8 Conclusion
This article has provided an overview of the precisely controlled synthesis of NPs
encapsulated by dendrimers and their catalytic applications. Since the first preparation of size-controlled NPs in the 1990s by Crooks, the use of dendritic nanocatalysts
has increased rapidly and has provided a variety of catalytic reactions such as
hydrogenation, C-C bond forming reactions, the oxidation of hydrocarbons and
alcohols, and the ORR. Monometallic and bimetallic NPs stabilized by various
dendrimers have been widely investigated with respect to catalytic application in
both homogeneous and heterogeneous systems. Catalysis generally proceeds in the
dendritic interior; therefore, the dendrimer plays a role as a nanoreactor to prevent
aggregation of the NPs. Functionalized dendrimers containing triazolyl units, developed by Astruc, led to the achievement of sub-parts per million levels of metal
loading catalysts and immobilization on magnetic NPs in pursuit of practical green
chemistry. Precise control of the atom-specified clusters has been achieved with
π-conjugated DPA derivatives. The sub-nanoclusters enhanced catalytic performance for electrochemical and organic reactions because of the reactive
amorphous structure and irregular electronic distribution of the cluster surface
[148]. Although recent enthusiasm with regard to multimetallic NPs leads to effective synergetic effects in catalysis, the synthesis technique for control of the size and
components has been difficult at the sub-nanometer scale. The approach to synthesize heteroatom clusters using the DPA template is much expected to develop the
uncultivated field for sophisticated catalysis [149, 150].
Acknowledgments This study was supported in part by JST ERATO Grant Number
JPMJER1503, Japan (K. Y.), JSPS KAKENHI Grant No. JP 15H05757 (K. Y.). We would like
to show our respect for the great efforts of all authors, whose names were listed in the references.
References
1. Okumura M, Fujitani T, Huang J, Ishida T (2015) ACS Catal 5:4699
2. Tomalia DA, Baker H, Dewald J, Hall M, Kallos G, Martin S, Roeck J, Ryder J, Smith P
(1985) Polym J 17:117
3. Tomalia DA, Dvornic PR (1994) Nature 372:617
4. Tomalia DA, Naylor AM, Goddard WA (1990) Angew Chem Int Ed Engl 29:138
5. Tomalia DA (1996) Macromol Symp 101:243
6. Tomalia DA, Fréchet JMJ (2002) J Polym Sci A Polym Chem 40:2719
7. Zhao M, Sun L, Crooks RM (1998) J Am Chem Soc 120:4877
8. Balogh L, Tomalia DA (1998) J Am Chem Soc 120:7355
9. Esumi K, Suzuki A, Aihara N, Usui K, Torigoe K (1998) Langmuir 14:3157
10. Tomalia DA, Hall M, Hedstrand DM (1987) J Am Chem Soc 109:1601
11. Tomalia DA, Berry V, Hall M, Hedstrand DM (1987) Macromolecules 20:1164
12. Naylor AM, Goddard III WA, Kiefer GE, Tomalia DA (1989) J Am Chem Soc 111:2339
13. Crooks RM, Zhao M, Sun L, Chechik V, Yeung LK (2001) Acc Chem Res 34:181
14. Scott RWJ, Wilson OM, Crooks RM (2005) J Phys Chem B 109:692
166
M. Tanabe and K. Yamamoto
This article has provided an overview of the precisely controlled synthesis of NPs
encapsulated by dendrimers and their catalytic applications. Since the first preparation of size-controlled NPs in the 1990s by Crooks, the use of dendritic nanocatalysts
has increased rapidly and has provided a variety of catalytic reactions such as
hydrogenation, C-C bond forming reactions, the oxidation of hydrocarbons and
alcohols, and the ORR. Monometallic and bimetallic NPs stabilized by various
dendrimers have been widely investigated with respect to catalytic application in
both homogeneous and heterogeneous systems. Catalysis generally proceeds in the
dendritic interior; therefore, the dendrimer plays a role as a nanoreactor to prevent
aggregation of the NPs. Functionalized dendrimers containing triazolyl units, developed by Astruc, led to the achievement of sub-parts per million levels of metal
loading catalysts and immobilization on magnetic NPs in pursuit of practical green
chemistry. Precise control of the atom-specified clusters has been achieved with
π-conjugated DPA derivatives. The sub-nanoclusters enhanced catalytic performance for electrochemical and organic reactions because of the reactive
amorphous structure and irregular electronic distribution of the cluster surface
[148]. Although recent enthusiasm with regard to multimetallic NPs leads to effective synergetic effects in catalysis, the synthesis technique for control of the size and
components has been difficult at the sub-nanometer scale. The approach to synthesize heteroatom clusters using the DPA template is much expected to develop the
uncultivated field for sophisticated catalysis [149, 150].
Acknowledgments This study was supported in part by JST ERATO Grant Number
JPMJER1503, Japan (K. Y.), JSPS KAKENHI Grant No. JP 15H05757 (K. Y.). We would like
to show our respect for the great efforts of all authors, whose names were listed in the references.
References
1. Okumura M, Fujitani T, Huang J, Ishida T (2015) ACS Catal 5:4699
2. Tomalia DA, Baker H, Dewald J, Hall M, Kallos G, Martin S, Roeck J, Ryder J, Smith P
(1985) Polym J 17:117
3. Tomalia DA, Dvornic PR (1994) Nature 372:617
4. Tomalia DA, Naylor AM, Goddard WA (1990) Angew Chem Int Ed Engl 29:138
5. Tomalia DA (1996) Macromol Symp 101:243
6. Tomalia DA, Fréchet JMJ (2002) J Polym Sci A Polym Chem 40:2719
7. Zhao M, Sun L, Crooks RM (1998) J Am Chem Soc 120:4877
8. Balogh L, Tomalia DA (1998) J Am Chem Soc 120:7355
9. Esumi K, Suzuki A, Aihara N, Usui K, Torigoe K (1998) Langmuir 14:3157
10. Tomalia DA, Hall M, Hedstrand DM (1987) J Am Chem Soc 109:1601
11. Tomalia DA, Berry V, Hall M, Hedstrand DM (1987) Macromolecules 20:1164
12. Naylor AM, Goddard III WA, Kiefer GE, Tomalia DA (1989) J Am Chem Soc 111:2339
13. Crooks RM, Zhao M, Sun L, Chechik V, Yeung LK (2001) Acc Chem Res 34:181
14. Scott RWJ, Wilson OM, Crooks RM (2005) J Phys Chem B 109:692
166
M. Tanabe and K. Yamamoto