Inherent Tunability Research Articles

Exploitation of Pore Structure for Increased CO2 Selectivity in Type 3 Porous Liquids.

CO2 capture requires materials with high adsorption selectivity and an industrial ease of implementation. To address these needs, a new class of porous materials was recently developed that combines the fluidity of solvents with the porosity of solids. Type 3 porous liquids (PLs) composed of solvents and metal-organic frameworks (MOFs) offer a promising alternative to current liquid carbon capture methods due to the inherent tunability of the nanoporous MOFs. However, the effects of MOF structural features and solvent properties on CO2-MOF interactions within PLs are not well understood. Herein experimental and computational data of CO2 gas adsorption isotherms were used to elucidate both solvent and pore structure influences on ZIF-based PLs. The roles of the pore structure including solvent size exclusion, structural environment, and MOF porosity on PL CO2 uptake were examined. A comparison of the pore structure and pore aperture was performed using ZIF-8, ZIF-L, and amorphous-ZIF-8. Adsorption experiments here have verified our previously proposed solvent size design principle for ZIF-based PLs (1.8× ZIF pore aperture). Furthermore, the CO2 adsorption isotherms of the ZIF-based PLs indicated that judicious selection of the pore environment allows for an increase in CO2 selectivity greater than expected from the individual PL components or their combination. This nonlinear increase in the CO2 selectivity is an emergent behavior resulting from the complex mixture of components specific to the ZIF-L + 2'-hydroxyacetophenone-based PL.

The effect of comb length on the in vitro and in vivo properties of self-assembled poly(oligoethylene glycol methacrylate)-based block copolymer nanoparticles.

Comb copolymer analogues of poly(lactic acid)-polyethylene glycol block copolymers (PLA-b-PEG) offer potential to overcome the inherent chemistry and stability limitations of their linear block copolymer counterparts. Herein, we examine the differences between P(L)LA10K-b-PEG10K and linear-comb copolymer analogues thereof in which the linear PEG block is replaced by poly(oligo(ethylene glycol) methacrylate) (POEGMA) blocks with different side chain (comb) lengths but the same overall molecular weight. P(L)LA10K-b-POEGMA47510K and P(L)LA10K-b-POEGMA200010K block copolymers were synthesized via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and fabricated into self-assembled nanoparticles using flash nanoprecipitation via confined impinging jet mixing. Linear-comb copolymer analogues based on PLA-b-POEGMA yielded smaller but still well-controlled nanoparticle sizes (88 ± 2 nm and 114 ± 1 nm respectively compared to 159 ± 2 nm for P(L)LA10K-b-PEG10K nanoparticles) that exhibited improved colloidal stability relative to linear copolymer-based nanoparticles over a 15 day incubation period while maintaining comparably high cytocompatibility, although the comb copolymer analogues had somewhat lower loading capacity for doxorubicin hydrochloride. Cell spheroid studies showed that the linear-comb copolymers promoted enhanced tumor transport and thus cell killing compared to conventional linear block copolymers. In vivo studies showed all NP types could passively accumulate within implanted CT26 tumors but with different accumulation profiles, with P(L)LA10K-b-POEGMA200010K NPs showing continuous accumulation throughout the full 24 h monitoring period whereas tumor accumulation of P(L)LA10K-b-POEGMA47510K NPs was significant only between 8 h and 24 h. Overall, the linear-comb copolymer analogues exhibited superior stability, biodistribution, spheroid penetration, and inherent tunability over linear NP counterparts.

A High-Entropy Oxide as High-Activity Electrocatalyst for Water Oxidation

High-entropy materials are an emerging pathway in the development of high-activity (electro)catalysts because of the inherent tunability and coexistence of multiple potential active sites, which may lead to earth-abundant catalyst materials for energy-efficient electrochemical energy storage. In this report, we identify how the multication composition in high-entropy perovskite oxides (HEO) contributes to high catalytic activity for the oxygen evolution reaction (OER), i.e., the key kinetically limiting half-reaction in several electrochemical energy conversion technologies, including green hydrogen generation. We compare the activity of the (001) facet of LaCr0.2Mn0.2Fe0.2Co0.2Ni0.2O3-δ with the parent compounds (single B-site in the ABO3 perovskite). While the single B-site perovskites roughly follow the expected volcano-type activity trends, the HEO clearly outperforms all of its parent compounds with 17 to 680 times higher currents at a fixed overpotential. As all samples were grown as an epitaxial layer, our results indicate an intrinsic composition–function relationship, avoiding the effects of complex geometries or unknown surface composition. In-depth X-ray photoemission studies reveal a synergistic effect of simultaneous oxidation and reduction of different transition metal cations during the adsorption of reaction intermediates. The surprisingly high OER activity demonstrates that HEOs are a highly attractive, earth-abundant material class for high-activity OER electrocatalysts, possibly allowing the activity to be fine-tuned beyond the scaling limits of mono- or bimetallic oxides.

