Stability Of Nanocrystals Research Articles

ZIF-8 with exceptional thermal stability: Role of organic cosolvents in phase control and structure stabilization

Thermal stability is one of the key factors in catalysis and high-temperature industrial applications. The thermal degradation of ZIF-8, particularly its nanocrystals, could result in a significant loss of surface area and crystallinity, limiting its large-scale applicability. In this study, ZIF-8 nanocrystals with improved thermal stability were synthesized at room temperature (RT) through a facile, one-pot method – an ultrasound-assisted, solvent-guided ZIF-8 growth. The effect of synthesis variables, including the type and concentration of solvent, ultrasonication, and synthesis time, in improving the material’s thermal stability was studied systematically. The as-prepared samples were analyzed by TGA/DSC, XRD, SEM/TEM, FTIR, and BET to monitor the weight loss with temperature, sample crystallinity, crystal morphology, chemical structure, and surface area. Notably, synthesis with 5 v/v% of n-hexane (ZIF-8new-ref) demonstrated the formation of highly-crystalline ZIF-8 nanocrystals with extraordinary thermal stability (with only ∼2.0–3.0 % weight loss up to 600 °C), large surface area (i.e., 975 m2 g−1), and an excellent particle size distribution in the range of 0.2–0.4 μm. More importantly, the short synthesis time (2 h) and sonication-assisted pretreatment of the precursor (for promoting solvent-ligand interaction) proved effective and played a crucial role in controlling ZIF-8’s thermal stability. The mechanism for the thermal stability enhancement was thus proposed. The highly thermally stable ZIF-8 nanocrystals were also synthesized with significantly reduced chemical usage, e.g., 1/11 of the normal ligand-to-metal ratio (70), achieving cost-effective and environmentally friendly synthesis.

Bright and Stable Perovskite Nanocrystals Lighted Up Remotely by Means of Wireless Power Transfer (Advanced Optical Materials 22/2023)

Bright and Stable Perovskite Nanocrystals Lighted Up Remotely by Means of Wireless Power Transfer (Advanced Optical Materials 22/2023)

Shape and Phase-Controlled One-Pot Synthesis of Air Stable Cationic AgCdS Nanocrystals, Optoelectronic and Electrochemical Hydrogen Evolution Studies.

CdS-based materials are extensively studied for photocatalytic water splitting. By incorporating Ag+ into CdS nanomaterials, the catalyst's charge carrier dynamic can be tuned for photo-electrochemical devices. However, photo-corrosion and air-stability of the heterostructures limit the photocatalytic device's performance. Here, a one-pot, single molecular source synthesis of the air-stable AgCdS ternary semiconductor alloy nanostructures byheat-up method is reported. Monoclinic and hexagonal phases of the alloy are tuned by judicious choice of dodecane thiol (DDT), octadecyl amine (ODA), and oleyl amine (OLA) as capping agents. Transmission electron microscope (TEM) and powder X-ray diffraction characterization of the AgCdS alloy confirm the monoclinic and hexagonal phase (wurtzite) formation. The high-resolution TEM studies confirm the formation of AgCdS@DDT alloy nanorods and their shape transformation into nano-triangles. The nanoparticle coalescence is observed for ODA-capped alloys in the wurtzite phase. Moreover, OLA directs mixed crystal phases and anisotropic growth of alloy. Optical processes in AgCdS@DDT nano-triangles show mono-exponential decay (3.97 ± 0.01ns). The monoclinic phase of the AgCdS@DDT nanorods exhibits higher electrochemical hydrogen evolution activity in neutral media as compared to the AgCdS@ODA/OLA alloy nanocrystals. DDT and OLA-capped alloys display current densities of 14.1 and 14.7mA cm-2 , respectively, at 0.8V (vs RHE).

