Self-assembly of perovskite nanocrystals:From driving forces to applications

Self-assembly of metal halide perovskite nanocrystals(NCs)into superlattices can exhibit unique collective properties,which have significant application values in the display,detector,and solar cell field.This review discusses the driving forces behind the self-assembly process of perovskite NCs,and the commonly used self-assembly methods and different self-assembly structures are detailed.Subsequently,we summarize the collective optoelectronic properties and application areas of perovskite superlattice structures.Finally,we conclude with an outlook on the potential issues and future challenges in developing perovskite NCs.

Alcohol solvent effect on the self-assembly behaviors of lignin oligomers

The interactions between lignin oligomers and solvents determine the behaviors of lignin oligomers self-assembling into uniform lignin nanoparticles(LNPs).Herein,several alcohol solvents,which readily interact with the lignin oligomers,were adopted to study their effects during solvent shifting process for LNPs’production.The lignin oligomers with widely distributed molecular weight and abundant guaiacyl units were extracted from wood waste(mainly consists of pine wood),exerting outstanding self-assembly capability.Uniform and spherical LNPs were generated in H_(2)O-n-propanol cosolvent,whereas irregular LNPs were obtained in H_(2)O-methanol cosolvent.The unsatisfactory self-assembly performance of the lignin oligomers in H_(2)O-methanol cosolvent could be attributed to two aspects.On one hand,for the initial dissolution state,the distinguishing Hansen solubility parameter and polarity between methanol solvent and lignin oligomers resulted in the poor dispersion of the lignin oligomers.On the other hand,strong hydrogen bonds between methanol solvent and lignin oligomers during solvent shifting process,hindered the interactions among the lignin oligomers for self-assembly.

Chitosan/Sodium Alginate Multilayer pH-Sensitive Films Based on Layer-by-Layer Self-Assembly for Intelligent Packaging

The abuse of plastic food packaging has brought about severe white pollution issues around the world.Developing green and sustainable biomass packaging is an effective way to solve this problem.Hence,a chitosan/sodium alginate-based multilayer film is fabricated via a layer-by-layer(LBL)self-assembly method.With the help of superior interaction between the layers,the multilayer film possesses excellent mechanical properties(with a tensile strength of 50 MPa).Besides,the film displays outstanding water retention property(blocking moisture of 97.56%)and ultraviolet blocking property.Anthocyanin is introduced into the film to detect the food quality since it is one natural plant polyphenol that is sensitive to the pH changes ranging from 1 to 13 in food when spoilage occurs.It is noted that the film is also bacteriostatic which is desired for food packaging.This study describes a simple technique for the development of advanced multifunctional and fully biodegradable food packaging film and it is a sustainable alternative to plastic packaging.

Combination therapy to overcome ferroptosis resistance by biomimetic self-assembly nano-prodrug

Ferroptosis has emerged as a potent form of no-apoptotic cell death that offers a promising alternative to avoid the chemoresistance of apoptotic pathways and serves as a vulnerability of cancer.Herein,we have constructed a biomimetic self-assembly nano-prodrug system that enables the co-delivery of gefitinib(Gefi),ferrocene(Fc)and dihydroartemisinin(DHA)for the combined therapy of both ferroptosis and apoptosis.In the tumor microenvironment,this nano-prodrug is able to disassemble and trigger drug release under high levels of GSH.Interestingly,the released DHA can downregulate GPX4 level for the enhancement of intracellular ferroptosis from Fc,further executing tumor cell death with concomitant chemotherapy by Gefi.More importantly,this nano-prodrug provides highly homologous targeting ability by coating related cell membranes and exhibits outstanding inhibition of tumor growth and metastasis,as well as no noticeable side-effects during treatments.This simple small molecular self-assembled nano-prodrug provides a new reasonably designed modality for ferroptosis-combined chemotherapy.

