Three-way catalysts are widely used to control criterion pollutant emissions from the increasing gasoline engines. With the stringent requirements of automotive pollutant emission standards in various countries, Rh has become an irreplaceable component of three-way catalysts due to its superior NOx elimination, high N2 selectivity, and simultaneous elimination of CO and hydrocarbons. In this review, we systematically review the recent development of Rh-based three-way catalysts in terms of potential supports and effective active center construction strategies. We further summarize the key role of Rh metal in the three-way catalytic mechanism and reaction kinetics. Finally, we conclude the current challenges and future opportunities facing Rh-based catalysts. It is believed that based on the deep understanding of Rh-based three-way catalysts, the design of Rh-based catalysts with good low-temperature catalytic performance and low cost is expected to be realized in the future.
Metal–organic frameworks (MOFs) represent a unique class of porous materials with tremendous potential for diverse applications. A key factor contributing to their versatility is their ability to precisely introduce functional groups at specific positions within pores and crystals. This review explores two prominent strategies for achieving the positional functionalization of MOFs: post-synthetic ligand exchange (PSE) and MOF-on-MOF. In PSE, the existing ligands within solid-state MOFs can be selectively replaced by the desired functional groups in solution through ligand dynamics. This invasive functionalization provides a flexible approach to fine-tuning the surface of the MOFs with the target functionality. Conversely, MOF-on-MOF strategies are additive methodologies involving the controlled growth of one MOF layer onto another. The functionality of the core and shell (or surface) can be independently controlled. This review critically examines the examples, strengths, limitations, and applications of these strategies, emphasizing their significance in advancing the field of MOF functionalization and paving the way for tailored multifunctional materials with precise and specific properties.
The multifaceted switches are part of our everyday life from the macroscopic to the molecular world. A molecular switch operating in the solution and in the crystalline state is very different. In this review, we summarize the state-of-the-art of smart molecular crystal switches based on molecular martensites. These crystal switches respond to external stimuli and reversibly change between states, retaining their macroscopic integrity. The operation of the switches predominantly relies on temperature alterations or mechanical stress, with emerging methods based on photothermal effects, photoisomerization, and host-guest chemistry. The capability of changing the molecular orientation and interaction in smart molecular crystal switches offers opportunities in several applications, including actuators, reversibly shaping structural materials, optoelectronic and magnetic materials, as well as switchable porous materials. Smart molecular crystal switches have vast potential in modern scientific and technological progress. The ongoing research shapes a rich landscape for innovation and future scientific exploration across diverse disciplines.
The smart emulsification and demulsification system with the light response is a useful tool in various industries, including green chemistry, catalytic reaction, pharmaceuticals, and environmental remediation. Herein, an ionic liquid crystal compound with a light triggered switch based on the azobenzene group [(4-{3-methyl-1-[3-(8-octyloxyoctyl)oxy-4-oxobutanoyl]imidazo-lium-1-yl}octyl) oxy] -N-(4-methylphenyl)benzene-1,2-diazene bromide (MOIAzo), was designed and synthesized, which could cause reversible transition between emulsification and demulsification through the light trigger. The ionic liquid has an efficient photoinduced liquefaction process, which dramatically lowers the melting point of ionic liquids from 79 to 9.2 °C. This significantly broadens the liquid state temperature of the ionic liquid crystal. The ionic liquid crystal MOIAzo exhibits both photoinduced and thermally induced nematic liquid crystal properties. The smart emulsion system was effectively employed in an eco-friendly water-saving dyeing process of cationic dyes for cationic dyeable polyester (CDP) fabrics, which used only half the amount of water compared with the conventional water bath dyeing method. After dyeing, the oil and water phases can be efficiently separated through the light irradiation, and the oil phase can be reused for the subsequent dyeing process. This novel smart emulsion dyeing method greatly reduces the water consumption and wastewater discharge. MOIAzo as a lighttriggered ionic liquid molecule opens up new dimensions in green chemistry.
In recent years, the use of light to selectively and precisely activate drugs has been developed along the fundamental concepts of photopharmacology. One of the key methods in this field relies on transiently silencing the drug activity with photocleavable protecting groups (PPGs). To effectively utilize light-activated drugs in future medical applications, physicians will require a reliable method to assess whether light penetrates deep enough into the tissues to activate the photoresponsive theragnostic agents. Here, we describe the development and evaluation of magnetic resonance (MR) imaging agents that allow for the detection of light penetration and drug activation in the tissues using non-invasive whole-body magnetic resonance imaging (MRI) and chemical exchange saturation transfer (CEST)-MRI modalities. The approach relies on the use of PPG-protected MR contrast agents, which upon irradiation with light change their imaging signal. A Gadolinium(III)-based MRI contrast agent is presented that undergoes a significant change in relaxivity (25%) upon uncaging, providing a reliable indicator of light-induced cargo release. Additionally, we introduce the first light-responsive CEST-MRI imaging agent, enabling positive signal enhancement (off-to-on) upon light activation, offering a novel approach to visualize the activation of photoactive agents in living tissues. This research provides a proof-of-principle for the noninvasive, whole-body imaging of light penetration and drug activation with high temporal resolution characteristic of MR methods.