Environmentally stable luminescent perovskite nanocrystals passivated and encapsulated by siloxane hybrids enabling reliable color-converted organic light-emitting diodes

Environmentally stable luminescent perovskite nanocrystals passivated and encapsulated by siloxane hybrids enabling reliable color-converted organic light-emitting diodes

Long term suppression of deep traps in CsPbBr3 nanocrystals by introducing slight lattice distortion

CsPbX3 (X = Br, Cl, I) nanocrystals have broad application prospects, due to their high luminescent efficiency and low preparation cost. However, the stability of CsPbBr3 nanocrystals prepared using conventional methods is poor; thus, large-scale applications have not yet been achieved. Currently, most of the methods aimed at improving the stability of CsPbBr3 nanocrystals involve inorganic or organic encapsulation, which makes it challenging to apply them to devices that operate with electrical injection. In this article, we report that CsPbBr3 nanocrystals prepared by the solvent quenching method, without any external encapsulation, can maintain excellent optical properties after long-term storage. Through the studies of temperature-dependent photoluminescence spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy, we have revealed that the nanocrystals prepared by solvent injection quenching method contain slight lattice distortion of the [PbBr]64- cages, which can lead to the formation of shallow trap states while suppressin the formation of deep traps, thereby maintaining excellent optical properties for long time.

CsPbCl3 → CsPbI3 Exchange in Perovskite Nanocrystals Proceeds through a Jump-the-Gap Reaction Mechanism.

Halide exchange is a popular strategy to tune the properties of CsPbX3 nanocrystals after synthesis. However, while Cl → Br and Br → I exchanges proceed through the formation of stable mixed-halide nanocrystals, the Cl ⇌ I exchange is more elusive. Indeed, the large size difference between chloride and iodide ions causes a miscibility gap in the CsPbCl3-CsPbI3 system, preventing the isolation of stable CsPb(ClxI1-x)3 nanocrystals. Yet, previous works have claimed that a full CsPbCl3 → CsPbI3 exchange can be achieved. Even more interestingly, interrupting the exchange prematurely yields a mixture of CsPbCl3 and CsPbI3 nanocrystals that coexist without undergoing further transformation. Here, we investigate the reaction mechanism of CsPbCl3 → CsPbI3 exchange in nanocrystals. We show that the reaction proceeds through the early formation of iodide-doped CsPbCl3 nanocrystals covered by a monolayer shell of CsI. These nanocrystals then leap over the miscibility gap between CsPbCl3 and CsPbI3 by briefly transitioning to short-lived and nonrecoverable CsPb(ClxI1-x)3 nanocrystals, which quickly expel the excess chloride and turn into the chloride-doped CsPbI3 nanocrystals found in the final product.

Non-cytotoxic, highly functionalized cellulose nanocrystals with high crystallinity and thermal stability derived from a novel agromass of Elettaria cardamomum, using a soft and benign mild oxalic acid hydrolysis

Non-cytotoxic, highly crystalline, and functionalized, thermally stable cellulose nanocrystals are extracted from the stems of Elettaria cardamom, a novel underutilised agromass, by employing a neat green, mild oxalic acid hydrolysis. The protocol involves a chemo-mechanical strategy of coupling hydrolysis with steam explosion and homogenization. The obtained CNC showed a crystallinity index of 81.51 %, an aspect ratio of 17.80 ± 1.03 and a high degradation temperature of about 339.07 °C. The extraction procedure imparted a high negative surface functionalization with a zeta potential value of −34.244 ± 0.496 mV and a polydispersity of 16.5 %. The CNC had no antibacterial activity, according to non-cytotoxic experiments conducted on four bacterial strains. This supports the notion of “One Health” in the context of AMR by demonstrating the safety of antibiotic resistance due to consistent exposure upon environmental disposal. The as-extracted nanocellulose crystals can be a potential candidate for commercial application in wide and diversified disciplines like food packaging, anti-infective surfaces for medical devices, biosensors, bioelectronics etc.

Bright and Stable Perovskite Nanocrystals Lighted Up Remotely by Means of Wireless Power Transfer

AbstractHalide perovskite nanocrystals (NCs) are an emerging family of low‐cost and high‐efficiency luminescent nanomaterials. They offer a broad gamut of emitted light colors owing to the broad bandgap tunability of the perovskite via anion variation. Previously, to lighten up perovskite NCs, they were placed between two electrodes to inject charge carriers or were integrated with commercial blue light‐emitting diodes powered by electric contacts. However, the opportunities for remote lighting of perovskite NCs have not been explored yet. In this work, the principles of wireless power transfer of electromagnetic energy are applied to light up perovskite NCs encapsulated into a polymer matrix. The photoluminescence and absorption spectra of the CsPbBr3 NCs in a polymer matrix on incident laser power density are experimentally studied. As a proof of concept, chess pieces are created consisting of the perovskite NCs and charge from a chessboard with an integrated metasurface‐based resonator that provides quasi‐homogeneous power distribution. The efficient lighting of the chess pieces with encapsulated NCs is demonstrated over the whole area of the chessboard at various heights up to ≈10 cm. The results of the study open the door for potential applications of perovskite NCs with remote lighting capability.

