Preparation, surface functionalization and application of Fe₃O₄ magnetic nanoparticles

Highlights

• Comprehensive summary of the main aspects of Fe₃O₄ magnetic nanoparticles related to their preparation and application.

• Classification and intrinsic properties of Fe₃O₄ magnetic nanoparticles were studied.

• Perspectives for the future developments of Fe₃O₄ magnetic nanoparticles were proposed.

Abstract

This paper reviews recent developments in the preparation, surface functionalization, and applications of Fe₃O₄ magnetic nanoparticles. Especially, it includes preparation methods (such as electrodeposition, polyol methods, etc.), organic materials (such as polymers, small molecules, surfactants, biomolecules, etc.) or inorganic materials (such as silica, metals, and metal oxidation/sulfide, functionalized coating of carbon surface, graphene, etc.) and its applications (such as magnetic separation, protein fixation, magnetic catalyst, environmental treatment, medical research, etc.). In the end, some existing challenges and possible future trends in the field were discussed.

Introduction

Submicron molecules made of inorganic or organic materials are called nanoparticles and have many new characteristics compared to micron-sized materials, such as small particlesize (1–100 nm) [1,2]. In nanomaterials, magnetic nanoparticles (MNP) not only have special magnetic properties such as superparamagnetism, high susceptibility, etc., but also have unique physical properties, biocompatibility, stability, and many other related attributes [3]. Fe₃O₄ nanoparticles (NPs) are widely used in separation technology [4], protein immobilization [5], catalysis [6], medical science [7], and environment [8]. The application of Fe₃O₄ NPs in medical science mainly involves targeted drug/gene delivery [9,10], biosensor [11,12], magnetic resonance imaging (MRI) [13,14], contrast enhancement [15,16] and hyperthermia [17,18], biophotonics [19,20], detection of cancer cells [21,22], diagnosis and magnetic field-assisted radiotherapy [23,24]，andtissue engineering [25,26].

In view of various applications, various methods for preparing Fe₃O₄ NPs have been developed, such as coprecipitation [27], hydrothermal [28], pyrolysis [29], sol–gel [30], microemulsion [31], sonochemical [32], electrodeposition method [33], polyol method [34], etc. The particle size control of nanoparticles has always been a major challenge in their application, and a suitable preparation method can be selected according to the desired size. To reduce their surface energy, magnetic iron oxide nanoparticles are very easy to agglomerate. At the same time, bare Fe₃O₄ NPs usually have high chemical activity and are particularly susceptible to oxidation, which often leads to a decline in magnetic properties. Therefore, improving the stability of magnetic nanoparticles is an essential step in its application, and functionalizing its surface is one of the main ways. The strategy of surface functionalization is roughly divided into the surface modification of organic materials and surface modification of inorganic materials. In practical applications, it has been shown that in most cases, the protective shell can be used for further functionalization while improving the stability and dispersibility of Fe₃O₄ NPs. Fig. 1 shows various typical morphology of several magnetic hybrid nanocomposites. However, with the development of magnetic nanocomposites, their application fields are still expanding rapidly, and the classification of these materials is not rigorous. Therefore, there is still no clear classification [35]. This article mainly introduces the core-shell structure of magnetic nanoparticles. (See Table 1.)

This article reviews the recent advances and applications of various Fe₃O₄ nanomaterial synthesis methods, their surface functionalization strategies, and research advances at home and abroad. The unique properties, application prospectsand development prospects of Fe₃O₄ nanostructures are also discussed.