Efficient conversion of lignin waste and self-assembly synthesis of C@MnCo_(2)O_(4)for asymmetric supercapacitors with high energy density

Lignin waste from the papermaking and biorefineries industry is a significantly promising renewable resource to prepare advanced carbon materials for diverse applications,such as the electrodes of supercapacitors;however,the improvement of their energy density remains a challenge.Here,we design a green and universal approach to prepare the composite electrode material,which is composed of lignin-phenolformaldehyde resins derived hierarchical porous carbon(LR-HPC)as conductive skeletons and the self-assembly manganese cobaltite(MnCo_(2)O_(4))nanocrystals as active sites.The synthesized C@MnCo_(2)O_(4)composite has an abundant porous structure and superior electronic conductivity,allowing for more charge/electron mass transfer channels and active sites for the redox reactions.The composite shows excellent electrochemical performance,such as the maximum specific capacitance of~726 mF cm^(-2)at 0.5 mV s^(-1),due to the significantly enhanced interactive interface between LR-HPC and MnCo_(2)O_(4)crystals.The assembled all-solid-state asymmetric supercapacitor,with the LR-HPC and C@MnCo_(2)O_(4)as cathode and anode,respectively,exhibits the highest volumetric energy density of 0.68 mWh cm^(-3)at a power density of 8.2 mW cm^(-3).Moreover,this device shows a high capacity retention ratio of~87.6%at 5 mA cm^(-2)after 5000 cycles.

Analysis on the formation principle and present situation of nano phase state of multi-component self-assembly of traditional Chinese compound medicine decoction

Traditional Chinese medicine decoction is a complex polydispersed phase system containing real solution,colloid solution,emulsion and suspension.The compound decoction of traditional Chinese medicine has complex components,including saponins,alkaloids,polysaccharides,flavonoids,amino acids and so on,which can be self-assembled to form gels,fibers,micelles,vesicles and so on.The self-assembled nano-phase not only neutralizes the single drug and reduces the toxicity and side effects,but also has its own pharmacological effects,which complement each other to achieve synergistic effect,so as to achieve the role of drug supplement,which is of research significance.The formation principle,solubilization and synergism principle and characterization method of multi-component self-assembly of traditional Chinese medicine compound decoction are discussed in this paper.

Factors resisting protein adsorption on hydrophilic/hydrophobic self-assembled monolayers terminated with hydrophilic hydroxyl groups

The hydroxyl-terminated self-assembled monolayer(OH-SAM),as a surface resistant to protein adsorption,exhibits substantial potential in applications such as ship navigation and medical implants,and the appropriate strategies for designing anti-fouling surfaces are crucial.Here,we employ molecular dynamics simulations and alchemical free energy calculations to systematically analyze the factors influencing resistance to protein adsorption on the SAMs terminated with single or double OH groups at three packing densities(∑=2.0 nm^(-2),4.5 nm^(-2),and 6.5 nm^(-2)),respectively.For the first time,we observed that the compactness and order of interfacial water enhance its physical barrier effect,subsequently enhancing the resistance of SAM to protein adsorption.Notably,the spatial hindrance effect of SAM leads to the embedding of protein into SAM,resulting in a lack of resistance of SAM towards protein.Furthermore,the number of hydroxyl groups per unit area of double OH-terminated SAM at ∑=6.5 nm^(-2) is approximately 2 to 3 times that of single OH-terminated SAM at ∑=6.5 nm^(-2) and 4.5 nm^(-2),consequently yielding a weaker resistance of double OH-terminated SAM towards protein.Meanwhile,due to the structure of SAM itself,i.e.,the formation of a nearly perfect ice-like hydrogen bond structure,the SAM exhibits the weakest resistance towards protein.This study will complement and improve the mechanism of OH-SAM resistance to protein adsorption,especially the traditional barrier effect of interfacial water.

High-performance self-assembly MnCo2O4 nanosheets for asymmetric supercapacitors

In this study,MnCo2O4 nanosheets were proposed to be utilized as an electrode material for supercapacitors.A two-step hydrothermal method with post-annealing treatment was employed in preparation of the nanostructures.MnCo2O4 electrode delivered a high specific capacitance of 2000 F g^-1 at 0.5 A g^-1,remarkable high-rate capability of 1150 F g^-1 at 20 A g^-1,and an excellent cycling stability of 92.3%at 5 A g^-1 after 5000 cycles.It is found that a three-electrode supercapacitor based on MnCo2O4 exhibits a promising electrochemical performance,better than the other similar materials,benefited from the synergistic effects of MnCo2O4 nanosheets.In fact,the self-assembly of nanosheets structure with high specific surface area and mesoporous structure can potentially enhance the electrochemical performance of supercapacitors.