Liquid foams with a lifetime of several days co-stabilized by monodisperse protein nanoparticles and mechanically stable starch nanocrystals

Liquid foams stabilized by protein nanoparticles generally have a lifetime less than several hours because of poor interface and unavoidable coalescence, which strictly limits their applications in, e.g., coffee toppings and milk shakes. In this study, stable foams with a lifetime of several days were prepared by protein nanoparticle-starch nanocrystal (SNC) complexes. The nanoparticles of rice proteins (RPs) or rice bran proteins (RBPs) were prepared by neutralization of their alkaline solutions by cationic exchange resins (CERs) that displace Na+ by releasing H+, leading to the formation of monodisperse, 20-nm nanoparticles facilitating diffusion to the water-air interface. The complexes were assembled by simply mixing proteins with SNCs, affording the formation of quite dispersed network structures (RP@SNCs or RBP@SNCs). During whipping, the protein nanoparticles performed as the diffusion initiators from the continuous phase to the biphasic interface, whereas the SNCs stabilized the interface and functioned as the spacers preventing the approaching of adjacent bubbles in the continuous phase. Moreover, RPs and RBPs had different affinities to SNCs, resulting in foams of varied stabilities. Our study represented a compelling example of structuring stable foams taking joint advantages of diffusion behaviors of protein nanoparticles and biphasic stabilization of SNCs.

A green versatile packaging based on alginate and anthocyanin via incorporating bacterial cellulose nanocrystal-stabilized camellia oil Pickering emulsions

This study aims to develop a versatile intelligent packaging based on alginate (Alg) and anthocyanin (Ant) by incorporating bacterial cellulose nanocrystal-stabilized camellia oil Pickering emulsions. Firstly, bacterial cellulose nanocrystals (BCNs) matrix produced from kombucha was incorporated with camellia oil into via ultrasonic triggering, forming a stable and multifunctional camellia oil-bacterial cellulose nanocrystal Pickering nanoemulsions (CBPE). The microstructure and rheology results of the emulsion confirmed the stabilized preparation of CBPE. Subsequently, the CBPE was integrated into the three-dimensional network structure composed of alginate/anthocyanin. The composite film (Alg-Ant-CBPE) was designed through Ca2+ crosslinking, intermolecular hydrogen bonding and dehydration condensation. The fabricated color indicator films with different concentrations of CBPE (0.1 %–0.4 %), showed varying degree of improvement in hydrophobicity, UV shielding, mechanical strength, thermal stability, water vapor barrier properties and antioxidant capacities. When applied to yogurt, the Alg-Ant-CBPE4 exhibited more pronounced color changes compared to Alg-Ant, enabling visual detection of food freshness. In conclusion, the incorporation of Pickering nanoemulsion provides an effective and promising approach to enhance the performance of polysaccharide-based intelligent packaging.

Highly bright and stable CsPbBr3 perovskite nanocrystals with amphiphilic polymer binding based dual-readout lateral flow immunoassay for detection of carcinoembryonic antigen

Rapid and highly sensitive detection of tumor marker (TM) is critical for the early diagnosis and treatment of cancers. Herein, utilizing highly bright and water-stable CsPbBr3 perovskite nanocrystals (NCs) capped with amphiphilic polymer ligand of octylamine-modified polyacrylic acid (OPA) and gold nanoparticles (AuNPs) as reporters, a lateral flow immunoassay (LFIA) strip is developed for fluorescence and colorimetric dual-mode detection of carcinoembryonic antigen (CEA). The prepared CsPbBr3 NCs capped by an amphiphilic polymeric of OPA ligand showed high stability and bright fluorescence. Moreover, the AuNPs immunoprobes were captured with CEA antigen and quench the green fluorescence of CsPbBr3/OPA NCs on the T line due to the inner filter effect (IFE). Therefore, CEA could be quantitative analyzed by the dual-readout of fluorescence and colorimetric signal. The detection limits of CEA can reach as low as 0.023 ng/mL and 0.027 ng/mL for the fluorescence and colorimetric mode, respectively. Good specificity and reproducibility were also demonstrated for this method. Finally, the CsPbBr3/OPA NCs-based LFIA showed good accuracy in detection of CEA level from clinical serum samples. This work firstly enables the application of CsPbBr3 perovskite NCs in a LFIA, displaying great potential in point-of-care clinical diagnosis.

