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Solution-processed perovskite solar cells (PSCs) have demonstrated a tremendous growth in power conversion efficiency (PCE). A high-quality, defect-free perovskite-based active layer is a key point to enhance PSC performance. Introduction of additives and interlayers have proved to be an effective tool to passivate surface defects, control crystal growth, and improve PSC stability. Antisolvent engineering has emerged recently as a new approach, which aims to adjust perovskite layer properties and enhance the PCE and stability of PSC devices. Here, we demonstrate that carbon dots (CDs) may serve as a prospective additive for antisolvent engineering. Nitrogen-rich amphiphilic CDs were synthesized from amines by a solvothermal method and used as an additive to chlorobenzene for a perovskite layer fabrication. The interaction between perovskite and functional groups in CDs promotes improved crystallization of an active perovskite layer and defects passivation, bringing higher PSCs efficiency, stability, and suppressed hysteresis. Under optimized CD concentration, the maximum PCE increased by 34% due to the improved short-circuit current and fill factor, and the device maintains 87% of its initial efficiency after 6 d of storage under ambient conditions., (© 2024 IOP Publishing Ltd.)

Nonlinear absorption of metal-halide perovskite nanocrystals (NCs) makes them an ideal candidate for applications which require multiphoton-excited photoluminescence. By doping perovskite NCs with lanthanides, their emission can be extended into the near-infrared (NIR) spectral region. We demonstrate how the combination of Yb 3+ doping and bandgap engineering of cesium lead halide perovskite NCs performed by anion exchange (from Cl - to Br - ) leads to efficient and tunable emitters that operate under two-photon excitation in the NIR spectral region. By optimizing the anion composition, Yb 3+ -doped CsPbCl x Br 3- x NCs exhibited high values of two-photon absorption cross-section reaching 2.3 × 10 5 GM, and displayed dual-band emission located both in the visible (407-493 nm) and NIR (985 nm). With a view of practical applications of bio-visualisation in the NIR spectral range, these NCs were embedded into silica microspheres which were further wrapped with amphiphilic polymer shells to ensure their water-compatibility. The resulting microspheres with embedded NCs could be easily dispersed in both toluene and water, while still exhibiting a dual-band emission in visible and NIR under both one- and two-photon excitation conditions.

Recently, increasing attention of researchers in the field of membrane technology has been paid to the development of membranes based on biopolymers. One of the well-proven polymers for the development of porous membranes is cellulose acetate (CA). This paper is devoted to the study of the influence of different parameters on ultrafiltration CA membrane formation and their transport properties, such as the variation in coagulation bath temperature, membrane shrinkage (post-treatment at 80 °C), introduction to casting CA solution of polymers (polyethylene glycol (PEG), polysulfone (PS), and Pluronic F127 (PL)) and carbon nanoparticles (SWCNTs, MWCNTs, GO, and C 60 ). The structural and physicochemical properties of developed membranes were studied by scanning electron and atomic force microscopies, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. The transport properties of developed CA-based membranes were evaluated in ultrafiltration of bovine serum albumin (BSA), dextran 110 and PVP K-90. All developed membranes rejected 90% compounds with a molecular weight from ~270,000 g/mol. It was shown that the combination of modifications (addition of PEG, PS, PL, PS-PL, and 0.5 wt% C 60 ) led to an increase in the fluxes and BSA rejection coefficients with slight decrease in the flux recovery ratio. These changes were due to an increased macrovoid number, formation of a more open porous structure and/or thinner top selective, and decreased surface roughness and hydrophobization during C 60 modification of blend membranes. Optimal transport properties were found for CA-PEG+C 60 (the highest water-394 L/(m 2 h) and BSA-212 L/(m 2 h) fluxes) and CA-PS+C 60 (maximal rejection coefficient of BSA-59%) membranes.

