Synthesis Of Nanocrystals Research Articles

Nucleation and Growth of Monodisperse and Monocrystalline Wurtzite CdSe Nanocrystals: Zinc Alkanoates as Neutral Ligands.

Here, we demonstrate that monocrystalline (free of stacking faults) wurtzite CdSe nanocrystals with monodisperse size, shape (dots, rods, or wires), and facet structure are synthesized in both strongly confined and weakly confined size regimes. Considering the unique c-axis of wurtzite CdSe, we introduce a new type of neutral ligand (e.g., zinc-alkanoate ones) to pair with their dominating nonpolar low-index facets. Nucleation of the stacking fault-free wurtzite seeds instead of zinc-blende tetrahedrons is identified as the key step, which is optimized by a set of conditions matching the neutral zinc-alkanoate ligands. In the following growth stage, conditions are much less stringent, although the neutral zinc-alkanoate ligands are still critical in achieving nearly atomically flat facets of those monocrystalline nanocrystals. In the strongly confined size regime, the ensemble photoluminescence (PL) full-width-at-half-maximum (FWHM) of wurtzite CdSe nanocrystals reaches a record low (59 meV). In the weakly confined size regime, dual-peak PL caused by thermal population is observed. Monodisperse and monocrystalline wurtzite CdSe nanocrystals show distinctively size-dependent optical properties, in comparison with their zinc-blende counterparts. Results here suggest that the atomically precise synthesis of colloidal semiconductor nanocrystals is feasible, implying an advanced class of nanomaterials for exploring various optical and optoelectronic applications.

Disorder-order transition-induced unusual bandgap bowing effect of tin-lead mixed perovskites.

Owing to the predominant merit of tunable bandgaps, tin-lead mixed perovskites have shown great potentials in realizing near-infrared optoelectronics and are receiving increasing attention. However, despite the merit, there is still a lack of fundamental understanding of the bandgap variation as a function of Sn/Pb ratio, mainly because the films are easy to segregate in terms of both composition and phase. Here, we report a fully stoichiometric synthesis of monocrystalline FAPb1-xSnxI3 nanocrystals as well as their atomic-scale imaging. On the basis of the systematic measurements of the monocrystalline materials, strain and Coulomb interaction-induced atomic ordering was revealed to be responsible for the unusual discontinuous bandgap jumping near x = 0.5 from the expected bowing effect. As a result, both FAPb0.6Sn0.4I3 and FAPb0.4Sn0.6I3 have the lowest bandgaps of around 1.27 electron volts, while that of FAPb0.5Sn0.5I3 is 1.33 electron volts. Correspondingly, their based light-emitting diodes can emit infrared lights with the wavelengths reaching 930 nanometers.

Band Gap Tuning in Mercaptoacetic Acid Capped Mixed Halides Perovskites and Effect of Solvents on Their Fluorescence Dynamics: A Potential Sensor for Polarity.

From synthesis to application, there are always certain interactions between the polar solvents and perovskite nanocrystals (NCs). To explain the effect of solvent polarity especially on the photoluminescence (PL) properties of NCs is highly desirable, especially for sensing applications. Herein We have synthesized the methylammonium lead mixed halides (MAPbCl3 - nBrn, where n = 0, 0.5, 1, 1.5) perovskite nanocrystals (NCs) at room temperature by using ligand-assisted re-precipitation (LARP) method, by employing mercaptoacetic acid (MAA) as a capping ligand. Different techniques have been employed to get information regarding the structural and optical properties of the synthesized material. Powder X-ray diffraction (PXRD) confirms the orthorhombic crystal structure of the MAPbCl3 - nBrn perovskite NCs. FT-IR (Fourier-transform infrared) analysis confirms the successful interaction of capping ligands with NCs. By increasing MABr precursor concentration during the synthesis of perovskite NCs, a red shift in the UV-Vis absorption and PL spectra has been observed. The steady-state photoluminescence (SSPL) and time-resolved photoluminescence (TRPL) techniques suggested that these perovskite NCs exhibit tunable PL relative to the substitution of Cl with Br in NCs. The comparative PL studies in non-polar (benzene) and polar (tetrahydrofuran (THF)) revealed that the PL properties are highly sensitive and selective toward the solvent chosen. All synthesized NCs possess longer PL lifetime in benzene than in THF. Relatively, perovskite NCs synthesized with 0.166 mM MABr precursor concentration show a longer PL lifetime (6.51 ns in benzene) as compared to other MABr concentrations. These studies not only propose that by controlling precursors concentration, one can synthesize NCs having tunable PL with a longer radiative PL lifetime, but also provide a comparative understanding of PL dynamics of NCs in different solvents.

