Three-State Thermochromic Smart Window for Building Energy-Saving

Smart windows that dynamically regulate solar spectrum transmission to reduce energy consumption in heating, ventilation, and air conditioning systems are highly desirable. However, the limited amplitude of the regulation and narrow wavelength control often degrade the modulation performance of existing smart windows. To improve solar modulation and thermal management, here we propose a three-state thermochromic smart window (TSSW) capable of modulation across the entire solar spectrum. The TSSW is mainly based on the unique phase transition properties of tungsten-doped vanadium dioxide (W-VO₂) and perovskite films, which can stepwise control the visible light and near-infrared (NIR) transmittance separately, leading to the adaptive transitions between cold, warm, and hot states. Results indicate that the TSSW achieves a solar modulation rate of 23.5%, with indoor solar irradiance decreasing from 413.6 W/m2 in the cold state to 374.5 W/m2 in the warm state, and down to 189.1 W/m2 in the hot state. The simulation results show that the annual total energy demand can be reduced by up to 102.09 WJ/m2 in some typical regions. Compared to Low-E glass and ordinary glass, this TSSW offers superior energy-saving potential, making it an ideal solution for reducing building energy consumption.

Multi-gradient energy-saving smart windows with thermo-response and multimodal thermal energy storage

Buildings, especially installed windows, account for a large proportion of global energy consumption. The research trend of smart windows leans towards multi-functional integration, concurrently achieving solar modulation and thermal management. However, sometimes a one-time performance switch cannot meet demands, making the design of multi-gradient adjustable smart windows particularly important. The combination of the temperature-responsive optical properties of hydroxypropyl cellulose (HPC), the high specific heat capability of water (sensible heat storage) and the solid-liquid phase transition of κ-carrageenan (latent heat storage) is proposed first and can be used to prepare the thermo-responsive hydrogel and multi-gradient energy-saving smart window with thermo-response and multimodal thermal energy storage (MGES smart window) quickly without long-term polymerization. The MGES smart window has excellent solar modulation capability (ΔTlum = 82.72% and ΔTsol = 68.65%) together with outstanding specific heat absorption ability (c = 4.2 kJ kg-1 K-1) and phase transition heat (ΔH = 1.23 kJ kg-1), showing superior energy saving and conserving performance. In demonstrations, the MGES smart windows can reduce the surface and indoor temperature by more than 15 °C and 10.6 °C compared with normal windows. Simulations suggest that they can cut off 45.1% of building energy consumption. To sum up, the MGES smart windows realize multi-aspect adjustment of energy, opening up a new avenue for green buildings.

3D Printable Active Hydrogels with Supramolecular Additive-Driven Adaptiveness

Smart hydrogels are a promising candidate for the development of next-generation soft materials due to their stimuli-responsiveness, deformability, and biocompatibility. However, it remains challenging to enable hydrogels to actively adapt to various environmental conditions like living organisms. In this work, supramolecular additives are introduced to the hydrogel matrix to confer environmental adaptiveness. Specifically, their microstructures, swelling behaviors, mechanical properties, and transparency can adapt to external environmental conditions. Moreover, the presence of hydrogen bonding provides the hydrogel with applicable rheological properties for 3D extrusion printing, thus allowing for the facile preparation of thickness-dependent camouflage and multistimuli responsive complex. The environmentally adaptive hydrogel developed in this study offers new approaches for manipulating supramolecular interactions and broadens the capability of smart hydrogels in information security and multifunctional integrated actuation.

Regulating Electrostatic Interactions toward Thermoresponsive Hydrogels with Low Critical Solution Temperature

Low critical solution temperature (LCST) of commonly used thermoresponsive polymers in water is basically dominated by hydrophobic interactions. Herein, a novel thermoresponsive system based on electrostatic interactions is reported. By simply loading aluminum chloride (AlCl3 ) into non-responsive poly(2-hydroxyethyl acrylate) (PHEA) hydrogels, PHEA-Al gels turn to have reversible thermoresponsive behavior between transparent and opaque without any volume change. Further investigations by changing metal ion-polymer compositions unravel the necessity of specific electrostatic interactions, namely, cation-dipole bonding interactions between hydroxy groups and trivalent metal ions. The thermoresponsive hydrogel demonstrates high transparency (≈95%), excellent luminous modulation capability (>98%), and cyclic reliability, suggesting great potential as an energy-saving material. Although LCST control by salt addition is widely known, salt-induced expression of thermoresponsiveness has barely been discussed before. This design provides a new approach of easy fabrication, low cost, and scalability to develop stimuli-responsive materials.

An eco-friendly photo-responsive hyaluronic acid-based supramolecular polysaccharide hybrid hydrogels for plant growth regulation and heavy metal ions adsorption

Agrochemicals are widely used in agricultural production, but they may cause agrochemicals residues and environmental pollution. Polysaccharide-based materials have emerged as a promising biopolymer carrier for agrochemicals delivery. Herein, an eco-friendly, photo-responsive supramolecular polysaccharide hybrid hydrogels (HA-AAP-Guano-CD@LP) was constructed from arylazopyrazole-modified hyaluronic acid (HA-AAP), guanidinium functionalized β-cyclodextrin (Guano-CD), and laponite clay (LP) via synergistic host-guest and electrostatic interactions, which could realize the controlled release of plant growth regulators such as naphthalene acetic acid (NAA) and gibberellin (GA) and promote the growth of Chinese cabbage and alfalfa. More interestingly, after releasing the cargo, the hydrogels could be used to capture heavy metal ions via strong complexation between the ions and carboxyl groups. This polysaccharide-based supramolecular hybrid hydrogels may provide a new strategy to realize the precision agriculture by the controlled delivery of plant growth regulators and synergetic adsorption of pollutants.

