 0.53 m/s, humidity 25%), the temperature inside the box can achieve a cooling temperature of 13 °C lower than that of the environment, which is 30 °C, and the theoretical cooling power is 96 W/m2. Compared with the commercial white coating, SiO2-CS-coating can save 70 kW·h of electric energy in 1 month, and the energy consumption is reduced by 36%. The work provides a scalable, widely applicable radiative-cooling coating for building comfort, which can greatly reduce indoor temperatures and is suitable for building surfaces.

High-efficient capture and degradation of formaldehyde based on the electric-field-enhanced catalytic effect.

Enhancing the generation of active groups is of great significance for alleviating the catalyst deactivation of formaldehyde (HCHO) by accelerating the decomposition of intermediate products. Herein, an electric-field-enhanced catalytic effect was proposed for the efficient capture and degradation of HCHO base on carbon cloth loaded manganese oxide catalyst (MnOx-CC). Under the action of electric field, MnOx can generate more hydroxyl radicals (•OH) and superoxide radicals (•O2-), thus accelerating the degradation of HCHO and intermediates at room temperature. After the introduction electric field (∼1 ×104 V/m), •O2- and •OH radical on the surface of MnOx-CC catalyst can be increased by 8 times and 23 times, respectively. At weight hourly space velocity of 300,000 mL/(gcat h) for ∼15 ppm HCHO, MnOx-CC-Electric Field catalyst reached the removal efficiency of 99.4%, and the CO2 conversion efficiency of 81.2%, without decrease significantly within 80 h. Theoretical calculation shows that the electric field can increase the electron state density of Mn atom at the Fermi level and reduce the adsorption energy of HCHO, O2 and H2O, thus promoting the generation of active groups and degradation of intermediate products. The electric-field-enhancement catalytic effect provides a new approach for the degradation of Volatile Organic Compounds.

Bimetallic oxide Cu2O@MnO2 with exposed phase interfaces for dual-effect purification of indoor formaldehyde and pathogenic bacteria.

The combination of materials with different functions is an optimal strategy for synchronously removing various indoor pollutants. For multiphase composites, exposing all components and their phase interfaces fully to the reaction atmosphere is a critical problem that needs to be solved urgently. Here, a bimetallic oxide Cu2O@MnO2 with exposed phase interfaces was prepared by a surfactant-assisted two-step electrochemical method, which shows a composite structure of non-continuously dispersed Cu2O particles anchored on flower-like MnO2. Compared with the pure catalyst MnO2 and bacteriostatic agent Cu2O, Cu2O@MnO2 respectively shows superior dynamic formaldehyde (HCHO) removal efficiency (97.2% with a weight hourly space velocity of 120 000 mL g-1 h-1) and pathogen inactivation ability (the minimum inhibitory concentration for 104 CFU mL-1 Staphylococcus aureus is 10 µg mL-1). According to material characterization and theoretical calculation, its excellent catalytic-oxidative activity is attributable to the electron-rich region at the phase interface which is fully exposed to the reaction atmosphere, inducing the capture and activation of O2 on the material surface, and then promoting the generation of reactive oxygen species that can be used for the oxidative-removal of HCHO and bacteria. Additionally, as a photocatalytic semiconductor, Cu2O further enhances the catalytic ability of Cu2O@MnO2 under the assistance of visible light. This work will provide efficient theoretical guidance and a practical basis for the ingenious construction of multiphase coexisting composites in the field of multi-functional indoor pollutant purification strategies.

Adsorption-enhanced catalytic oxidation for long-lasting dynamic degradation of organic dyes by porous manganese-based biopolymeric catalyst.

