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Metal halide perovskite nanocrystals (NCs) exhibit impressive optical and electronic properties, making them an important class of functional materials with promising applications in solar cells, light emitting diodes (LEDs), photodetectors, and photocatalysts. In addition to the widely studied 0-dimensional (0D) metal halide perovskite NCs, such as nanocubes, low dimensional perovskites, such as 2D all-inorganic perovskite (AIP) NCs, subsist with directionally relevant quantum confinement. These anisotropic NCs have the propensity to exhibit interesting optoelectronic properties that are exceedingly difficult to introduce into 0D systems, yet as of late are largely unexplored. In this review, we discuss the recent synthetic progress of 2D all-inorganic metal halide perovskite NCs with ABX3 structure. Specifically, we highlight the discrete composition control of the cations (A and B sites) and anions (X site) by dopant incorporation and alloying in 2D metal halide perovskite NCs. We will also discuss more complex perovskite crystal structures, such as Ruddlesden–Popper double perovskites, and compare these materials to 0D perovskite systems. Ultimately, our work culminates in the future interests and perspectives of this field with a focus on the wide applicability of 2D systems and the large variance in structure capable with discrete compositional tuning.

Selective cleavage of C–C bonds can be a valuable tool for various applications including polymer degradation and biomass utilization. Performing chemical transformations involving C–C bond cleavag...

All-inorganic halide perovskite nanocrystals (NCs) offer impressive optoelectronic properties for light harvesting, energy conversion, and photoredox applications, with two-dimensional (2D) perovskite NCs further increasing these prospects due to their improved photoluminescence (PL) tuneability, impressive color purity, high in-plane charge transport, and large lateral dimensions which is advantageous for device integration. However, the synthesis of 2D perovskites is still challenging, especially toward large-scale applications. In this study, through the control of surface ligand composition and concentration of a mixture of short (octanoic acid and octylamine, 8-carbon chain) and long (oleic acid and oleylamine, 18-carbon chain) ligands, we have developed an extremely facile ligand-mediated synthesis of 2D CsPbX3 (X = Cl, Br, or mixture thereof) nanoplatelets (NPLs) at room temperature in an open vessel. In addition, the developed method is highly versatile and can be applied to synthesize Mn-doped CsPbX3 NPLs, showing a systematic increase in the total PL quantum yield (QY) and the Mn-dopant emission around 600 nm with increasing Mn and Cl concentrations. The reaction occurs in toluene by the introduction of CsX, PbX2, and MnX2 precursors under ambient conditions, which requires no harsh acids, avoids excessive lead waste, little thermal energy input, and is potentially scalable toward industrial applications.

Doping through the incorporation of transition metal ions allows for the emergence of new optical, electrical, and magnetic properties in quantum dots (QDs). While dopants can be introduced into QDs through many synthetic methods, the control of dopant location and host-dopant (H-D) coupling through directional dopant movement is still largely unexplored. In this work, we have studied dopant behaviors in Mn:CdS/ZnS core/shell QDs and found that dopant transport behavior is very sensitive to the temperature and microenvironments within the QDs. The migration of Mn toward the alloyed interface of the core/shell QDs, below a temperature boundary (Tb) at ∼200 °C, weakens the H-D interactions. At temperatures higher than the Tb, however, dopant ejection and global alloying of CdS/ZnS QDs can occur, leading to stronger H-D coupling. The behavior of incorporated dopants inside QDs is fundamentally important for understanding doping mechanisms and the host-dopant interaction-dependent properties of doped nanomaterials.

Transition-metal ions doped nanocrystals (NCs), specifically Mn-doped NCs, hold great potential in the field of photocatalysis, especially, to improve photocatalytic performance for singlet oxygen (1O2) generation. Here, we report the design of a novel Mn-doped NC-based nanocomposites, specifically, silica-coated Mn-doped CdS/ZnS NCs decorated with Pt NCs (denoted as Mn-NCs@SiO2-Pt), which enhance photocatalytic 1O2 generation. Owing to the long-lived Mn excited state (on the order of ms), the energy-transfer between Mn-NCs and molecular oxygen is facilitated with the assistance of the Pt NCs adhered to the Mn-NC@SiO2 surface. Therefore, the Mn-NCs@SiO2-Pt composites, integrate the advantages of Mn-doped NCs, a protective silica layer, and Pt NCs to exhibit excellent catalytic activity and selectivity for the selective oxidation of primary benzylic alcohols to aldehydes through an 1O2 engaged oxidation process under visible-light irradiation. This work paves the way for enhancing catalytic performance via facilitated energy transfer relaxation by utilizing the long-lived excited-state of Mn2+ dopant ions in nanocomposites.