Self-Adhesive Self-Healing Thermochromic Ionogels for Smart Windows with Excellent Environmental and Mechanical Stability, Solar Modulation, and Antifogging Capabilities

Current thermochromic materials used in smart windows still face challenges, such as poor mechanical and environmental stability, unsatisfactory solar modulation capacity, and low transparency. Herein, the first self-adhesive self-healing thermochromic ionogels with excellent mechanical and environmental stability, antifogging capability, transparency, and solar modulation capability by loading binary ionic liquids (ILs) into rational-designed self-healing poly(urethaneurea) with acylsemicarbazide (ASCZ) moieties that have reversible and multiple hydrogen bonds are reported and their feasibility as smart windows with reliability and long service life is demonstrated. The self-healing thermochromic ionogels can switch between transparent and opaque without leakage or shrinkage, by the constrained reversible phase separation of ILs within the ionogels. The ionogels have the highest transparency and solar modulation capability among reported thermochromic materials and such excellent solar modulation capability can be well maintained after undergoing 1000 transitions, stretches, and bends, and storage at -30 °C, 60 °C, 90% RH, and vacuum environment for 2 months. The formation of high-density hydrogen bonds among the ASCZ moieties contributes to the excellent mechanical strength of the ionogels and allows the thermochromic ionogels to spontaneously heal their damages and be fully recycled at room temperature without the loss of thermochromic capabilities.

Conformation- and Coordination Mode-Dependent Stimuli-Responsive Salicylaldehyde Hydrazone Zn(II) Complexes

Luminescent Zn(II) complexes that respond to external stimuli are of wide interest due to their potential applications. Schiff base with O,N,O-hydrazone shows excellent luminescence properties with multi-coordination sites for different coordination modes. In this work, three salicylaldehyde hydrazone Zn(II) complexes (1, 2a, 2b) were synthesized and their stimuli-responsive behaviors in different states were explored. Only complex 1 exhibits reversible and self-recoverable photochromic and photoluminescence properties in solution. This may be due to the configuration eversion and the excited-state intramolecular proton transfer (ESIPT) process. In the solid state, 2a has obvious mechanochromic luminescence property, which is caused by the destruction of intermolecular interactions and the transformation from crystalline state to amorphous state. 2a and 2b have delayed fluorescence properties due to effective halogen bond interactions in structures. 2a could undergo crystal-phase transformation into its polymorphous 2b by force/vapor stimulation. Interestingly, 2b shows photochromic property, which can be attributed to the electron transfer and generation of radicals induced by UV irradiation. Due to different conformations and coordination modes, the three Zn(II) complexes show different stimuli-responsive properties. This work presents the multi-stimuli-responsive behaviors of salicylaldehyde hydrazone Zn(II) complexes in different states and discusses the response mechanism in detail, which may provide new insights into the design of multi-stimuli-responsive materials.

Fluorescent Nanoassemblies in Water Exhibiting Tunable LCST Behavior and Responsive Light Harvesting Ability

Responsive fluorescent nanomaterials have been received considerable attention in recent years. In this work, a bola-type amphiphilic molecule, CSO, was synthesized which contains a hydrophobic cyanostilbene core and hydrophilic oligo(ethylene glycol) (OEG) coils at both sides. The cyanostilbene group is aggregation-induced emission (AIE) active, while the OEG coils are thermo-responsive. As a result, the CSO molecules can self-assemble into blue-fluorescent nanoassemblies with lower critical solution temperature (LCST) behavior in aqueous media. It is noteworthy that the LCST behavior can be reversibly regulated with changes in concentration and the introduction of K⁺ . Intriguingly, fluorescence of CSO assembly shows a blue-shift upon heating. Finally, by employing CSO as a light capturing antenna and energy donor, an artificial light harvesting system with tunable emission and thermo-responsive characteristics was fabricated. This study not only demonstrates an integrated approach to create responsive fluorescent nanomaterials, but also shows great potential for producing luminescent materials and mimicking photosynthesis in nature.

