[Land Change Simulation and Grassland Carbon Storage in the Loess Plateau Based on SSP-RCP Scenarios].

Exploring the spatial distribution of land use/coverage (LUCC) and ecosystem carbon reserves in the future of climate change can provide a scientific basis for optimizing the distribution of land resources and formulating social economic sustainable development policies. In this study, we integrated the plaques generating land use simulation (PLUS) model and ecosystem services and weighing comprehensive evaluation (InVEST) model. Based on the CMIP6-based sharing socio-economic path and representative concentration path (SSP-RCP), we evaluated the Loess Plateau for time and space dynamic changes in LUCC and ecosystem carbon reserves, analyzed the impact of driving factors on different regions, and explored the correlation between carbon reserves in various regions. The results showed:① In the future, the three scenarios were similar to the LUCC changes. The area of cultivated land, grassland, and unused land would be reduced to varying degrees, and the construction land had expanded sharply. The increase in the three scenarios was 29.23%-53.56% (SSP126), 34.59%-63.28% (SSP245), and 42.80%-73.27% (SSP585). ② Compared with that in 2020, the carbon reserves of SSP126 sites in 2040 increased by 1.813 8×106 t, and in the remaining scenarios it would continue to decline. By 2060, the grassland carbon reserves in the three scenarios decreased by 13.391×106, 33.548×106, and 85.871×106 t, respectively. ③ From the perspective of space correlation, the carbon reserves of the Loess Plateau were correlated between cities. The difference in future scenarios was not significant. The hotspots were distributed in the middle and north of the research area. There was no obvious cold spot area. ④ The changes in land use were predicted to increase or lose carbon reserves. Forestry, cultivated land, and grassland had more carbon reserves those in than other land types. Increasing their area and restrictions on the conversion of other land types should increase the ecosystem carbon reserves.

Key Role of Asymmetric Photothermal Effect in Selectively Chiral Switching of Plasmonic Dimer Driven by Circularly Polarized Light.

Strong interaction between circularly polarized light and chiral plasmonic nanostructures can enable controllable asymmetric photophysical processes, such as selective chiral switching of a plasmonic nanorod-dimer. Here, we uncover the underlying physics that governs this chiral switching by theoretically investigating the interplay between asymmetric photothermal and optomechanical effects. We find that the photothermally induced local temperature rises could play a key role in activating the dynamic chiral configurations of a plasmonic dimer due to the temperature-sensitive molecular linkages located at the gap region. Importantly, different temperature rises caused by the opposite handedness of light could facilitate selective chiral switching of the plasmonic dimer driven by asymmetric optical torques. Our analyses on the wavelength-dependent selectively chiral switching behaviors are in good agreement with the experimental observations. This work contributes to a comprehensive understanding of the physical mechanism involved in the experimentally designed photoresponsive plasmonic nanosystems for practical applications.

Plasmonic Nanosensors with Extraordinary Sensitivity to Molecularly Enantioselective Recognition at Nanoscale Interfaces.

Molecular chirality recognition plays a pivotal role in chiral generation and transfer in living systems and makes important contribution to the development of diverse applications spanning from chiral separation to soft nanorobots. To detect chirality recognition, most of the molecular sensors described to date are based on the design and preparation of the host-guest complexation with chromophore or fluorophore at the reporter unit. Nevertheless, the involved tedious procedures and complicated chemical syntheses hamper their practical applications. Here, we report the plasmonically chiroptical detection of molecular chirality recognition without the need for a chromophore or fluorophore unit. This facile methodology is based on plasmonic nanotransducers that can convert molecular chirality recognitions occurring at nanoscale interfaces into asymmetrically amplified plasmonic circular dichroism readouts, enabling enantiospecific recognition and quantitative determination of the enantiomeric excess of small amino acids. Importantly, such a plasmon-based chirality sensing shows 102-103 amplification in the plasmonic circular dichroism signals from the detections of racemate and near-racemate of molecular analysts, demonstrating an extraordinary sensitivity to the host-guest enantioselective interactions. Furthermore, with advantages of easy-processing, cost-effective, and specific to interfacial molecular chirality, our chiroptical sensing scheme could hold considerable promise toward applications of enantioselective high-throughput screening in biology, stereochemistry, and pharmaceutics.