Silicon carbide (SiC) is a wide-band gap semiconductor that exceeds other semiconducting materials (except diamond) in electrical, mechanical, chemical, and radiation stability. In this paper, we report a novel approach to fabrication of SiC nano films on a Si substrate, which is based on the endotaxial growth of a SiC crystalline phase in a graphite-like carbon (GLC) matrix. GLC films were formed by carbonization of rigid rod polyimide (PI) Langmuir-Blodgett (LB) films on a Si substrate at 1000 °C in vacuum. After rapid thermal annealing of GLC films at 1100 °C and 1200 °C, new types of heterostructures SiC(10 nm)/GLC(20 nm)/Si(111) and SiC(20 nm)/GLC(15 nm)/SiC(10 nm)/Si(111) were obtained. The SiC top layer was formed due to the Si-containing gas phase present above the surface of GLC film. An advantage of the proposed method of endotaxy is that the SiC crystalline phase is formed within the volume of the GLC film of a thickness predetermined by using PI LB films with different numbers of monolayers for carbonization. This approach allows growing SiC layers close to the 2D state, which is promising for optoelectronics, photovoltaics, spintronics., (© 2024 IOP Publishing Ltd.)

Although chirality plays an important role in the natural world, it has also attracted much scientific attention in nanotechnology, in particular, spintronics and bioapplications. Chiral carbon dots (CDs) are promising nanoparticles for sensing and bioimaging since they are biocompatible, ecofriendly, and free from toxic elements. Herein, green and red emissive chiral CDs are fabricated via surface modification treatment of achiral CDs at room temperature. After modification with l-cysteine molecules, the treated CDs demonstrate an intense chiral signal in the region of 200-300 nm with a dissymmetry factor up to 2.3 × 10 -4 and high photoluminescence quantum yields of 19% and 15% for green and red emission bands, respectively. These CDs preserve their chiral signal in different ion systems, such as those with pH changes or in the presence of metal ions, along with remarkably low cytotoxicity, making them potential candidates for use as photoluminescent labels for biological objects.

Redox-responsive drug delivery systems present a promising avenue for drug delivery due to their ability to leverage the unique redox environment within tumor cells. In this work, we describe a facile and cost-effective one-pot synthesis method for a redox-responsive delivery system based on novel trithiocyanuric acid (TTCA) nanoparticles (NPs). We conduct a thorough investigation of the impact of various synthesis parameters on the morphology, stability, and loading capacity of these NPs. The great drug delivery potential of the system is further demonstrated in vitro and in vivo by using doxorubicin as a model drug. The developed TTCA-PEG NPs show great drug delivery efficiency with minimal toxicity on their own both in vivo and in vitro . The simplicity of this synthesis, along with the promising characteristics of TTCA-PEG NPs, paves the way for new opportunities in the further development of redox-responsive drug delivery systems based on TTCA.

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 cm 2 ·V -1 ·s -1 .

Chemically synthesized carbon dots (CDs) have attracted a lot of attention as an eco-friendly and cost-efficient light-emitting material, and functionalization of CD surfaces with additives of different natures is a useful way to control their properties. In this study, we show how a post-synthetic treatment of CDs with citric acid, benzoic acid, urea and o -phenylenediamine changes their chemical composition and optical properties. In particular, it results in the formation of carboxyl/imide/carbonyl groups at the CD surface, leading to the appearance of additional blue (or for CDs treated with phenylenediamine, blue and green) emissive optical centers on top of the remaining emission from the original CDs. Most importantly, the increased oxidation degree alongside a decreased relative amount of carbon and nitrogen in such treated CDs decreases their highest occupied molecular orbital (HOMO) energy level by up to 0.9 eV (the maximal value was observed for CDs treated with o -phenylenediamine). Moreover, the Fermi energy level shifted above the lowest unoccupied molecular orbital (LUMO) energy level for some of the treated CD samples. Thus, the energy structure of CDs can be tuned and optimized for further applications through the functionalization of their surface with organic additives.

Carbon dots can be used for the fabrication of colloidal multi-purpose complexes for sensing and bio-visualization due to their easy and scalable synthesis, control of their spectral responses over a wide spectral range, and possibility of surface functionalization to meet the application task. Here, we developed a chemical protocol of colloidal complex formation via covalent bonding between carbon dots and plasmonic metal nanoparticles in order to influence and improve their fluorescence. We demonstrate how interactions between carbon dots and metal nanoparticles in the formed complexes, and thus their optical responses, depend on the type of bonds between particles, the architecture of the complexes, and the degree of overlapping of absorption and emission of carbon dots with the plasmon resonance of metals. For the most optimized architecture, emission enhancement reaching up to 5.4- and 4.9-fold for complexes with silver and gold nanoparticles has been achieved, respectively. Our study expands the toolkit of functional materials based on carbon dots for applications in photonics and biomedicine to photonics.

