Decrease In Size Of Nanoparticles Research Articles

Size and Ion-Doping Effects on Magnetic, Optical, and Phonon Properties of CuAlO2 Nanoparticles

The magnetic, optical, and phonon properties of ion-doped CuAlO2 nanoparticles on the Cu or Al site are theoretically investigated. The room temperature ferromagnetism in CuAlO2 nanoparticles can be due to the surface, size, and doping effects. The magnetization increases with the decreasing nanoparticle size. The different radii of the transition metal ion and the host Cu ion lead to compressive strain, to the enhancment of the exchange interaction constants, and to increased magnetization Ms and Curie temperature TC. By substitution with Mn or Cr on the Al site, tensile strain, a decrease in Ms, and an increase in dopants are observed. The size and ion-doping influence on the band-gap energy is also discussed. The phonon energy ω decreases, whereas the phonon damping γ increases with increasing temperature and decreasing NP size. They show a kink around TC ∼ 400 K. The behavior of ω and γ for different ion dopings is observed.

Characterizing Nanoparticle Release Patterns of Laser Powder Bed Fusion in Metal Additive Manufacturing: First Step Towards Mitigation Measures.

Laser Powder Bed Fusion (L-PBF) is a well-known Additive Manufacturing (AM) technology with a wide range of industrial applications. Potential occupational exposures to metal nanoparticles (NP) as by-products could occur in these processes, and no cogent occupational exposure limits are available. To contribute to this assessment, a monitoring campaign to measure the NP release pattern in two metal L-PBF facilities was carried out in two academic laboratories adopting L-PBF technology for research purposes. The monitored processes deal with two devices and three feedstock types, namely stainless steel (AISI 316L), aluminium-silicon alloy (A357) and pure copper, which are associated with different levels of industrial maturity. Prolonged environmental and personal real-time monitoring of NP concentration and size were performed, temperature and relative humidity were also measured during environmental monitoring. The measurements reveal a controlled NP release of the monitored processes, resulting in an average reduced exposure of the operators during the whole working shift, in compliance with proposed limit values (20 000 n cm-3 for density >6000 kg m-3 or 40 000 n cm-3 for density <6000 kg m-3). Nonetheless, the monitoring results show release events with an increase in NP concentration and a decrease in NP size corresponding with several actions usually performed during warm-up and cleaning, leading to exposures over 40-50 000 n cm-3 during a considerable time interval, especially during the manufacturing of pure copper powder. The results show that the actions of the operators, boundary conditions (relative humidity) and set-up of the L-PBF device have an impact on the amount of NP released and their size. Several release events (significant increase in NP concentration and decrease in NP size) are identified and associated with specific job tasks of the workers as well as building conditions. These results contribute to the definition of NP release benchmarks in AM processes and provide information to improve the operational conditions of L-PBF processes as well as safety guidelines for operators.

Antimicrobial Activity and Sorption Behavior of Al2O3/Ag Nanocomposites Produced with the Water Oxidation of Bimetallic Al/Ag Nanoparticles.

The water oxidation of bimetallic Al/Ag nanoparticles has been shown to yield nanoscale structures whose morphology, phase composition and textural characteristics are determined by the synthesis conditions. Flower-like nanoscale structures with silver nanoparticles, with an average size of 17 nm, are formed in water at 60 °C. Under hydrothermal conditions at temperatures of 200 °C and a pressure of 16 MPa, boehmite nanoplatelets with silver nanoparticles, with an average size of 22 nm, are formed. The oxidation of Al/Ag nanoparticles using humid air at 60 °C and 80% relative humidity results in the formation of rod-shaped bayerite nanoparticles and Ag nanoparticles with an average size of 19 nm. The thermal treatment of nanoscale structures obtained at a temperature of 500 °C has been shown to lead to a phase transition into γ-Al2O3, while maintaining the original morphology, and to a decrease in the average size of the silver nanoparticles to 12 nm and their migration to the surface of nanoscale structures. The migration of silver to the nanoparticle surface influences the formation of a double electric layer of particles, and leads to a shift in the pH of the zero-charge point by approximately one, with the nanostructures acquiring pronounced antimicrobial properties.

