具有可调纳米尺度尺寸和成分的锰铁氧体簇的稳定水悬浮液

摘要

我们报告了锰铁氧体簇（MFC）的一锅水热合成，可对材料尺寸和成分进行独立控制。磁分离允许快速纯化，而使用磺化聚合物的表面功能化可确保材料在生物相关介质中不聚集。由此产生的产品非常适合生物医学应用。

摘要

锰铁氧体簇（MFC）是数十至数百个初级纳米晶体的球形组件，其磁性在各种应用中都很有价值。在这里，我们描述了如何在水热工艺中形成这些材料，该过程允许独立控制产品簇尺寸（从30到120nm）和所得材料的锰含量。酒精反应介质中加入的水总量和锰与铁前驱体的比例等参数是实现多种类型的MFC纳米级产品的重要因素。快速纯化方法使用磁分离来回收材料，使磁性纳米材料的克数生产非常有效。我们克服了磁性纳米材料聚集的挑战，将高电荷的磺酸盐聚合物应用于这些纳米材料的表面，产生胶体稳定的MFC，即使在高盐度环境中也保持非聚集性。这些非聚集、均匀和可调的材料是生物医学和环境应用的优秀前瞻性材料。

引言

与纯氧化铁相比，在适当的条件下，在氧化铁晶格中加入锰作为掺杂剂可以增加材料在高外加磁场下的磁化。因此，锰铁氧体（MnxFe3-xO4）纳米颗粒由于其高饱和磁化，对外部磁场的强烈响应和低细胞毒性而成为非常理想的磁性纳米材料^{1，2，3，4，}5。单域纳米晶体以及这些纳米晶体的簇（称为多域粒子）已在各种生物医学应用中进行了研究，包括药物递送，用于癌症治疗的磁热疗和磁共振成像（MRI）^6，7，8。例如，Hyeon小组在2017年使用单结构域锰铁氧体纳米颗粒作为Fenton催化剂来诱导癌症缺氧，并利用该材料的_T2contrast进行MRI跟踪⁹。令人惊讶的是，鉴于这些和其他对铁氧体材料的积极研究，与纯氧化铁（_Fe3O4）纳米材料相比，几乎没有体内

研究方案

1. 控制中间商联总直径和铁氧体组成的中间商联苯合成

1. 清洗并彻底干燥所有用于合成的玻璃器皿。合成中的水量会影响MFC的尺寸，因此确保玻璃器皿中没有残留水至关重要^16，26。
   1. 要清洗玻璃器皿，请用水和洗涤剂冲洗，并用烧瓶刷擦洗以清除碎屑。彻底冲洗以除去所有洗涤剂，然后用去离子水冲洗完毕。
   2. 要干燥玻璃器皿，请摇动玻璃器皿表面的水滴，然后放入60°C的烤箱中直至完全干燥。
   3. 用37%盐酸冲洗聚苯搪（PPL）反应器，以除去以前使用中的任何碎屑。为此，将反应器及其盖子放在一个大烧杯中，并充满盐酸，直到反应器完全淹没。让它静置30分钟，然后倒出盐酸。用水连续冲洗装有反应器的烧杯1-2分钟，然后将反应器放入烤箱中晾干。
2. 使用自动移液器将 20 mL 乙二醇转移到带有磁性搅拌棒的 50 mL 烧杯中。
3. 称出所需量的氯化铁（_FECl3·_6H2 O，固体）以达到1.3mM的最终浓度，并将其加入烧杯中。将烧杯放在搅拌盘上，以480 rpm的速度打开，开始连续搅拌烧杯。
   注意：由于这是水合物，因此必须快速测量和添加，以避免从环境空气中意外吸收水分。
4. 称取250mg聚丙烯酸（PAA，Mw〜6，00....

结果

水热处理后，反应混合物变成粘稠的黑色分散体，如图 1所示。纯化后的结果是高度浓缩的MFC溶液，其行为类似于铁磁流体。当放置在手持式磁铁（<0.5 T）附近时，小瓶中的液体在几秒钟内就会做出反应，形成宏观的黑色团块，当磁铁放置在不同的位置时，可以四处移动。

该合成产生的产物的尺寸和铁氧体组成取决于反应混合物中加入的水量和锰与铁前.......

讨论

这项工作证明了锰铁氧体纳米晶体的改性多元醇合成，这些纳米晶体聚集在一起形成均匀的纳米级聚集体²⁹。在该合成中，氯化铁（III）和氯化锰（II）进行强制水解反应和还原，形成_分子MnxFe3-xO4。这些铁氧体分子在反应器中的高温和高压下形成初级纳米晶体，最终组装成球形聚集体，这里称为磁铁矿铁氧体簇（MFC）。没有足够的反应时间或足够.......