At present research, we highlight ultrasonic treatment as a new way to create materials with a gradient change of chemical or physical properties. We demonstrate the possibility to fabricate novel materials with biocide activity based on simple and cheap Cu-Zn alloy. In this research, we propose a green preparative technique for the sonication of an alloy in an alkali solution. The method leads to a significant visual change and differentiation of particles into three different fractions. Due to the chemical micro gradients in media near the solid surface under intensive sonication, fast formation of specific functional groups occurs on the particles' surface. The particles were studied X-ray diffraction analysis (XRD) analysis, the field-emission scanning electron microscope (SEM) as well as electron backscatter diffraction (EBSD) mode, X-ray Photoelectron Spectroscopy (XPS), the differential pulse anodic stripping voltammetry (DPASV) technique. A strong correlation of both methods proves a redistribution of copper ions from Fraction I to Fraction III that influence for the antibacterial properties of the prepared material. The different biocidal activity was demonstrated for each separated Fraction that could be related to their different phase content and ability to release the different types of ions., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

The influence of the bottom TiO 2 interfacial layer grown by atomic layer deposition on the ferroelectric properties of the TiN/Hf 0.5 Zr 0.5 O 2 /TiN capacitors is systematically investigated. We show that the integration of the TiO 2 layer leads to an increase in the polar orthorhombic phase content in the Hf 0.5 Zr 0.5 O 2 film. In addition, the crystalline structure of the Hf 0.5 Zr 0.5 O 2 film is highly dependent on the thickness of the TiO 2 inset, with monoclinic phase stabilization after the increase of TiO 2 thickness. Special attention in this work is given to the key reliability parameters-retention and endurance. We demonstrate that the integration of the TiO 2 inset induces valuable retention improvement. Using a novel approach to the depolarization measurements, we show that the depolarization contribution to the retention loss is insignificant, which leaves the imprint effect as the root of the retention loss in TiN/TiO 2 /Hf 0.5 Zr 0.5 O 2 /TiN devices. We believe that the integration of the insulator interfacial layer suppresses the scavenging effect from the bottom TiN electrode, leading to a decrease in the oxygen vacancy content in the Hf 0.5 Zr 0.5 O 2 film, which is the main reason for imprint mitigation. At the same time, although the observed retention improvement is very promising for the upcoming technological integration, the field cycling testing revealed the endurance limitations linked to the phase transitions in the TiO 2 layer and the rise of the effective electric field applied to the Hf 0.5 Zr 0.5 O 2 film., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

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 CsPbBr 3 NPls with different Cd 2+ sources. We show that the interplay between Cd 2+ 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 CsPbBr 3 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 Cd 2+ facilitate further utilization of perovskite NPls in nonlinear optics, photonics, and lightning.

Today, the development of nanomaterials with sensing properties attracts much scientific interest because of the demand for low-cost nontoxic colloidal nanoprobes with high sensitivity and selectivity for various biomedical and environment-related applications. Carbon dots (CDs) are promising candidates for these applications as they demonstrate unique optical properties with intense emissions, biocompatibility, and ease of fabrication. Herein, we developed synthesis protocols to obtain CDs based on o-phenylenediamine with a variety of optical responses depending on additional precursors and changes in the reaction media. The obtained CDs are N-doped (N,S-doped in case of thiourea addition) less than 10 nm spherical particles with emissions observed in the 300−600 nm spectral region depending on their chemical composition. These CDs may act simultaneously as absorptive/fluorescent sensing probes for solvent polarity with ∆S/∆ENT up to 85, for ∆ENT from 0.099 to 1.0 and for pH values in the range of 3.0−8.0, thus opening an opportunity to check the pH in non-pure water or a mixture of solvents. Moreover, CDs preserve their optical properties when embedded in cellulose strips that can be used as sensing probes for fast and easy pH checks. We believe that the resulting dual-purpose sensing nano probes based on CDs will have high demand in various sensing applications.