Low-temperature organic solvent-based synthesis of amorphous porous carbon nanoparticles with high specific surface area at ambient atmosphere

The conventional synthesis of porous carbon materials is primarily relied on the activation and template process. This work successfully develops a one-step method for preparing amorphous porous carbon nanoparticles (APCNs) with a high specific surface area (SSA) in organic solvents under ambient atmosphere. The APCNs are formed mainly by the reaction of ferrocene with ammonium chloride at only 180 °C for 1 h in different solvents. Several ferrocene derivatives and KOH activation are also utilized to improve the textural properties of the APCNs. It is found that the high solubility of (C 5 H 5 ) 2 Fe and FeCl 3 ·6H 2 O in a solvent is the most essential factor associated with the decrease of carbon nanoparticle size. The smaller the nanoparticle size, the larger the SSA of APCNs. The APCNs prepared in phenoxyethanol have a median size of 32.74 nm, exhibiting an SSA of 689 m 2 /g. The high solubility of NH 4 Cl can also contribute to reducing the nanoparticle size. The binary solvent consisting of phenoxyethanol and glycol has an excellent solubility for (C 5 H 5 ) 2 Fe, FeCl 3 ·6H 2 O, and NH 4 Cl, in which the prepared APCNs have a median size 11.48 nm and a higher SSA of 936 m 2 /g. Besides, the benzoyl substituted group on the cyclopentadiene can facilitate formation of small mesopores. The oxygen and nitrogen are in situ doped in the APCNs. Activation is also effective, and the SSA of APCNs reaches a maximum value of 1575 m 2 /g at a KOH ratio of 2:1. The solvent-based synthesis is unique and competitive in terms of high efficiency and energy conservation. • A novel liquid-phase method for preparing amorphous porous carbon nanoparticles is developed based on an oxidation mechanism. • The synthesis is carried out at ambient atmosphere at 180 °C. • The specific surface area and pore volume are 936.11 m 2 /g and 1.45 cm 3 /g, respectively.

A Two-Pronged Strategy for Enhanced Deep-Tumor Penetration and NIR-II Multimodal Imaging-Monitored Photothermal Therapy.

The second near-infrared (NIR-II)-induced photothermal therapy (PTT) has attracted a great deal of attention in recent years due to its non-invasiveness and because it uses less energy. However, the penetration of photothermal agents into solid tumors is seriously impeded by the dense-tumor extracellular matrix (ECM) containing cross-linked hyaluronic acid (HA), thereby compromising the ultimate therapeutic effects. Herein, acid-labile metal-organic frameworks were employed as nanocarriers to efficiently mineralize hyaluronidase (HAase) and encapsulate Ag2S nanodots by a one-pot approach under mild conditions. The obtained nanocomposites (AHZ NPs) maintained enzyme activity and changed in size to prolong blood circulation and complete delivery of the cargo to the tumor. Moreover, the released HAase could specifically break out the HA to loosen ECM and enable the Ag2S nanodots to breeze through the tumor matrix space and gain access to the deep tumor. Under near-infrared laser irradiation, the AHZ NPs displayed remarkable fluorescence, outstanding photoacoustic signals, and excellent photothermal properties in the whole tumor. This work offers a promising two-pronged strategy via a decrease in nanoparticle size and the degradation of dense ECM for NIR-II multimodal imaging-guided PTT of deep tumors.

Size-dependent effects of the thermal transport at gold nanoparticle-water interfaces.

The transfer of heat from a plasmonic nanoparticle to its water environment has numerous applications in the fields of solar energy conversion and photothermal therapies. Here, we use nonequilibrium molecular dynamics to investigate the size dependence of the interfacial thermal conductance of gold nanoparticles immersed in water and with tunable wettability. The interfacial thermal conductance is found to increase when the nanoparticle size decreases. We rationalize such a behavior with a generalized acoustic model, where the interfacial bonding decreases with the nanoparticle size. The analysis of the interfacial thermal spectrum reveals the importance of the low frequency peak of the nanoparticle spectrum as it matches relatively well the oxygen peak in the vibrational spectrum. However, by reducing the nanoparticle size, the low frequency peak is exacerbated, explaining the enhanced heat transfer observed for small nanoparticles. Finally, we assess the accuracy of the continuum heat transfer equations to describe the thermal relaxation of small nanoparticles with initial high temperatures. We show that, before the nanoparticle loses its integrity, the continuum model succeeds in describing with small percentage deviations the molecular dynamics data. This work brings a simple methodology to understand, beyond the plasmonic nanoparticles, thermal boundary conductance between a nanoparticle and its environment.