Improving the adsorption kinetics of metal-oxide catalysts is critical for the enhancement of catalytic performance in heterogeneous catalytic oxidation reactions. Herein, based on the biopolymer pomelo peels (PP) and metal-oxide catalyst manganese oxide (MnOx), an adsorption-enhanced catalyst (MnOx-PP) was constructed for catalytic organic dyes oxidative-degradation. MnOx-PP shows excellent methylene blue (MB) and total carbon content (TOC) removal efficiency of 99.5 % and 66.31 % respectively, and keeps the long-lasting stable dynamic degradation efficiency during 72 h based on the self-built continuous single-pass MB purification device. The chemical structure similarity and negative-charge polarity sites of the biopolymer PP improve the adsorption kinetics of organic macromolecule MB, and construct the adsorption-enhanced catalytic oxidation microenvironment. Meanwhile, the adsorption-enhanced catalyst MnOx-PP obtains lower ionization potential and O2 adsorption energy to promote the continuous generation of active substance (O2*, OH*) for the further catalytic oxidation of adsorbed MB molecules. This work explored the adsorption-enhanced catalytic oxidation mechanism for the degradation of organic pollutants, and provided a feasible technical idea for designing adsorption-enhanced catalysts for the long-lasting efficient removal of organic dyes.

Single-Mode Lasing in Plasmonic-Enhanced Woven Microfibers for Multifunctional Sensing.

Single-mode plasmonic lasing has great potential for use in photonic and sensing applications. In this work, single-mode lasing is realized using a plasmonic-enhanced woven microfiber that shows ultrahigh sensitivity to the ambient environment. This plasmonic-enhanced microfiber is fabricated by spraying Ag nanospheres onto rhodamine 6G-doped polymer microfibers. Single-mode laser emission with an ultranarrow linewidth (0.1 nm) and a low threshold (18.8 kW/mm2) is achieved in the microfiber using the effects of mode selection and plasmonic enhancement provided by the Ag nanospheres. A large wavelength shift in the single-mode lasing is observed when the proposed laser is used as a sensor and exposed to a humid or acidic environment. The wavelength shift is attributed to refractive index variations in the microfiber caused by either moisture absorption or chemical reactions. In humidity sensing, the laser's sensitivity is as high as 826.6 pm/% relative humidity (RH) and the detection limit is 0.051% RH. An innovative strategy for acetic acid gas sensing is proposed that uses the chemical reaction with rhodamine 6G, and its minimum response time is 5 min. Because of the microfiber's excellent fabric compatibility, a wearable sensor is fabricated by weaving the plasmonic-enhanced microfiber into clothes, and this sensor demonstrates extreme bending stability. The results reported here provide a novel approach to the design and fabrication of ultrasensitive wearable sensors for multifunctional sensing applications.

Atomically Dispersed Platinum Modulated by Sulfide as an Efficient Electrocatalyst for Hydrogen Evolution Reaction.

Catalytically active metals atomically dispersed on supports presents the ultimate atom utilization efficiency and cost-effective pathway for electrocatalyst design. Optimizing the coordination nature of metal atoms represents the advanced strategy for enhancing the catalytic activity and the selectivity of single-atom catalysts (SACs). Here, we designed a transition-metal based sulfide-Ni3S2 with abundant exposed Ni vacancies created by the interaction between chloride ions and the functional groups on the surface of Ni3S2 for the anchoring of atomically dispersed Pt (PtSA-Ni3S2). The theoretical calculation reveals that unique Pt-Ni3S2 support interaction increases the d orbital electron occupation at the Fermi level and leads to a shift-down of the d -band center, which energetically enhances H2O adsorption and provides the optimum H binding sites. Introducing Pt into Ni position in Ni3S2 system can efficiently enhance electronic field distribution and construct a metallic-state feature on the Pt sites by the orbital hybridization between S-3p and Pt-5d for improved reaction kinetics. Finally, the fabricated PtSA-Ni3S2 SAC is supported by Ag nanowires network to construct a seamless conductive three-dimensional (3D) nanostructure (PtSA-Ni3S2@Ag NWs), and the developed catalyst shows an extremely great mass activity of 7.6 A mg-1 with 27-time higher than the commercial Pt/C HER catalyst.

Platinum single-atom catalyst coupled with transition metal/metal oxide heterostructure for accelerating alkaline hydrogen evolution reaction.