Thermo-Responsive Poly(N-isopropylacrylamide)/Hydroxypropylmethyl Cellulose Hydrogel with High Luminous Transmittance and Solar Modulation for Smart Windows

Thermochromic smart windows are considered to be promising energy-saving devices for reducing energy consumption in buildings. The ideal materials for thermochromic smart windows should have high transmittance, high solar modulation, low phase-transition temperature, and excellent high-temperature thermal stability, which are difficult to achieve simultaneously. This work reports a simple one-step low-temperature polymerization method to prepare a thermo-responsive poly(N-isopropylacrylamide)/hydroxypropylmethyl cellulose (PNIPAM/HPMC) hydrogel achieving the above performances simultaneously. The low-temperature polymerization environment endowed the hydrogel with a high luminous transmittance (T_lum) of 90.82%. HPMC as a functional material effectively enhanced the mechanical properties and thermal stability of the hydrogel. Meanwhile, the PNIPAM/HPMC hydrogel showed a low phase-transition temperature (∼32 °C) and high solar modulation (ΔT_sol = 81.52%), which proved that it is an ideal material for thermochromic smart windows. Moreover, a PNIPAM/HPMC smart window exhibited high light transmittance (T_380-760 = 86.27%), excellent light modulation (ΔT₃₆₅ = 74.27%, ΔT_380-760 = 86.17%, and ΔT₉₄₀ = 63.93%), good indoor temperature regulation ability and stability, which indicated that it was an attractive candidate for application in reducing energy consumption in buildings. This work also provides an option and direction for modifying PNIPAM-based thermochromic smart windows.

Smart thermally responsive perovskite materials: Thermo-chromic application and density function theory calculation

With the continuous improvement of human's requirements for temperature control suitable for living, the energy consumption of electrical appliances such as air conditioners has become a major challenge in traditional architectural design. Generally, most of the solar energy passes through the glass to enter and exit the building, but the traditional glass can hardly control the light and heat energy, causing the indoor temperature to change dramatically with the environment. Therefore, it is more urgent to develop green and efficient smart windows. Perovskite is a temperature-adaptive material, which has the ability of phase transition and can adjust its band gap for thermochromic applications. In this work, we study the perovskite-based thermochromic smart window. As a new application of perovskite, a number of experiments have been carried out. However, there is still a lack of theoretical analysis on phase transition mechanisms and crystal structure prediction. Density functional theory (DFT) calculation is the most useful tool in optoelectronics, especially for perovskite crystal. Here, we extracted typical cases from published literature for analysis and comparison and summarized the crystal structure, electronic structure stability, interface engineering, and thermal characteristics employing DFT calculation We believe this work will pave the way for DFT application for the study of thermochromic perovskite.

Metal-Terpyridine Assembled Functional Materials for Electrochromic, Catalytic and Environmental Applications

Molecular assembly induced by metal-terpyridine-based coordinative interactions has become an emergent research topic due to its ease of synthesis and diverse applications. This article highlights recent significant developments in the metal-terpyridine-based supramolecular architectures. At first, the design aspect of the molecular building blocks has been described, followed by elaboration on how the ligand backbone plays an important role for achieving different dimensionalities of the resulting assemblies which exhibit a wide range of potential applications. After that, we discussed different synthetic approaches for constructing these assemblies, and finally, we focused on their significant developments in three specific areas, viz., electrochromic materials, catalysis and a new application in wastewater treatment. In the field of electrochromic materials, these assemblies made important advancements in various aspects like sub-second switching time (<1 s), low switching voltage (<1 V), increased switching stability (>10000 cycles), tuning of multiple colors by using multimetallic systems, fabrication of charge storing electrochromic devices, utilizing and storing solar energy etc. Similarly, the catalysis field witnessed application of the metal-terpyridine assemblies in C-H monohalogenation, heterogeneous Suzuki-Miyaura coupling, photocatalysis, reduction of carbon dioxide, etc. Finally, the environmental application of these coordination assemblies includes capturing Cr(VI) from waste water efficiently with high capture capacity, good recyclability, wide pH independency etc.

Novel smart window using photonic crystal for energy saving

Smart windows are emerging as an effective way of minimizing energy consumption in buildings. They attracted the major relevance for minimizing energy consumption in buildings. More research studies are needed to design smart windows with operating wide range and don’t require additional energy to operate. We suggest a novel smart window structure using photonic crystal to regulate the solar radiation intensity by preventing it from penetrating the buildings in summer. For the first time, the suggested smart window photonic crystal at room temperature is proposed. The suggested smart window can block about 400 nm of near-infrared. This smart window model doesn’t require additional heat or electric input to operate.

Cyclodextrin-pillar[n]arene hybridized macrocyclic systems

Cyclodextrin (CD) and pillar[n]arene are significant macrocyclic host molecules in supramolecular chemistry, and have either similar or contrasting physicochemical properties, for example, both can provide capable cavities available for recognizing various favorite guest molecules, while they usually possess different solubility in aqueous solutions, and exhibit diverse chiral characteristics. To balance their similarity and differences inherited from each chemical structure and incorporate both advantages, the CD-pillar[n]arene hybrid macrocyclic system was recently developed. In this review, we will focus on the preparation and application of CD-pillar[n]arene hybrid macrocyclic systems. Both noncovalent interactions and covalent bonds were employed in the synthesis strategies of building the hybrid macrocyclic system, which was in the form of host-guest inclusion, self-assembly, conjugated molecules, and polymeric structures. Furthermore, the CD-pillar[n]arene hybrid macrocyclic system has been primarily applied for the removal of organic pollutants from water, induced chirality, as well as photocatalysis due to the integration of both cavities from CD and pillar[n]arene as hybrid hosts and chiral characteristics inherited from their chemical structures.