Coupling high entropy oxide with hollow carbon spheres by rapid microwave solvothermal strategy for boosting oxygen evolution reaction

High entropy oxides (HEOs) are promising oxygen evolution electrocatalysts due to the unique structure, inherent tunability, as well as excellent catalytic activity and stability. Herein, (FeCoNiCrMn)3O4 nanoparticles coupling with the hollow-mesoporous carbon spheres (HCS) has been designed and fabricated by a rapid and efficient microwave solvothermal followed by annealing. The prepared (FeCoNiCrMn)3O4 nanoparticles are highly dispersed on the HCS surface with an average particle size of approximately 3.3 nm. The composite with large surface areas can facilitate mass transfer and gas release, and it allows more active sites to be exposed. The obtained (FeCoNiCrMn)3O4/hollow-mesoporous carbon sphere composite catalyst with the optimal HEO load (HEO/HCS-3) exhibits outstanding oxygen evolution reaction (OER) electrocatalytic performance with a low overpotential of 263 mV at 10 mA cm−2, and a small Tafel slope of 41.24 mV dec−1, better than the pure (FeCoNiCrMn)3O4 and commercial RuO2 catalyst. The long-term durability of HEO/HCS-3 is also achieved by continuous electrolysis in 1 M KOH solution for more than 100 h. The outstanding catalytic performance of the composite can be ascribed to the clever structural design and the well-matched synthetic method. This research can guide the construction of high-efficient OER catalysts.

Local cation ordering in compositionally complex Ruddlesden–Popper n = 1 oxides

The Ruddlesden–Popper (RP) layered perovskite structure is of great interest due to its inherent tunability, and the emergence and growth of the compositionally complex oxide (CCO) concept endows the RP family with further possibilities. Here, a comprehensive assessment of thermodynamic stabilization, local order/disorder, and lattice distortion was performed in the first two reported examples of lanthanum-deficient Lan+1BnO3n+1 (n = 1, B = Mg, Co, Ni, Cu, Zn) obtained via various processing conditions. Chemical short-range order (CSRO) at the B-site and the controllable excess interstitial oxygen (δ) in RP-CCOs are uncovered by neutron pair distribution function analysis. Reverse Monte Carlo analysis of the data, Metropolis Monte Carlo simulations, and extended x-ray absorption fine structure analysis implies a modest degree of magnetic element segregation on the local scale. Further, ab initio molecular dynamics simulations results obtained from special quasirandom structure disagree with experimentally observed CSRO but confirm Jahn–Teller distortion of CuO6 octahedra. These findings highlight potential opportunities to control local order/disorder and excess interstitial oxygen in layered RP-CCOs and demonstrate a high degree of freedom for tailoring application-specific properties. They also suggest a need for expansion of theoretical and data modeling approaches in order to meet the innate challenges of CCO and related high-entropy phases.

Pharmaceutical Applications of Ionic Liquids: A Personal Account.

Ionic liquids (ILs) have been extensively used in drug formulation and delivery as designer solvents and other components because of their inherent tunability and useful physicochemical and biopharmaceutical properties. ILs can be used to manage some of the operational and functional challenges of drug delivery, including drug solubility, permeability, formulation instability, and in vivo systemic toxicity, that are associated with conventional organic solvents/agents. Furthermore, ILs have been recognized as potential solvents to address the polymorphism, limited solubility, poor permeability, instability, and low bioavailability of crystalline drugs. In this account, we discuss the technological progress and strategies toward designing biocompatible ILs and explore potential biomedical applications, namely the solubilization of small and macromolecular drugs, the creation of active pharmaceutical ingredients, and the delivery of pharmaceuticals.

Tunable Radio Frequency Antenna Based on Phase Change Materials.

In conventional communication systems, dedicated tunable circuit elements are used to realize different functions and achieve performance metrics. For example, tuning the center frequency or the input impedance of an antenna in a radio frequency (RF) system is performed by complex impedance-matching circuits. In this paper, the antenna utilizes the temperature-induced irreversible mechanical deformation of a shape memory alloy (SMA) as a natural way to tune the antenna's shape and configuration, thereby providing inherent tunability without bulky circuit elements. This paradigm of material programming for impedance tuning of an SMA-based antenna is validated by both numerical simulation and measurements.