The lipase monolayer film self-assembly on the negatively charged poly(ethylene terephthalate) substrate

The PET-CO2- film was prepared and the lipase was assembled on the surface of the PET-CO2- substrate The structure at the surface and activity of lipase/PET monolayer were studied by ATR-FTIR and AFM, and other methods.

Self-assembly to monolayer graphene film with high electrical conductivity

Monolayer chemically converted graphene （CCG） nanosheets can be homogeneously self-assembled onto silicon wafer modified by 3-aminopr- opyl triethoxysilane （APTES） to form very thin graphene film. The CCG film was characterized by FT-IR, XRD, SEM, TEM and AFM. Results show that CCG sheets formed monolayer film after assembled onto silicon wafer and there is a very tight chemical bond between sheets and wafer. Furthermore, the electrical measurements revealed that the monolayer graphene film has an excellent electrical conductivity.

Experimental Study on Self-assembly of KLD-12 Peptide Hydrogel and 3-D Culture of MSC Encapsulated within Hydrogel In Vitro

To synthesize KLD-12 peptide with sequence of AcN-KLDLKLDLKLDL-CNH2 and trigger its self-assembly in vitro, to encapsulate rabbit MSCs within peptide hydrogel for 3-D culture and to evaluate the feasibility of using it as injectable scaffold for tissue engineering of IVD. KLD-12 peptide was purified and tested with high performance liquid chromatography （HPLC） and mass spectroscopy （MS）. KLD-12 peptide solutions with concentrations of 5 g/L, 2.5 g/L and 1 g/L were triggered to self-assembly with 1 xPBS in vitro, and the self-assembled peptide hydrogel was morphologically observed. Atomic force microscope （AFM） was employed to examine the inner structure of self-assembled peptide hydrogel. Mesenchymal stem cells （MSCs） were encapsulated within peptide hydrogel for 3-D culture for 2 weeks. Calcein-AM/PI fluorescence staining was used to detect living and dead cells. Cell viability was observed to evaluate the bioactivity of MSCs in KLD-12 peptide hydrogel. The results of HPLC and MS showed that the relative molecular mass of KLD-12 peptide was 1467.83, with a purity quotient of 95.36%. KLD-12 peptide at 5 g/L could self-assemble to produce a hydrogel, which was structurally integral and homogeneous and was able to provide sufficient cohesion to retain the shape of hydrogel. AFM demonstrated that the self-assembly of KLD-12 peptide hydrogel was successful and the assembled material was composed of a kind of nano-fiber with a diameter of 3040 nm and a length of hundreds of nm. Calcein-AM/PI fluorescence staining revealed that MSCs in KLD-12 peptide hydrogel grew well. Cell activity detection exhibited that the A value increased over the culture time. It is concluded that KLD-12 peptide was synthesized successfully and was able to self-assemble to produce nano-fiber hydrogel in vitro. MSCs in KLD-12 peptide hydrogel grew well and proliferated with the culture time. KLD-12 peptide hydrogel can serve as an excellent injectable material of biological scaffolds in tissue engineering of IVD.

A Facile Self-assembly Synthesis of Hexagonal ZnO Nanosheet Films and Their Photoelectrochemical Properties

Here, large-scale and uniform hexagonal zinc oxide(ZnO) nanosheet films were deposited onto indium tin oxide(ITO)-coated transparent conducting glass substrates via a facile galvanic displacement deposition process. Compared with other commonly used solution methods, this process avoids high temperature and electric power as well as supporting agents to make it simple and cost-effective. The as-fabricated ZnO nanosheet films have uniform hexagonal wurtzite structure. The photoelectrochemical(PEC) cell based on ZnO nanosheet film/ITO photoelectrode was also fabricated and its performance was improved by optimizing the solution concentration. A higher photocurrent density of*500 l A cm^(-2)under AM 1.5 G simulated illumination of 100 m W cm^(-2)with zero bias potential(vs. Ag/AgCl electrode) was obtained, which may ascribe to the increased surface-to-volume ratio of disordered Zn O nanosheet arrays. Our developed method may be used to deposit other oxide semiconductors, and the Zn O nanosheet film/ITO PEC cell can be used to design low-cost optoelectronic and photoelectrochemical devices.