General Route to Colloidally Stable, Low-Dispersity Manganese-Based Ternary Spinel Oxide Nanocrystals.

While certain ternary spinel oxides have been well-explored with colloidal nanochemistry, notably the ferrite spinel family, ternary manganese (Mn)-based spinel oxides have not been tamed. A key composition is cobalt (Co)-Mn oxide (CMO) spinel, CoxMn3-xO4, that, despite exemplary performance in multiple electrochemical applications, has few reports in the colloidal literature. Of these reports, most show aggregated and polydisperse products. Here, we describe a synthetic method for small, colloidally stable CMO spinel nanocrystals with tunable composition and low dispersity. By reacting 2+ metal-acetylacetonate (M(acac)2) precursors in an amine solvent under an oxidizing environment, we developed a pathway that avoids the highly reducing conditions of typical colloidal synthesis reactions; these reducing conditions typically push the system toward a monoxide impurity phase. Through surface chemistry studies, we identify organic byproducts and their formation mechanism, enabling us to engineer the surface and obtain colloidally stable nanocrystals with low organic loading. We report a CMO/carbon composite with low organic contents that performs the oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 0.87 V vs RHE in 1.0 M potassium hydroxide at 1600 rpm, rivaling previous reports for the highest activity of this material in ORR electrocatalysis. We extend the general applicability of this procedure to other Mn-based spinel nanocrystals such as Zn-Mn-O, Fe-Mn-O, Ni-Mn-O, and Cu-Mn-O. Finally, we show the scalability of this method by producing inorganic nanocrystals at the gram scale.

Dexamethasone acetate nanocrystals: characterization and dissolution studies in presence of polymorphic phases.

A drug with poor water-solubility, like Dexamethasone acetate, can present lower bioavailability conventional for pharmaceutical formulations, and the presence of polymorphs in the raw material can lead to drug quality problems. In this study, nanocrystals of dexamethasone acetate were synthesized by high pressure homogenizer (HPH) method in surfactant poloxamer 188 (P188) solid dispersion and the bioavailable in raw material with polymorphism presence was evaluated. The powder pre-suspension was prepared by the HPH process, and the nanoparticles formed were incorporated in P188 solutions. The nanocrystals formed were characterized by techniques of XRD, SEM, FTIR, thermal analysis by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), dynamic light scattering (DLS) to analyze the particle size and zeta potential, and in vitro evaluation by dissolution studies. The characterization techniques were adequate to show the presence of raw material with physical moisture between two dexamethasone acetate polymorphs. The nanocrystals formed in the presence of the P188 in the formulation showed a considerable increase in the rate of dissolution of the drug in the medium and in the size of the stable nanocrystals, even in the presence of dexamethasone acetate polymorphs. The results showed that it was possible to produce dexamethasone nanocrystals by HPH process with regular size by the presence of the small amount of P188 surfactant. This article presents a novelty in the development of dexamethasone nanoparticles that have different polymorphic forms in their physical composition.

BSA-assisted ultrasound synthesis of water stable CsPbBr3 nanocrystals for sensitive fluorescent detection of hydrogen sulfide in human serum.

A bovine serum albumin (BSA)-assisted ultrasonication strategy was developed for the synthesis of CsPbBr3 nanocrystals (NCs) with stable fluorescence properties in aqueous solution. Such a preparation method is simple, fast and does not require complex equipment. The results show that the synthesized CsPbBr3 NCs are homogeneous in particle size and have good solubility and stability in water. The CsPbBr3 NCs have been utilized as fluorescence probe for rapid detection of hydrogen sulfide (H2S) in human serum. The reaction of H2S with the lead sites on the surface of CsPbBr3 NCs produces lead sulfide (PbS), resulting in the decrease of fluorometric intensity of CsPbBr3 NCs. Our designed fluorescent assay has a linear S2- detecting range of 10 ~ 800nM with a detection limit of 7.05nM. The assay was used to determineH2S in human serum with spiked recoveries ranging from 94.98% to 102.69%. This work opens new avenues for the application of halide lead perovskite in different biosensing areas.