Application of New Energy Thermochromic Composite Thermosensitive Materials of Smart Windows in Recent Years

Thermochromic smart windows technology can intelligently regulate indoor solar radiation by changing indoor light transmittance in response to thermal stimulation, thus reducing energy consumption of the building. In recent years, with the development of new energy-saving materials and the combination with practical technology, energy-saving smart windows technology has received more and more attention from scientific research. Based on the summary of thermochromic smart windows by Yi Long research groups, this review described the applications of thermal responsive organic materials in smart windows, including poly(N-isopropylacrylamide) (PNIPAm) hydrogels, hydroxypropyl cellulose (HPC) hydrogels, ionic liquids and liquid crystals. Besides, the mechanism of various organic materials and the properties of functional materials were also introduced. Finally, opportunities and challenges relating to thermochromic smart windows and prospects for future development are discussed.

A glycol nanomedicine via metal-coordination supramolecular self-assembly strategy for drug release monitoring and chemo-chemodynamic therapy

A glycol nanomedicine based on metal-coordination supramolecular self-assembly strategy of GluCC (a copper complex of glucose modified coumarin derivative) and a chemotherapeutic agent of doxorubicin (DOX) was successfully developed. In...

Acetonitrile-induced structure fine-tuning of a trinuclear zinc complex showing multistimuli responsive luminescence

A trinuclear zinc complex (1) exhibits mechanochromic and acidochromic luminescence properties with five-color switching. The structure of complex 2 shows that the acetonitrile molecules induce fine-tuning of the structures compared with 1.

Functional polydiynes prepared by metathesis cyclopolymerization of 1,7-dihalogen-1,6-heptadiyne derivatives

The MCP route used for the polymerization of 1,6-heptadiynes was successfully applied to the polymerization of 1,7-dihalogen-1,6-heptadiynes, and the target polymers were obtained in high yield with high molecular weight and unique UCST behavior.

Liquid Crystals: Versatile Self-Organized Smart Soft Materials

Smart soft materials are envisioned to be the building blocks of the next generation of advanced devices and digitally augmented technologies. In this context, liquid crystals (LCs) owing to their responsive and adaptive attributes could serve as promising smart soft materials. LCs played a critical role in revolutionizing the information display industry in the 20th century. However, in the turn of the 21st century, numerous beyond-display applications of LCs have been demonstrated, which elegantly exploit their controllable stimuli-responsive and adaptive characteristics. For these applications, new LC materials have been rationally designed and developed. In this Review, we present the recent developments in light driven chiral LCs, i.e., cholesteric and blue phases, LC based smart windows that control the entrance of heat and light from outdoor to the interior of buildings and built environments depending on the weather conditions, LC elastomers for bioinspired, biological, and actuator applications, LC based biosensors for detection of proteins, nucleic acids, and viruses, LC based porous membranes for the separation of ions, molecules, and microbes, living LCs, and LCs under macro- and nanoscopic confinement. The Review concludes with a summary and perspectives on the challenges and opportunities for LCs as smart soft materials. This Review is anticipated to stimulate eclectic ideas toward the implementation of the nature's delicate phase of matter in future generations of smart and augmented devices and beyond.

Lanthanide Luminescence Supramolecular Switch Based on Photoreactive Ammonium Molybdate

Lanthanide supramolecular assemblies as photoswitches have attracted much attention in the fields of cellular imaging and light-emitting materials. However, the regulation of lanthanide luminescence behavior by redox of metal ions is rare. Herein, we constructed a lanthanide luminescence supramolecular switch, that is, a binary assembly constructed by mono-(6-ethylenediamine-6-deoxy)-β-cyclodextrin (ECD) and ammonium molybdate tetrahydrate ((NH₄)₆Mo₇O₂₄·4H₂O, Mo₇), and further assembled into ternary assemblies with polyoxometalate Na₉[XW₁₀O₃₆]·32H₂O (X-POM, X = Eu and Dy), which was comprehensively characterized by UV-vis, fluorescence, NMR, Fourier transform infrared, dynamic light scattering, scanning electron microscopy, and ζ potential. Thanks to the oxygen-shielding effect of secondary supramolecular assembly, the photoreduction process of Mo₇ (VI) could occur rapidly and efficiently. Due to the high Förster resonance energy transfer (FRET) efficiency of X-POM and Mo₇ (V) in supramolecular assembly, the photoreduction process is accompanied by fluorescence quenching. In addition, the oxidation process of the Mo₇ (V) could be rapidly promoted by heating, which allowed the X-POM fluorescence to recover. Interestingly, ECD-mediated ternary supramolecular assemblies not only tune the lanthanide luminescence but also strongly increase the lanthanide luminescence behavior, leading to the emission of strong narrow red light at ⁵D₀-⁷F₄, which can be successfully applied to two-dimensional code anticounterfeiting. In this study, a new approach is provided for the construction of lanthanide luminescence supramolecular switches tuned by photoreactive polyoxometalate.