Elemental Reaction Steps between Elemental Sulfur and Metal Carboxylate during the Synthesis of Metal Sulfide Nanocrystals in Hydrocarbon Solvents

Elemental Reaction Steps between Elemental Sulfur and Metal Carboxylate during the Synthesis of Metal Sulfide Nanocrystals in Hydrocarbon Solvents

Dual-drive acoustic micromixer for rapid nucleation and ultrafast growth of perovskite nanoparticles.

All-inorganic cesium lead halide perovskites have garnered significant attention owing to their favorable optical properties. Microfluidics-based acoustic mixers are capable of achieving rapid nucleation and ultrafast growth kinetics. Nevertheless, conventional acoustic mixers rely on the response of microstructures to the acoustic field for mixing fluids, the majority of these disturbances occur in the central region of the channel, with minimal impact on the fluid within the side walls. This paper proposes a novel acoustic mixer that combines the effects of sharp corners and bubbles in response to the acoustic field, thereby producing effective disturbance of the fluid throughout the channel. The combined effect enables the micromixer to achieve complete mixing at different inlet flow ratios with mixing times as low as 5 ms. The superiority of acoustic mixers in controlling the nanocrystal formation stage was further validated through the synthesis of chalcogenide nanocrystals using the LARP method. The millisecond mixing time facilitated the rapid formation of nanocrystals and their subsequent rapid growth. The results demonstrate that the green luminescence intensity at 520 nm of the samples synthesized using the acoustic micromixer is 118% higher than that of the samples synthesized using an intermittent reactor. The novel micromixer broadens the range of applications and offers a promising avenue for the large-scale continuous synthesis of high-quality lead-halide perovskite nanocrystals (NCs).

Passivation, phase, and morphology control of CdS nanocrystals probed using fluorinated aromatic amines and solid-state NMR spectroscopy.

Nanocrystals are widely explored for a range of medical, imaging, sensing, and energy conversion applications. CdS nanocrystals have been reported as excellent photocatalysts, with thin film CdS also highly important in photovoltaic devices. To optimise properties of nanocrystals, control over phase, facet, and morphology are vital. Here, CdS nanocrystals were synthesised by the solvothermal decomposition of a Cd xanthate single source precursor. To attempt to control CdS nanocrystal surfaces and morphology, the solvent used in the nanocrystal synthesis was altered from pure trioctylphosphine oxide (TOPO) to a mixed TOPO : fluorinated aromatic amine (3-fluorobenzyl amine (3-FlBzAm) or 3-fluoroaniline (3-FlAn)), where 19F provides a sensitive NMR-active surface probe. Powder X-ray diffraction found that the CdS nanocrystals synthesised from TOPO : 3-FlAn solvent mixtures were predominantly cubic whilst the TOPO : 3-FlBzAm synthesised nanocrystals were predominantly hexagonal. Raman spectroscopy identified hexagonal CdS in all samples. Solid-state NMR of 113Cd, 19F, 13C, and 1H was employed to investigate the local Cd environments, surface ligands, and ligand interactions. This showed there was a mixture of CdS phases present in all samples and that surfaces were capped with TOPO : fluorinated aromatic amine mixtures, but also that there was a stronger binding affinity of 3-FlBzAm compared with 3-FlAn on the CdS surface, which likely impacts growth mechanisms. This work highlights that fluorinated aromatic amines can be used to probe NC surfaces and also control NC properties through their influence during NC growth.