A High-Entropy Oxide as High-Activity Electrocatalyst for Water Oxidation.

High-entropy materials are an emerging pathway in the development of high-activity (electro)catalysts because of the inherent tunability and coexistence of multiple potential active sites, which may lead to earth-abundant catalyst materials for energy-efficient electrochemical energy storage. In this report, we identify how the multication composition in high-entropy perovskite oxides (HEO) contributes to high catalytic activity for the oxygen evolution reaction (OER), i.e., the key kinetically limiting half-reaction in several electrochemical energy conversion technologies, including green hydrogen generation. We compare the activity of the (001) facet of LaCr0.2Mn0.2Fe0.2Co0.2Ni0.2O3-δ with the parent compounds (single B-site in the ABO3 perovskite). While the single B-site perovskites roughly follow the expected volcano-type activity trends, the HEO clearly outperforms all of its parent compounds with 17 to 680 times higher currents at a fixed overpotential. As all samples were grown as an epitaxial layer, our results indicate an intrinsic composition-function relationship, avoiding the effects of complex geometries or unknown surface composition. In-depth X-ray photoemission studies reveal a synergistic effect of simultaneous oxidation and reduction of different transition metal cations during the adsorption of reaction intermediates. The surprisingly high OER activity demonstrates that HEOs are a highly attractive, earth-abundant material class for high-activity OER electrocatalysts, possibly allowing the activity to be fine-tuned beyond the scaling limits of mono- or bimetallic oxides.

Electronically Ambivalent Hydrodefluorination of Aryl‐CF3 groups enabled by Electrochemical Deep‐Reduction on a Ni Cathode

AbstractThe Ar‐CF2H moiety is featured in an increasing number of bioactive compounds due to its unique combination of properties. The hydrodefluorination of Ar‐CF3 compounds is a direct and efficient route toward this motif. As reported methods for this transformation have focused on specific substrate families, herein we describe a general—electronically ambivalent—procedure for the single‐step direct mono‐hydrodefluorination of a variety of feedstock and functionalized Ar‐CF3 compounds. Exploiting the inherent tunability of electrochemistry and the selectivity enabled by a Ni cathode, the deep reduction garners high selectivity for ArCF2H products, with good to excellent yields up to gram scale. The protocol has been extended to a single‐step di‐hydrodefluorination yielding benzyl fluorides. The late‐stage peripheral editing of a single CF3 feedstock to construct fluoromethyl (CF2H, CFH2) moieties will aid the rapid diversification of lead‐compounds and compound libraries.

Electronically Ambivalent Hydrodefluorination of Aryl-CF3 groups enabled by Electrochemical Deep-Reduction on a Ni Cathode.

We report a general procedure for the direct mono- and di-hydrodefluorination of ArCF3 compounds. Exploiting the tunability of electrochemistry and the selectivity enabled by a Ni cathode, the deep reduction garners high selectivity with good to excellent yields up to gram scale. The late-stage peripheral editing of CF3 feedstocks to construct fluoromethyl moieties will aid the rapid diversification of lead-compounds and compound libraries.

An overview of biomedical applications of choline geranate (CAGE): a major breakthrough in drug delivery.

A number of studies are on the way to advancing the field of biomedical sciences using ionic liquids (ILs) and deep eutectic solvents (DESs) in view of their unique properties and inherent tunability. These significant solvents tend to enhance the physical properties of the drug, increase their bioavailability and promote the delivery of recalcitrant drugs to the body. One such widely investigated tempting multipurpose IL/DES system is choline geranate (CAGE), which has gained significant interest due to its biocompatible and highly potent antiseptic behavior, which also facilitates its sanitizing ability to combat the coronavirus. This review focuses on total advancements in biomedical applications of CAGE. This biocompatible IL/DES has made facile the solubilization of hydrophobic and hydrophilic drugs and delivery of intractable drugs through physiological barriers by stabilizing proteins and nucleic acids. Therefore, it has been used as a transdermal, subcutaneous, and oral delivery carrier and as an antimicrobial agent to treat infectious diseases and wounds as approved by laboratory and clinical translations. Moreover, current challenges and future outlooks are also highlighted to explore them more purposefully.

Recent Advances in Ionic Liquids in Biomedicine.