Supramolecular Assembly and Reversible Transition and of Chitosan Fluorescent Micelles by Noncovalent Modulation

Chitosan-based intelligent artificial systems have been of increasing interest for their biocompatibility, multifunctionality, biological activity, and low cost. Herein, we report the fabrication of supramolecular nanoparticles based on water-soluble chitosan (WCS) and 1,1 ${}^{\prime }$ ,1 ${}^{″}$ ,1 ${}^{″\prime }$ -(ethene-1,1,2,2-tetrayl)tetrakis(benzene-4,1-diyl) tetrakis(azanediyl)tetraacetic acid (TPE-(N-COOH)4), which is capable of reversible transition between polyion complexes (PICs) and hydrogen bonding complexes (HBCs) with tunable aggregation-induced emission driven by pH value. The PIC micelles could be formed via electrostatic interaction between ammonium cations and carboxylate anions under mild alkaline conditions. The formation of the micelles dramatically blocks the nonradiative pathway and enhances the fluorescence of TPE moieties, and the maximum fluorescence intensity was achieved near the isoelectric point due to the restriction of intramolecular motion. In addition, the fluorescence intensity and size of the PIC micelles exhibited a temperature response in the range from 20 to 80°C. Upon adjusting the solution pH to 2, the PIC micelles were reconstructed into hydrogen-bonding complexes while the hydrogen bonding interaction between the protonated carboxyl groups of TPE-(N-COOH)4 and chitosan. Moreover, the size of the micelles underwent a remarkable decrease, whereas the fluorescence emission was further enhanced by ~6.25-fold. The pH actuated micellar transition from PIC to HBC with tunable fluorescence performance is fully reversible. This study provides novel multifunctional materials that are of great importance for their potential application in the fields of optoelectronic devices and chemical and biomedical sensors.

Luminescent lanthanide-macrocycle supramolecular assembly

A series of macrocyclic compounds, including crown ether, cyclodextrin, cucurbituril and pillararene, bound to various specific organic/inorganic/biological guest molecules and ions through various non-covalent interactions, can not only make a single system multifunctional but also endow the system with intelligence, especially for luminescent materials. Due to their excellent luminescence properties, such as long-lived excited states, sharp linear emission bands and large Stokes shift, lanthanides have shown great advantages in luminescence, and have been more and more applied in the design of advanced functional luminescent materials. Based on reported research, we summarize the progress of lanthanide luminescent materials based on different macrocyclic compounds from ion or molecule recognition to functional nano-supramolecular assembly of the lanthanide-macrocycle supramolecular system including photo-reaction mediated switch of lanthanide luminescent molecules, multicolor luminescence, ion detection and cell imaging of rare-earth up-conversion of macrocyclic supramolecular assembly. Finally, we put forward the prospects of future development of lanthanide luminescent macrocyclic supramolecular materials.

Self-assembly of propeller-shaped amphiphilic molecules: control over the supramolecular morphology and photoproperties of their aggregates

The aggregation-induced emission (AIE) effect is an important feature for luminescence studies, which can offer a broader range of applications for fluorescent materials. Herein, we report the morphological control and photoproperties of amphipathic propeller-shaped rod-coil molecules based on a benzene-1,3,5-tricarboxamide (BTA) unit, which restricts the intramolecular rotation and leads to the AIE effect during the self-assembly process. Investigations on the assembly of these molecules have revealed that tetragonal perforated lamella, hexagonal columnar, body-centered tetragonal micellar, and hexagonal close-packed nanostructures were spontaneously formed in the solid-state. In the solution-state, these molecules assemble into nanosheet-like aggregates, bowl-like objects, and spherical nanoparticles, respectively. The morphology of the molecular aggregates can be controlled by modifying the molecular chain length or introducing lateral methyl groups in the coil chain. Notably, these molecular assemblies exhibit strong AIE phenomena in a mixed THF/H2O solution and can be used as smart soft materials due to the restriction of their intramolecular motion.

Radiochromic Hydrogen-Bonded Organic Frameworks for X-ray Detection

Porous materials have been investigated as efficient photochromic platforms for detecting hazardous radiation, while the utilization of hydrogen bonded organic frameworks (HOFs) in this field has remained intact. Herein, two HOFs were synthesized through self-assembly of tetratopic viologen ligand and formic acid (PFC-25, PFC-26), as a new class of "all-organic" radiochromic smart material, opening a gate for HOFs in this field. PFC-26 is active upon both X-ray and UV irradiation, while PFC-25 is only active upon X-ray irradiation. The same building block yet different radiochromic behaviors of PFC-25 and PFC-26 allow us to gain a deep mechanistic understanding of the factors that control the detection specificity. Theoretical and experimental studies reveal that the degree of π-conjugation of viologen ligand is highly related to the threshold energy of triggering a charge transfer, therefore being a vital factor for the particularity of radiochromic materials. Thanks to its convenient processibility, nanoparticle size, and UV silence, PFC-25 can be further fabricated into a portable naked-eye sensor for X-ray detection, which shows obvious color change with the merits of high transmittance contrast, good sensitivity (reproducible dose threshold of 3.5 Gy), and excellent stability. The work exhibits the promising practical potentials of HOF materials in photochromic technology.

