Unraveling the influence of surface roughness on oil displacement by Janus nanoparticles

Janus nanoparticles(JNPs)possess great potential in recovering the residual oil from reservoirs,however,the fundamental interaction mechanisms among nanoparticles,the oil,and reservoir wall characteristics remain to be elucidated.In this work,models of oil trapping grooves with different geometric features are subjected to molecular dynamics simulations for investigating the influences of roughness parameters on oil displacement dynamics by JNPs.Four key surface geometry parameters and different degrees of surface hydrophobicity are considered.Our results indicate that JNPs hold an outstanding performance in displacing residual oil on weakly to moderately hydrophobic surfaces.Overall,smaller entry and exit angles,the larger aspect ratio of the oil trapping grooves,and a bigger tip length of the rough ridges lead to superior oil recovery.Among the key geometric parameters,the aspect ratio of the oil trapping grooves plays the dominant role.These insights about the interaction of surface properties and JNPs and the resulting trapped oil displacement could serve as a theoretical reference for the application of JNPs for targeted reservoir conditions.

Novel concept of nano-additive design:PTFE@silica Janus nanoparticles for water lubrication

Polytetrafluoroethylene(PTFE)has been widely used as a lubrication additive for reducing friction and wear;however,the hydrophobic nature of PTFE restricts its application in eco-friendly water-based lubrication systems.In this study,for the first time,we designed novel PTFE@silica Janus nanoparticles(JNs)to meet the requirement for additives in water-based lubricants,which have excellent dispersion stability in water attributed to the unique amphiphilic structure.By introducing the lubrication of the aqueous dispersion of the JNs with a concentration of 0.5 wt%,the coefficient of friction(COF)and wear volume were reduced by 63.8%and 94.2%,respectively,comparing to those with the lubrication of pure water.Meanwhile,the JNs suspension also exhibits better lubrication and wear-resistance performances comparing to commercial silica and PTFE suspensions.The excellent tribological behaviors of PTFE@silica JNs as nano-additives could be attributed to the synergetic effect of the two components,where the PTFE provided lubrication through the formed tribofilms on the friction pairs,and the rigid silica further enhanced the wear-resistance performance.Most importantly,the unique structure of JNs makes it possible to use PTFE as an additive in water-lubrication systems.Our study shed light on the design and application of novel JNs nanomaterials as additives to meet the requirements of future industrial applications.

NIR-Ⅱ responsive Janus nanoparticles amplify immunogenic cell death for enhanced cancer immunotherapy

Immunotherapy brings new hope for tumor treatment by inducing immunogenic cell death(ICD)of tumor cells.However,insufficient immunogenicity and low immune response rate greatly limit antitumor immunity.Herein,by optimizing the composition and morphology,the rational design of Janus nanoparticles composed of Fe_(3)O_(4) nanospheres and SiO_(2)nanorods was realized for enhanced cancer immunotherapy through amplified ICD.After glucose oxidase(GOx)was loaded by the Janus nanoparticles,the resultant M-FS-GOx consumes glucose at tumor sites to generate gluconic acid and hydrogen peroxide(H_(2)O_(2))for starvation therapy while the H_(2)O_(2)supply promotes the production of highly toxic·OH to achieve effective chemodynamic therapy(CDT).Under a 1064 nm light irradiation,the photothermal effect of M-FS-GOx enhances the enzyme activity of GOx for improved starvation therapy.Furthermore,both tumor-associated antigens released during the process of ICD and the intrinsic immunoadjuvant property of M-FS-GOx stimulate dendritic cell maturation to activate antitumor immune responses.This work provides a promising strategy for the construction of Janus nanoparticles to achieve enhanced cancer immunotherapy through combination therapy-amplified ICD.

pH-responsive superstructures prepared via the assembly of Fe_(3)O_(4) amphipathic Janus nanoparticles