Advancement in extraction of metals (Sb and As) from crystal glass by mechanochemical method and recovery of metal using ZnS nanoparticles synthesized from Cassia fistula plant extract

Due to the presence of antimony, lead, cadmium, arsenic, and nickel in crystal glass, glass waste disposal from crystal glass manufacturer are a health hazard. In the supply chain, recovering and recycling metals might reduce pollution. Antimony and arsenic were removed from waste crystal glass by using a novel mechanochemical method. Initially, crystal glass is crushed into powder for activation and then chemically treated with pentetic acid. pentetic acid was used as a chelating agent. By employing pentetic acid as a chelating agent and a mechanochemical method, we were able to remove 99.3 (%) mass of Sb and As heavy metals from crystal glass and first time in this work, nanoparticles were used to recovery the metals from waste glass. The maximum recovery of Sb and As was observed at 13 nm and a minimum at 95 nm, respectively. This increase in the recovery of metals with the decrease in size of nanoparticles was due to an increase in surface area.

Magnetic and electric properties of multiferroic CuBr[formula omitted

We propose a microscopic model in order to investigate the multiferroic properties of CuBr2 in dependence on temperature, size, magnetic field and ion doping. Using a Green’s function technique we have calculated the magnetization, the heat capacity, the polarization and the dielectric constant. The specific heat has at the magnetic transition temperature TN a clear peak which disappears by applying an external magnetic field h. The polarization increases whereas the dielectric constant decreases with increasing h due to strong magnetoelectric coupling. In a CuBr2 nanoparticle appears a weak ferromagnetism due to the uncompensated spins on the surface. The magnetization increases with decreasing nanoparticle size. The Neel temperature rises strongly applying by ion doping a compressive strain and decreases by a tensile strain.

Template synthesis of luminescent oligoperoxide coated YBO3 nanoparticles doped with Ce3+, Tb3+ and Eu3+ ions

The template synthesis with different concentrations of heterofunctional oligoperoxide NVP-co-VEP-co-GMA (2-tert-butylperoxy-5-methyl-1-hexene-3-yne) was performed to obtain inorganic nanoparticles of controlled size. An increase of polymer concentration provides the decrease of nanoparticle size and polydispersity index. As a result of template synthesis, the polymer molecules were adsorbed unto the nanoparticle surface forming irreversibly attached functional shell protecting the nanoparticles from aggregation. Such the polymer coated nanoparticles showed significantly lower aggregation even after high-temperature annealing, which is necessary to increase their luminescence efficiency. The luminescence spectral-kinetic study of YBO3–Ce, YBO3–Ce, Tb and YBO3–Ce,Tb, Eu nanoparticles revealed an efficient nonradiative transfer of excitation energy from Ce to Tb ions in YBO3–Ce, Tb and from Ce to Tb to Eu in YBO3–Ce,Tb, Eu nanoscale host. The potential use of YBO3–Ce, YBO3–Ce, Tb and YBO3–Ce,Tb, Eu nanoparticles for biological imaging was demonstrated by the luminescence microscopy.

Effective coordination numbers from EXAFS: general approaches for lanthanide and actinide dioxides.

Extended X-ray absorption fine structure (EXAFS) is a comprehensive and usable method for characterizing the structures of various materials, including radioactive and nuclear materials. Unceasing discussions about the interpretation of EXAFS results for actinide nanoparticles (NPs) or colloids were still present during the last decade. In this study, new experimental data for PuO2 and CeO2 NPs with different average sizes were compared with published data on AnO2 NPs that highlight the best fit and interpretation of the structural data. In terms of the structure, PuO2, CeO2, ThO2, and UO2 NPs exhibit similar behaviors. Only ThO2 NPs have a more disordered and even partly amorphous structure, which results in EXAFS characteristics. The proposed new core-shell model for NPs with calculated effective coordination number perfectly fits the results of the variations in a metal-metal shell with a decrease in NP size.