Surface chemistry engineering enables polar solvent resistant and highly emissive perovskite nanocrystals for multifunctional applications

The extremely poor stability of perovskite nanocrystals (NCs) in polar solvent is a critical unsolved problem and seriously hinder their practical application scenarios. Herein, a surface chemistry engineering strategy is proposed for synthesizing robust CsPbX3 (X = Cl, Br, I) NCs in non-toxic ethanol-based solvent by building an extensive inter-ligand H-bond network on perovskite lattice. The obtained unsealed CsPbX3 NCs show unprecedented year-long stability in ethanol. Notably, a water (∼6–50%, v/v) post-treatment can obviously decrease surface defects of NCs, thus yielding a significant enhancement in their emission efficiency (increased from 9.6% to 83.4% for CsPbBr3 NCs in ethanol). We further translated the obtained CsPbBr3 NCs to fluorescent sensor and visible-light-driven photocatalysts, achieving ultra-high sensitivity (limit of detection is 11 nM) and high photocatalytic efficiency (>99% removal within 10 min). Overall, the low-cost, easy-to-process, highly efficient and ethanol/water tolerant perovskites NCs indicate their promising application prospect in multifunctional photoelectric devices.

Understanding optical and structural properties of the CH3NH3PbI3 nanocrystal thin films under humidity conditions

Low-dimensional organic-inorganic hybrid perovskite materials have drawn a lot of interest in optoelectronic applications because of their unique optoelectronic performance in comparison to their bulk counterparts. There is an influence of humidity conditions on the stability of perovskite in both positive and negative ways. The passivation of surface and bulk defects in the thin film of perovskite by the H2O molecules is a positive way. The negative way is that the material's stability will hinder the commercialization of perovskite-based devices. Herein, CH3NH3PbI3 nanocrystals are synthesized by the hot-injection method. The optical and structural properties of the thin film of the synthesized nanocrystals under different humidity conditions are studied through photoluminescence (PL), TRPL, Raman, X-ray diffraction (XRD), UV–Vis, spectroscopic ellipsometry, and FTIR techniques for 4 weeks. The redshift in the PL spectra of the thin film with an increase in PL intensity and carrier lifetime is caused by the shallow trap-assisted radiative recombination and localization of the charge carriers at the interface of the CH3NH3PbI3/water. The XRD, Raman, and FTIR peaks of the thin film are also shifted due to defect formation and structure distortion of the CH3NH3PbI3 crystal lattice. The thin films of these nanocrystals exhibit very high PLQY of 56% and 60% after 5 h and 1 week respectively. The results pave the way to analyse the stability of CH3NH3PbI3 nanocrystals through their optical and structural behaviour under different humidity conditions. The results also reflect that the photoemission of the synthesized material can be tuned by regulating the defect density and the structural deformation of the nanocrystals under controlled humidity conditions.

Zwitterionic Carbazole Ligands Enhance the Stability and Performance of Perovskite Nanocrystals in Light-Emitting Diodes.

We introduce a new carbazole-based zwitterionic ligand (DCzGPC) synthesized via Yamaguchi esterification which enhances the efficiency of lead halide perovskite (LHP) nanocrystals (NCs) in light-emitting diodes (LED). A facile ligand exchange of the native ligand shell, monitored by nuclear magnetic resonance (NMR), ultraviolet-visible (UV-vis), and photoluminescence (PL) spectroscopy, enables more stable and efficient LHP NCs. The improved stability is demonstrated in solution and solid-state LEDs, where the NCs exhibit prolonged luminescence lifetimes and improved luminance, respectively. These results represent a promising strategy to enhance the stability of LHP NCs and to tune their optoelectronic properties for further application in LEDs or solar cells.

Surface Engineering of Metal and Semiconductor Nanocrystal Assemblies and Their Optical and Electronic Devices.