The strategy of using Fe_(3)O_(4) amphiphilic Janus nanoparticles(Fe_(3)O_(4)@AJNPs)bearing b-cyclodextrin(b-CD)and aminopyridine(APD)functionalized polymethyl methacrylate(PGMA)to construct pH-stimuli responsive co-assemblies through host-guest interactions between b-CD and APD was proposed.The spherical co-assemblies with an average diameter about 210nm were excellent magnetic responsive and quite stable even up to 2 months in deionized water.The pH-liable capability of these co-assemblies was revealed by disassembly of the formed superstructures with destruction of the built inclusion complexes.The disassembly process was monitored by SEM,TEM,DLS and fluorescent molecules probe.After disassembly of the co-assemblies caused by protonation of nitrogens in APD,hydrophobic PGMA-APD lacking of interactions with the Fe_(3)O_(4)@AJNPs chains was precipitated,and the remained Fe_(3)O_(4)@AJNPs turned to re-assemble to selfassemblies.Besides,the recyclable Fe_(3)O_(4)@APJNs could reassembly with additional PGMA-APD to build co-assemblies with a uniform morphology for several times.These pH-sensitive co-assemblies with high stability,good magnetic responsiveness and cytocompatibility could be used as pH-responsive vehicles within which to encapsulate drugs for subsequent controlled release.

Multiple-Sized Amphiphilic Janus Gold Nanoparticles by Ligand Exchange at Toluene/Water Interface

Amphiphilic Janus gold nanoparticles （GNPs） are prospected to encapsulate drug molecules in cancer therapy and to serve as heterogeneous catalysts at oil/water interfaces, where Janus GNPs with differ- ent sizes are required. In this work, multiple-sized precursor GNPs were synthesized by seeded growth method protected with tris（hydroxymethyl）phosphine oxide （THPO） ligand molecule, and a ligand ex- change reaction with triphenylphosphine （PPh3） at the toluene/water interface was employed to prepare amphiphilic Janus GNPs. UV-vis and transmission electron microscopy （TEM） analyses indicate that the as-prepared GNPs are nanocrystals with average diameters of 2.3 nm, 9.5 nm, 16.1 nm and 18.8 nm, re- spectively. Contact angle, Raman and X-ray photonic spectroscopy （XPS） analyses reveal that the self- assembled GNP films exhibit hydrophilic on one side and hydrophobic on another, owing to the adsorption of hydrophilic ligands （THPO and THP） and a similar amount of hydrophobic ligands （PPh3 and PPh30）. Angle-resolved XPS analysis further demonstrates that the individual GNPs actually possess hydro- philic and hydmphobic compartments on the surface, which regularly packed by supramolecular interactions at toluene/water interface to form the self-assembled GNP films.

Janus γ-Fe2O3/SiO2-based nanotheranostics for dual-modal imaging and enhanced synergistic cancer starvation/chemodynamic therapy

Multimodal cancer synergistic therapy exhibited remarkable advantages over monotherapy in producing an improved therapeutic efficacy. In this work, Janus-type γ-Fe2 O3/SiO2 nanoparticles(JFSNs) are conjugated with glucose oxidase(GOx) for synergistic cancer starvation/chemodynamic therapy. The γ-Fe2O3 hemisphere of JFSNs can perform photoacoustic/T2 magnetic resonance dual-modal imaging of tumors.GOx on the surface of JFSNs catalyzes the decomposition of glucose and produces H2O2 for cancer starvation therapy. Subsequently, the γ-Fe2O3 hemisphere catalyzes the disproportionation of H2O2 to generate highly reactive hydroxyl radicals in an acidic tumor microenvironment. The close distance between GOx and JFSNs ensures adequate contact between the γ-Fe2O3 hemisphere and its substrate H2O2, thus enhancing the catalytic efficiency. This synergy of glucose depletion, biotoxic H2O2 and hydroxyl radicals significantly suppresses 4 T1 mammary tumor growth with minimal adverse effects.

The construction of pseudo-Janus silica/surfactant assembly and their application to stabilize Pickering emulsions and enhance oil recovery

Nanoparticles with high surface energy and chemical activity have drawn substantial attention in petroleum industry. Recently, Janus nanoparticles exhibited tremendous potential in enhanced oil recovery (EOR) due to their asymmetric structures and properties. In this study, a series of amphiphilic pseudo-Janus@OTAB (PJ@C18) nanoparticles with different concentrations of stearyltrimethylammoium bromide (OTAB) were successfully fabricated. The structures and properties of PJ@C18 were characterized by Fourier transform infrared spectroscopy and ζ-potential measurements. Based on the emulsification experimental results, the interaction models and the self-assembly behavior between hydrophilic nanoparticles (SiO_(2)@NH_(2)) and OTAB molecules at the oil/water interface were proposed, which was further confirmed via the measurements of the contact angle and dynamic interfacial tension. Interestingly, it was found that the change of pH value from 7.5 to 4.0 caused the type reversal of the PJ@C18-1000 stabilized Pickering emulsions. Furthermore, the PJ@C18-1000 stabilized Pickering emulsion system with excellent salt and temperature tolerances (10000 mg∙L^(–1), 90℃) significantly improved the oil recovery in the single-tube (more than 17%) and double-tube (more than 25%) sand pack model flooding tests. The findings of this study could help to better understand the construction mechanism of pseudo-Janus silica/surfactant assembly and the potential application of PJ@C18-1000 stabilized Pickering emulsions for EOR.