Size-dependent visible-light-enhanced Cr(VI) bioreduction by hematite nanoparticles

Light irradiation would affect the electron transfer between dissimilatory metal-reducing bacteria (DMRB) and semiconducting minerals, which may impose a great influence on the biogeochemistry cycle of heavy metals. However, the size effect of semiconducting minerals on the its electron transfer with DMRB and microbial Cr(VI) reduction under visible light irradiation is little known. Herein, the Cr(VI) reduction by Shewanella oneidensis MR-1 (MR-1) was investigated in the presence of hematite nanoparticles with average diameters of 10 nm and 50 nm in dark and under visible light irradiation. It is found that hematite nanoparticles adhered onto MR-1 cells to form the composites, leading to the decrease in surface sites and Zeta potential. Hematite mediated-Cr(VI) bioreduction rate under visible light irradiation was 0.342 h−1, which is 3.4 folds enhancement compared with that in dark and 4.4 folds compared with the MR-1 alone under visible light irradiation. Decreasing nanoparticle size of hematite from 50 nm to 10 nm promoted the Cr(VI) reduction under visible light irradiation but impeded it in dark. It was deduced that the bioelectrons from MR-1 could promote the separation of photoelectron-hole pairs of light-irradiated hematite, which consequently enhanced the Cr(VI) bioreduction by MR-1-hematite composites. Moreover, mutant strains experiments demonstrated the vital role of c-cytochrome for the conducting network actively established by MR-1 with hematite nanoparticles. Those findings expand the understanding of the electron transfer pathway for enhancing Cr(VI) reduction by hematite-MR-1 composites, and the impact of particle size on the interaction between semiconducting mineral and electroactive bacteria under light irradiation.

Size, external fields and ion doping effects on the multiferroic properties of hexagonal YMnO[formula omitted] nanoparticles

The size, external field and doping dependence of different properties of hexagonal YMnO3 nanoparticles (NPs) is theoretically investigated. The spontaneous magnetization Ms increases with increasing electric field and decreasing NP size N. The polarization decreases with increasing magnetic field h. The band gap increases with decreasing N. The phonon mode ω̄0 = 167 cm−1 shows a kink at TN due to strong spin–phonon interaction. Applying h the kink disappears. By doping with different ions at the Mn site, due to the observed different strains Ms can increase or decrease. By large Ti ion doping, above a critical x value, is taken into account that there appears a hexagonal–orthorhombic phase transition. The Gd and Sr substitution on the Y place in YMnO3 NPs is also discussed. The dielectric function as a function of temperature, NP size and h is studied. The electron and phonon contributions to the specific heat Cp are shown.

A review on parameters affecting nanoparticles stabilized foam performance based on recent analyses

In recent years, much attention has been paid to the addition of nanoparticles (NPs) into the surfactant foam structure to form durable foams. Although surfactant foam as an enhanced oil recovery (EOR) technique significantly increases the viscosity of the injected fluid compared to gas injection, it has been observed that the foam structure does not have the required stability in cases such as high temperatures and high salinity. Although NP addition increases stability, the extent of this increase depends on several parameters, including NP properties (i.e., size, type, surface wettability) and reservoir properties (i.e., salinity of formation water, presence of oil, reservoir temperature), process parameters (i.e., NP concentration and flow rate), synergistic effects between the surface charge of NPs and the net charge of surfactant, and NP loss in the porous medium. This study aims to review and summarize the findings of previous studies to conclude the effects of each of the parameters above on foam stability, identify differences, and determine gaps for future studies. Throughout this report, a study background is provided, followed by the concept of stability and how to determine it in different tests for NP-surfactant foam. Next, the mechanisms of increasing stability by NP addition are briefly presented. Lastly, previous findings related to the effect of each parameter on NP foam stability are presented and discussed. Although several detailed reviews of NP-stabilized foam have been published previously, the present study differs from them in that the effects of additional parameters were investigated by reviewing new findings. Moreover, an attempt has been made to discuss the effects of parameters from different angles and according to their role in the mechanisms of NP-stabilized foam, such as particle detachment energy and maximum capillary pressure. The findings of this review show that i) oil presence lowers foam stability, ii) increasing NP concentration as well as decreasing NP size, temperature, NP retention, and salinity lead to increased stability, and iii) for parameters including NP surface wettability, NP types, and shear rate/flow velocity there are optimum points that result in the best foam performance. NP loss in a porous medium is an economically damaging process that occurs through mechanisms including adsorption, mechanical entrapment and log-jamming, and particles settling due to gravity. Depending on the type of mechanism, the strategy for minimizing or removing the influence of these mechanisms differs. However, there is currently no way to determine and measure the contribution of each of these mechanisms to the total retention in dynamic tests, which could be a specific topic for future research.