Influence of Lewis basicity on the S2- induced synthesis of 0D Cs4PbBr6 hexagonal nanocrystals and its implications for optoelectronics.

Perovskite nanocrystals (NCs) with their excellent optical and semiconductor properties have emerged as primary candidates for optoelectronic applications. While extensive research has been conducted on the 3D perovskite phase, the zero-dimensional (0D) form of this promising material in the NC format remains elusive. In this paper, a new synthesis strategy is proposed. According to the Hard-Soft Acid-Base (HSAB) principle, a novel class of hexagonal semiconductor nanocrystals (Cs4PbBr6 HNCs) derived from 0D perovskite Cs4PbBr6 is synthesized by doping an appropriate amount of PbS precursor solution into bromide. These Cs4PbBr6 HNCs are characterized and compared in detail to CsPbBr3 cubic nanocrystals (CsPbBr3 CNCs) as a reference. The Cs4PbBr6 HNCs exhibit significantly enhanced photoluminescence (PL) compared to CsPbBr3 CNCs, with an external quantum efficiency (EQE) reaching 24.19%. Furthermore, they demonstrate superior UV stability compared to CsPbBr3 CNCs. Comparative analysis of their physical properties and morphology, along with detailed investigations into band structures, density of states, and lifetime decay through DFT calculations, is provided. The practical application potential is validated by encapsulating them into backlight LEDs, covering 121.5% and 90.7% of the color gamut of NTSC and Rec. Our research provides comprehensive insights into the photophysical properties of inorganic halide perovskite nanomaterials and explores their potential in the field of optoelectronics.

Steric stabilization of colloidal UiO-66 nanocrystals with oleylammonium octadecylphosphonate.

We report the synthesis and characterization of octahedral UiO-66 nanocrystals (d = 17-25 nm) terminated with amine, oleate, and octadecylphosphonate ligands. Acetate capped UiO-66 nanocrystals were dispersed in toluene using oleic acid and oleylamine. Ligand exchange with octadecylphosphonic acid produces ammonium octadecylphosphonate terminated nanocrystals with coverages of 2.6-3.2 chains per nm2 that stabilize colloidal dispersions in nonpolar solvents. Liquid phase 1H and 31P nuclear magnetic resonance (NMR) spectra of the linkers and surface ligands display line shapes that are broadened by slow tumbling of the nanocrystals. Octadecylphosphonate functionalized MOFs have up to ∼30% carbon dioxide absorption capacities compared to bulk UiO-66 after correcting for the ligand mass. These results illustrate the intriguing perspective that MOF nanocrystals can be characterized and manipulated like a macromolecular complex and represent an important milestone in the nascent field of MOF surface science.

Synthesis of shape-tunable PbZrTiO3 nanocrystals with lattice variations for piezoelectric energy harvesting and human motion detection.

PbZr0.7Ti0.3O3 cubes with tunable sizes and cuboids have been hydrothermally synthesized. PbZrTiO3 cubes with three different Zr : Ti atomic percentages were also prepared. Analysis of synchrotron X-ray diffraction (XRD) patterns reveals the presence of two lattice components for these samples. Fast Fourier Transform (FFT) processing of high-resolution transmission electron microscopy (HR-TEM) images shows discernible lattice spot differences between the inner bulk and surface layer region for a PbZr0.7Ti0.3O3 cube, while a cuboid has distinct lattice spot deviations. The lattice variations yield different dielectric constant numbers for these two samples, despite being bound by the same crystal faces. The PbZrTiO3 crystals give size- and composition-dependent band gaps. Cuboids show notably larger piezoelectric and ferroelectric responses than cubes. Piezoelectric nanogenerators (PENGs) containing 30 wt% cuboids produce the highest open-circuit voltage of 20.36 V and short-circuit current of 2300 nA. The PENGs harvest energy through bending/releasing cycles to power devices and show photothermal pyroelectric activity. Moreover, a single 30 wt% cuboid PENG device integrated into a shoe insole can deliver an impressive 96.8% accuracy for human motion detection using a machine learning approach. This work illustrates that considerable lattice variation through crystal shape control is effective in enhancing material properties.

