Table 1

Influence of pH upon stability of AuNPs

pH

Before synthesis

pH

After synthesis

Color

Stability

After 1 h stored at 22°C

Stability

After 6 h stored at 22°C

Stability

After 2 months Stored at 4°C

4.25

3.72

Light pink

Stable

Stable

Small aggregation

4.25

3.72

Light pink

Stable

Stable

Small aggregation

5.55

4.75

Light red

Stable

Stable

Small aggregation

6.6

5.92

Light red

Stable

Stable

Stable

7.45

6.11

Light red

Stable

Stable

Stable

8.8

6.42

Light red

Stable

Stable

Stable

9.23

6.55

Medium red

Stable

Stable

Stable

9.34

6.32

Purple

Stable

Stable

Medium aggregation

10.3

8.10

Blue

Stable

Some aggregation

Heavy aggregation

11.4

10.96

Light blue

Crashed

Crashed

Crashed

Young et al. Nanoscale Research Letters 2011 6:428   doi:10.1186/1556-276X-6-428