Smart molecules have attracted increasing attention due to their transformative role in creating the next generation of smart structures and devices. Smart bistable coordination complexes are a class of functional complexes which have two stable states that can be reversibly switched in response to external stimuli. Such bistable molecules play a vital role in various applications, such as sensors, data storage, spintronics, smart windows, optical switches, information encryption and decryption, displays, actuators, etc. Herein, the recent research studies into the development of these smart bistable metal coordination complexes are reviewed. According to the different external stimuli, these smart bistable coordination systems have been classified and summarized, including light-responsive systems, thermally-responsive systems, electrically-responsive systems, mechanicallyresponsive systems, and some other cases. These systems are further subdivided according to the changes in signals (e.g., color, fluorescence, spin state, crystalline phase) under external stimuli. The design principles of each type of smart bistable metal complexes as well as their broad and innovative applications are comprehensively described. Finally, the challenges and opportunities in this field are briefly analyzed and discussed.
Aqueous rechargeable batteries using abundant multi-ion cations have received increasing attention in the energy storage field for their high safety and low cost. Layered double hydroxides (LDHs) possess a two-dimensional structure and exhibit great potential as cathodes for multi-ion intercalation. However, the insufficient active sites of LDHs result in low capacities in the discharging process. Interestingly, the LDHs after the deprotonation process exhibit favorable electrochemical performance of multi-cation intercalation. The deprotonation process of LDHs has been widely found in the oxygen evolution reaction and energy storage field, where LDHs lose H in laminates and converts to deprotonated γ-phase MOOHs (MOOs). Herein, we take a comprehensive overview of the dynamics structure transformation of the deprotonation process of LDHs. Furthermore, the development of advanced aqueous battery cathode and metal battery anode based on deprotonated LDHs for energy storage is explored and summarized. Finally, the perspective of deprotonated LDHs in the energy storage field is discussed.
Smart chiral liquid crystal elastomers are a class of soft photonic crystals with periodic nanostructures. There are two kinds of chiral liquid crystal elastomers with structural colors: cholesteric liquid crystal elastomers with a one-dimensional helical nanostructure and blue-phase liquid crystal elastomers with a three-dimensional photonic crystal nanostructure. The self-assembled nanostructure of chiral liquid crystal elastomers can be dynamically controlled under external stimulation, and the reflected color can be adjusted throughout the visible light range. Along with the development of innovative material systems and cutting-edge manufacturing technologies, researchers have proposed diverse strategies to design and synthesize chiral liquid crystal elastomers and have thoroughly investigated their properties and potential applications. Here, we provide a systematic review of the progress in the design and fabrication of smart chiral liquid crystal elastomers, focusing on the cholesteric liquid crystal elastomers via surface-enforced alignment, bar coating, 3D printing, anisotropic deswelling methods as well as the three-dimensional self-assembly of blue-phase liquid crystal elastomers without additional alignment. Smart chiral liquid crystal elastomers are able to respond quickly to external stimuli and have a wide range of applications in areas such as adaptive optics, color-changing camouflage, soft robotics, and information encryption. This review concludes with a perspective on the opportunities and challenges for the future development of smart chiral liquid crystal elastomers.
Glutathione (GSH)-activated prodrugs are promising for overcoming the limitations of conventional anti-tumor drugs. However, current GSH-responsive disulfide groups exhibit unregulated reactivity, making it impossible to precisely control the drug release rate. We herein report a series of GSH-responsive prodrugs with a “three-in-one” molecular design by integrating a fluorescence report unit, stimuliresponsive unit and chemodrug into one scaffold with tunable aromatic nucleophilic substitution (SNAr) reactivity. The drug release rate of these prodrugs is tailored by modification of substituent groups with different electron-withdrawing or -donating abilities on the BODIPY core. Furthermore, the prodrugs self-assemble in water to form nanoparticles that serve as photosensitizers to produce reactive oxygen species upon irradiation for photodynamic therapy (PDT). The PDT process also increases the concentration of GSH in cells, further promoting the release of drugs for chemotherapy. This strategy provides a powerful platform for sequential photodynamic and chemotherapy with tunable drug release rates and synergistic therapeutic effects.