Rational synthesis of MOF-Derived Cobalt-Based binary selenides nanocrystals for electrochemical oxygen evolution reaction

Rational synthesis of MOF-Derived Cobalt-Based binary selenides nanocrystals for electrochemical oxygen evolution reaction

Improvement of UV-photodetector using nanoparticles synthesized by laser ablation in liquid: A review

Laser ablation in liquid (LAL) has emerged over the past decade as a powerful technique for the synthesis of nanomaterials and the fabrication of functional nanostructures. Its ability to tackle diverse challenges in nanotechnology highlights its growing significance. This review systematically evaluates recent advancements in LAL, focusing on the synthesis of nanocrystals and nanostructures. We begin by outlining the fundamental principles of the LAL process, with particular attention to critical laser parameters such as pulse wavelength, duration, pulse width, repetition rate, energy density (fluence) and the characteristics of the ablation medium. The review then explores the mechanisms that govern nanoparticle formation, with an emphasis on the control of particle shape and size during synthesis. Recent studies on LAL-generated nanomaterials, including bismuth oxide (Bi2O3), silver nanoparticles (Ag NPs) and germanium nanoparticles (Ge NPs), are discussed, highlighting their applications in ultraviolet photodetection. Key advantages of LAL, along with its limitations, are critically assessed, and potential strategies for overcoming these challenges are proposed. We conclude by identifying future research directions that will help advance the application of LAL in nanotechnology, particularly in the field of UV photodetectors.

Conversion of Flexible Spin Crossover Metal-Organic Frameworks Macrocrystals to Nanocrystals Using Ultrasound Energy: A Study on Structural Integrity by MicroED and Charge-Transport Properties.

Metal-Organic Frameworks (MOFs) attract attention for their intrinsic porosity, large surface area, and functional versatility. To fully utilize their potential in applications requiring precise control at smaller scales, it is essential to overcome challenges associated with their bulk form. This is particularly difficult for 3D MOFs with spin crossover (SCO) behavior, which undergo a reversible transition between high-spin and low-spin states in response to external stimuli. Maintaining their structural integrity and SCO properties at the nanoscale remains a significant challenge, yet these properties make them ideal candidates for sensors, data storage, and molecular switch applications. This study reports the synthesis of nanocrystals of the well-known SCO MOF [Fe2(H0.67bdt)3]·xH2O (1, x = 0-10, bdt2- = 1,4-benzeneditetrazolate), which exhibits both magnetic and charge transport properties. The nanocrystals are obtained through sonication of macrocrystals, and the preservation of their crystalline structure at the nanoscale is explored using Microcrystal Electron Diffraction (MicroED). A comparison between macro- and nanocrystals highlights the structural integrity and the preservation of charge-transport properties, underlining the potential for further miniaturization of MOFs for advanced technological applications.

Controllable Synthesis of Magnetic 2D Non-Layered Cobalt Sulfide Nanocrystals Using Chemical Vapor Deposition.

Among 2-dimensional (2D) non-layered transition-metal chalcogenides (TMCs), cobalt sulfides are highly interesting because of their diverse structural phases and unique properties. The unique magnetic properties of TMCs have generated significant interest in their potential applications in future spintronic devices. In addition, their high conductivity, large specific surface area, and abundant active sites have attracted attention in the field of catalysis. However, the synthesis of phase-controllable 2D non-layered cobalt sulfide nanocrystals remains challenging. In the present study, a method is reported in which ambient-pressure chemical vapor deposition (APCVD) is used to synthesize 2D non-layered cobalt sulfide nanocrystals on insulating substrates. By controlling the growth temperature, the transition of nanocrystal phases from pyrite-structured CoS2 to cubic Co3S4 and hexagonal CoS is achieved. Magnetotransport studies revealed metallic and ferromagnetic behaviors at temperatures below the Curie temperature for CoS2. In addition, electrical measurements of Co3S4- and CoS-based devices showed conventional metallic behaviors, including temperature- and magnetic field-dependent ordinary Hall effects. These findings demonstrate the potential of APCVD for synthesizing high-quality 2D non-layered cobalt sulfide nanocrystals with controllable phases, paving the way for their application in spintronics and catalysis.