From self-assembly to quantum guiding: A review of magnetic atomic structures on noble metal surfaces

Recent advances in the study of magnetic atomic structures on noble metal surfaces are reviewed. These include one- dimensional strings, two-dimensional hexagonal superlattices, and novel structures stabilized by quantum guiding. The combined techniques of low-temperature scanning tunneling microscopy, kinetic Monte Carlo simulations, and ab initio calculations reveal that surface-state-mediated adatom-step and adatom-adatom interactions are the driving forces for self- assembly of these structures. The formation conditions are further discussed by comparing various experimental systems and the kinetic Monte Carlo simulations. Using scanning tunneling spectroscopy and tight-binding calculations together, we reveal that the spectra of these well-ordered structures have characteristic peaks induced by electronic scattering processes of the atoms within the local environment. Moreover, it is demonstrated that quantum confinement by means of nano-size corrals has significant influence on adatom diffusion and self-assembly, leading to a quantum-guided self-assembly.

Preparation of Bentonite Supported Nano Titanium Dioxide Photocatalysts by Electrostatic Self-assembly Method

Electrostatic self-assembly method （ESAM） was used to prepare bentonite supported-nano titanium dioxide photocatalysts. The materials were characterized by X-ray diffraction （XRD）, fourier transform infrared spectroscopy （FT-IR） and scanning electron microscopy （SEM）. Methyl orange was used to estimate the photocatalytic activity of the materials. The effects of the calcination temperature and silane dosage on the photocatalytic activity of the samples were investigated. The experimental results show that the bentonite facilitates the formation of anatase and restrains the transformation of anatase to rutile. Part of nano-size TiO2 particles insert into the galleries of bentonite. The photocatalysts exhibit a synergistic effect of adsorption and photocatalysis on methyl orange. Photocatalysts prepared by ESAM method exhibit higher photocatalytic activity and better recycle ability than those of the traditional method.

Perylene diimide self-assembly: From electronic structural modulation to photocatalytic applications

As an emerging organic semiconductor,perylene diimide(PDI)self-assembly has attracted tremendous attention in the aspects of solar cells,sensors,fluorescence probes and n-transistors,etc.In term of photocatalysis,various photocatalysts based on PDI self-assembly exhibit some unique properties,such as intrinsicΠ-Πstacking structure,fast internal charge transfer,band-like electronic structure,flexible structural modifiability,well-defined morphological adjustability and excellent light absorption.This paper mainly presents recent progress on PDI self-assembly regarding how to regulate the electronic structure of PDI self-assembly.In addition,the photocatalytic applications of PDI self-assembly and its complexes were reviewed,such as environmental remedy,energy productions,organic synthesis and photodynamic/photothermal therapy,further highlighting related photocatalytic mechanisms.Finally,the review contents and some perspectives on photocatalytic research of PDI selfassembly were summarized,and some key scientific problems were put forward to direct related photocatalytic research in future.

Aqueous Self-Assembly of Block Copolymers to Form Manganese Oxide-Based Polymeric Vesicles for Tumor Microenvironment-Activated Drug Delivery

Molecular self-assembly is crucially fundamental to nature.However,the aqueous self-assembly of polymers is still a challenge.To achieve self-assembly of block copolymers [(polyacrylic acid-block-polyethylene glycol-block-polyacrylic acid(PAA68-b-PEG86-b-PAA68)] in an aqueous phase,manganese oxide(MnO2) is first generated to drive phase separation of the PAA block to form the PAA68-b-PEG68-b-PAA68/MnO2 polymeric assembly that exhibits a stable structure in a physiological medium.The polymeric assembly exhibits vesicular morphology with a diameter of approximately 30 nm and high doxorubicin(DOX) loading capacity of approximately 94%.The transformation from MnO2 to Mn2+caused by endogenous glutathione(GSH)facilitates the disassembly of PAA68-b-PEG68-b-PAA68/MnO2 to enable its drug delivery at the tumor sites.The toxicity of DOXloaded PAA68-b-PEG68-b-PAA69/MnO2 to tumor cells has been verified in vitro and in vivo.Notably,drug-loaded polymeric vesicles have been demonstrated,especially in in vivo studies,to overcome the cardiotoxicity of DOX.We expect this work to encourage the potential application of polymer self-assembly.

