Gold nanofluids synthesised using antioxidant catechin, its characterisation and studies on nucleation

Figures & data

Table 1. Benefits of nanofluids containing nanoparticles versus microparticles.[3]

Properties	Microparticles	Nanoparticles
Stability	Settle	Stable
Surface/volume ratio	1	1000 times larger than microparticles
Clog in microchannel	Yes	No
Erosion/abrasion of microchannels	Yes	No

Figure 1. Green nanofluids containing gold nanoparticles.

Table 2. Composition of four different nanofluids synthesised using catechin (CAT) and tannic acid (TAE).

Code	AuNP nanofluids	Catechin (ml)	Tannic acid (ml)	HAuCl4 (ml)	Total reaction volume (ml)	Temp (°C)
A	TAE + AuNP	–	5	5	10	25
B	1:1 CAT:TAE + AuNP	2.5	2.5	5	10	25
C	1:4 CAT:TAE + AuNP	1	4	5	10	25
D	CAT +AuNP	5	–	5	10	25

Figure 2. DSC thermogram for nanofluids containing AuNP. (a) TAE +AuNP nanofluid; (b) 1:1 CAT:TAE + AuNP nanofluid; (c) 1:4 CAT:TAE + AuNP nanofluid; (d) CAT + AuNP nanofluid; (e) overlay of DSC thermograms for the four AuNP nanofluids.

Figure 3. Dielectric properties of green-synthesised AuNP nanofluids. (a) Dielectric constant (ɛ'); (b) dielectric loss factor (ɛ"); (c) dissipation factor (tan δ).

Table 3. Particle size analysis of AuNP size in nanofluids.

Sl. no.	AuNP Nanofluids	Min. (nm)	Max. (nm)	Mean (nm)	Std. dev. (±)	Particle Shape	UV–vis λmax (nm)
(1)	TAE + AuNP	13.8	67.0	40.6	14.0	Triangles, rectangle-inclined, polygon, spherical, quasi-spherical	550
(2)	1:1 CAT:TAE + AuNP	13.3	40.2	27.1	6.2	Mostly spherical to quasi-spherical (thin layer)	552
(3)	1:4 CAT:TAE + AuNP	22.6	65.3	50.6	6.8	Mostly spherical to quasi-spherical (thick layer)	550
(4)	CAT + AuNP	20.8	57.8	39.4	6.7	Quasi-spherical (core – shell type encapsulation)	560

Figure 5. UV–vis spectra for gold nanofluids with SPR peak, (a) TAE + AuNP; (b) 1:1 CAT:TAE + AuNP; (c) 1:4 CAT:TAE + AuNP; (d) CAT + AuNP.

Figure 6. TEM image of CAT + AuNP nanofluid for nucleation study. (a) Catechin on grid and (b) reaction on grid.

Das SK, Choi SUS, Yu W, Pradeep T. Nanofluids science and technology. Hoboken (NJ): John Wiley & Sons, Inc.; 2008.

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