Bidentate Lewis Base Ligand-Mediated Surface Stabilization and Modulation of the Electronic Structure of CsPbBr3 Perovskite Nanocrystals.

The desorption of conventional ligands from the surface of halide perovskite nanocrystals (NCs) often causes their structural instability and deterioration of the optoelectronic properties. To address this challenge, we present an approach of using a bidentate Lewis base ligand, namely, 1,4-bis(diphenylphosphino)butane (DBPP), for the synthesis of CsPbBr3 NCs. The phosphine group of DBPP has a strong interaction with the PbBr2 precursor, forming a highly crystalline intermediate complex during the reaction. In the presence of oleic acid, the uncoordinated phosphine group of DBPP is converted into the phosphonium cation, which strongly binds to the surface bromide of the formed CsPbBr3 NCs through hydrogen bonding. Density functional theory calculations suggest that DBPP can strongly bind to the undercoordinated lead and surface bromide ions of CsPbBr3 NCs through its unprotonated and protonated phosphine groups, respectively. The robust binding of DBPP to the surface of perovskite NCs helps to preserve their structural integrity under various environmental stresses. Moreover, the electron density and energy levels are regulated in DBPP-capped CsPbBr3 NCs by the donation of electrons from the ligands to the NCs, resulting in their improved photocatalytic CO2 reduction performance. Our study highlights the potential of using bidentate ligands to stabilize the surface of perovskite NCs and modulate their optical and electronic properties.

Colloidal AInSe2 (A = K, Rb, Cs) Nanocrystals with Tunable Crystal and Band Structures.

Wide band gap AInSe2 (A = K, Rb, Cs) is an important interlayer material for improving the efficiency of Cu(In,Ga)(S,Se)2 (CIGS) solar cells. Compared to high-vacuum deposition and solid-state synthesis, a less energy-intensive method is of interest for its fabrication. Herein, we present the rapid, low-temperature colloidal synthesis of AInSe2 nanocrystals that opens a pathway for convenient solution processing. The crystal structures and electronic band structures of the nanocrystals were studied, and their particle morphology was found to be dependent on the choice of alkali metal and selenium precursors. Homogeneous solid solution (K,Rb,Cs)InSe2 nanocrystals were synthesized using a mixture of alkali metal precursors. Their compositions, lattice parameters, and band gaps were easily tuned based on the K:Rb:Cs precursor ratio, providing potential for interface engineering of CIGS nanocrystal-based solar cells.

Synthesis of cellulose nanocrystals from jute fibers for reinforcement in bio-nanocomposite films: fabrication and characterization

Synthesis of cellulose nanocrystals from jute fibers for reinforcement in bio-nanocomposite films: fabrication and characterization

Adsorption studies on the removal of lead ions by magnetic cellulose nanocrystals as an eco-friendly nanoadsorbent derived from maize waste

ABSTRACT This study describes the synthesis and characterisation of magnetic cellulose nanocrystal (MCNC) nanocomposite derived from maize stalk as an adsorbent for the adsorptive removal of Pb(II) from wastewater. The FT-IR analysis revealed the presence of C=O, COOH, CH, OH and Fe3O4 stretching frequencies, while the P-XRD diffractograms confirmed the monoclinic type 1 cellulose with 1β lattice and magnetite cubic spinel phases. The needle, rod and spherical or irregular and irregular shapes were observed for CNC, magnetite and the MCNC, respectively, as shown in the TEM images. The P-XRD confirmed particle sizes of 31, 14 and 21 nm for CNC, magnetite and MCNC, respectively. For the morphology, SEM indicated a smooth fibroid surface of CNC, while the magnetite showed rod-like and spherical structures indicating the presence of iron and oxygen. The UV-Vis spectra displayed the presence of both CNC and magnetite. Furthermore, the thermal stability studies indicated that MCNC was stable after 600°C. The BET displayed the surface area, pore size and pore volume of the MCNC as 56 m2/g, 98Å and 0,1465 cm3/g.Å, respectively. The optimum conditions of the adsorption process were investigated by using multivariate optimisation tools, and the optimal conditions were 60 mg, 5 min, 10 ppm, pH 6 and 60°C. The maximum removal of 97% was obtained for Pb(II) with acceptable precision (≤3%) and adsorption capacity 47 mg/g. The MCNC demonstrated reusability for four consecutive cycles with the highest removal of 96%. However, for real wastewater samples, a removal of 53% was achieved. These results showed that the adsorption best fitted Langmuir isotherms and Pseudo first order with the endothermic and spontaneous thermodynamic reaction. The Temkin isotherm revealed the endothermic nature of the interaction between the adsorbent surface and Pb(II) ions, while the Frenkel–Halsey–Hill isotherm confirmed the non-multilayer interaction of the adsorbent and Pb(II) ions.

