Chain-Conformation-Directed Polymerization Cyclization for Effective Synthesis of Macrocycles in Bulk.

Biological cyclization is highly efficient, and this can be attributed to the conformation of the backbone of the biopolymer. Taking advantage of metal-coordination geometry, we developed a method for conformation-directed polymerization cyclization through rational design of metal carbonyl monomers that could be used to produce cyclic macromolecules, even in bulk. P FpR [P Fp=(PPh2 (CH2 )3 Cp)Fe(CO)2 with the phosphine group tethered on the cyclopentadiene (Cp) ring; R=CH3 or (CH2 )5 CH3 ] was designed and synthesized for migration insertion polymerization to generate P(P FpR) with the polymer backbone containing Cp-Fe bonds. Growth of the backbone led to a cyclic conformation with close end-to-end distances, which facilitated the cyclization. This conformation-directed cyclization was attributed to the piano-stool metal-coordination geometry of the repeating units and the low rotational barrier of the Cp-Fe bonds in the backbone. The produced macrocycles, which contain a metal carbonyl coordination structure in their backbones, are rigid, unlike many organic macrocycles. The macrocycles thus have a large excluded volume. This new type of metal carbonyl macrocycle will be of interest as a building block for supramolecular chemistry and in the exploration of novel materials.

Polymeric Nanocarriers Based on Cyclodextrins for Drug Delivery: Host-Guest Interaction as Stimuli Responsive Linker.

Stimuli responsive polymers have been extensively studied as nanocarriers for drug delivery systems (DDSs), especially those based on supramolecular interactions. Cyclodextrin (CD) is one kind of widely applied host molecule, and the host-guest interactions between CD and different counterparts can respond to different stimuli and thus can be applied as responsive linkers for polymeric DDSs. In this review, the polymeric nanocarriers based on the host-guest interactions between CD and ferrocene, azobenzene, and benzimidazole as DDSs are summarized, with redox, light, and pH sensitivity, respectively. The mechanisms for the stimuli responsive ability of the linkers, the application of them for construction of DDSs with different polymer structures, and the controlled release behaviors have been focused. In addition, the outlook and challenge of these systems are discussed.

Multiple-Channel Information Encryption Based on Quantum Dot Absorption Spectra.

Large-capacity information encryption has attracted significant interest in the information age. The diversity and controllability of spectra have positioned them to be widely applied for information encryption. Current spectra-based information encryption methods commonly rely on either spectral alteration induced by external stimuli or the utilization of narrowband channels within spectra. However, these methods encounter a common challenge in attaining both high security and large capacity simultaneously. To address these issues, we propose a multiple-channel information encryption system based on quantum dot (QD) absorption spectra. The diversity of QD absorption spectra and their broadband features ensure that the encrypted spectra can hardly be decrypted without knowing the correct channel matrix. Meanwhile, the large capacity is realized through the combination of multiple QD spectral channels with a theoretical maximum capacity of 24.0 bits in a single spectrum. In order to optimize the performance of our proposed system, the selection principle of the channel matrix is established to achieve the rapid identification of the optimal channel matrix in several milliseconds. The additivity of QD spectral channels and the consistency of QD spectra are also explored to minimize the impact of errors on information decryption. Furthermore, two spectral encryption scenarios of spatial pattern and spectral pattern are applied to demonstrate the feasibility, showcasing their ability to achieve both a high level of security and large capacity. Owing to the advantages offered by QD spectra, the QD spectra-based information system exhibits excellent potential for broader applications in information storage, authentication, and computing.

Multidimensional Information Encryption and Storage: When the Input Is Light.

The issue of information security is closely related to every aspect of daily life. For pursuing a higher level of security, much effort has been continuously invested in the development of information security technologies based on encryption and storage. Current approaches using single-dimension information can be easily cracked and imitated due to the lack of sufficient security. Multidimensional information encryption and storage are an effective way to increase the security level and can protect it from counterfeiting and illegal decryption. Since light has rich dimensions (wavelength, duration, phase, polarization, depth, and power) and synergy between different dimensions, light as the input is one of the promising candidates for improving the level of information security. In this review, based on six different dimensional features of the input light, we mainly summarize the implementation methods of multidimensional information encryption and storage including material preparation and response mechanisms. In addition, the challenges and future prospects of these information security systems are discussed.

