RESEARCH

Colloidal nanocrystals (NCs) are particles with dimensions typically below 100 nm constituted of crystalline materials such as metals and ionic compounds (e.g., metal oxides, chalcogenides, or fluorides), which are homogeneously dispersed in a liquid medium where a layer of surface-bound molecules (surface ligands) prevents aggregation. Colloidal NC represents an exciting material class where surface and finite-size effects result in prominent phenomena not observed in bulk, including enhanced catalytic activity, novel optical properties, or tunable magnetic behavior. For this reason, the science of NCs holds appealing promises in the development of cleaner energy sources, fabrication of sustainable high-added value materials, design of optoelectronic devices, or creation of efficient disease therapies. However, the ability to precisely fabricate NCs and control their self-assembly behavior is crucial for maximizing their positive impact. In this scenario, our research interests focus on the design of functional surface ligands and the development of colloidal routes exploiting ultrafast pulsed laser irradiation to synthesize, stabilize, and assemble high quality NCs for optical and catalytic applications.

Synthesis and Modification of Colloidal Nanocrystals

Today’s most advanced colloidal NCs are mainly produced via hot injection and seed-mediated bottom-up strategies or their variants (e.g., heat-up or solvothermal approaches). Their strength and versatility rely on the (spatio)temporal separation of NC nucleation from growth. Thereby, they can provide unmatched control over the properties of NCs by enabling the synthesis of NCs with defined sizes, shapes, elemental distributions, crystal lattice defects, and surface chemistry. During the last few years, I have focused on developing and understanding seed-mediated protocols for anisotropic metal NC synthesis. Currently, my team is exploring seed-mediated and heat-up strategies to grow multimetallic NCs, anisotropic metal-semiconductor heterostructures, and multielemental oxides and chalcogenides

The excitation of colloidal NCs with ultrafast pulsed laser irradiation facilitates NC heat up to temperatures well above the nanomaterial melting and boiling points in timescales, which are hardly achievable via standard heating methods. In the last nine years, I have explored routes to exploit the ultrafast heating and cooling dynamics triggered by femtosecond and nanosecond laser pulses to obtain metal NCs with unprecedented morphologies and optical features. The potential of pulsed lasers to weld and melt colloidal NCs without compromising their colloidal stability is currently being exploited to synthesize high-entropy alloy NCs or control dopant concentration in chalcogenide NCs. 

RELEVANT PUBLICATIONS

Chem. Mater. 2024, 36 (4), 1982–1997

Chem. Mater. 2023, 35 (22), 9603–9612

 Adv. Optical Mater. 2021, 9, 2002134

Nanomaterials 2021, 11(6), 1427

J. Phys. Chem. Lett. 2020, 11 (3), 670–677

Science 2020, 368 (6498), 1472–1477

ACS Nano 2019, 13 (4), 4424–4435

Science 2017, 358 (6363), 640–644

Self-Assembly of Nanocrystals

Self-assembly of colloidal NCs offers potential routes to fabricate structured materials with enhanced functionalities, often resulting from the magnification of component properties or the rise of new features in the assembled structure. In our group, strategies for directed self-assembly and self-assembly in confined space are exploited to create nano and submicron structures with defined superlattices, long-range order at the atomic level, or multicomponent nature. Thereby, we aim to create complex nanomaterials with, for example, magnetoplasmonic features or multiple catalytic active sites.  

RELEVANT PUBLICATIONS

Acc. Chem. Res. 2022, 55, 12, 1599–1608

Langmuir 2023, 39 (10), 3580–3588

J. Phys. Chem. C 2017, 121, 20, 10899–10906

Functional Surface Ligands

Surface ligands with desired functionalities are fundamental for NC technology, as they play an active role in preventing NC aggregation, directing NC morphology evolution during growth, and dictating self-assembly behavior. However, a significant issue found in colloidal nanoparticles is that, in many cases, no surface ligands are available to properly control the stabilization and assembly of colloidal NCs. My team is actively developing a toolbox strategy to synthesize functional polymeric surface ligands with highly tunable hydrophobicity, molecular mass, and anchoring moieties. This methodology shall allow us to control NC stability in different polar and apolar media, phase transfer, self-assembly behavior, and morphology during growth, regardless of the NC composition and dimensions.