ConspectusColloidal nanocrystals (NCs) are composed of inorganic cores and organic or inorganic ligand shells and serve as building blocks of NC assemblies. Metal and semiconductor NCs are well known for the size-dependent physical properties of their cores. The large NC surface-to-volume ratio and the space between NCs in assemblies places significant importance on the composition of the NC surface and ligand shell. Nonaqueous colloidal NC syntheses use relatively long organic ligands to control NC size and uniformity during growth and to prepare stable NC dispersions. However, these ligands create large interparticle distances that dilute the metal and semiconductor NC properties of their assemblies. In this Account, we describe postsynthesis chemical treatments to engineer the NC surface and design the optical and electronic properties of NC assemblies. In metal NC assemblies, compact ligand exchange reduces the interparticle distance and drives an insulator-to-metal transition tuning the dc resistivity over a 1010 range and the real part of the optical dielectric function from positive to negative across the visible-to-IR region. Juxtaposing NC and bulk metal thin films in bilayers allows the differential chemical and thermal addressability of the NC surface to be exploited in device fabrication. Ligand exchange and thermal annealing densifies the NC layer, creating interfacial misfit strain that triggers folding of the bilayers and is used to fabricate, with only one lithography step, large-area 3D chiral metamaterials. In semiconductor NC assemblies, chemical treatments such as ligand exchange, doping, and cation exchange control the interparticle distance and composition to add impurities, tailor stoichiometry, or make entirely new compounds. These treatments are employed in longer studied II-VI and IV-VI materials and are being developed as interest in III-V and I-III-VI2 NC materials grows. NC surface engineering is used to design NC assemblies with tailored carrier energy, type, concentration, mobility, and lifetime. Compact ligand exchange increases the coupling between NCs but can introduce intragap states that scatter and reduce the lifetime of carriers. Hybrid ligand exchange with two different chemistries can enhance the mobility-lifetime product. Doping increases carrier concentration, shifts the Fermi energy, and increases carrier mobility, creating n- and p-type building blocks for optoelectronic and electronic devices and circuits. Surface engineering of semiconductor NC assemblies is also important to modify device interfaces to allow the stacking and patterning of NC layers and to realize excellent device performance. It is used to construct NC-integrated circuits, exploiting the library of metal, semiconductor, and insulator NCs, to achieve all-NC, solution-fabricated transistors.

Velocity field distribution control in antisolvent flow realizing highly stable and efficient perovskite nanocrystals

Achieving highly stable and efficient perovskite nanocrystals (NCs) without applying functional additives or encapsulation, particularly sustaining the stability in ultra-dilute solution, is still a formidable challenge. Here, we show the FAPbI3 perovskite NCs with achieved ∼100 % photoluminescence quantum yield (PLQY) and low defect density (∼0.2 cm−3 per NCs), which is obtained by controlling the velocity field distribution of antisolvent flow in ligand-assisted reprecipitation process. The NCs show incredible reproducibility with narrow deviation of PLQY and linewidth between batch by batch, as well as remarkable stability of maintaining over 80 % PLQY, either in an ultra-diluted solution (9.3 × 10-6 mg/mL), or storing in ambient condition after 90 days with concentration of 0.09 mg/mL. The results in this work demonstrate the interplay of fluid mechanics and crystallization kinetics of perovskite, which pioneers a novel and unprecedent understanding for improving the stability of perovskite NCs for efficient quantum light source.

Advancements in Perovskite Nanocrystal Stability Enhancement: A Comprehensive Review.

Over the past decade, perovskite technology has been increasingly applied in solar cells, nanocrystals, and light-emitting diodes (LEDs). Perovskite nanocrystals (PNCs) have attracted significant interest in the field of optoelectronics owing to their exceptional optoelectronic properties. Compared with other common nanocrystal materials, perovskite nanomaterials have many advantages, such as high absorption coefficients and tunable bandgaps. Owing to their rapid development in efficiency and huge potential, perovskite materials are considered the future of photovoltaics. Among different types of PNCs, CsPbBr3 perovskites exhibit several advantages. CsPbBr3 nanocrystals offer a combination of enhanced stability, high photoluminescence quantum yield, narrow emission bandwidth, tunable bandgap, and ease of synthesis, which distinguish them from other PNCs, and make them suitable for various applications in optoelectronics and photonics. However, PNCs also have some shortcomings: they are highly susceptible to degradation caused by environmental factors, such as moisture, oxygen, and light, which limits their long-term performance and hinders their practical applications. Recently, researchers have focused on improving the stability of PNCs, starting with the synthesis of nanocrystals and optimizing (i) the external encapsulation of crystals, (ii) ligands used for the separation and purification of nanocrystals, and (iii) initial synthesis methods or material doping. In this review, we discuss in detail the factors leading to instability in PNCs, introduce stability enhancement methods for mainly inorganic PNCs mentioned above, and provide a summary of these approaches.