Stimuli-responsive DNA-based logic gates have emerged as a promising field at the intersection of synthetic biology and nanotechnology. These gates exploit the unique properties of DNA molecules to perform programmable computational operations in response to specific stimuli. This review provides a comprehensive overview of recent advancements in the design, working principles, and applications of stimuli-responsive DNA-based logic gates. The progress made in developing various types of logic gates triggered by metal ions, pH, oligonucleotides, small molecules, proteins, and light is highlighted. The applications of these logic gates in imaging and biosensing, drug delivery, synthetic biology and molecular computing are discussed. This review underscores the significant contributions and future prospects of stimuli-responsive DNA-based logic gates in advancing the field of nanotechnology.
It is a great challenge to discover novel chemical reactions suitable for biological analysis in a living system. The development of novel protein thiol blocking agents is a crucial need for exploring protein thiol functions in protein refolding, signal transduction, and redox regulation. We are always keen on seeking novel chemical reactions applied to endogenous biological macromolecules or protein thiol sensing, blocking, and labeling. In the present work, we have successfully developed a novel agent to block protein thiol by enhanced electron-withdrawing inductive effects. This sensing and blocking process was detailedly monitored by UV-vis, fluorescent spectra, and SDS-Page gel separation. The spectral studies demonstrated that the agent could react ultrafastly with thiol within seconds at μM level. Furthermore, fluorescent imaging in cells and in vivo was further used for the validation of its ability to sensing and blocking thiol, providing evidence of downregulated protein thiols in Parkinson’s disease. The enhanced electronwithdrawing inductive effect strategy in this work may provide a general guideline for designing protein thiol agent.
This comprehensive review delves into a unique intersection of hydrogels as smart molecules and their transformative applications in ophthalmology. Beginning with the foundational definition, properties, and classification of hydrogels, the review explores their synthesis and responsive capabilities. Specific applications examined encompass topical drug delivery, contact lenses, intravitreal drug delivery, ocular adhesives, vitreous substitutes, and cell-based therapy. A methodical analysis, including an overview of relevant ocular structures and a comparative evaluation of hydrogel-based solutions against traditional treatments, is conducted. Additionally, potential constraints, translation challenges, knowledge gaps, and research areas are identified. Our methodical approach, guided by an extensive literature review from 2017 to 2023, illuminates the unprecedented opportunities offered by hydrogels, along with pinpointing areas for further inquiry to facilitate their transition into clinical practice.
Metastable endoperoxides with beta-amyloid fibrils targeting benzothiazole moieties were designed and synthesized. Singlet oxygen released from these endoperoxides by thermal cycloreversion reaction was shown to cause significant structural changes on the amyloid assemblies. Most importantly, the cytotoxicity of the beta-amyloid fibrils on the PC12 cells were significantly reduced in the presence of endoperoxides. This observation, coupled with the fact that neither external oxygen, nor light is needed for this transformation, is very promising.
The integration of robust photon-absorption capacity, high reactive oxygen species yields and photothermal conversion efficiency (PCE) into a single phototheranostic nano-agents is ideal but rarely reported. This study employed a dual-acceptor engineering strategy utilizing isoindigo and selenium-substituted [1,2,5]thiadiazolo[3,4-c]pyridine to augment the molar extinction coefficient and spin-orbit coupling effect, respectively, resulting in a substantial enhancement of photonabsorption ability and non-radiative decay energy-release process of donoracceptor type phototherapy molecules. As the optimal phototherapy agent, IID-PSe exhibited a high molar extinction coefficient two times that of photosensitizer, excellent 1O2 yield (15%) and PCE (34%), exhibiting great potential for phototherapy. After encapsulating with DSPE-PEG2000, IID-PSe NPs showed excellent anti-tumor phototherapy ability both in vitro and in vivo. This work provides an effective idea for designing high-performance photosensitive dyes with high efficiency phototherapy output.
Computational chemistry methods are playing an increasingly pivotal role in chemical experiments. From quantum chemistry simulations to finite element simulations, researchers can always find an appropriate simulation method to elucidate the specific mechanisms at a certain resolution scale. However, in organic or inorganic synthesis, the synthesis mechanisms span multiple spatial and temporal scales of chemical experiments. Furthermore, the intricate nature of these mechanisms renders it impossible for any single simulation method to provide a comprehensive depiction of the entire process. In this perspective, using zeolite and polymer synthesis simulations as examples, we stress the significance of fullscale modeling techniques for chemical experiments and urge the corresponding sophisticated simulation platform.