Single-atom catalysts provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However, the sluggish activity of the catalysts for alkaline water dissociation has hampered advances in highly efficient hydrogen production. Herein, we develop a single-atom platinum immobilized NiO/Ni heterostructure (PtSA-NiO/Ni) as an alkaline hydrogen evolution catalyst. It is found that Pt single atom coupled with NiO/Ni heterostructure enables the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*), which efficiently tailors the water dissociation energy and promotes the H* conversion for accelerating alkaline hydrogen evolution reaction. A further enhancement is achieved by constructing PtSA-NiO/Ni nanosheets on Ag nanowires to form a hierarchical three-dimensional morphology. Consequently, the fabricated PtSA-NiO/Ni catalyst displays high alkaline hydrogen evolution performances with a quite high mass activity of 20.6 A mg-1 for Pt at the overpotential of 100 mV, significantly outperforming the reported catalysts.

Organic Molecule Assisted Growth of Perovskite Films Consisting of Square Grains by Surface-Confined Process.

Organic-inorganic perovskite single crystals are promising in the field of optoelectronics due to their excellent optoelectronic properties. However, the ion transport of perovskite precursor is poor in confined spaces, which results in difficulty in the preparation of perovskite single-crystal films. Herein, MAPbBr3 films consisting of square grains were fabricated by the surface-confined process using the organic molecule PEAI (phenethylammonium iodide). Under the effect of oversaturation gradient, PEA+ is combined with the surface of perovskite grain from top to side, which constrains the lateral growth of grains and induces a downward growth of perovskite, leading to the formation of square grains. With the improvement of concentration PEAI, the perovskite film exhibits a decreased side length of grains (from 0.98 to 12.96 µm) and increased grain number and coverage, as well as crystallinity. The perovskite single crystalline grain films with PEAI showed double photoluminescence (PL) emission peaks due to the existence of iodine-rich perovskite. This work may provide a practical way to fabricate high-quality perovskite films for perovskite photoelectronic devices.

Influence of Fluorinated Components on Perovskite Solar Cells Performance and Stability.

Several valuable scientific investigations have been conducted these last few years in materials design and device engineering for perovskite solar cells (PSCs) to make them competitive compared to traditional silicon-based photovoltaic technologies. Consequently, high power conversion efficiency beyond 25% is nowadays reported. However, their long-term stability remains a significant challenge to overcome. Herein, the influence of fluorinated compounds on each layer of PSCs devices and their impact on the resulted device performances and stability is spotlighted. The fluorinated compounds exhibit attractive properties due to their very high electronegativity attributed to the fluorine atom, and their strong hydrophobicity. Thus, the introduction of these compounds is found to be a successful strategy to positively suppress the surface trap states, enhancing charge collection and reducing interfacial charge recombination. Besides, a better film quality and better energy level alignment is obtained, resulting in the improvement of device photovoltaic parameters such as the open-circuit voltage (Voc ), short-circuit current (Jsc ), and fill factor (FF), and then, the device's overall power conversion efficiency (PCE). Their long-term stability is also found to further be improved.

Rapid degradation behavior of encapsulated perovskite solar cells under light, bias voltage or heat fields.

When the power conversion efficiency (PCE) of perovskite solar cells (PSCs) rapidly approaches that of commercial solar cells, the stability becomes the most important obstacle for the commercialization of PSCs. Aside from the widely studied slow PCE degradation, the PSCs also show a unique rapid PCE degradation. Although the degradation due to oxygen and humidity can be avoided by encapsulation, that due to bias voltage, light and heat could not be effective suppressed and will lead to considerable degradation. Usually, the rapid PCE degradation is believed to be from ion migration. However, a systematic investigation is yet to be carried out. This work quantitatively and systematically investigated the relationships between external fields (bias voltage, light or heat), ion migration and device performance. By comparing the performance of reference PSCs after 90 min degradation under these fields, we conclude that (1) the electric field affects the spatial distribution of mobile ions; (2) the light field changes the mobile ion densities and drives the ion migration; (3) the heat field results in perovskite decomposition as well as changing the mobile ion densities. In addition to the analysis of the reference device, we experimentally proved that the improved device stability upon introducing phenethylammonium iodide (PEAI) or poly-methyl methacrylate (PMMA) layers originates from the inhibition of mobile ion density and migration.

Mechanism of PbI2 in Situ Passivated Perovskite Films for Enhancing the Performance of Perovskite Solar Cells.