Manganese-doped cesium lead chloride (CsPbCl3) perovskite nanocrystals (NCs) have recently garnered attention because of their unique magneto-optical properties, giving them potential in a variety ...

As a green synthetic approach, visible light-driven photosynthesis is highly desirable in arylation of inert alkyl halides, as they are important precursors in the total synthesis of natural products and pharmaceuticals. However, the high bond dissociation energy of aryl halides is typically out of the range of a single visible-light photon. Here, we propose an essential initiation and subsequent electron-transfer step process for visible light-driven aryl halide reduction, and identify the key pyrrole radical anion intermediate, that acts as the strong reduction species. We propose a photoinduced disproportionation (PDP) approach without the addition of any photocatalysts or additives to afford radical anions of pyrrole derivatives, which have enough reduction power to transfer an electron to aryl halide, giving rise to the corresponding aryl radical to afford the desired C–H arylated heterocyclic product. Once generated, the heterocyclic product can undergo the same photoinduced disproportionation (PDP) process to activate aryl halides, thereby promoting the reaction rate. This unprecedented initiation step, which was carried out in the absence of photocatalysts and additives under ambient conditions, can also be used for coupling a wide range of (hetero)aryl halides and pyrrole derivatives, as well as the synthesis of drug intermediates and biorelevant compounds.

The ability to dope transition-metal ions into semiconductor nanocrystals (NCs) allows for the introduction and exploitation of new extrinsic properties in the original intrinsic material. Although...

The introduction of dopants plays a key role in the physical properties of semiconductors for optoelectronic applications. However, doping is generally challenging for nanocrystals (NCs), especially for two-dimensional (2D) NCs, due to the self-annealing effect and high surface energies required for dopant addition. Here, we report an efficient doping strategy for Mn-doped 2D CsPbCl3 (i.e., Mn:CsPbCl3) nanoplatelets (NPLs) through a postsynthetic solvothermal process. While the original lightly doped 2D Mn:CsPbCl3 NPLs were obtained from growth doping, higher Mn doping efficiencies were achieved through diffusion doping under pressure-mediated solvothermal conditions, resulting in enhanced Mn photoluminescence (PL). Surprisingly, a new CsMnCl3 phase with complete dopant substitution by spinodal decomposition was observed with extended solvothermal treatment, which is confirmed by powder X-ray diffraction, X-ray absorption fine structure, and electron paramagnetic resonance. Compared with Mn:CsPbCl3 NPLs,...

Shape control is critical and offers an efficient way to tune the properties of nanocrystals (NCs). Here we present the growth of two-dimensional (2-D) all-inorganic CsPbX3 (X = Cl, Br, I) perovskite NCs through the assembly of corresponding 1-D nanorods (NRs) under solvothermal conditions. Both 2-D CsPbX3 perovskite nanoplatelets (NPLs) and nanosheets (NSs) with a wide lateral size range from ∼100 nm to ∼1 μm and thickness of a few unit cells can be obtained by the control of the solvothermal reaction time. The present work provides a general strategy for rational fabrication of 2-D CsPbX3 (X = Cl, Br, I) perovskite NCs without the assistance of anion exchange. The obtained fluorescent 2-D all-inorganic perovskite NCs have great potential in practical photovoltaic applications.