Despite the great potential of Hf 0.5 Zr 0.5 O 2 (HZO) ferroelectrics, reliability issues, such as wake-up, fatigue, endurance limitations, imprint and retention loss, impede the implementation of HZO to nonvolatile memory devices. Herein, a study of the reliability properties in HZO-based stacks with the conventional TiN top electrode and Ru electrode, which is considered a promising alternative to TiN, is performed. An attempt to distinguish the mechanisms underlying the wake-up, fatigue and retention loss in both kinds of stacks is undertaken. Overall, both stacks show pronounced wake-up and retention loss. Moreover, the fatigue and retention loss were found to be worsened by Ru implementation. The huge fatigue was suggested to be because Ru does not protect HZO against oxygen vacancies generation during prolonged cycling. The vacancies generated in the presence of Ru are most likely deeper traps, as compared to the traps formed at the interface with the TiN electrode. Implementing the new procedure, which can separate the depolarization-caused retention loss from the imprint-caused one, reveal a rise in the depolarization contribution with Ru implementation, accompanied by the maintenance of similarly high imprint, as in the case with the TiN electrode. Results show that the mechanisms behind the reliability issues in HZO-based capacitors are very electrode dependent and simple approaches to replacing the TiN electrode with the one providing, for example, just higher remnant polarization or lower leakages, become irrelevant on closer examination.

Carbon dots (CDs) are light-emitting nanoparticles that show great promise for applications in biology and medicine due to the ease of fabrication, biocompatibility, and attractive optical properties. Optical chirality, on the other hand, is an intrinsic feature inherent in many objects in nature, and it can play an important role in the formation of artificial complexes based on CDs that are implemented for enantiomer recognition, site-specific bonding, etc. We employed a one-step hydrothermal synthesis to produce chiral CDs from the commonly used precursors citric acid and ethylenediamine together with a set of different chiral precursors, namely, L-isomers of cysteine, glutathione, phenylglycine, and tryptophan. The resulting CDs consisted of O,N-doped (and also S-doped, in some cases) carbonized cores with surfaces rich in amide and hydroxyl groups; they exhibited high photoluminescence quantum yields reaching 57%, chiral optical signals in the UV and visible spectral regions, and two-photon absorption. Chiral signals of CDs were rather complex and originated from a combination of the chiral precursors attached to the CD surface, hybridization of lower-energy levels of chiral chromophores formed within CDs, and intrinsic chirality of the CD cores. Using DFT analysis, we showed how incorporation of the chiral precursors at the optical centers induced a strong response in their circular dichroism spectra. The optical characteristics of these CDs, which can easily be dispersed in solvents of different polarities, remained stable during pH changes in the environment and after UV exposure for more than 400 min, which opens a wide range of bio-applications., (© 2022. The Author(s).)

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.

The development of new strategies for the mass synthesis of SiC nanocrystals with high structure perfection and narrow particle size distribution remains in demand for high-tech applications. In this work, the size-controllable synthesis of the SiC 3C polytype, free of sp 2 carbon, with high structure quality nanocrystals, was realized for the first time by the pyrolysis of organosilane C 12 H 36 Si 6 at 8 GPa and temperatures up to 2000 °C. It is shown that the average particle size can be monotonically changed from ~2 nm to ~500 nm by increasing the synthesis temperature from 800 °C to 1400 °C. At higher temperatures, further enlargement of the crystals is impeded, which is consistent with the recrystallization mechanism driven by a decrease in the surface energy of the particles. The optical properties investigated by IR transmission spectroscopy, Raman scattering, and low-temperature photoluminescence provided information about the concentration and distribution of carriers in nanoparticles, as well as the dominant type of internal point defects. It is shown that changing the growth modes in combination with heat treatment enables control over not only the average crystal size, but also the LO phonon-plasmon coupled modes in the crystals, which is of interest for applications related to IR photonics.

Since chirality is one of the phenomena often occurring in nature, optically active chiral compounds are important for applications in the fields of biology, pharmacology, and medicine. With this in mind, chiral carbon dots (CDs), which are eco-friendly and easy-to-obtain light-emissive nanoparticles, offer great potential for sensing, bioimaging, enantioselective synthesis, and development of emitters of circularly polarized light. Herein, chiral CDs have been produced via two synthetic approaches using a chiral amino acid precursor l/d-cysteine: (i) surface modification treatment of achiral CDs at room temperature and (ii) one-pot carbonization in the presence of chiral precursor. The chiral signal in the absorption spectra of synthesized CDs originates not only from the chiral precursor but from the optical transitions attributed to the core and surface states of CDs. The use of chiral amino acid molecules in the CD synthesis through carbonization results in a substantial (up to 8 times) increase in their emission quantum yield. Moreover, the synthesized CDs show two-photon absorption which is an attractive feature for their potential bioimaging and sensing applications.