Tailoring Broad-Band-Absorbed Thermoplasmonic 1D Nanochains for Smart Windows with Adaptive Solar Modulation

Controlling solar transmission through windows promises to reduce building energy consumption. A new smart window for adaptive solar modulation is presented in this work proposing the combination of the photothermal one-dimensional (1D) Au nanochains and thermochromic hydrogel. In this adaptive solar modulation system, the Au nanochains act as photoresponsive nanoheaters to stimulate the optical switching of the thermochromic hydrogel. By carefully adjusting the electrostatic interactions between nanoparticles, different chain morphologies and plateau-like broad-band absorption in the NIR region are achieved. Such broad-band-absorbed 1D nanochains possess excellent thermoplasmonic effect and enable the solar modulation with compelling features of improved NIR light shielding, high initial visible transmittance, and fast response speed. The designed smart window based on 1D Au nanochains is capable of shielding 94.1% of the solar irradiation from 300 to 2500 nm and permitting 71.2% of visible light before the optical switching for indoor visual comfort. In addition, outdoor cooling tests in model house under continuous natural solar irradiation reveal the remarkable passive cooling performance up to ∼7.8 °C for the smart window based on 1D Au nanochains, showing its potential in the practical application of building energy saving.

3,6-Fluoren[5]arenes: synthesis, structure and complexation with fullerenes C60 and C70

3,6-Fluoren[5]arenes with big and rich-electron cavities were conveniently synthesized, which could form stable 1 : 1 complexes with fullerenes in solution.

Reversible Chromatic Change of Supramolecular Gels for Visual and Selective Chiral Recognition of Histidine

In the present work, a chemical reaction has been performed for supramolecular gels to achieve multiple-stimuli-responsive smart soft materials. Simple chiral binaphthalene-based receptors can condense with histidine (His) to yield a Schiff base, which would help to achieve visual chiral recognition of unprotected l/d-His through gel formation along with specific selectivity toward 20 amino acids. Through intermolecular hydrogen bonds, the resultant Schiff base molecules assemble with excess His molecules to form three-dimensional (3D) networks of metastable cross-linked nanospheres and stable nanofibers in EtOH/water and MeOH/water, respectively. Significantly, this condensation reaction exhibits unique reversible and chromatic phenomena between sol-gel phase transitions in EtOH/water, which provide a way to design chemical reaction-based multivisual-change supramolecular gels for sensing and switching applications.

Ultralow-Molecular-Weight Stimuli-Responsive and Multifunctional Supramolecular Gels Based on Monomers and Trimers of Hydrazides

The simpler, the better. A series of simple, neutral and ultralow-molecular-weight (MW: 140-200) hydrazide-derived supramolecular gelators have been designed and synthesized in two straightforward steps. For non-conjugated cyclohexane-derived hydrazides, their monomers can self-assemble to form gels through intermolecular hydrogen bonds and dipole-dipole interactions. Significantly, conjugated phthalhydrazide can self-aggregate into planar and circular trimers through intermolecular hydrogen bonds and then self-assemble to form gels through intermolecular π-π stacking interactions. It is interesting that these simple gelators exhibit unusual properties, such as self-healing, multi-response fluorescence, and visual and selective recognition of chiral (R)/(S)-1,1'-binaphthalene-2,2'-diamine and S^2- through much different times of gel re-formation and blue-green color change, respectively. These results underline the importance of supramolecular gels and extend the scope of supramolecular gelators.

Actively Operable Thermoresponsive Smart Windows for Reducing Energy Consumption

Efficient usage of finite energy resources is a core approach for preventing major blackouts caused by a severe lack of energy. Smart windows, which modulate thermal energy transferred from the incident sunlight, have attracted tremendous interest as an alternative technology for resolving the fast-approaching energy crisis by suppressing unnecessary energy usage such as air conditioning or heating inside buildings. Here, we demonstrate a set of materials and design concepts for doubly responsive smart windows, which efficiently reduce the consumption of our limited energy reserves. The proposed smart windows are based on the concept of combining the lower critical solution temperature of thermoresponsive polymer hydrogels and the electrical actuation of graphene-based flexible heaters; this combination serves to actively control the passive-type moving thermoresponsive smart window. The proposed smart windows exhibit a highly tunable transparency of above 90%, which corresponds to an almost instantaneous change from high transmission of the incident light to the complete blockage of its penetration under thermal or electrical stimulation. In particular, when the windows of a mockup house are replaced with the developed flexible smart windows, the increment rate of the indoor temperature under white light irradiation reduces drastically. This type of active light control system is expected to create a new opportunity for achieving cost savings on heating, cooling, and lighting through management of light energy transmitted into the interior of a house.

Low-Cost, Robust Pressure-Responsive Smart Windows with Dynamic Switchable Transmittance

Mechanically responsive smart windows with adjustable light transmittance have attracted more and more attention due to their great potential in our daily life. However, their fabrication normally requires complicated preparation such as oxygen plasma treatment and high-cost materials (i.e., poly(dimethylsiloxane) (PDMS)), which hinders their practical applications. Herein, a principally different mechanically responsive smart window, i.e., a pressure-responsive smart window, is reported, which is achieved by harnessing the synergistic interactions (i.e., hydrogen bonding and surface roughness compensation) between the two constituent parts, i.e., hydrogel and agar films. The pressure-responsive smart window features the ultrafast response time (37.5 ms) and high transmittance changes (∼50%) with excellent repeatability, which can be stained with different colors and operated on a flexible substrate. Since the pressure-responsive smart window enables the utilization of the low-cost material and does not require the external energy input, it is anticipated that it may have great potential in practical applications.