材料

Name	Company	Catalog Number	Comments
0.1 Micron Vaccum Filtration Filter	Thermo Fisher Scientific	NC9902431	for filtration of aggregated clusters after synthesis and surface coating to achieve a uniform solution
2-Acrylamido-2-methylpropane sulfonic acid (AMPS, 99%)	Sigma-Aldrich	282731-250G	reagent used in copolymer to surface coat nanoclusters and functionalize them for biological media
2,2′-Azobis(2-methylpropionitrile) (AIBN)	Sigma-Aldrich	441090-100G	reagent used in copolymer making as the free ridical generator
4-Morpholineethanesulfonic acid, 2-(N-Morpholino)ethanesulfonic acid (MES)	Sigma-Aldrich	M3671-250G	acidic buffer used to stabilize nanocluster surface coating process
Acrylic acid	Sigma-Aldrich	147230-100G	reagent used in copolymer to surface coat nanoclusters and functionalize them for biological media; anhydrous, contains 200 ppm MEHQ as inhibitor, 99%
Analytical Balance	Avantor	VWR-205AC	used to weigh out solid chemical reagents for use in synthesis and dilution
Digital Sonifier and Probe	Branson	B450	used to sonicate nanocluster solution during surface coating to break up aggregates
Dopamine hydrochloride	Sigma-Aldrich	H8502-25G	used in surface coating for ligand exchange reaction
Ethylene glycol (anhydrous, 99.8%)	Sigma-Aldrich	324558-2L	reagent used as solvent in hydrothermal synthesis of nanoclusters
Glass Vials (20mL)	Premium Vials	B1015	container for nanocluster solution during washing and surface coating as well as polymer solutions
Graduated Beaker (100mL)	Corning	1000-100	container for mixing of solid and liquid reagents during hydrothermal synthesis (to be transferred into autoclave reactor before oven)
Handheld Magnet	MSC Industrial Supply, Inc.	92673904	1/2" Long x 1/2" Wide x 1/8" High, 5 Poles, Rectangular Neodymium Magnet low strength magnet used to precipitate nanoclusters from solution (field strength is increased with steel wool when needed)
Hydrochloric acid (ACS grade, 37%)	Fisher Scientific	7647-01-0	for removing leftover nanocluster debris and cleaning autoclave reactors for next use
Hydrothermal Autoclave Reactor	Toption	TOPT-HP500	container for finished reagent mixture to withstand high temperature and pressure created by the oven in hydrothermal synthesis
Iron(III) Chloride Hexahydrate (FeCl3·6H2O, ACS reagent, 97%)	ACS	236489-500G	reagent used in synthesis of nanoclusters as source of iron (III) that becomes iron (II) in finished nanocluster product (keep dry and weigh out quickly to avoid water contamination)
Labware Washer Brushes	Fisher Scientific	13-641-708	used to wash and clean glassware before synthesis
Magnetic Stir Plate	Thermo Fisher Scientific	50093538	for mixing of solid and liquid reagents during hydrothermal synthesis
Manganese chloride tetrahydrate (MnCl2·4H2O, 99.0%, crystals, ACS)	Sigma-Aldrich	1375127-2G	reagent used in synthesis of nanoclusters as source of manganese
Micropipette (100-1000μL)	Thermo Fisher Scientific	FF-1000	for transferring liquid reagents such as water and manganese chloride
N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC)	Sigma-Aldrich	25952-53-8	used in surface coating to assist in ligand exchange of copolymer (keep bulk chemical in freezer and diluted solution in refrigerator)
N,N-Dimethylformamide (DMF)	Sigma-Aldrich	227056-2L	reagent used in copolymer making as the solvent
Polyacrylic acid sodium salt (PAA, Mw~6,000)	PolyScience Inc.	06567-250	reagent used in hydrothermal synthesis to initially coat the nanoclusters (eventually replaced in surface coating step)
Poly(ethylene glycol) methyl ether acrylate	Sigma-Aldrich	454990-250ML	reagent used in copolymer to surface coat nanoclusters and functionalize them for biological media; average Mn 480, contains 100 ppm BHT as inhibitor, 100 ppm MEHQ as inhibitor
Reagents Acetone, 4L, ACS Reagent	Cole-Parmer	UX-78920-66	used as solvent to precipitate nanoclusters during washing
Single Channel Pipette, Adjustable 1-10 mL	Eppendorf	3123000080	for transferring ethylene glycol and other liquids
Steel Wool	Lowe's	788470	used to increase the magnetic field strength in the vial to aid in precipitation of nanoclusters for washing and surface coating
Stirring Bar	Thomas Scientific	8608S92	for mixing of solid and liquid reagents during hydrothermal synthesis
Table Clamp	Grainger	29YW53	for tight sealing of autoclave reactor to withstand high pressure of oven during hyrothermal synthesis
Urea (ACS reagent, 99.0%)	Sigma-Aldrich	U5128-500G	reagent used in hydrothermal synthesis to create a basic solution
Vaccum Filtration Bottle Tops	Thermo Fisher Scientific	596-3320	for filtration of aggregated clusters after synthesis and surface coating to achieve a uniform solution
Vacuum Controller V-850	Buchi	BU-V850	for filtration of aggregated clusters after synthesis and surface coating to achieve a uniform solution
Vacuum Oven	Fisher Scientific	13-262-51	used to create high temperature and pressure needed for nanocluster formation in hydrothermal synthesis