Thermal Conductivity of Ionic Liquid-Based Nanofluids Containing Magnesium Oxide and Aluminum Oxide Nanoparticles

A promising nanomaterial, magnesium oxide (MgO) and a commonly studied nanomaterial, aluminum oxide (Al2O3) were used to enhance the thermal conductivity of two ionic liquids, i.e., 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCa]) and 1-ethyl-3-methylimidazolium tricyanomethanide ([emim][TCM]) of potential as heat transfer medium. Effects of nanoparticle material, size, shape as well as mass concentration on thermal conductivity enhancement were investigated experimentally, along with stability analysis of the nanoparticle suspensions. The thermal conductivity of [emim][TCM] can be enhanced by up to 40% by adding 15 wt.% of polyhedral MgO nanoparticles. The thermal conductivity of Al2O3 ionanofluids does not vary much with nanoparticle size while that of MgO ionanofluids tends to increase as the nanoparticle size decreases. The Maxwell-Garnett model and the Hamilton–Crosser model could estimate the thermal conductivity of [emim][DCa]-based nanofluids containing Al2O3 and MgO nanoparticles, respectively, while under-prediction prevailed for [emim][TCM]-based nanofluids. Besides, challenges were encountered during zeta potential measurements created by the ionic liquids themselves. New methods need to be developed to correctly measure the zeta potential of ionic liquid-based nanofluids.

Modelling for the variation of thermal conductivity of metallic nanoparticles

In the present study, we have proposed a simple model able to explain the variation of thermal conductivity of nanoparticles with size at different shapes using the concept of cohesive energy model. During present study, it has been found that the kapitza resistance plays a major role to predict the thermal conductivity of nanoparticles, at their lower dimensions. For this study, we have selected the samples of metallic nanoparticles like copper, nickel, zirconia, indium, lead and tin. The thermal conductivity of nanoparticles has found to decrease with decreasing size of nanoparticles. The variation of thermal conductivity of nanomaterial has been explained on the basis of the fact that the effect of size becomes more prominent when it is comparable to the phonon mean free path. The computed results using the present model are, then, compared with available experimental data and found consistently in good agreement with the available experimental data.

Optimizing the geometry of aerodynamic lens injectors for single-particle coherent diffractive imaging of gold nanoparticles.

Single-particle X-ray diffractive imaging (SPI) of small (bio-)nanoparticles (NPs) requires optimized injectors to collect sufficient diffraction patterns to allow for the reconstruction of the NP structure with high resolution. Typically, aerodynamic lens-stack injectors are used for NP injection. However, current injectors were developed for larger NPs (>100 nm), and their ability to generate high-density NP beams suffers with decreasing NP size. Here, an aerodynamic lens-stack injector with variable geometry and a geometry-optimization procedure are presented. The optimization for 50 nm gold-NP (AuNP) injection using a numerical-simulation infrastructure capable of calculating the carrier-gas flow and the particle trajectories through the injector is also introduced. The simulations were experimentally validated using spherical AuNPs and sucrose NPs. In addition, the optimized injector was compared with the standard-installation 'Uppsala injector' for AuNPs. Results for these heavy particles showed a shift in the particle-beam focus position rather than a change in beam size, which results in a lower gas background for the optimized injector. Optimized aerodynamic lens-stack injectors will allow one to increase NP beam density, reduce the gas background, discover the limits of current injectors and contribute to structure determination of small NPs using SPI.

Characterization of Extracellular Vesicles Labelled with a Lipophilic Dye Using Fluorescence Nanoparticle Tracking Analysis.

Research on extracellular vesicles (EVs) has intensified over the past decade, including fluorescent membrane labeling of EVs. An optimal fluorescent method requires the size of EVs to be preserved after labeling. Lipophilic fluorescent dyes, such as CellMask™ Green (CMG), have been widely used for this purpose. Here, we investigated conditions affecting the optimum CMG labeling of EVs derived from human choriocarcinoma cells (JAr) and different biological fluids using fluorescence NTA (fl-NTA). The effect of CMG labeling on the size, concentration and zeta potential (ZP) on JAr EVs purified with different methods were measured along with biological fluid-derived EVs. With the increase of CMG dye concentration, a significant decrease in the mean size of fluorescent nanoparticles (fl-NPs) was observed. The ZP of fl-NPs originating from JAr cells with the lowest and highest dye concentrations showed a significant shift towards more and less negative ZP values, respectively. Differences in the concentration of fl-NPs were observed for JAr EVs purified using size-exclusion chromatography (SEC) alone and SEC in combination with tangential flow filtration. The proportion of CMG labeling of NPs varied across different biological sources. CMG labeling may be a reliable technique for the detection of EVs using fl-NTA.

