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Gold nanoparticles smaller than 5 nm were encapsulated in the special space of the loop-cluster corona on a polymer vesicle. They exhibited high catalytic activity in the reduction of nitrophenols, but with remarkable oxygen-induced induction times.

Comb-like copolymers are usually structured by grafting polymeric side chains onto main polymer chain. There are few reports of comb-on-comb polymers in which dense secondary side chains are grafted onto primary side chain. In this work, we synthesized comb polymers with grafted-on-graft side chains (c-PEI-g-Acyl) via an effective acylation reaction of comb polymers possessing polyethyleneimine (PEI) side chain with long-alkyl acyl chlorides. For comparison, we also synthesized homopolymers l-PEI-g-Acyls via reaction of linear PEI with long-alkyl acyl chlorides. Then, we investigated their crystalline feature in the film formation by XRD, DSC and SEM, and found that the polymers tend to form hexagonal lamella structures with bilayer alkyl spacing. The comb polymers c-PEI-g-Acyls and linear polymers l-PEI-g-Acyls were used in preparation of honeycomb film by the "breath-figure" process by dropping chloroform solution of the polymers on substrate. Different to many honeycomb polymeric films which are supported by amorphous phase, interestingly, our polymers easily afford honeycomb films which are supported by crystalline lamellae frames under higher humidity condition. It was found that the comb polymers of c-PEI-g-Acyls with longer PEI primary side chain and long alkyl secondary side chain have advantages in producing honeycomb film than linear polymers of l-PEI-g-Acys.

In chirality research area, it is of interest to reveal the chiral feature of inorganic nanomaterials and their enantioselective interactions with biomolecules. Although common Raman spectroscopy is not regarded as a direct chirality analysis tool, it is in fact effective and sensitive to study the enantioselectivity phenomena, which is demonstrated by the enantio-discrimination of amino acid enantiomers using the polydopamine-modified intrinsically chiral SiO2 nanofibers in this work. The Raman scattering intensities of an enantiomer of cysteine are more than twice as high as those of the other enantiomer with opposite handedness. Similar results were also found in the cases of cystine, phenylalanine, and tryptophan enantiomers. In turn, these organic molecules could be used as chirality indicators for SiO2, which was clarified by the unique Raman spectra-derived mirror-image relationships. Thus, an indirect chirality detection method for inorganic nanomaterials was developed.

Au nanoparticles (NPs) labeled with the handedness tag of "d-" or "l-", which were detached from inorganic chiral silica, showed both intrinsic chirality and surface enhanced Raman scattering (SERS) activity. In the presence of these chiral Au substrates, it was found that the enantiomer of cystine with the same handedness tag of Au NPs would show stronger Raman scattering signal intensities than those of the enantiomer with the opposite tag, where the differences could be over three times. Consequently, this work afforded a novel enantioselective recognition method on ordinary Raman spectroscopy by using chiral plasmonic metallic nanomaterials.

Chiral silica, which acts as a nucleating agent of poly(ε-caprolactone) (PCL), was demonstrated to induce excess handedness of lamellar twist in the banded spherulites of PCL blended with poly(vinyl butyral). The d- and l-forms of silica enhanced the right- and left-handed twists, respectively. The influences of chiral silica on the twist handedness were statistically significant. These results indicate that the handedness of twisting can be controlled upon primary nucleation. The organic substances used as chiral templates of silica had no effect on the handedness; silica was shown to govern the handedness. The possible mechanisms of the chirality transfer are discussed.

Circularly polarized luminescence (CPL) is an interesting phenomenon representing the unequal emission of left-handed and right-handed polarized light from an emitter. CPL is promising in chirality characterizations and various optical applications. Traditionally, research on CPL is centered on organic substances. In recent years, CPL present on inorganic ones has also become a nascent topic, which is significant to explore novel chirality- and luminescence-related properties and applications in inorganic materials. This minireview summarizes the recent progress on the following two aspects: 1) how to endow common inorganic luminophores with CPL activity; 2) how to use emerging chiral inorganic nanomaterials to design CPL-active systems. The general synthesis strategies, optical properties, applications and outlook of CPL-active inorganic materials are demonstrated.