Transition metal ion doped one-dimensional (1-D) nanocrystals (NCs) have advantages of larger absorption cross sections and polarized absorption and emissions in comparison to 0-D NCs. However, direct synthesis of doped 1-D nanorods (NRs) or nanowires (NWs) has proven challenging. In this study, we report the synthesis of 1-D Mn-doped ZnSe NWs using a colloidal hot-injection method and shell passivation for core/shell NWs with tunable optical properties. Experimental results show optical properties of the NWs are controlled by the composition and thickness of the shell lattice. It was found that both the host–Mn energy transfer and Mn–Mn coupling are strongly dependent on the type of alloy at the interface of doped core/shell NWs. For Mn-doped type I ZnSe/ZnS core/shell NWs, the ZnS shell passivation can enhance florescence quantum yield with little effect on the location of the incorporated Mn dopant due to the identical cationic Zn2+ site available for Mn dopants throughout the core/shell NWs. However, ...

Dynamic materials have been given an increased amount of attention in recent years with an expectation that they may exhibit properties on demand. Especially, the combination of fluorescent quantum dots (QDs) and light-responsive organic switches can generate novel photo-switchable materials for diverse applications. In this work, a highly reversible dynamic hybrid system is established by mixing dual-color emitting Mn-doped CdS-ZnS quantum dots (QDs) with photo-switchable diarylethene molecules. We show that the diarylethene 1,2-bis(5-(3,5-bis(trifluoromethyl)phenyl)-2-methylthiophen-3-yl)cyclopent-1-ene (switch molecule 1) performs fabulous photo-switching property (between its open, 1o and closed, 1c forms), and high fatigue resistance in this hybrid system. The emission color switching between blue and pink of the system can be induced mainly by selective quenching/recovering of the Mn- photoluminescence (PL) of the QDs due to the switchable absorbance of the molecule 1. Mechanistic studies show that quenching of QD emission following UV illumination was caused by both Förster resonance energy transfer (FRET) and reabsorption by surrounding 1c molecules in the case of the Mn-PL, and solely by reabsorption in the case of badngap- (BG-)PL. This photo-switchable system could be potentially used in applications ranging from self-erasing paper to super-resolution fluorescence imaging.

High-quality perovskite films are predominantly prepared by anti-solvent assisted spin-coating method. However, small device size and narrow operation window limit their applications in practical and scalable production. Here, a spontaneously supersaturated nucleation strategy is developed to fabricate high-quality perovskite films without any antisolvents. The rapid precipitation behavior of the precursor solutions could be triggered by the volatilization of methylamine ethanol at the initial film formation stage, forming uniform and compact intermediate phase films. Mirror-like large area (10 cm × 10 cm) methylammonium lead triiodide (MAPbI3) perovskite films with micrometer-sized grains can be achieved by phase transition via annealing. The average power conversion efficiency (PCE) of 19.4% is achieved for 0.1 cm2 perovskite solar cells (PSCs). The 1 cm2 device shows a PCE of 17.57% and retains 96.8% after aging for 39 days in the air with a relative humidity of 5–30%. The perovskite module based on the perovskite films prepared by our strategy exhibits a PCE of 13.13%. The perovskite film fabrication method developed in this work shows high reproducibility of the fabrication process due to the spontaneous nucleation process. Meanwhile, it also exhibits significant potential in the application of scalable solution processing deposition techniques toward the commercialization of PSCs.

Inherent poor stability of perovskite nanocrystals (NCs) is the main impediment preventing broad applications of the materials. Here, TiO2 shell coated CsPbBr3 core/shell NCs are synthesized through the encapsulation of colloidal CsPbBr3 NCs with titanium precursor, followed by calcination at 300 °C. The nearly monodispersed CsPbBr3/TiO2 core/shell NCs show excellent water stability for at least three months with the size, structure, morphology, and optical properties remaining identical, which represent the most water-stable inorganic shell passivated perovskite NCs reported to date. In addition, TiO2 shell coating can effectively suppress anion exchange and photodegradation, therefore dramatically improving the chemical stability and photostability of the core CsPbBr3 NCs. More importantly, photoluminescence and (photo)electrochemical characterizations exhibit increased charge separation efficiency due to the electrical conductivity of the TiO2 shell, hence leading to an improved photoelectric activity in water. This study opens new possibilities for optoelectronic and photocatalytic applications of perovskites-based NCs in aqueous phase.