Engineering Janus gold nanorod–titania heterostructures with enhanced photocatalytic antibacterial activity against multidrugresistant bacterial infection

Photocatalytic antibacterial approach shows great potential in treating multidrug-resistant bacterial infections.However,the bactericidal efficiency heavily depends on the photocatalytic activity of semiconductor materials,which is limited by the fast recombination of photogenerated electron–hole pairs.Janus nano-heterostructures with spatial control growth of TiO_(2)nanoparticles(NPs)at one end of gold nanorods(Au NRs)are designed via surface ligand regulation for photocatalytic sterilization and infected wound healing.The asymmetric nanostructure of Janus gold nanorod-titanium dioxide nanoparticles(Janus AuNR-TiO_(2) NPs)promotes the directional migration of charge carriers and is more conducive to the spatial separation of electron–hole pairs.Moreover,the injection of hot electrons and enhancement of plasmon near-fields from the surface plasmon resonance(SPR)effect further improve the photocatalytic efficiency of Janus AuNR-TiO_(2) NPs.Under simulated sunlight irradiation,large amounts of reactive oxygen species(ROS)are generated for photocatalytic antibacterial activity.Enhanced bactericidal efficiency up to 99.99%against methicillin-resistant Staphylococcus aureus(MRSA)is achieved in vitro.Furthermore,Janus AuNR-TiO_(2) NPs exhibit superior biocompatibility,structural stability,and also remarkably accelerate MRSA-infected wound healing.Taking the above all into consideration,Janus AuNR-TiO_(2) NPs,as an efficient antibacterial photocatalyst,offers a promising strategy for MRSA infectious therapy.

Au-Fe_3O_4 heterostructures for catalytic, analytical, and biomedical applications

Heterostructures are a series of nanomaterials combining different components into a single nanostructure. Au-FeOheterostructures have received considerable attentions because of their superior properties coming from both individual and combinational features of gold and iron oxide nanoparticles. Their intrinsically peculiar magnetic, optical properties, and structure designability greatly enhance and broaden their potential applications in catalysis, assay, multimodal imaging, and synergistic treatment for tumor. In this review, we systematically introduce the preparation methods of Au-FeOheterostructures and their potential applications in the biomedical field, focusing on the unique synergistic effect caused by the combination of gold and iron oxide structures. This review will provide insights into the structure control in adjusting the function of heterogeneous or hybrid material, such as Au-FeOheterostructures, to implement their biomedical applications.

Efficient recovery and enrichment of rare earth elements by a continuous flow micro-extraction system

The excessive exploitation of rare earth elements(REEs)has caused major losses of non-renewable resources and damage to the ecosystem.The processes of mining and smelting produce massive amounts of wastewater with low concentrations of REEs.Consequently,the enrichment and recovery of low-concentration REEs from wastewater has significant economic and environmental value.For this purpose,operation under large phase ratios(the flow rate ratio between the aqueous phase and extractant)is more desirable and economically viable.However,the traditional REE extraction process suffers from the uneven dispersion of the extractant and the difficulty of phase separation,which leads to long extraction times and large consumption of extractants.Hence,there is an urgent need to develop a green and efficient technique to extract low concentrations of REEs from wastewater.In this work,a droplet-based microfluidic technique was used to continuously extract and recover low-concentration REEs at large phase ratios.Snowman-shaped magnetic Janus nanoparticles were added to the continuous phase as emulifiers to failitate uniform extractant dispersion and rapid phase separation.Several key factors affecting the extraction efficiency,including pH,residence time,and the amount of added Janus nanoparticles,were systematically investigated.Compared to batch extraction,droplet-based microfluidic extraction with the addition of Janus nanoparticles showed the advantages of a large speific surface area and fast phase separation during extraction.Meanwhile,the Janus nanoparticles exhibited good emulsification performance after three extraction cycles,In summary,the Janus nanoparticle-stabilized droplet generated by microfluidic methods provides a feasible path for the efficient enrichment and recovery of low-concentration REEs.