Photoluminescent polymers can be divided into two types of structures: one is the well-known conventional π-conjugated rigid chain polymers bearing π-conjugated chromophores in their side chains, and the other is the common flexible polymers without π-conjugated chromophores in their main or side chains but with a feature of clustering electron-rich and/or dipole groups in their main and/or side chains. In this work, we found a new photoluminescent polymer comprising theophylline (T) and imidazole (I) residues in a suitable ratio in the side chains on the common polystyrenic block (PVB-T/I). We synthesized a block copolymer (denoted as P2) consisting of hydrophobic PVB-T/I and hydrophilic poly(

Two types of double-hydrophilic comb-coil block copolymers, (PVBC-g-PMOZ)-b-PNIPAM and (PVBC-g-PEI)-b-PNIPAM, possessing combs of poly(methyloxazoline) (PMOZ)/crystalline poly(ethyleneimine) (PEI) ...

The Pd catalyst for Suzuki–Miyaura or the other C–C coupling reactions is one of the central tools in organic synthesis related to medicine, agricultural chemicals and advanced materials. However, recycling palladium is a bottleneck for developing the extreme potential of Pd in chemistry. Herein, we established a new heterogeneous Pd catalytic system in which the catalyst is a nanopetal-gathered flower-like microsphere self-assembled from PdCl2 and alkyl-linked bis-theophyllines. The microflowers catalyzed quantitatively the reaction of aryl bromides and phenylboronic acid in aqueous media at room temperature. It was found that the reaction proceeds better in an air atmosphere than in nitrogen gas even though the Pd(II) species employed was lowered to 0.001 mol% in the substance. Very interestingly, the microflowers could be recycled 20 times without deactivation in the C–C coupling reaction between bromobenzene and phenylboronic acid in the presence of sodium chloride. We found that the sodium chloride added played an important role in maintaining the morphology of microflowers and preventing the formation of metallic Pd particles.

Asymmetric tetrahedral carbon is the basic structural unit of many organic compounds in life and its molecular chirality plays a key role in regulating biological functions. Silica (SiO2) is highly earth abundant and its basic unit is also the tetrahedral form of SiO4. However, much less attention has been paid to the molecular-scale chirality of SiO2 frameworks with repeating SiO4 units because it is challenging to enantioselectively control the molecular structures of SiO2. Research into the chiral molecular structures of SiO2 deserves to be a significant topic for understanding widespread chiral phenomena and for exploring the chiral properties hidden in inorganic matter. This review highlights the asymmetric synthesis strategies that endow SiO2 with chirality transferred from asymmetric carbon at the molecular scale. The chirality transfer ability of SiO2 is also demonstrated for the construction of various inorganic and/or organic chiral materials with a wide range of applications in asymmetric synthesis, circularly polarized luminescence and Raman scattering-based chiral recognition.

Polydopamine (PDA) and silver (Ag) nanoparticles were first generated on chiral silica nanofibers and then detached from silica to form PDA/Ag composites. The as-obtained PDA/Ag showed surface-enhanced Raman scattering (SERS) activity but very weak circular dichroism optical activity. Interestingly, the PDA/Ag substrates could make a pair of tyrosine (or phenylalanine) enantiomers show different Raman scattering signal intensities, where the differences could reach 3 times. In contrast, PDA/Ag prepared by using racemic or achiral silica did not exhibit such discrimination performance. Therefore, this research offered a novel SERS-based enantiomeric differentiation method with the assistance of plasmonic metal-containing substrates stemmed from intrinsically chiral inorganic silica.

It has been generally recognized that chiral inorganic materials can be efficiently fabricated via a templated-synthesis route in the presence of chiral organic components of molecules or aggregates. However, there are few examples regarding the reverse process, that is, chirality transfer from chiral inorganics to other organics. Herein, we developed an asymmetric synthesis of chiral phenolic resins (RF) by employing synthetic chiral silica bonded covalently with amine residues as an asymmetric medium to asymmetrically mediate the polymerization of resorcinol (R) with formaldehyde (F). The resultant composites, consisting of RF resins and SiO2, showed chiroptical signals with a mirror relationship that appeared remarkably in their circular dichroism (CD) spectra around the adsorption bands of the RF resins. Interestingly, the RF resins still retained CD activities even after the removal of the chiral silica using HF (aq.), suggesting efficient chirality transfer from the chiral silica to the phenolic resins. We proposed that the origin of the chirality in the RF resins is the appearance of axial asymmetry due to the formation of distorted calixarene-like cyclic structures, which is supported by the emergence of chirality from the reaction of C-tetramethylcalix[4]resorcinarene and formaldehyde catalyzed by chiral silica-bonded amine residues.

