Yb3+-CsPbClxBr3−x perovskite nanocrystals with a high two-photon absorption cross-section of 2.3 × 105 GM embedded into amphiphilic silica microspheres emit visible and near-infrared light under two-photon infrared excitation in toluene and water.

Active optical materials with intrinsic chirality, in particular, circularly polarized luminescence (CPL), are highly demanded for utilization in data processing, bioimaging, and photocatalytic asymmetric synthesis. Crystal structure engineering, chiral assembly, and chirality imprinting by chiral ligands were proposed for fabrication of CPL-active materials. The former approach is applicable to colloidal perovskite nanocrystals (PNCs), which attract significant attention due to their outstanding optical properties and high tunability. However, the issues of chiral perovskite NC stability, control of the bandgap, and achieving high photoluminescence quantum yield and emission dissymmetry factor simultaneously remain unresolved. To overcome these obstacles, we developed mixed-halide chiral perovskite NCs by simultaneous anion and ligand exchanges, which provide the passivation of surface defects and induce a chiral response. As a result, the chiral PNCs exhibit CPL with dissymmetry factors up to 3.4 x 10- 2 and a photoluminescence quantum yield up to 98 %, making the proposed approach promising for chirality imprinting.

Subject of study. Lead-free perovskite nanocrystals (LFPNCs), their main characteristics, synthesis methods, and optical properties are examined. Aim of study. The aim is to analyze the state-of-the-art research data on the synthesis methods and optical properties of LFPNCs. In addition, the formation processes of LFPNCs, their main synthesis methods, and the dependence of nanocrystal size and photoluminescence quantum yield (PLQY) on synthesis parameters (such as method, temperature, and ligand type) are determined. Main results. The formation of LFPNCs is analyzed based on the LaMer and cluster growth models. According to the research data, the primary methods for preparing these nanocrystals (NCs) are hot-injection and ligand-assisted reprecipitation (LARP). Evidently, the average size of LFPNCs increases with increasing reaction temperature. For NCs synthesized by LARP, increasing the reaction temperature to 100°C leads to a slight decrease in the quantum yield. However, for the NCs prepared by hot-injection, the PLQY remains independent of the temperature. Additionally, using oleic acid as a ligand results in a narrow size distribution of NCs, whereas using a mixture of ligands results in NCs exhibiting the highest PLQY. Practical significance. The literature analysis results show that the LARP method is the most promising for synthesizing LFPNCs owing to its ease of implementation, energy efficiency, and scalability. The LFPNCs produced using this method can be applied as active materials in sensor technologies, photovoltaics, and optoelectronic devices.

Lead chalcogenide nanocrystals (NCs) are an emerging class of photoactive materials that have become a versatile tool for fabricating new generation photonics devices operating in the near-IR spectral range. NCs are presented in a wide variety of forms and sizes, each of which has its own unique features. Here, we discuss colloidal lead chalcogenide NCs in which one dimension is much smaller than the others, i.e., two-dimensional (2D) NCs. The purpose of this review is to present a complete picture of today’s progress on such materials. The topic is quite complicated, as a variety of synthetic approaches result in NCs with different thicknesses and lateral sizes, which dramatically change the NCs photophysical properties. The recent advances highlighted in this review demonstrate lead chalcogenide 2D NCs as promising materials for breakthrough developments. We summarized and organized the known data, including theoretical works, to highlight the most important 2D NC features and give the basis for their interpretation.

Lead chalcogenide nanoplatelets (NPLs) have emerged as a promising material for devices operating in the near IR and IR spectrum region. Here, we first apply the cation exchange method to PbSe/PbS core/shell NPL synthesis. The shell growth enhances NPL colloidal and environmental stability, and passivates surface trap states, preserving the main core physical properties. To prove the great potential for optoelectrical applications, we fabricate a photoconductor using PbSe/PbS NPLs. The device demonstrates enhanced conductivity and responsivity with fast rise and fall times, resulting in a 13 kHz bandwidth. The carrier transport was investigated with the field effect transistor method, showing p-type conductivity with charge mobility of 1.26 × 10−2 cm2·V−1·s−1.

Anion-assisted cation doping in a nonpolar solvent at room temperature has been proposed as a universal method to create multiple-band emitting lead halide perovskite nanostructures.

Near-IR semiconductor colloidal nanoplatelets (NPs) are a new and promising class of materials for the development of photodetectors because they can effectively absorb visible and infrared optical radiation. In this work, we study the photoconductivity of HgTe colloidal nanoplatelets with ligands of 1,2-ethanedithiol and tetrabutylammonium iodide. It has been shown that the choice of ligands is a key factor in achieving high operational characteristics. It has been shown that the photoconductivity sensitivity reaches 0.995 and the specific detectivity reaches 1.2·10 9 J Jones when 1,2-ethadithiol is used as ligands. Keywords: Near-IR, photodetectors, specific detectivity, EDT, TBAI.

