Stability Studies of Magnetite Nanoparticles in Environmental Solutions

In the presented paper, studies of magnetite nanoparticle stability in selected environmental solutions are reported. The durability tests were performed in four types of liquids: treated and untreated wastewater, river water, and commercial milk (0.5% fat). Nanoparticles before and after deposition in the testing conditions were measured by transmission electron microscopy, X-ray diffraction, infrared spectroscopy, and Mössbauer spectroscopy. The amount of Fe atoms transferred into the solutions was estimated on the basis of flame atomic absorption spectroscopy. The analysis of the obtained results shows good stability of the tested nanoparticles in all water solutions. They do not change their structure or magnetic properties significantly, which makes them a good candidate to be used as, for example, detectors of specific compounds or heavy metals. On the other hand, studies show that particles are stable in environmental conditions for a long period of time in an unchanged form, which can cause their accumulation; therefore, they may be hazardous to living organisms.

INFLUENCE OF SYNTHESIS CONDITIONS ON AGGREGATIVE STABILITY OF Ag ALCOSOLS

Впервые в работе представлены результаты исследования влияния типа спиртовой среды на свойства высококонцентрированных золей наночастиц серебра. С помощью спектрофотометрии установлено наличие селективной полосы поглощения, обусловленной поверхностным плазмонным резонансом наночастиц серебра. Измерение дзета-потенциала показало, что вне зависимости от типа среды поверхность наночастиц серебра заряжена отрицательно. Обнаружено, что наиболее агрегативно устойчивые частицы, сохраняющие стабильность в концентрированных растворах хлорида натрия, получены в среде изопропилового спирта и характеризуются дзета-потенциалом, равным -99,8 мВ. For the first time, the paper presents the results of investigation the effect of the type of alcoholic medium on the properties of highly concentrated sols of silver nanoparticles. Spectrophotometry revealed the presence of a selective absorption band corresponding to the surface plasmon resonance of silver nanoparticles. Measurement of the zetta potential showed that, regardless of the type of medium, the surface of silver nanoparticles is negatively charged. It was found that the most aggregatively stable particles that retain stability even in concentrated sodium chloride solutions were obtained in isopropyl alcohol and are characterized by the zetta potential equal to -99,8 mV. Keywords: silver nanoparticles, optical properties, electroacoustic spectroscopy, zeta potential, nanoparticle stability.

Experimental Investigation of Stability of Silica Nanoparticles at Reservoir Conditions for Enhanced Oil-Recovery Applications

To be effective enhanced oil-recovery (EOR) agents, nanoparticles must be stable and be transported through a reservoir. However, the stability of a nanoparticle suspension at reservoir salinity and temperature is still a challenge and how it is affected by reservoir rocks and crude oils is not well understood. In this work, for the first time, the effect of several nanoparticle treatment approaches on the stability of silica nanoparticles at reservoir conditions (in the presence of reservoir rock and crude oil) was investigated for EOR applications. The stability of nanoparticle suspensions was screened in test tubes at 70 °C and 3.8 wt. % NaCl in the presence of reservoir rock and crude oil. Fumed silica nanoparticles in suspension with hydrochloric acid (HCl), polymer-modified fumed nanoparticles and amide-functionalized silica colloidal nanoparticles were studied. The size and pH of nanoparticle suspension in contact with rock samples were measured to determine the mechanism for stabilization or destabilization of nanoparticles. A turbidity scanner was used to quantify the stability of the nanoparticle suspension. Results showed that both HCl and polymer surface modification can improve nanoparticle stability under synthetic seawater salinity and 70 °C. Suspensions of polymer-modified nanoparticles were stable for months. It was found that pH is a key parameter influencing nanoparticle stability. Rock samples containing carbonate minerals destabilized unmodified nanoparticles. Crude oil had limited effect on nanoparticle stability. Some components of crude oil migrated into the aqueous phase consisting of amide-functionalized silica colloidal nanoparticles suspension. Nanoparticles modification or/and stabilizer are necessary for nanoparticle EOR application.

SYNTHESIS AND STABILITY OF RESVERATROL-GOLD NANOPARTICLE-POLYETHYLENE GLYCOL-FOLIC ACID CONJUGATES

Objective: Gold nanoparticles (AuNPs) can be used as targeted drug delivery systems, however, AuNPs have high surface energy and easily aggregate,thus negatively impacting nanoparticle stability. Therefore, it is necessary to add a stabilizing agent to AuNPs. To synthesize AuNPs stabilized bypolyethylene glycol conjugated to folic acid (FA), thus creating a model drug (resveratrol [RSV]) carrier that targets FA receptors on cancer cells.Methods: AuNPs were synthesized using the Turkevich method and stabilized by adding FA conjugated to polyethylene glycol (PEG). After RSV wasloaded, the conjugate was physically characterized and subjected to stability tests.Results: The RSV-AuNP had an average particle size of 51.97 nm (polydispersity index [PDI] 0.694, zeta potential – 24.6 mV). The RSV-AuNP-PEG-FAconjugate (RSV-AuNP-PEG-FA) had an average particle size of 195.6 nm (PDI=0.233, zeta potential=−21.1 mV). Stability tests showed that RSV-AuNPPEG-FA was more stable than RSV-AuNP. Furthermore, RSV-AuNP-PEG-FA and RSV-AuNP were more stable in buffer pH 7.4 and bovine serum albumin2% than in buffer pH 4, cysteine 1%, and NaCl 0.9% solutions.Conclusion: PEG-FA conjugates can improve the stability of RSV-loaded AuNP.

Efficient reductive amination of HMF with well dispersed Pd nanoparticles immobilized in a porous MOF/polymer composite

Making heterogeneous catalysis greener by improving nanoparticle stability in a MOF support modified with short polymeric chains.

Improved catalytic effect and metal nanoparticle stability using graphene oxide surface coating and reduced graphene oxide for hydrogen generation from ammonia–borane dehydrogenation

GO and rGO supported metal NPs exhibited excellent catalytic performance for AB hydrolysis. It also provided a high turnover frequency (TOF) at 25 °C.