The redistribution and migration mechanism of nitrogen in the hydrothermal co­carbonization process of sewage sludge and lignocellulosic wastes.

Blending lignocellulosic wastes (such as cornstalk, CS) into sewage sludge (SS) for hydrothermal carbonization (HTC) could contribute to the importance of the hydrothermal solid product (hydrochar) as a substitute for fossil fuel. However, the interactions between SS and CS changed the fate of Nitrogen (N), affecting the clean combustion utilization of hydrochar. This study focused on the influence of SS-CS interactions on the redistribution and migration behavior of N during the co-HTC process by tuning the mass ratio of SS to CS (SS:CS), reaction temperature, and residence time. Under the hydrothermal condition of 220 °C, 2 h, and SS:CS = 1:1, the high heating value of hydrochar and the energy recovery efficiency (ERE) respectively reached 15.89 MJ/kg and 71.19%. Further raising the temperature to 250 °C, the hydrochar was enhanced in the coalification degree, whereas ERE decreased to 61.86%. Part of the amino-N in sludge organics was fractured during the co-HTC process and reacted with carbohydrate and intermediate products, such as 5-hydroxymethylfurfural, which degraded from CS, to generate heterocyclic-N compounds (including pyridine, pyrrole, and pyrazine). The remaining amino-N formed pyridine-N, pyrrole-N, and quaternary-N through various solid-solid conversions. The heterocyclic-N polymerized and formed melanoidins, which thereafter polymerized with aromatic clusters to form the N-containing polyaromatic char. Therefore, the N retention rate (NRR) was enhanced and showed a synergistic effect. NRR was increased by raising the proportion of CS or extending time, reaching 57.02% at SS:CS = 1:1 and 8 h. Conversely, rising temperatures resulted in a downward trend of NRR with a phased increase at 220 °C-250 °C.

Electrochemical Redox Switchable Dispersion of Single-Walled Carbon Nanotubes in Water.

We present a new, efficient approach to achieve superior dispersibility of single-walled carbon nanotubes (SWNTs) in water by integrating reversible host-guest interaction and π-π stacking. In this approach, ß-cyclodextrin (ß-CD) was first modified with a pyrene group to be adsorbed onto the wall of pristine SWNTs via π-π stacking, followed by further functionalization with ferrocene (Fc)-terminated water-soluble poly(ethylene glycol) (PEG) through supramolecular host-guest interaction between ß-CD and Fc. Upon alternate electrochemical oxidative/reductive stimuli, the reversible host-guest pair enabled the PEG-Fc@Py-CD@SWNTs to exhibit switchable conversion between dispersion and aggregation states. Electric field controllable PEG-Fc@Py-CD@SWNTs with good reversibility and intact nanotube structure may find potential applications in selective screening of SWNTs, biosensors, and targeted drug delivery.

Electrochemical Stimulated Pickering Emulsion for Recycling of Enzyme in Biocatalysis.

Potential-stimulated Pickering emulsions, using electrochemical responsive microgels as particle stabilizers, are prepared and used for biocatalysis. The microgels are constructed from cyclodextrin functionalized 8-arm poly(ethylene glycol) (8A PEG-CD) and ferrocene modified counterparts (8A PEG-Fc) via CD/Fc host-guest chemistry. Taking advantage of the redox reaction of Fc, the formation and deformation of the microgels and corresponding Pickering emulsions can be reversibly stimulated by external potential, and have been used for the hydrolysis of triacetin and kinetic resolution reaction of (R,S)-1-phenylethanol catalyzed by lipases. Potential stimulated destabilization of the emulsion realizes an effective separation of the products and enzyme recycling.