The use of ionic liquids and deep eutectic solvents in biomedical applications has grown dramatically in recent years due to their unique properties and their inherent tunability. This review will introduce ionic liquids and deep eutectics and discuss their biomedical applications, namely solubilization of drugs, creation of active pharmaceutical ingredients, delivery of pharmaceuticals through biological barriers, stabilization of proteins and other nucleic acids, antibacterial agents, and development of new biosensors. Current challenges and future outlooks are discussed, including biocompatibility, the potential impact of the presence of impurities, and the importance of understanding the microscopic interactions in ionic liquids in order to design task‐specific solvents.

Polariton lasing and energy-degenerate parametric scattering in non-resonantly driven coupled planar microcavities

Abstract Multi-level exciton-polariton systems offer an attractive platform for studies of non-linear optical phenomena. However, studies of such consequential non-linear phenomena as polariton condensation and lasing in planar microcavities have so far been limited to two-level systems, where the condensation takes place in the lowest attainable state. Here, we report non-equilibrium Bose–Einstein condensation of exciton-polaritons and low threshold, dual-wavelength polariton lasing in vertically coupled, double planar microcavities. Moreover, we find that the presence of the non-resonantly driven condensate triggers interbranch exciton-polariton transfer in the form of energy-degenerate parametric scattering. Such an effect has so far been observed only under excitation that is strictly resonant in terms of the energy and incidence angle. We describe theoretically our time-integrated and time-resolved photoluminescence investigations by an open-dissipative Gross–Pitaevskii equation-based model. Our platform’s inherent tunability is promising for construction of planar lattices, enabling three-dimensional polariton hopping and realization of photonic devices, such as all-optical polariton-based logic gates.

Defects Formation and Amorphization of Zn-MOF-74 Crystals by Post-Synthetic Interactions with Bidentate Adsorbates.

The controlled introduction of defects into MOFs is a powerful strategy to induce new physiochemical properties and improve their performance for target applications. Herein, we present a new strategy for defect formation and amorphization of the canonical MOF-74 frameworks based on fine-tuning of adsorbate-framework interactions in the metal congener, hence introducing structural defects. Specifically, we demonstrate that controlled interactions between the MOF and bidentate ligands adsorbed in the pores initiates defect formation and eventual amorphization of the crystal. These structural features unlock properties that are otherwise absent in the ordered framework, such as broad-band fluorescence. The ability to introduce defects by adsorbate-framework interactions, coupled with the inherent tunability and modularity of these structures, provides a new route for the synthesis of diverse heterogeneous and hybrid materials.

Aluminum Ion Species Transport in Pure and Additive Modulated Deep Eutectic Solvents (DES) Electrolytes

The need for safe, low cost, high energy and density storage devices is ubiquitous the world over. Satisfying this need requires various energy storage and conversion applications, one of which is the aluminum ion batteries. One problem with expansion in their development and commercialization is the availability of optimized electrolytes. Recently, deep eutectic solvents (DES) have gained attention as electrolytes for energy storage devices. These solvents are similar to ionic liquids, but are generally cheaper and easier to prepare. Additionally, they are known to dissolve metal oxides which plague AIBs operation, and their solubility is dependent on the hydrogen bond donor. Because of their inherent tunability, we studied the effect of AlCl3 concentration (1:1 – 1.7:1 molar ratio), amide type (acetamide (AA), butyramide (BA), propionamide (PA)), viscosity reducing additive type and concentration, on the aluminum ion species and transport in AlCl3:amide DES electrolytes using multi-Nuclear (1H, 27Al) Magnetic Resonance (NMR) and AC Impedance Spectroscopy techniques, as a function of temperature. Below are a few noteworthy observations. Figure 1. VFT plots of the ionic conductivity for AlCl3:AA (left) and AlCl3:PA (right) DES electrolytes. Thirdly, the variable temperature 1H and 27Al spectra and T1 data for the pure and additives included DES electrolytes were very dependent on concentration, additive type and concentration, and species type. For example, in the 1:1 molar ratio electrolyte, the assigned AlCl2(amide)+ species had the longest T1, while the AlCl2(amide)2 + had the shortest. Additionally, the inclusion of additives such as fluoroethylene carbonate (FEC) and propylene carbonate (PC) caused species specific increasing local ion dynamics, possibly through the reduction of bulk viscosity effects and Coulombic interactions. These results and more will be expounded upon in our presentation.Firstly, for both AlCl3:PA and AlCl3:BA DES electrolytes, a maximum in ionic conductivity was observed at the 1.3:1 molar ratio. For AlCl3:AA DES the maximum occurred at the 1.5:1 molar ratio. Secondly, for the three amides conductivity values fell in the range of ~1 – 11 mS/cm over the temperature range of 288 – 363K. Additionally, the temperature dependence displayed curve-like behavior and were fitted using the VFT equation to reveal high levels of fragility and dynamic behaviors similarities to some pure ILs where the effective inter-conversion between the trans and cis conformations of the anion facilitated faster ion dynamics. Figure 1