Perovskite solar cells (PSCs) have gained tremendous research interest because of their tolerance of defects, low cost, and facile processing. In PSC devices, PbI2 has been utilized to passivate defects at perovskite film surfaces and GBs; however, a systematic mechanism of PbI2 in situ passivation for enhancing the solar cells efficiency has not been fully explored. Here, this work, we systematically studies the effect of the precise PbI2 ratio and the PbI2 in situ passivation mechanism based on trap density, carrier lifetime, Fermi level, and so forth. This study finds the appropriate ratio of I/Pb to be around 2.57:1 using energy-dispersive spectroscopy. After the moderate excess PbI2 in situ passivation, the trap density is reduced from 6.12 × 1016 to 3.38 × 1016 cm-3, and the carrier lifetime is extended from 168.35 to 368.77 ps by using fs-TA spectroscopy. This result indicates that the moderate excess PbI2 in situ passivation can reduce the trap density and suppress the nonradiative recombination. The efficiency of solar cell has shown a nearly 11.3% improvement of 19.55% for an I/Pb ratio of 2.57:1 compared with 2.69:1. It also demonstrates that the efficiency of PSCs can be enhanced effectively by PbI2 in situ passivation.

Highly Stable Transparent Conductive Electrodes Based on Silver-Platinum Alloy-Walled Hollow Nanowires for Optoelectronic Devices.

In industrial manufacturing, alloying can contribute to the passivation of active metals and markedly improve their corrosion resistance. This inspires us to solve the current critical problem of Ag nanowires (Ag NWs) that have poor stability against chemical and electrochemical corrosion. These problems have seriously limited the applications of Ag NWs in optoelectronic devices where they are used for transparent conductive electrodes. Here, a kind of transparent conductive electrode based on Ag@Pt alloy-walled hollow nanowires (Ag@Pt AHNWs) is successfully fabricated by introducing 12 mol % Pt into long Ag NWs to form Ag@Pt alloy. The as-synthesized electrodes exhibit better optical transmittance (82% at the wavelength of 550 nm) under high electrical conductivity (28.73 Ω/sq-1), high thermal stability up to 400 °C for 11 h, and remarkable mechanical flexibility (remaining stable after 5000 cycles bending), as well as high resistance against chemical and electrochemical corrosion. The Ag@Pt AHNWs electrodes are further applied in a primary bifunctional polyaniline electrochemical device, and the device shows promising flexibility, noticeable multicolor performances, and high specific capacitance because of the remarkable mechanical flexibility and electrochemical stability of Ag@Pt AHNWs. This work will provide an optional approach for the preparation of other metal nanomaterial electrodes with high stability.

Smart Floor with Integrated Triboelectric Nanogenerator As Energy Harvester and Motion Sensor.

A smart floor is demonstrated by integrating a square-frame triboelectric nanogenerator (SF-TENG) into a standard wood floor. The smart floor has two working modes based on two pairs of triboelectric materials: one is purposely chosen polytetrafluoroethylene films and aluminum (Al) balls, and the other is the floor itself and the objects that can be triboelectrically charged, such as basketball, shoe soles, and Scotch tape, etc. Utilizing the Al balls enclosed inside shallow boxes, the smart floor is capable of harvesting vibrational energy and, hence, provides a nonintrusive way to detect sudden falls in elderly people. In addition, when the basketball is bounced repeatedly on the floor, the average output voltage and current are 364 ± 43 V and 9 ± 1 µA, respectively, and 87 serially connected light-emitting diodes can be lit up simultaneously. Furthermore, the friction between the triboelectrically chargeable objects and the floor can also induce an alternating current output in the external circuit without the vibration of the Al balls. Normal human footsteps on the floor produce a voltage of 238 ± 17 V and a current of 2.4 ± 0.3 µA. Therefore, this work presents a smart floor with built-in SF-TENG without compromising the flexibility and stability of the standard wood floor and also demonstrates a way to harvest ambient energy solely by using conventional triboelectric materials in our daily life.

Triboelectric Nanogenerator Enhanced Nanofiber Air Filters for Efficient Particulate Matter Removal.