Structural, Optical, and Photocatalytic Properties of ZnSe Nanoparticles Influenced by the Milling Time

ZnSe nanoparticles (NPs) were prepared by combining both hydrothermal and mechanical milling methods. Transmission electron microscopy images show that fabricated ZnSe NPs with a sphere-like shape have an average size (d) in the range of 20–100 nm, affected by changing the milling time from 10 to 60 min. All the samples crystalize in zincblende-type structure without impurities, as confirmed by analyzing X-ray diffraction patterns, Raman spectra, and energy-dispersive X-ray spectroscopy. Carefully checking Raman spectra, we have observed the broadening and redshift of vibration modes as decreasing NP size, which are ascribed to extra appearance of disorder and defects. The photoluminescence study has found a blue emission at 462 nm attributed to the excitonic near-band edge and a broad defect-related emission around 520–555 nm. Increasing milling time leads to the decrease in the exciton-emission intensity, while the defect-related emissions increase gradually. Interestingly, as decreasing d, we have observed an improved photodegradation of Rhodamine B under UV irradiation, proving application potentials of ZnSe NPs in photocatalytic activity.

Structure and Dynamics of Highly Attractive Polymer Nanocomposites in the Semi-Dilute Regime: The Role of Interfacial Domains and Bridging Chains.

Detailed molecular dynamics (MD) simulations are employed to study how the presence of adsorbed domains and nanoparticle bridging chains affect the structural, conformational, thermodynamic, and dynamic properties of attractive polymer nanocomposite melts in the semi-dilute regime. As a model system we have chosen an unentangled poly(ethylene glycol) (PEG) matrix containing amorphous spherical silica nanoparticles with different diameters and at different concentrations. Emphasis is placed on properties such as the polymer mass density profile around nanoparticles, the compressibility of the system, the mean squared end-to-end distance of PEG chains, their orientational and diffusive dynamics, the single chain form factor, and the scattering functions. Our analysis reveals a significant impact of the adsorbed, interfacial polymer on the microscopic dynamic and conformational properties of the nanocomposite, especially under conditions favoring higher surface-to-volume ratios (e.g., for small nanoparticle sizes at fixed nanoparticle loading, or for higher silica concentrations). Simultaneously, adsorbed polymer chains adopt graft-like conformations, a feature that allows them to considerably extend away from the nanoparticle surface to form bridges with other nanoparticles. These bridges drive the formation of a nanoparticle network whose strength (number of tie chains per nanoparticle) increases substantially with increasing concentration of the polymer matrix in nanoparticles, or with decreasing nanoparticle size at fixed nanoparticle concentration. The presence of hydroxyl groups at the ends of PEG chains plays a key role in the formation of the network. If hydroxyl groups are substituted by methoxy ones, the simulations reveal that the number of bridging chains per nanoparticle decreases dramatically, thus the network formed is less dense and less strong mechanically, and has a smaller impact on the properties of the nanocomposite. Our simulations predict further that the isothermal compressibility and thermal expansion coefficient of PEG-silica nanocomposites are significantly lower than those of pure PEG, with their values decreasing practically linear with increasing concentration of the nanocomposite in nanoparticles.

Enhanced Oil Recovery with Size-Dependent Interactions of Nanoparticles Surface-Modified by Zwitterionic Surfactants

This study reports the size-dependent interactions of silica nanoparticle (NP) dispersions with oil, which facilitate oil recovery from sandstone rock. Herein, we studied various 7–22 nm sized colloidal silica NPs (CSNPs; the colloidal state when dispersed in aqueous solutions) and fumed silica nanoparticles (FSNPs; the dry powder state). Interfacial tension at the oil-nanofluids interface declined with decreasing NP size in a range from 7 to 22 nm. This is because NP spatial density at the interface increased with smaller particle size, thereby, the interface area per NP decreased to approximately 1/30, and interfacial energy had reduced enough. In addition, smaller NPs more strongly were adsorbed to the rock because of improved diffusion in suspension and increased adsorption density. This caused creating a wedge film between oil and rock, which changed the oil contact angle. Due to this effect, core flooding experiments indicated that oil recovery increased with decreasing particle size. However, FSNP dispersions exhibited low recovery factor because of particle aggregation. This phenomenon may facilitate massive permeability reduction, thus causing oil trapping inside rock pore. We found that both the sizes and types of CSNPs and FSNP affected the Interfacial tension at oil-water interface and rock surface wettability, which influenced ultimate oil recovery.