The optical properties of chemically synthesized carbon dots (CDs) can be widely tuned via doping and surface modification with heteroatoms such as nitrogen, which results in a range of potential applications. Herein, two most commonly used synthesis approaches, namely, solvothermal and microwave-assisted thermal treatments, have been used for the preparation of CDs from phloroglucinol using three different nitrogen containing solvents, namely, ethylenediamine, dimethylformamide, and formamide. Based on the analysis of the morphology and optical properties, we demonstrate the tenability of the CD appearance from amorphous or well-carbonized spherical particles to onion-like ones, which is controlled by solvent polarity, whereas the thermal treatment conditions mostly influence the degree of N-doping and the nature of emissive centers of CDs formed. The findings of this study expand the toolkit of the available CDs with variable morphology and energy structure.

Resistive switching (RS) device behavior is highly dependent on both insulator and electrode material properties. In particular, the bottom electrode (BE) surface morphology can strongly affect RS characteristics. In this work, Ru films with different thicknesses grown on a TiN layer by radical-enhanced atomic layer deposition (REALD) are used as an inert BE in TaO x -based RS structures. The REALD Ru surface roughness is found to increase by more than 1 order of magnitude with the increase in the reaction cycle number. Simultaneously, a wide range of RS parameters, such as switching voltage, resistance both in low and high resistance states, endurance, and so forth, monotonically change. A simplified model is proposed to explain the linkage between RS properties and roughness of the Ru surface. The field distribution was simulated based on the observed surface morphologies, and the resulting conducting filament formation was anticipated based on the local field enhancement. Conductive atomic force microscopy confirmed the theoretical expectations.

Technological applications involving 2D MoS 2 require transfer of chemical vapor deposition (CVD) grown material from its original substrate and subsequent lithographic processes. Inevitably, those steps contaminate the surface of the 2D material with polymeric residues affecting the electronic and optical properties of the MoS 2 . Annealing in forming gas is considered an efficient treatment to partially remove such residues. However, hydrogen also interacts with MoS 2 creating or saturating sulfur vacancies. Sulfur vacancies are known to be at the origin of n-doping evident in the majority of as-grown MoS 2 samples. In this context, investigating the impact of thermal annealing in forming gas on the electronic and optical properties of MoS 2 monolayer is technologically important. In order to address this topic, we have systematically studied the evolution of CVD grown MoS 2 monolayer using Raman spectroscopy, photoluminescence, x-ray photoelectron spectroscopy and transport measurements through a series of thermal annealing in forming gas at temperatures up to 500 °C. Efficient removal of the polymeric residues is demonstrated at temperatures as low as 200 °C. Above this value, carrier density modulation is identified by photoluminescence, x-ray photoelectron spectroscopy and electrical characterization and is correlated to the creation of sulfur vacancies. Finally, the degradation of the MoS 2 single layer is verified with annealing at or above 350 °C through Raman and photocurrent measurements., (© 2020 IOP Publishing Ltd.)

The combination of oxide and heavier chalcogenide layers in thin film photovoltaics suffers limitations associated with oxygen incorporation and sulfur deficiency in the chalcogenide layer or with a chemical incompatibility which results in dewetting issues and defect states at the interface. Here, we establish atomic layer deposition (ALD) as a tool to overcome these limitations. ALD allows one to obtain highly pure Sb 2 S 3 light absorber layers, and we exploit this technique to generate an additional interfacial layer consisting of 1.5 nm ZnS. This ultrathin layer simultaneously resolves dewetting and passivates defect states at the interface. We demonstrate via transient absorption spectroscopy that interfacial electron recombination is one order of magnitude slower at the ZnS-engineered interface than hole recombination at the Sb 2 S 3 /P3HT interface. The comparison of solar cells with and without oxide incorporation in Sb 2 S 3 , with and without the ultrathin ZnS interlayer, and with systematically varied Sb 2 S 3 thickness provides a complete picture of the physical processes at work in the devices., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)