We developed a high-efficiency rotating triboelectric nanogenerator (R-TENG) enhanced polyimide (PI) nanofiber air filter for particulate matter (PM) removal in ambient atmosphere. The PI electrospinning nanofiber film exhibited high removal efficiency for the PM particles that have diameters larger than 0.5 µm. When the R-TENG is connected, the removal efficiency of the filter is enhanced, especially when the particle diameters of the PM are smaller than 100 nm. The highest removal efficiency is 90.6% for particles with a diameter of 33.4 nm and the highest efficiency enhancement reaches 207.8% at the diameter of 76.4 nm where the removal efficiency enhanced from 27.1% to 83.6%. This technology with zero ozone release and low pressure drop offers an approach for air cleaning and haze treatment.

Antibacterial Composite Film-Based Triboelectric Nanogenerator for Harvesting Walking Energy.

As a green and eco-friendly technology, triboelectric nanogenerator (TENG) can harvest energy from human motion to generate electricity, so TENGs have been widely applied in wearable electronic devices to replace traditional batteries. However, the surface of these TENGs is easily contaminated and breeds bacteria, which is a threat to human health. Here, we report an antibacterial composite film-based triboelectric nanogenerator (ACF-TENG) that uses Ag-exchanged zeolite (Ag-zeolite) and polypropylene (PP) composite film as the triboelectric layer. Adding a small amount of Ag-zeolite with excellent antibacterial properties can increase the dielectric permittivity and improve the surface charge density of composite films, which enhances the output performance of the ACF-TENG. The open-circuit voltage (VOC), short-circuit current (ISC), and transferred charge (QTr) of the ACF-TENG are about 193.3, 225.4, and 233.3% of those of a pure PP film-based TENG, respectively. Because of the silver in the Ag-zeolite, the ACF-TENG can effectively kill Escherichia coli and fungi. When used in insoles, the ACF-TENG can resist the athlete's foot fungus effectively and work as a power source to light up light-emitting diodes and charge capacitors. The ACF-TENG has wide application prospects in self-powered medical and healthcare electronics.

Fine-Tuning Ligand to Modulate the Magnetic Anisotropy in a Carboxylate-Bridged Dy2 Single-Molecule Magnet System.

A series of dinuclear Dy(III) compounds with the general formula [Dy2(µ2-anthc)4(anthc)2(L)2] (anthc(-) = 9-anthracenecarboxylate, L = 2,2'-bipyridyl (1), 1,10-phenanthroline (2), and 4,7-dimethyl-1,10-phenanthroline (3)) were synthesized and magnetically characterized. These compounds exhibit single-molecule magnet (SMM) behavior in the absence of the direct-current field, which is rarely observed for carboxylate-bridged dinuclear Dy2 system. With the first coordination sphere of Dy(III) centers being fixed, the energy barrier was modulated by sequentially modifying the terminal neutral L ligands in this Dy2 system. Theoretical calculations revealed that the symmetry of the charge distribution surrounding the Dy(III) centers in 1-3 is the decisive factor to determine the relaxation of the SMMs. The combination of the larger charge distribution along the magnetic axis and lower charge distribution in the equatorial plane (hard plane) formed by five coplanar coordination atoms including two N atoms provided by an L ligand led to a strong easy-axis ligand field in these compounds. This work presents a rational method to modulate the dynamic magnetic relaxation of the lanthanide SMMs through fine-tuning electrostatic potential of the atoms on the hard plane.

Two-dimensional Zn(II) and one-dimensional Co(II) coordination polymers based on benzene-1,4-dicarboxylate and pyridine ligands.

