## 2 Structure, Synthesis, and Properties of Bimetallic CuFe Nanoparticles
### Synthesis and Properties
#### 2.2.2 Chemical Reduction  
FeCu nanoparticles have also been produced by chemical reduction [40; 41; 42; 43; 44; 45; 46; 47]. FeCu nanoparticles were synthesized from chemical reduction of Cu and Fe dodecyl sulfate (Fe(DS)\({}_{2}\) and Cu(DS)\({}_{2}\)) by sodium borohydride (NaBH\({}_{4}\)) and their magnetic properties were studied by [PERSON] et al. [40]. To prevent oxidation, the synthesis was carried out under a nitrogen atmosphere. The authors found single fcc phase alloys and superparamagnetic behavior above 10 K.  
The reduction of FeSO\({}_{4}\).7H\({}_{2}\)O and CuSO\({}_{4}\).5H\({}_{2}\)O aqueous mixture with sodium borohydride and stirring with the activated carbon was used for the synthesis of C/FeCu. Particles with the average size of 20 nm and a chain-like arrangement with Fe\({}_{2}\)O\({}_{3}\) and Cu\({}_{2}\)O phases were reported [41]. A two-step reduction method with using FeSO\({}_{4}\).7H\({}_{2}\)O stabilized by sodium citrate and CuSO\({}_{4}\).5H\({}_{2}\)O with sodium borohydride under N\({}_{2}\) protection were used by [PERSON] et al. [42] for the synthesis of Cu doped Fe@Fe\({}_{2}\)O\({}_{3}\) nanoparticles with average size of a dozen of nanometers and different weight ratio Fe/Cu (1:1, 1:2, 3:10, 1:5, 1:10, 1:20 by weight). The effectiveness of arsenic removal from water by these particles was tested (reported in Section 3). In order to maintain or increase the stability of the particles, stabilizers such as chitosan (CS), green tea (GT), or carboxymethyl cellulose (CMC) are used. [PERSON] et al. [43] developed the bimetallic FeCu nanoparticles stabilized by chitosan (CS) with a diameter of 50-100 nm. They chose chitosan due to its biodegradability in the environment and the content of amine and hydroxyl groups, which should strongly bind to nZVI and effectively stabilize nanoparticles. They reported that the concentration of chitosan influences crystal nucleation and aggregation of FeCu particles, and higher chitosan amount results in a more uniform dispersion of FeCu nanoparticles in chitosan. The best amount of chitosan and Cu in CS-CuFe nanocomposites is 2 wt% and 3 wt%, respectively, both in terms of stabilization and catalytic properties. Green synthesis with green tea (GT) extracts as a reducing agent and stabilizer was used for the preparation of composite of GT and nZVICu nanoparticles with an average size of 60-120 nm [44]. FeCu alloy nanoparticles encapsulation in carbon (FeCu@C) by a combination of a chemical reduction of ferric nitrate Fe(NO\({}_{3}\))\({}_{3}\).9H\({}_{2}\)O and copper nitrate Cu(NO\({}_{3}\))\({}_{2}\).3H\({}_{2}\)O in alcohol solution and annealing carbonization (Figure 6) was performed by [PERSON] et al. [45]. The core-shell nanoparticles, with FeCu\({}_{4}\) core and amorphous carbon shell, with particles size ranging from 24 nm to 73 nm, and coating thickness of approximately 5 nm were produced. The obtained material presented ultra-soft magnetic properties. FeCu nanoparticles of various composition (Fe:Cu = 8:2, 5:5, 2:8) prepared by the reduction of iron and copper nitrates were dispersed on the two various media, highly ordered \"platelet\" graphite nanofibers GNF and amorphous silica [46]. Size of nanoparticles supported on \"platelet\" GNF is equal 13.1 nm, 11.1 nm, 12.7 nm for Fe:Cu = 8:2, 5:5, 2:8, respectively and is twice as large on average as those supported in silica equal to 5.6 nm, 7.6 nm, 8.1 nm for Fe:Cu = 8:2, 5:5, 2:8, respectively. Comparison of catalytic activity and selectivity of those systems shows that the performance of the metal catalysts supportedon the graphite nanofibers was better than that on the silica system, what is connected with the nature of the interaction of nanoparticles with the support. The CuFe bimetallic nanoparticles with Cu/Fe molar ratios of 10.00, 3.00, 0.33 and 0.10 were prepared by a simultaneous reduction of cupric and ferric nitrates with sodium borohydride (NaBH\({}_{4}\)) in ethylene glycol (EG) under Ar atmosphere by [PERSON] et al. [47; 48].