Nonlinear Amplification of Chirality in Self-Assembled Plasmonic Nanostructures.

Molecular chirality transfer and amplification is at the heart of the fundamental understanding of chiral origin and fabrication of artificial chiral materials. We investigate here the nonlinear amplification effect in the chiral transfer from small molecules to assembled plasmonic nanoparticles. Our results show clearly a recognizable nonlinear behavior of the electronic and plasmonic circular dichroism activities, demonstrating the validity of the "majority-rules" principle operating in both the three-dimensional interface-confined molecularly chiral environment and the assembled plasmonic nanoparticles. Such twin "majority-rules" effects from the self-assembled organic-inorganic nanocomposite system have not been reported previously. By establishing a direct correlation between the dynamic template of the molecularly chiral environment and the nonlinear chiral amplification in the nanoparticle assemblies, this study may provide an insightful understanding of the hierarchical and cooperative chiral information transfer from molecular levels to nanoscales.

Recognition of chiral zwitterionic interactions at nanoscale interfaces by chiroplasmonic nanosensors.

The ability to detect chiral molecules renders plasmonic nanosensors as promising tools for the study of chirality phenomena in living systems. Using gold nanorod based plasmonic nanosensors, we investigated here typically chiral zwitterionic electrostatic (Zw-Es) and hydrogen-bonding (Hb) interactions occurring via amine and carboxylic groups at nanoscale interfaces in aqueous solutions. Our results reveal that the plasmonic circular dichroism responses of the nanosensors can have both conformational sensitivity and chiral selectivity to the interfacial molecular interactions. Such a dual function of the plasmonic nanosensors enables a new chiroptical way to differentiate between chiral Zw-Es and Hb interactions, to monitor the transformation between these two interaction forces, and particularly to recognize homochiral Zw-Es interactions in solution. Together with the surface enhanced Raman scattering (SERS) technique, this plasmonic CD based biosensing could have important values for the insightful understanding of chirality-dependent molecular recognition in biological and pharmaceutical systems.

Plasmonic polymers with strong chiroptical response for sensing molecular chirality.

We report on the chiroptical transfer and amplification effect observed in plasmonic polymers consisting of achiral gold nanorod monomers linked by cysteine chiral molecules in an end-to-end fashion. A new strategy for controlling the hot spots based circular dichroism (CD)-active sites in plasmonic polymers was developed to realize tailored and reproducible chiroptical activity in a controlled way. We showed that by regulating the bond angles between adjacent nanorods and the degree of polymerization in the linear plasmonic polymer, weak molecular chirality in the ultraviolet spectral region can be amplified by more than two orders of magnitude via the induced CD response in the visible/near infrared region. We demonstrate that this plasmonic polymer can be used to provide not only the Raman "fingerprint" information for identifying the molecular identity but also the CD signatures for (i) resolving the enantiomeric pairs of cysteine molecules at a small quantity level, and (ii) quantifying the enantiomeric purity of the chiral analytes. Chiral analyses by chiroptically responsive plasmonic polymers may find important applications in bioscience and biomedicine.

Distinct kinetics of molecular gelation in a confined space and its relation to the structure and property of thin gel films.

Thin films of molecular gels formed in a confined space have potential applications in transdermal delivery, artificial skin, molecular electronics, etc. The microstructures and properties of thin gel films can be significantly different from those of their bulk counterparts. However, so far a comprehensive understanding of the effects of spatial confinement on the molecular gelation kinetics, fiber network structure and related mechanical properties is still lacking. In this work, using rheological techniques, we investigated the effect of one-dimensional confinement on the formation kinetics of fiber networks in the molecular gelation process. Fractal analyses of the kinetic information in terms of an extended Dickinson model enabled us to describe quantitatively the distinct kinetic signature of molecular gelation. The structural features derived from gelation kinetics support well the fractal patterns of the fiber networks acquired by optical and electron microscopy. With the kinetics-structure correlation, we can gain an in-depth understanding of the confinement-induced differences in the structure and consequently the mechanical properties of a model molecular gelling system. Particularly, the confinement induced structural transition, from a three-dimensional, dense and compact spherulitic network composed of highly branched fibers to a quasi-two-dimensional sparse spherulitic network composed of less branched fibers and entangled fibrils at the boundary areas, renders a gel film to become less stiff but more ductile. Our study suggests here a new strategy of engineering the fiber network microstructure to achieve functional gel films with unusual but useful properties.