Constructing Alternated Heterobimetallic [Fe(II)/Os(II)] Supramolecular Polymers with Diverse Solubility for Facile Fabrication of Voltage-Tunable Multicolor Electrochromic Devices

Metallo-supramolecular polymer (MSP)-based electrochromic devices (ECDs) have drawn much attention because of their variable colors and attractive electrochromic (EC) properties. However, fabrication of voltage-tunable multicolor ECDs using single MSP is yet hard to realize. We anticipated alternate introduction of two different redox-active metal ions in an MSP combined with the adjustment of counteranions could be a solution to fabricate multicolor ECDs. The heterometals will induce color variability upon voltage alteration, and counteranions will help to tune the solubility of MSP in different solvents. In an attempt to fulfill this target, we have synthesized four heterobimetallic supramolecular polymers (HBPs) having different counteranions (BF₄^-, Cl^-, PF₆^-, and OAc^-), in which Fe(II) and Os(II) are alternately complexed by two terpyridine units. To apply as EC material, the HBPs should be soluble in methanol and insoluble in acetonitrile for the preparation of EC film as well as ECDs. However, among the HBPs, only HBP-OAc is found to meet this requirement. The EC behaviors of the spray-coating film of HBP-OAc on an indium tin oxide (ITO)-coated glass substrate are investigated in terms of maximum transmittance contrast, coloration voltage, response time, coloration efficiency, and operational stability, which exhibits reversible multicolor electrochromism (the initial purple color of the film is changed to violet followed by greenish-yellow) upon alteration of the voltage from 0.0 to 0.7 V [required to oxidize the Os(II) ion] and to 1.0 V [required to oxidize the Fe(II) ion]. The film is also integrated into a laminated ECD by using lithium-based gel electrolyte. Finally, as a proof-of-concept, a prototype voltage-tunable multicolor EC display (6 cm × 2.5 cm) is fabricated by using a designed image containing a flower, leaves, and a flower pot, which exhibits six different types of multicolor image upon application of tunable voltages.

Multifunctional inorganic nanomaterials for energy applications

Our society has been facing more and more serious challenges towards achieving highly efficient utilization of energy. In the field of energy applications, multifunctional nanomaterials have been attracting increasing attention. Various energy applications, such as energy generation, conversion, storage, saving and transmission, are strongly dependent upon the electrical, thermal, mechanical, optical and catalytic functions of materials. In the nanoscale range, thermoelectric, piezoelectric, triboelectric, photovoltaic, catalytic and electrochromic materials have made major contributions to various energy applications. Inorganic nanomaterials' unique properties, such as excellent electrical and thermal conductivity, large surface area and chemical stability, make them highly competitive in energy applications. In this review, the latest research and development of multifunctional inorganic nanomaterials in energy applications were summarized from the perspective of different energy applications. Furthermore, we also illustrated the unique functions of inorganic nanomaterials to improve their performances and the combination of the functions of nanomaterials into a device. However, challenges may be traced back to the limitations set by scaling the relations between multifunctional inorganic nanomaterials and energy devices.

A fast-switching electrochromic device with a surface-confined 3D metallo-organic coordination assembly

Demonstrated herein is a fast (<1 s)-switching solid-state electrochromic device (t = 0.49 s for coloration and 0.90 s for bleaching), fabricated with a novel imidazolium-linked [Fe(terpyridine)2]2+ chromophore-based surface-confined three dimensional metallo-organic coordination assembly. The device also exhibits promising electrochromic attributes such as high coloration efficiency (η = 275 cm2 C-1), moderate operating voltage (from -2 V to +3.2 V) and transmittance contrast (ΔT = 40%), and high cycling stability (up to 4500 cycles).

A novel AIE chemosensor based on a coumarin functionalized pillar[5]arene for multi-analyte detection and application in logic gates

A novel coumarin functionalized pillar[5]arene (PX) with AIE fluorescence could sequentially detect multiple analytes in aqueous medium with high sensitivity.

1,8-Dioxapyrene-based electrofluorochromic supramolecular hyperbranched polymers

A 1,8-dioxapyrene-based electrofluorochromic supramolecular polymer was constructed through the coordination of terpyridine ligands with Eu³⁺ ions. The polymer can be used in anti-counterfeiting inks.

A viologen-based multifunctional Eu-MOF: photo/electro-modulated chromism and luminescence

A novel viologen-based multifunctional Eu-MOF integrating photochromism, photomodulated fluorescence, and electrochromic and electroluminochromic properties was investigated.

Triple responsive room temperature luminescence, photochromism and photomagnetism in a Dy(iii)-based linear chain complex

Triple responses of room temperature fluorescence, photochromism and photomagnetism tuned by photo/thermo-switched radicals were realized in a Dy(iii)-based metal–organic complex.

Supramolecular assemblies controlled by cucurbit[n]uril size (n = 6, 7, 8 and 10)

The differing cavity size of the Q[n] determines the binding interactions between the benzyl substituted 4-pyrrolidinopyridinium salt and each Q[n]. Single crystal X-ray diffraction of the guest as well as two host–guest complexes is reported.

