Design Principle of a Water-Dispersed Photocatalytic Perovskite through Ligand Deconstruction

Abstract

Strategically designed surface modifiers that produce stable perovskite nanocrystals (NCs) and allow efficient charge extraction in polar solvents are critical for perovskite photocatalysis. We designed a multifunctional bolaamphiphilic ligand (NKE-12) with multidentate ionic groups at both ends, which significantly increases the colloidal stability of CsPbBr3 NCs in an aqueous medium without affecting their structural integrity and catalytic attributes. Ligand deconstruction via K and E fragmented ligands revealed synergistic actions of the cationic and anionic functionalities in surface passivation, phase separation, and water localization away from the surface of NKE-12-modified CsPbBr3 NCs. Multidimensional nuclear magnetic resonance experiments and contact angle measurements further suggested surface interactions and improved hydrophilicity via ionic terminal groups that account for water stability. Photogenerated hole-transfer dynamics of CsPbBr3/​NKE-12 NCs to a probe molecule 6,7-dihydroxy­coumarin was studied using transient absorption spectroscopy. Overall, this study paves the way for ligand design principles for surface engineering to develop water-stable perovskite photocatalysts.

Synergistic binding between an engineered interface and functionalized ferrocene offers remarkable charge extraction efficiency in lead halide perovskites

“…S11b†) were fitted with two binding energy peaks at 399.74 eV and 401.65 eV, corresponding to –NH 2 and –NH 3 + , respectively. 73 The well-defined N 1s peaks in CPB NK-12 suggest an effective ligand exchange between NK-12 and more dynamic native OAm/OAc ligands.…”

“…Although PLQY values are comparable for CPB and CPB NK-12, the NK-12 ligand has been shown to enhance passivation of CPB (OAm/OAc capped) in toluene as discussed in our previous report. 73…”

Binding Strength-Guided Shuttling of Charge Carriers from Perovskite Nanocrystals to Molecular Acceptors

“…The bleach recovery spectra in Figure a–d corresponds to the evolution of the excitonic absorbance of CsPbBr 3 due to increased ground-state population via radiative and nonradiative recombination of electron–hole pairs generated upon pump excitation. A difference in the rate of absorption recovery in the presence of ferrocenyl molecules could be observed due to an additional competing pathway of photogenerated hole transfer. , On the lower energy side, the positive absorption next to the bleach signal can be associated with polarons’ formation or be linked to hot excitons. , …”

“…However, regardless of the plentiful research progress on the optoelectronic and photovoltaic front, − perovskite NCs have remained rather unexplored for photocatalytic applications. − Not to mention that the large extinction coefficient (10 6 M –1 cm –1 ) of CsPbBr 3 perovskite NCs in the visible range provides immense opportunities to explore its light absorption and the associated photocatalytic applications. Nevertheless, their insufficiency at this forefront accounts for the fact that they are unstable in polar solvents and involve surfactants with high energy barriers, which also prevents redox relays from accessing active surface sites. − Apart from that, efficient charge transfer is also crucial for any photocatalytic system. It can get hindered in perovskite NCs due to charge recombination and accumulation of the charge-transfer product close to the photocatalyst surface. , This, essentially necessitates a need to understand and optimize the various factors governing interfacial charge-transfer processes.…”

Enhancing Photocatalytic Attributes of Perovskite Nanocrystals in Aqueous Media via Ligand Engineering

“…The CsPbBr 3 NCs synthesized via a hot injection method were treated with the NKE-12 ligand in a postsynthetic treatment, following our previous report (Figure a) . Briefly, a 3.3 mM solution of NKE-12 was added to the capped CsPbBr 3 NCs solution in toluene (∼1 μM) in a 1:2 ratio during constant stirring (further details are provided in the Experimental Section).…”