Coordination polymers constructed from metal ions and organic ligands have attracted considerable attention owing to their diverse structural topologies and potential applications. Ligands containing carboxylate groups are among the most extensively studied because of their versatile coordination modes. Reactions of benzene-1,4-dicarboxylic acid (H2BDC) and pyridine (py) with Zn(II) or Co(II) yielded two new coordination polymers, namely, poly[(µ4-benzene-1,4-dicarboxylato-κ(4)O:O':O'':O''')(pyridine-κN)zinc(II)], [Zn(C8H4O2)(C5H5N)]n, (I), and catena-poly[aqua(µ3-benzene-1,4-dicarboxylato-κ(3)O:O':O'')bis(pyridine-κN)cobalt(II)], [Co(C8H4O2)(C5H5N)2(H2O)]n, (II). In compound (I), the Zn(II) cation is five-coordinated by four carboxylate O atoms from four BDC(2-) ligands and one pyridine N atom in a distorted square-pyramidal coordination geometry. Four carboxylate groups bridge two Zn(II) ions to form centrosymmetric paddle-wheel-like Zn2(µ2-COO)4 units, which are linked by the benzene rings of the BDC(2-) ligands to generate a two-dimensional layered structure. The two-dimensional layer is extended into a three-dimensional supramolecular structure with the help of π-π stacking interactions between the aromatic rings. Compound (II) has a one-dimensional double-chain structure based on Co2(µ2-COO)2 units. The Co(II) cations are bridged by BDC(2-) ligands and are octahedrally coordinated by three carboxylate O atoms from three BDC(2-) ligands, one water O atom and two pyridine N atoms. Interchain O-H...O hydrogen-bonding interactions link these chains to form a three-dimensional supramolecular architecture.

A ball-bearing structured triboelectric nanogenerator for nondestructive damage and rotating speed measurement.

A ball-bearing structure based triboelectric nanogenerator (B-TENG) with interdigitative-electrodes was developed that can not only collect energy from rotational kinetic energy, but also serve as a self-powered and multifunctional sensor. The B-TENG relies on the rolling electrification between PTFE balls on Cu interdigitative-electrodes, which delivers an open-circuit voltage of ∼40 V and a short-circuit current of ∼1.2 µA at a rotating speed of 300 rpm for 4 mm PTFE balls. Using the output signals of B-TENG, a nondestructive detection for the damage of PTFE balls was realized without demounting the bearing. Besides, based on the periodic signals produced from B-TENG, the rotation speed of ball-bearing can be obtained according to the time difference between several cycles.

Structural Optimization of Triboelectric Nanogenerator for Harvesting Water Wave Energy.

Ocean waves are one of the most abundant energy sources on earth, but harvesting such energy is rather challenging due to various limitations of current technologies. Recently, networks formed by triboelectric nanogenerator (TENG) have been proposed as a promising technology for harvesting water wave energy. In this work, a basic unit for the TENG network was studied and optimized, which has a box structure composed of walls made of TENG composed of a wavy-structured Cu-Kapton-Cu film and two FEP thin films, with a metal ball enclosed inside. By combination of the theoretical calculations and experimental studies, the output performances of the TENG unit were investigated for various structural parameters, such as the size, mass, or number of the metal balls. From the viewpoint of theory, the output characteristics of TENG during its collision with the ball were numerically calculated by the finite element method and interpolation method, and there exists an optimum ball size or mass to reach maximized output power and electric energy. Moreover, the theoretical results were well verified by the experimental tests. The present work could provide guidance for structural optimization of wavy-structured TENGs for effectively harvesting water wave energy toward the dream of large-scale blue energy.

Removal of Particulate Matter Emissions from a Vehicle Using a Self-Powered Triboelectric Filter.

Particulate matter (PM) pollution from automobile exhaust has become one of the main pollution sources in urban environments. Although the diesel particulate filter has been used in heavy diesel vehicles, there is no particulate filter for most gasoline cars or light-duty vehicles because of high cost. Here, we introduce a self-powered triboelectric filter for removing PMs from automobile exhaust fumes using the triboelectrification effect. The finite element simulation reveals that the collision or friction between PTFE pellets and electrodes can generate large triboelectric charges and form a space electric field as high as 12 MV/m, accompanying an open-circuit voltage of ∼6 kV between the two electrodes, which is comparable to the measured value of 3 kV. By controlling the vibration frequency and fill ratio of pellets, more than 94% PMs in aerosol can be removed using the high electric field in the triboelectric filter. In real automobile exhaust fumes, the triboelectic filter has a mass collection efficiency of ∼95.5% for PM2.5 using self-vibration of the tailpipe.