From kinetic-structure analysis to engineering crystalline fiber networks in soft materials.

Understanding the role of kinetics in fiber network microstructure formation is of considerable importance in engineering gel materials to achieve their optimized performances/functionalities. In this work, we present a new approach for kinetic-structure analysis for fibrous gel materials. In this method, kinetic data is acquired using a rheology technique and is analyzed in terms of an extended Dickinson model in which the scaling behaviors of dynamic rheological properties in the gelation process are taken into account. It enables us to extract the structural parameter, i.e. the fractal dimension, of a fibrous gel from the dynamic rheological measurement of the gelation process, and to establish the kinetic-structure relationship suitable for both dilute and concentrated gelling systems. In comparison to the fractal analysis method reported in a previous study, our method is advantageous due to its general validity for a wide range of fractal structures of fibrous gels, from a highly compact network of the spherulitic domains to an open fibrous network structure. With such a kinetic-structure analysis, we can gain a quantitative understanding of the role of kinetic control in engineering the microstructure of the fiber network in gel materials.

Controlling nanoparticle formation via sizable cages of supramolecular soft materials.

We present a new generic strategy to fabricate nanoparticles in the "cages" within the fibrous networks of supramolecular soft materials. As the cages can be acquired by a design-and-production manner, the size of nanoparticles synthesized within the cages can be tuned accordingly. To implement this idea, both selenium and silver were chosen for the detailed investigation. It follows that the sizes of selenium and silver nanoparticles can be controlled by tuning the pore size of the fiber networks in the material. When the concentration of the gelator is high enough, monodisperse nanoparticles can be prepared. More interestingly, the morphology of the nanoparticles can be altered: silver disks can be formed when the concentrations of both the gelator and silver nitrate are sufficiently low. As the fiber network serves as a physical barrier and semisolid support for the nanoparticles, the stability in the aqueous media and the ease of application of these nanoparticles can be substantially enhanced. This robust surfactant-free approach will not only allow the controlled fabrication of nanoparticles, but also can be applied to the fabrication of composite materials for robust applications.

Nanoengineering of a biocompatible organogel by thermal processing.

The formation of most organogels requires the compatibility of both the gelator and solvent. It is very desirable if the rheological properties of a gel can be manipulated to achieve the desired performance. In this paper, a novel organogel was developed and its rheological properties and fiber network were engineered by controlling the thermal processing conditions. The gel was formed by the gelation of 12-hydroxystearic acid as a gelator in benzyl benzoate. It was observed that the degree of supercooling for gel formation has a significant effect on the rheological properties and fiber network structure. By increasing supercooling, the elasticity of the gel was enhanced, and the correlation length of the fibers was shortened, leading to the formation of denser fiber networks. The good biocompatibility of both the gelator and solvent makes this gel a promising vehicle for a variety of bioapplications such as controlled transdermal drug release and in vivo tissue repair.

Architecture of fiber network: from understanding to engineering of molecular gels.

A new approach of engineering of molecular gels was established on the basis of a nucleation-initiated network formation mechanism. A variety of gel network structures can be obtained by regulating the starting temperature of the sol-gel transition. This enables us to tune the network from the spherulitic domains pattern to the extensively interconnected fibrillar network. As the consequence of fibrous network structure turning, desirable rheological and other in-use properties of the materials can be obtained accordingly. This approach of micro-/nanostructural fabrication may open up a new route for micro-/nanofunctional materials engineering in general.

Architecture of a biocompatible supramolecular material by supersaturation-driven fabrication of its fiber network.

The architecture of a biocompatible organogel formed by gelation of a small molecule organic gelator, N-lauroyl-L-glutamic acid di-n-butylamide, in isostearyl alcohol was investigated based on a supersaturation-driven crystallographic mismatch branching mechanism. By controlling the supersaturation of the system, the correlation length that determines the mesh size of the fiber network was finely tuned and the rheological properties of the gel were engineered. This approach is of considerable significance for many gel-based applications, such as controlled release of drugs that requires precise control of the mesh size. A direct cryo-transmission electron microscopy (TEM) imaging technique capable of preserving the network structure was used to visualize its nanostructure.