(a) Overarching Theme:  Engineering noble metal nanoclusters for biomedical and catalytic applications

(b) Research Contributions:

Dr. Xie is well known for his seminal works on subnanometer-sized metal nanoclusters, an emerging class of functional materials for biomedical and catalytic applications. He is pivotal in developing a number of novel pathways for the synthesis of fluorescent and atomically precise metal nanoclusters, all of which are now widely used in the nanocluster community. Dr. Xie was the first to propose the concept of “total synthesis” for metal nanoclusters, revealing the formation chemistry of metal nanoclusters at the atomic level and elucidating the luminescence fundamentals of metal nanoclusters at the molecular level. On the application front, Dr. Xie pioneered the design of metal nanocluster radiosensitizers for cancer radiotherapy and traceable antimicrobial agents. Dr. Xie’s publications in prestigious journals and keynote/invited talks at international conferences on materials, chemistry and chemical engineering over the past nine years have raised NUS’ global reputation in contributions to research on noble metal nanoclusters. Specific contributions are elaborated below:

1. Development (and Understanding) of Novel Synthetic Chemistries for Metal Nanoclusters

• Novel synthetic strategies (g., protein-directed nanocluster synthesis, carbon monoxide (CO)-reduction method; and stoichiometric synthesis) – these methods are now widely used in the nanocluster community. (Selected publications: Adv. Mater. 2018, 1802751 (Review); Coord. Chem. Rev. 2016, 329, 1 (Review); JACS 2018, 140, 11370; Nat. Commun. 2017, 8, 1555; JACS 2015, 137, 2128; Angew. Chem. 2015, 54, 184; Angew. Chem. 2014, 53, 4623; ACS Nano 2012, 6, 7920; JACS 2009, 131, 888)

• Understanding the growth mechanisms of gold nanoclusters by using ESI mass spectrometry; proposed the concept of “total synthesis” in metal nanocluster synthesis. (Selected publications: Angew. Chem. 2019, 58, 11967 (Minireview); Acc. Chem. Res. 2018, 51, 1338 (Accounts); JACS 2019, DOI: 10.1021/jacs.9b05776 (cover article); Nat. Commun. 2018, 9, 1979; Nat. Commun. 2018, 9, 2379; Nat. Commun. 2017, 8, 927; JACS 2014, 136, 10577)

2. Elucidation of Fundamental Properties of Metal Nanoclusters

• The first to propose and validate the currently accepted aggregation-induced-emission (AIE) mechanism for luminescent metal nanoclusters. (Selected publications: J. Phys. Chem. L 2016, 7, 962 (Perspectives); Angew. Chem. 2020, DOI: 10.1002/anie.201916675; Angew. Chem. 2019, 58, 8139; JACS 2012, 134, 16662)

• Discovered the first red-emitting gold nanocluster (Au22SR18) with precise molecular composition and structure. (Selected publication: JACS 2014, 136, 1246)

3. Exploration of Biomedical and Catalytic Applications of Metal Nanoclusters

• Pioneered the design of silver and gold nanocluster-based antimicrobial agents. (Selected publications: Coord. Chem. Rev. 2018, 357, 1 (Review); Adv. Funct. Mater. 2019, 1904603 (cover article); 2016, 10, 7934; ACS Nano 2017, 11, 6904; ACS Nano 2016, 10, 7934)

• Pioneered the design of gold nanocluster-based radiosensitizers for cancer radiotherapy. (Selected publications: Mater. Horiz. 2017, 4, 817 (Review); Adv. Mater. 2019, 31, 1901015; Adv. Mater. 2014, 26, 4565)
• Modeled metal nanocluster catalysts design. (Selected publications: Coord. Chem. Rev. 2016, 322, 1 (Review); PNAS 2018, 115, 10588)