Distinctly Different Morphologies of Bimetallic Au-Ag Nanostructures and Their Application in Submicromolar SERS-Detection of Free Base Porphyrin
Abstract
:1. Introduction
2. Materials and Methods
2.1. Chemicals
2.2. Nomenclature
2.3. Syntheses of the AuNP Serving as Seeds
- (a)
- synthesis of AuBH-fr
- (b)
- synthesis of AuBOH-fr
- (c)
- synthesis of AuBhr (borohydride-reduced AuNPs aged for 7 months)
- (d)
- synthesis of AuCitr-fr and AuCitr (citrate-reduced AuNPs freshly prepared and aged for 7 months, respectively)
2.4. Syntheses of the Final Colloidal Au-AgNSs
- (i)
- AuBH-fr_Ag+_Asc: 0.5 mL of AuBH-fr was added to 12.5 mL of 0.2 mM AgNO3 aqueous solution, followed by 250 µL of 10 mM ascorbic acid aqueous solution. The final colloidal Au-AgNSs were stirred at the rate of 1350 rpm for 10 s, then at the rate of 850 rpm for additional 25 min.
- (ii)
- AuBOH-fr_Ag+_Asc: the same synthetic procedure as (i), however, 0.5 mL of AuBOH-fr was employed. The stirring and timing were the same as in (i).
- (iii)
- AuBhr_Ag+_Asc: the same synthetic procedure as (i), however, 0.5 mL of AuBhr colloid was added. The stirring and timing were the same as in (i).
- (iv)
- AuCitr-fr_Ag+_Asc: the synthetic procedure was the same as in (i), however, 0.5 mL of AuCitr-fr was introduced. The stirring and timing were the same as in (i).
- (v)
- AuCitr_Ag+_Asc: the synthetic procedure was the same as in (i), however, 0.5 mL of AuCitr (i.e., aged AuCitr seeds) was employed. The stirring and timing were the same as in (i).
- (vi)
- AuBhr_Asc_Ag+: the procedure of this Au-AgNSs preparation was very similar to that described in (iii) with the only exception: a reversed order of reactants was used during the second step. Briefly, 0.5 mL of the seed solution AuBhr (aged for 7 months) was added to 250 µL of 10 mM ascorbic acid aqueous solution, followed by the addition of 12.5 mL of 0.2 mM AgNO3 aqueous solution. The stirring and timing were the same as in (i).
- (vii)
- AuCitr_Asc_Ag+: the synthetic procedure was the same as in (vi), however, 0.5 mL of AuCitr (instead of AuBhr) was employed.
2.5. Methods
3. Results and Discussion
3.1. Direct Impact of Au Seed Type on Morphologies of Final Au-AgNSs
3.1.1. Au-AgNSs Stemming from Au Seeds Prepared by Reduction Induced by Borohydride
3.1.2. Au-AgNSs Stemming from Au Seeds Prepared by Reduction Induced by Citrate
3.1.3. Reason for Different Morphologies of Au-AgNSs
3.2. Other Characteristics of Au-AgNSs Prepared by Using AuBhr or AuCitr Seeds
3.2.1. Sizes of Au-AgNSs Determined by DLS and Values Discussed in Comparison to TEM
3.2.2. Extinction Spectra of Au Seeds and of Final Au-AgNSs
3.3. Classical vs. Reverse Order of Reactants in Seed-Mediated Growth Procedure of Au-AgNSs
3.4. Kinetics of Au-AgNSs Generation
3.5. SERS Application of Au-AgNSs
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Seed Solution Code | Final Colloidal Au-AgNSs Code |
---|---|
AuBH-fr | AuBH-fr_Ag+_Asc |
AuBOH-fr | AuBOH-fr_Ag+_Asc |
AuCitr-fr | AuCitr-fr_Ag+_Asc |
AuBhr | AuBhr_Ag+_Asc |
AuBhr | AuBhr_Asc_Ag+ |
AuCitr | AuCitr_Ag+_Asc |
AuCitr | AuCitr_Asc_Ag+ |
Sample Code | Mean Particle Sizes and Their Percentual Contents Based on Light Intensity Changes | pH Values | |||
---|---|---|---|---|---|
[nm] | [%] | [nm] | [%] | ±0.05 | |
AuBhr seeds | 44 ± 12 | 46 | 9 ± 1 | 54 | 7.80 |
AuBhr_Ag+_Asc | 67 ± 38 | 76 | 11 ± 4 | 24 | 3.44 |
AuBhr_Asc_Ag+ | 55 ± 27 | 70 | 7 ± 3 | 30 | 3.49 |
AuCitr seeds | 41 ± 13 | 59 | 14 ±4 | 35 | 6.02 |
AuCitr_Ag+_Asc | 65 ± 34 | 80 | 10 ± 4 | 20 | 3.69 |
AuCitr_Asc_Ag+ | 74 ± 39 | 76 | 13 ± 5 | 24 | 3.73 |
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Vilímová, I.; Šišková, K. Distinctly Different Morphologies of Bimetallic Au-Ag Nanostructures and Their Application in Submicromolar SERS-Detection of Free Base Porphyrin. Nanomaterials 2021, 11, 2185. https://doi.org/10.3390/nano11092185
Vilímová I, Šišková K. Distinctly Different Morphologies of Bimetallic Au-Ag Nanostructures and Their Application in Submicromolar SERS-Detection of Free Base Porphyrin. Nanomaterials. 2021; 11(9):2185. https://doi.org/10.3390/nano11092185
Chicago/Turabian StyleVilímová, Iveta, and Karolína Šišková. 2021. "Distinctly Different Morphologies of Bimetallic Au-Ag Nanostructures and Their Application in Submicromolar SERS-Detection of Free Base Porphyrin" Nanomaterials 11, no. 9: 2185. https://doi.org/10.3390/nano11092185