A High-Efficiency Ridged Magnetically Insulated Transmission Line Oscillator

In this study, we investigate the effect of the inclusion of ridged disk vanes on the operation of a magnetically insulated transmission line oscillator (MILO), using a combination of “cold” (without electron beam) and “hot” (with electron beam) simulations. Cold simulation shows that the inclusion of ridged-disks in a ridged MILO (RMILO) enhances its slow wave structure’s (SWS’s) coupling impedance, thus improving its power efficiency. Moreover, since the ridges’ effect on frequency is weak, the MILO’s inherent tunability is maintained. In hot simulation, the RMILO obtains a 3-dB tunable frequency range of 0.96–2.18 GHz with an applied voltage of 603 kV, in contrast to the 1.04–2.01-GHz range obtained with a conventional MILO (CMILO), owing to the former’s improved power efficiency. With this voltage, the device generates the high power microwave (HPM) with a maximum output power of 7.1 GW at a frequency of 1.40 GHz, corresponding to a power efficiency of 22.6%. The maximum power efficiency of 24.5%, corresponding to a 13.5-GW output, was obtained by increasing the applied voltage to 807 kV, an increase of 20.2% compared to the power efficiency obtained with a CMILO in the same condition.

Aluminum Ion Species Transport in Pure and Additive Modulated Deep Eutectic Solvents (DES) Electrolytes

The need for safe, low cost, high energy and density storage devices is ubiquitous the world over. Satisfying this need requires various energy storage and conversion applications, one of which is the aluminum ion batteries. One problem with expansion in their development and commercialization is the availability of optimized electrolytes. Recently, deep eutectic solvents (DES) have gained attention as electrolytes for energy storage devices. These solvents are similar to ionic liquids, but are generally cheaper and easier to prepare. Additionally, they are known to dissolve metal oxides which plague AIBs operation, and their solubility is dependent on the hydrogen bond donor. Because of their inherent tunability, we studied the effect of AlCl3 concentration (1:1 – 1.7:1 molar ratio), amide type (acetamide (AA), butyramide (BA), propionamide (PA)), viscosity reducing additive type and concentration, on the aluminum ion species and transport in AlCl3:amide DES electrolytes using multi-Nuclear (1H, 27Al) Magnetic Resonance (NMR) and AC Impedance Spectroscopy techniques, as a function of temperature. Below are a few noteworthy observations.Firstly, for both AlCl3:PA and AlCl3:BA DES electrolytes, a maximum in ionic conductivity was observed at the 1.3:1 molar ratio. For AlCl3:AA DES the maximum occurred at the 1.5:1 molar ratio. secondly, the 27Al spectra the 1:1 molar ratio DES electrolytes showed three well resolved peaks at about 101, 88 and 74 ppm, assigned to [AlCl2(amide)2]+, AlCl4 -, and [AlCl2(amide)2]+ respectively. An example of this is shown in Figure 1 for the 1.0:1 (left) AlCl3:PA. With increasing AlCl3 concentration, the narrow well resolved peaks gave way to broadened, asymmetric spectra with two to three visible but not separated peaks. This is also shown in Figure 1 (right) for the 1.3:1 (right) AlCl3:PA. A fourth peak also appeared for DES electrolytes which could be due to free AlCl3:amide species. Figure 1. 27Al variable temperature spectra for 1.0:1 (left) and 1.3:1 (right) AlCl3:Propionamide (PA).Thirdly, like the spectra, the 27Al T1 data for the pure DES electrolytes were very dependent on salt concentration and the species type. For the 1:1 molar ratio electrolyte, the AlCl2(amide)+ species had the longest T1, while the AlCl2(amide)2 +had the shortest. Fourthly, with the inclusion of additives such as propylene carbonate (PC) both the 1H and 27Al T1increased, indicating increasing local ion dynamics possibly through the reduction of bulk viscosity effects and Coulombic interactions. In addition to this, PC also caused additional resolution of the [AlCl2(amide)2]+ species - which was not observed in the pure DES. These results and more will be expounded upon in our presentation. Figure 1

