I am attempting to synthesize Copper Nanoparticles using ascorbic acid and sodium alginate as per:

Article Study on antibacterial alginate-stabilized copper nanopartic...

The protocol is as follows:

"The precursor (0.1 M, Cu[NO3]2) was completely dissolved

in 100 mL of nanopure water under magnetic stirring. Then

this solution was heated to the synthesis temperature (95°C)

in a Thomas microwave oven. Once the synthesis temperature

was reached, 50 mL of ascorbic acid solution (containing the

proper quantities of reducing agent) was added to the hot

solution and stirred continuously at 60 rpm. After ascorbic

acid addition, the blue solution turned dark green, thus indicating

the immediate nucleation of Cu NPs. Finally, the colloidal

dispersions were deposited onto NaAlg by microwave

heating for 1 hour (88°C). The Cu(NO3)2 and NaAlg amount

were kept constant for all stabilized Cu NPs at a molar ratio of

1. The weight loss of stabilized Cu NPs was measured upon

drying until constant weight at 110°C."

As the protocol fails to mention how to add the Copper NPs to the alginate solution, I added the reduced (green) Cu solution dropwise to the viscous alginate while stirring and heating. My product was in two separate and immiscible layers. I do not know why. Did the copper fail to deposit onto the alginate? Should I heat the solution to 110 and remove all solvent?