Carbon dots (CDs) with an emission in the near infrared spectral region are attractive due to their promising applications in bio-related areas, while their fabrication still remains a challenging task. Herein, we developed a template-assisted method using porous silica microspheres for the formation of CDs with optical transitions in the near infrared. Two organic dyes, Rhodamine 6G and IR1061 with emission in the yellow and near infrared spectral regions, respectively, were used as precursors for CDs. Correlation of morphology and chemical composition with optical properties of obtained CDs revealed the origin of their emission, which is related to the CDs' core optical transitions and dye-derivatives within CDs. By varying annealing temperature, different kinds of optical centers as derivatives of organic dyes are formed in the microsphere's pores. The template-assisted method allows us to synthesize CDs with an emission peaked at 1085 nm and photoluminescence quantum yield of 0.2%, which is the highest value reported so far for CDs emitting at wavelengths longer than 1050 nm.

Semiconductor 2D nanostructures are a new platform for the creation of modern optoelectronic devices. Layered 2D PbSe-MoS2 nanostructures with efficient photoinduced charge transfer from PbSe nanoplatelets (NPLs) to MoS2 were created. When PbSe NPLs with short organic ligands are deposited onto a thin layer of MoS2 NPLs, a decrease in their photoluminescence intensity and a decrease in the average photoluminescence lifetime are observed. When a layered 2D PbSe-MoS2 nanostructure is illuminated with IR radiation, a photocurrent appears, which indicates the contribution of PbSe NPLs to the electrical response of the system. Ultrathin layers of transition metal dichalcogenides sensitized with nanostructures based on lead chalcogenides can be used in photodetectors with a spectral sensitivity region extended to the near-IR range. Keywords: nanoplatelets, transition metal dichalcogenides, charge transfer, near infrared region.

Semiconductor 2D nanostructures are a new platform for the creation of modern optoelectronic devices. Layered 2D PbSe-MoS2 nanostructures with efficient photoinduced charge transfer from PbSe nanoplatelets (NPLs) to MoS2 were created. When PbSe NPLs with short organic ligands are deposited onto a thin layer of MoS2 NPLs, a decrease in their photoluminescence intensity and a decrease in the average photoluminescence lifetime are observed. When a layered 2D PbSe-MoS2 nanostructure is illuminated with IR radiation, a photocurrent appears, which indicates the contribution of PbSe NPLs to the electrical response of the system. Ultrathin layers of transition metal dichalcogenides sensitized with nanostructures based on lead chalcogenides can be used in photodetectors with a spectral sensitivity region extended to the near-IR range.

Doping the semiconductor nanocrystals is one of the most effective ways to obtain unique materials suitable for high-performance next-generation optoelectronic devices. In this study, we demonstrate a novel nanomaterial for the near-infrared spectral region. To do this, we developed a partial cation exchange reaction on the HgTe nanoplatelets, substituting Hg cations with Pb cations. Under the optimized reaction conditions and Pb precursor ratio, a photoluminescence band shifts to ~1100 nm with a quantum yield of 22%. Based on steady-state and transient optical spectroscopies, we suggest a model of photoexcitation relaxation in the HgTe:Pb nanoplatelets. We also demonstrate that the thin films of doped nanoplatelets possess superior electric properties compared to their pristine counterparts. These findings show that Pb-doped HgTe nanoplatelets are new perspective material for application in both light-emitting and light-detection devices operating in the near-infrared spectral region.

Lead halide perovskite nanoplatelets (NPls) attract significant attention due to their exceptional and tunable optical properties. Doping is a versatile strategy for modifying and improving the optical properties of colloidal nanostructures. However, the protocols for B-site doping have been rarely reported for 2D perovskite NPls. In this work, we investigated the post-synthetic treatment of CsPbBr3 NPls with different Cd2+ sources. We show that the interplay between Cd2+ precursor, NPl concentrations, and ligands determines the kinetics of the doping process. Optimization of the treatment allows for the boosting of linear and nonlinear optical properties of CsPbBr3 NPls via doping or/and surface passivation. At a moderate doping level, both the photoluminescence quantum yield and two-photon absorption cross section increase dramatically. The developed protocols of post-synthetic treatment with Cd2+ facilitate further utilization of perovskite NPls in nonlinear optics, photonics, and lightning.

We report the creation of layered 2D PbSe-MoS2 nanostructures which demostrate efficient electron transfer from PbSe nanoplatelet to MoS2 nanoplatelet. Charge transfer was confirmed by means of Results of the work show that ultrathin layers of transition metal dichalcogenides sensitized by 2D lead chalcogenide nanostructures can be effectively used in photodetectors with a spectral sensitivity extended to the near-IR range.