Design, synthesis, and characterization of novel organic–inorganic hybrid polymeric materials for electroluminescence applications

Design and syntheses of two electroluminescent metallopolymers from a novel, multidentate, redox active, and di-anionic organic building block.

An easily accessible isospiropyran switch

In the presence of SiCl4, three molecules of 5'-bromo-2'-hydroxyacetophenone underwent an unexpected tandem aldol condensation to give a novel isospiropyran switch (69%), with X-ray crystallography confirming its structure. The strong Brønsted acid CH3SO3H turned the colorless isospiropyran into its protonated and open form possessing red color. This process was reversed using the Et3N base, with the acid/base toggling repeatable for at least six times (UV-Vis). When printed on a silica plate, however, the isospiropyran formed a blue-colored product due to, as posited, its stabilization by hydrogen bonding (HB) to silica. An exposure to HB-competing ethyl acetate temporarily "erased" the print only to be brought back by subjecting the plate to a higher temperature for evaporating the solvent. The isospiropyran described here is an easily accessible, chromic, modular and switchable compound that one can incorporate into dynamic materials or use for building chemosensors, molecular machines and organic electronic devices.

An azine-containing bispillar[5]arene-based multi-stimuli responsive supramolecular pseudopolyrotaxane gel for effective adsorption of rhodamine B

An azine-containing bispillar[5]arene was designed and synthesized by the reaction of aldehyde functionalized-pillar[5]arene and hydrazine. Then, a novel bispillar[5]arene-based supramolecular pseudopolyrotaxane has been successfully prepared via host-guest interaction. Interestingly, by taking advantage of the host-guest interactions, π-π stacking interactions and hydrogen bonding interactions, the multi-stimuli-responsive gel-sol phase transitions of such a supramolecular pseudopolyrotaxane gel were successfully realized under different stimuli, such as acid, temperature, concentration, and competitive guests. Moreover, this supramolecular system could effectively adsorb dye molecule rhodamine B. It is worth noting that this supramolecular pseudopolyrotaxane gel prepared in cyclohexanol solution (BP5·G·C) could be used as an adsorbent material for adsorbing rhodamine B with adsorption efficiency of 98.4%. Meanwhile, the adsorption efficiency was 97.6% for supramolecular pseudopolyrotaxane gel prepared in DMSO-H2O (v : v, 8 : 2) binary solution (BP5·G·D), also indicating the superior adsorption effect of BP5·G·D toward the dye molecule rhodamine B.

X-ray and UV Dual Photochromism, Thermochromism, Electrochromism, and Amine-Selective Chemochromism in an Anderson-like Zn7 Cluster-Based 7-Fold Interpenetrated Framework

Smart materials are highly desirable over the recent decade due to the growing demand of complicated nature. Stable stimuli-responsive smart materials exhibit widespread potential for applications in smart windows, sensors, separators, chemical valves, and release platforms but are rare. Despite being good candidates, viologen-based multifunctional smart materials are still a challenging task for chemists. To obtain such materials, the judicious strategy is to introduce polynuclear metal-carboxylate clusters as electron donors into a stable framework to increase chromic sensitivity. Toward this endeavor, we have synthesized a novel viologen-based polymer with a unique Anderson-like metal-carboxylate cluster, [Zn₇(bpybc)₃(o-BDC)₆]·2NO₃·6H₂O (bpybc = 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium, o-BDC = o-benzenedicarboylic acid) (1), which is a particular 7-fold interpenetrated framework with a 3D pcu network in which bpybc ligand as the linker and Zn₇O₃₀C₁₂ as the second building unit (Zn₇ SBU) were used as 6-connected nodes. More importantly, it shows excellent chromic behavior in response to multiple external stimuli especially soft X-ray and UV dual light, temperature, electricity, and organic amines, which stand out in the viologen-based polymers. Interestingly, the coloration process of 1 from "core" to "edge" is observed upon heating at the appropriate temperature, which has not yet been found in other reported thermochromic materials. Of particular interest for 1 is the couple of quaternary stimuli-sensitive abilities because it simultaneously meets the following conditions: (i) the capability of withstanding high light, higher temperature, extreme pH, and other harsh conditions; and (ii) the high sensitivity to external stimuli keeping away from photodegradation, thermal relaxation, side reactions, and so on. To be noted, 1 has high thermal stability and chemical stability, which are excellent advantages as smart materials. To further develop possible practical utilization, 1 has been doped into the polymer matrixes to construct a hybrid film, which not only keeps the response to external stimuli but also significantly improves the repeatability of the photochromic process, indicating that a new smart device with multi-stimuli-responsive functions will emerge successively in the future.

A novel photochromic hybrid containing trinuclear [Cd3Cl12]6− clusters and protonated tripyridyl-triazines

A novel organic–inorganic hybrid [H₃TPT]₂[Cd₃Cl₁₂] exhibits excellent photochromic performance with ultrafast photoresponsive rate, obvious coloration contrast and high thermal stability.

A simple and visual approach for enantioselective recognition through supramolecular gels with specific selectivity

(S)/(R)1 enantioselectively self-assemble to form a gel or solution with one enantiomer of (S)/(R)BINAM with specific selectivity.