Aqueous-Phase Synthesis of Pt and PGM-Based Nanocrystals with a Controllable Size

Aqueous-Phase Synthesis of Pt and PGM-Based Nanocrystals with a Controllable Size

An Interstitial Boron Inserted Metastable Hexagonal Rh Nanocrystal for Efficient Hydrogen Oxidation Electrocatalysis

AbstractConstructing metastable phase structure plays an important role in changing the physicochemical properties and improving the catalytic performance of nanocrystals. Unfortunately, the synthesis of metastable phase metallic nanocrystals is highly challenging, mainly due to the thermodynamically unstable ground‐state. Here, we report a synthesis of unconventional metastable hexagonal rhodium nanocrystal (Bint−Rhhcp/C) via interstitial boron insertion. The insertion of boron atoms into the interstitial sites of cubic Rh lattice not only induces the atomic arrangements from face‐centered cubic (fcc) to hexagonal close‐packed (hcp), but also stabilizes the metastable hexagonal Rh structure. Benefiting from the phase transition and interstitial boron doping, the Bint−Rhhcp/C catalyst exhibits remarkable catalytic performance toward hydrogen oxidation reaction (HOR) under alkaline media, with a mass activity of 1.413 mA μgPGM−1. Experimental measurements including in situ surface‐enhanced infrared absorption spectroscopy (SEIRAS) and density functional theory (DFT) calculations indicate that the strengthened adsorption of hydroxyl species on the electrode surface of Bint−Rhhcp/C is responsible for the reconstruction of interfacial water structure and increased water proportions in the gap region in the electric double layers. As a result, the increased water connectivity and hydrogen bond network facilitate high‐efficiency hydrogen transfer across the interface, thereby boost the alkaline HOR performance.

Seedless and Surfactant-Free Synthesis of Polyhedron Gold Nanocrystals Enclosed by High-Index Facets for Enhanced Electrochemical Detection of Benzoyl Peroxide in Flour.

Polyhedron gold nanocrystals enclosed by high-index facets (HIF-Au NCs) are in high demand but are very difficult to prepare. To address this issue, we presented a simple, seedless method for synthesizing uniform HIF-Au NCs in an aqueous solution, which remarkably reduced the synthesis difficulty. Interestingly, the protonated N2H4 which served as both the reducing and capping agent played a crucial role in modulating the kinetic growth of the HIF-Au NCs. The resulting HIF-Au NCs exhibited distinct electronic oxidation inertness toward alcohol but demonstrated exceptional activity in the electrocatalytic oxidation of peroxides. To demonstrate their sensing capabilities, an electrode decorated with HIF-Au NCs was used to selectively detect benzoyl peroxide (BPO) in flour. BPO is a prohibited whitening agent that may be illegally added to flour and other products, posing potential health risks. The results demonstrate that this assay offers a promising method for the sensitive and selective detection of BPO. In conclusion, this research provides a straightforward pathway for obtaining HIF-Au NCs and further demonstrates their use in electronic sensing. It is expected that HIF-Au NCs will serve as a powerful tool in plasmon-enhanced spectroscopies, catalysis, and sensing applications.