Metal halide perovskite nanocrystals (NCs) attract much attention for light-emitting applications due to their exceptional optical properties. More recently, perovskite NCs have begun to be considered a promising material for nonlinear optical applications. Numerous strategies have recently been developed to improve the properties of metal halide perovskite NCs. Among them, B-site doping is one of the most promising ways to enhance their brightness and stability. However, there is a lack of study of the influence of B-site doping on the nonlinear optical properties of inorganic perovskite NCs. Here, we demonstrate that Cd2+ doping simultaneously improves both the linear (higher photoluminescence quantum yield, larger exciton binding energy, reduced trap states density, and faster radiative recombination) and nonlinear (higher two- and three-photon absorption cross-sections) optical properties of CsPbBr3 NCs. Cd2+ doping results in a two-photon absorption cross-section, reaching 2.6 × 106 Goeppert-Mayer (GM), which is among the highest reported for CsPbBr3 NCs.

Near-IR semiconductor colloidal nanoplatelets (NPs) are a new and promising class of materials for the development of photodetectors because they can effectively absorb visible and infrared optical radiation. In this work, we study the photoconductivity of HgTe colloidal nanoplatelets with ligands of 1,2-ethanedithiol and tetrabutylammonium iodide. It has been shown that the choice of ligands is a key factor in achieving high operational characteristics. It has been shown that the photoconductivity sensitivity reaches 0.995 and the specific detectivity reaches 1.2×109 Jones when 1,2-ethadithiol is used as ligands.

Carbon dots have been modified using UV irradiation (405 nm laser light). UV irradiation of carbon dots has led to various changes in optical properties, which in turn means photomodification of the carbon dots surface. With an increase in light transmission, we have obtained the increasing intensity of photoluminescence and a blue shift by the laser irradiation of the carbon dots. The proposed method can help to adapt and improve the optical properties of carbon dots and can be used in applications, for example, in the optical encryption field.

The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si (111) substrates, was investigated. A significant dependence of the photoluminescence (PL) dynamics of the InAsP insertions on the ligand type was shown, which was associated with the changes in the excitation translation channels in the heterostructure. This change was caused by a different interaction of the ligand shells with the surface of InP NWs, which led to the formation of different interfacial low-energy states at the NW-ligand boundary, such as surface-localized antibonding orbitals and hybridized states that were energetically close to the radiating state and participate in the transfer of excitation. It was shown that the quenching of excited states associated with the capture of excitation to interfacial low-energy traps was compensated by the increasing role of the "reverse transfer" mechanism. As a result, the effectiveness of TOPO-CdSe/ZnS QDs as a novel surface passivation coating was demonstrated.

Photophysical properties of hybrid structures based on CdSe/ZnS quantum dots (QDs) and tetraphenylporphyrin (TPP) molecules have been studied. The hybrid structures are characterized by higher singlet oxygen (SO) generation compared to free TPP molecules due to high intracomplex Forster Resonance Energy Transfer (FRET) efficiency and saving TPP in the monomeric form in the hybrid structures. We show that all energy transferred from QDs to TPP is fully used to generate singlet oxygen since there are no new nonradiative channels in the structures. We believe that our result will stimulate renewed interest in QD based structures with photosensitizers as theranostics agents.

The luminescence photodynamics of an array of InP/InAsP/InP nanowires formed via molecular beam epitaxy onto a Si(III) substrate is investigated in this work. Using several kinetic models, the experimental data acquired by a 633-nm room-temperature laser excitation have been analyzed. The kinetics of luminescence decay of the InAsP nanoinsert is shown to be best described in the context of the model of contact quenching. The total time of decay of the excited state (the radiative lifetime) of the InAsP nanoinsert is estimated to be τ ~ 40 ns. The reasons of unexpectedly long duration of the excitation transfer from InP are discussed as well.

Semiconductor colloidal nanoplatelets (NPLs) are a promising new class of nanostructures that can bring much impact on lightning technologies, light-emitting diodes (LED), and laser fabrication. Indeed, great progress has been made in optimizing the optical properties of the NPLs for the visible spectral range, which has already made the implementation of a number of effective devices on their basis possible. To date, state-of-the-art near-infrared (NIR)-emitting NPLs are significantly inferior to their visible-range counterparts, although it would be fair to say that they received significantly less research attention so far. In this study, we report a comprehensive analysis of steady-state and time-dependent photoluminescence (PL) properties of four monolayered (ML) PbSe NPLs. The PL measurements are performed in a temperature range of 78–300 K, and their results are compared to those obtained for CdSe NPLs and PbSe quantum dots (QDs). We show that multiple emissive states, both band-edge and trap-related, are responsible for the formation of the NPLs’ PL band. We demonstrate that the widening of the PL band is caused by the inhomogeneous broadening rather than homogeneous one, and analyze the possible contributions to PL broadening.