Trapped Photons Induced Ultrahigh External Quantum Efficiency and Photoresponsivity in Hybrid Graphene/Metal‐Organic Framework Broadband Wearable Photodetectors

AbstractMetal‐organic frameworks (MOFs) have recently emerged as attractive materials for their tunable properties, which have been utilized for diverse applications including sensors, gas storage, and drug delivery. However, the high porosity and poor electrical conductivity of MOFs restrict their optoelectronic applications. Owing to the inherent tunability, a broadband photon absorbing MOF can be designed. Combining the superior properties of the MOFs along with ultrahigh carrier mobility of graphene, for the first time, this study reports a highly sensitive, broadband, and wearable photodetector on a polydimethylsiloxane substrate. The external quantum efficiency of the hybrid photodetector is found to be >5 × 108%, which exceeds all the reported values of similar devices. The porosity of the MOF and ripple structure graphene can assist the trapping of photons at the light‐harvesting layer. The device photoresponsivity is found to be >106 A W−1 with a response time of <150 ms, which is approximately ten times faster than the current standards of the graphene‐organic hybrid photodetectors. In addition, utilizing the excellent flexibility of the graphene layer the wearability of the devices with stretchability up to 100% is demonstrated. The unique discovery of MOF‐based high‐performance photodetectors opens up a new avenue in organic–inorganic hybrid optoelectronics.

Transdermal insulin delivery using choline-based ionic liquids (CAGE)

Transdermal delivery of pharmaceuticals using ionic liquids and deep eutectic solvents (DES) has attracted significant interest due to the inherent tunability of the molecules and their capacity to transport large molecules across the skin. Several key properties of DESs including viscosity, miscibility and possible transport enhancement can be controlled through the choice of ions and their ratio in DES. Herein we investigate the effect of cation/anion ratio using Choline and Geranic acid (CAGE) based DES. We synthesized variants of CAGE by controlling the ratio of Choline to Geranic acid over a range of 1:4 to 2:1. Physicochemical properties including viscosity, conductivity and diffusivity were measured. Effect of CAGE on skin permeability was assessed using insulin in ex vivo porcine skin. Each variant was found to have distinct properties, including interionic interactions, viscosity, and conductivity. In addition, the effect of CAGE on stratum corneum lipids, as assessed by FTIR, was dependent on its composition. Transport enhancement was also composition-dependent, as the variants containing excess geranic acid (1:2 and 1:4, but not geranic acid alone) exhibited higher insulin delivery into the dermis compared to other compositions, demonstrating the importance of investigating the effect of ion ratios on drug delivery.

Topological Hall effect in ferromagnetic/non-ferromagnetic metals heterojunctions

In a magnetic system, the spin orbit coupling can combine with the exchange interaction to generate an anisotropic exchange interaction that favors a chiral arrangement of the magnetization. This is known as the Dzyaloshinskii-Moriya interaction (DMI). Contrary to the Heisenberg exchange interaction, which leads to collinear alignment of lattice spins, the form of DMI is therefore very often to cant the spins by a small angle. If DMI is strong enough to compete with the Heisenberg exchange interaction and the magnetic anisotropy, it can stabilize chiral domain wall structure such as skyrmion. When a conduction electron passes through a chiral domain wall, the spin of the conduction electron will experience a fictitious magnetic field (Berry curvature) in real space, which deflects the conduction electrons perpendicular to the current direction. Therefore, it will cause an additional contribution to the observed Hall signal that is termed topological Hall effect (THE). The THE has attracted much attention since it is a promising tool for probing magnetic skyrmions. Recent extensive experiments have focused on the the THE in the ferromagnetic/non-ferromagnetic metal heterojunctions due to the inherent tunability of magnetic interactions in two dimensions. We firstly review the THE in ferromagnetic multilayers, in which the domain wall energy with interfacial DMI can be written as =4AK-D, where Dis the effective DMI energy constant, A the exchange constant, K the anisotropy constant. For the most favorable chirality, it lowers the energy. The limit of this situation is when goes to zero, which defines the critical DMI energy constant Dc=4AK/. Therefore, the domain wall energy would be negative and the chiral domain walls should proliferate if D Dc, and the methods that can modulate D and Dc to reduce have been explored. We have also reviewed the THE in MnGa/heavy metal bilayers. The largest THE signals have been found based on the MnGa films with smallest Dc, which correspondingly results in the smallest . The large topological portion of the Hall signal from the total Hall signal has been extracted in the whole temperature range from 5 to 300 K and the magnitude of fictitious magnetic field has been determined.