Data for: Dominant role of trioctylphosphine on the particle size and various properties of CoO nanoparticles

2.1. Synthesis of CoO nanoparticles Cobalt acetate tetrahydrate (CAT), Co(CH3COO)2.4H2O (≥ 99 %) purchased from Sisco Research Laboratories Pvt. Ltd, OA (70%) and TOP (90%) from Sigma Aldrich were used as-received for preparation of CoO NPs. 2.1.1 First Method Typically, 2 g CAT, 8 ml OA and 2 ml TOP are mixed in three neck round-bottom flask and heated at the rate of 10 0C/min in nitrogen atmosphere. The pink-like crystals of CAT start to decompose turning solution colour to light blue around at 80 0C, to dark blue with increase in temper-ature and finally to dark brown at around 180 0C up to 200 0C at which 2 h is maintained; this indicates the formation of NPs. This solution is then cooled to 30oC, and centri-fuged by adding n-hexane to extract and wash the NPs. The washing is performed three times for remove the ac-cess OA and TOP, not bound on NPs surface. The particles dried at 60oC in vacuum drier are used for various charac-terizations. This sample was coded as CoO1. Another sam-ple prepared at 230 0C while other reaction conditions re-maining the same is coded as CoO2. 2.1.2 Second Method 0.25 ml of preheated TOP at 200oC is added in a solution of 2 g CAT and 8 ml OA, already degassed at 120-130oC for 30 min. The resulting solution is further heated to 230oC for 5.5 h under nitrogen atmosphere. The pink colour of CAT changes to blue and finally to a brownish colour due to the formation of CoO NPs. Cooling down to 30 oC, the reaction product is then washed and dried similarly as above; sample is denoted as CoO3. Other samples coded as CoO4, CoO5, CoO6, CoO7 and CoO8 for TOP concen-tration of 0.25 ml, 1 ml, 3 ml, 8 ml and 12 ml, respectively, with other conditions remaining the same are then prepared in 1.5 h. Additional samples coded as CoO9, CoO10 and CoO11 are then respectively prepared in 8 ml OA only, combination of 8 ml OA with 12 ml TOP, like CoO3, and 10 ml TOP only, at 260oC in 2 h in each with other condi-tions remaining the same to see the effect of surfactant/s and reaction temperate. To make NPs biocompatible, SiO2 was coated on the prepared powder of CoO8 using a standard method, described elsewhere23.

2.1 氧化钴（CoO）纳米颗粒的合成
所用原料包括购自Sisco Research Laboratories Pvt. Ltd的乙酸四水合钴（Cobalt acetate tetrahydrate, CAT，化学式为Co(CH₃COO)₂·4H₂O，纯度≥99%），以及购自西格玛奥德里奇（Sigma Aldrich）的油酸（Oleic acid, OA，70%纯度）和三辛基膦（Tri-n-octylphosphine, TOP，90%纯度），所有原料均直接使用，未做额外纯化处理。

2.1.1 第一种合成方法
典型实验步骤如下：称取2 g CAT、8 mL OA与2 mL TOP加入三口圆底烧瓶，在氮气氛围下以10 ℃/min的速率升温。当温度升至约80 ℃时，CAT的粉红色晶体开始分解，溶液颜色逐渐变为浅蓝色；随温度进一步升高，溶液变为深蓝色；最终在180~200 ℃时溶液变为深棕色，维持该温度2 h，此过程标志着CoO纳米颗粒的成功合成。随后将反应溶液冷却至30 ℃，加入正己烷（n-hexane）后离心萃取并洗涤纳米颗粒，重复洗涤三次以去除未结合在纳米颗粒表面的过量OA与TOP。将洗涤后的颗粒置于60 ℃真空干燥箱中干燥，即可用于后续各项表征，该样品编号为CoO1。另一份在230 ℃下制备、其余反应条件保持一致的样品编号为CoO2。

2.1.2 第二种合成方法
先将2 g CAT与8 mL OA的混合溶液在120~130 ℃下脱气30 min，随后加入0.25 mL预先在200 ℃预热的TOP。将所得混合溶液在氮气氛围下继续升温至230 ℃并恒温反应5.5 h。反应过程中，CAT的粉红色逐渐变为蓝色，最终因CoO纳米颗粒的生成而变为棕褐色。冷却至30 ℃后，反应产物按照前述方法洗涤并干燥，该样品编号为CoO3。
为考察表面活性剂用量对产物的影响，保持其余反应条件不变，分别调整TOP添加量为0.25 mL、1 mL、3 mL、8 mL和12 mL，反应时间调整为1.5 h，所得样品依次编号为CoO4、CoO5、CoO6、CoO7和CoO8。
此外，为探究表面活性剂种类与反应温度的影响，在260 ℃、恒温反应2 h的条件下，按照以下配方分别制备样品：仅使用8 mL OA的CoO9、与CoO3配方一致（8 mL OA+12 mL TOP）的CoO10，以及仅使用10 mL TOP的CoO11，其余反应条件均保持一致。
为使制备的CoO纳米颗粒具备生物相容性，采用已报道的标准方法（详见文献23）在CoO8的粉体表面包覆了二氧化硅（SiO₂）。