Hierarchical Self-assembly of Well-Defined Louver-Like P-Doped Carbon Nitride Nanowire Arrays with Highly Effcient Hydrogen Evolution

Self-assembled nanostructure arrays integrating the advantages of the intrinsic characters of nanostructure as well as the array stability are appealing in advanced materials.However,the precise bottom-up synthesis of nanostructure arrays without templates or substrates is quite challenging because of the general occurrence of homogeneous nucleation and the difficult manipulation of noncovalent interactions.Herein,we first report the precisely manipulated synthesis of well-defined louver-like P-doped carbon nitride nanowire arrays(L-PCN)via a supramolecular self-assembly method by regulating the noncovalent interactions through hydrogen bond.With this strategy,CN nanowires align in the outer frame with the separation and spatial location achieving ultrastability and outstanding photoelectricity properties.Significantly,this self-assembly L-PCN exhibits a superior visible light-driven hydrogen evolution activity of 1872.9μmol h^−1 g^−1,rendering a^25.6-fold enhancement compared to bulk CN,and high photostability.Moreover,an apparent quantum efficiency of 6.93%is achieved for hydrogen evolution at 420±15 nm.The experimental results and first-principles calculations demonstrate that the remarkable enhancement of photocatalytic activity of L-PCN can be attributed to the synergetic effect of structural topology and dopant.These findings suggest that we are able to design particular hierarchical nanostructures with desirable performance using hydrogen-bond engineering.

Folic Acid Self-Assembly Enabling Manganese Single-Atom Electrocatalyst for Selective Nitrogen Reduction to Ammonia

Efficient and robust single-atom catalysts(SACs)based on cheap and earth-abundant elements are highly desirable for electrochemical reduction of nitrogen to ammonia(NRR)under ambient conditions.Herein,for the first time,a Mn-N-C SAC consisting of isolated manganese atomic sites on ultrathin carbon nanosheets is developed via a template-free folic acid self-assembly strategy.The spontaneous molecular partial dissociation enables a facile fabrication process without being plagued by metal atom aggregation.Thanks to well-exposed atomic Mn active sites anchored on two-dimensional conductive carbon matrix,the catalyst exhibits excellent activity for NRR with high activity and selectivity,achieving a high Faradaic efficiency of 32.02%for ammonia synthesis at−0.45 V versus reversible hydrogen electrode.Density functional theory calculations unveil the crucial role of atomic Mn sites in promoting N_(2) adsorption,activation and selective reduction to NH_(3) by the distal mechanism.This work provides a simple synthesis process for Mn-N-C SAC and a good platform for understanding the structure-activity relationship of atomic Mn sites.

Self-assembly of Quasi-monocrystal CdCO_3 Nanorings

Hierarchical CdCO3 nanostructures with complex morphologies, such as tetragonal, pentagonal and hexagonal nanorings, can be prepared via self-assembly of nanocrystals in a solvothermal environment. XRD pattern indicated that the product is trigonal CdCO3 phase （PDF#850989） with cell constants a = 6.112 A and a = 47.4°. Based on our experimental results, a possible nanoring formation mechanism was proposed.

Hierarchical processes in β-sheet peptide self-assembly from the microscopic to the mesoscopic level

Under appropriate physicochemical conditions, short peptide fragments and their synthetic mimics have been shown to form elongated cross-fl nanostructures through self-assembly. The self-assembly process and the resultant peptide nanos- tructures are not only related to neurodegenerative diseases but also provide inspiration for the development of novel bionanomaterials. Both experimental and theoretical studies on peptide self-assembly have shown that the self-assembly process spans multiple time and length scales and is hierarchical, β-sheet self-assembly consists of three sub-processes from the microscopic to the mesoscopic level： β-sheet locking, lateral stacking, and morphological transformation. De- tailed atomistic simulation studies have provided insight into the early stages of peptide nanostructure formation and the interplay between different non-covalent interactions at the microscopic level. This review gives a brief introduction of the hierarchical peptide self-assembly process and focuses on the roles of various non-covalent interactions in the sub-processes based on recent simulation, experimental, and theoretical studies.