Shape-persistent macrocycles and 3D nanocages have been prepared in one-pot under MeCN-promoted dynamic covalent bond conditions starting from silane catecholates, whose structures were confirmed by X-ray crystallography. Cation-exchange reactions of macrocycles and nanocages were performed along with the encapsulation of ammonium ions within the cavity of an anionic macrocycle and a tetrahedral nanocage.

Constructing novel chiral inorganic nanomaterials is an emerging branch in chirality research. In this work, by employing a solid magnesiothermic reaction at 500-600 °C, we reduced chiral SiO2 nanofibers with average diameter ∼10 nm into chiral Si nanoplates with a size of about several hundred nm. The chirality of the as-prepared Si was judged by the pair of signals with a mirror relationship between 400-500 nm that appeared on the solid-state diffuse reflectance circular dichroism (DRCD) spectra for the l- and d-form Si. Furthermore, the chirality was also confirmed by induced vibrational circular dichroism (VCD) signals corresponding to the absorption bands in the infrared range of achiral organics (polyvinylpyrrolidone K90 and trimethoxyphenylsilane) absorbed onto chiral Si. The as-used SiO2 nanofibers possessed an ultra high-temperature (up to 900 °C) resistant chirality, which would be due to the asymmetric arrangement of Si and O atoms in small chiral domains (

In this research, we extended a bioinspired and templated synthesis way for SiO2 to carbonaceous materials, with the success in morphology control and inducing chirality at the nano-scale. The biopolymer-analogue polyamine, i.e., polyethyleneimine (PEI) was employed as a catalytic template for SiO2 formation, and the as-formed PEI@SiO2 hybrids, which combine the rigidity of SiO2 and the chemical activity of PEI, were further used as hard-templates and basic catalysts for the deposition of phenolic resin on PEI@SiO2 under mild conditions. Through further carbonization and etching SiO2, SiO2/carbon composites and carbonaceous materials were produced, respectively. After characterization of these products by SEM, TEM, XPS, Raman spectroscopy, FT-IR, and TG-DTA, it was demonstrated that the morphologies were well transmitted in these successive steps. By taking advantage of the diverse modulation ways on the morphologies and structures of initial PEI templates, it is easy to achieve SiO2/carbon and carbonaceous products with different morphologies, including nanofibrils, nanobelts, and nanotubes. Moreover, this process could also fulfill a steady chirality transmission. When PEI complexed with chiral tartaric acid, the resulting chiral complex could function both as a template and chirality source, and finally chiral nanostructured carbonaceous products were obtained.

Acid–base complexes prepared from sub-5 μm polyethyleneimine (PEI) microballs and dicarboxylic acids such as adipic acid (AA), succinic acid (SA), meso-tartaric acid (m-TA) as well as mucic acid (MA) were used as catalytic templates in hydrolytic condensation of tetramethoxy silane (TMOS). By means of FT-IR, 13C NMR, 29Si NMR, XRD, SEM, TGA and nitrogen sorption isotherms, we thoroughly investigated the effects of the dicarboxylic acids complexed with PEI microballs on the resultant silica structures. We found that in this silica deposition process, the presence of the dicarboxylic acids of adipic acid (AA) and succinic acid (SA), which do not have alcoholic groups, could adapt to deposit high content of silica than the alcoholic acids of meso-tartaric acid (m-TA) and mucic acid (MA). More interestingly, the surface structures of the resultant silica microballs were different with different types of acids. The presence of m-TA and MA with meso-type alcoholic structures produced nanofibre or nanoplate-covered silica microballs, while the presence of AA and SA led to the formation of nanoparticles-covered silica microballs. Accompanying these structural features, the BET surface areas of the four types of acid-mediated silica microballs after calcination at 800 °C appeared remarkably different with the order of 615 > 430 > 133 > 96 m2 g−1, respectively, corresponding to the contribution of MA, m-TA, SA and AA. These results evidently indicate that the structures of the dicarboxylic acids associated with PEI microballs play a messenger-like role to tune the silica structures.

Polystyrenic microspheres in the sub 5 micrometer size range (micro-gel) with –CH2Cl active sites were synthesized via the dispersion polymerization of 4-chloromethylstyrene, divinyl benzene and methoxy polyethylene glycol acrylate. Then, theophylline residues were introduced onto the polystyrenic microspheres via the substitution of the chloride in the –CH2Cl group to prepare chelate type microspheres of μ-T2. It was found that the microspheres have co-continuous structures, monodispersed particle sizes, and excellent solvent and water wettability. Using the μ-T2 microspheres possessing theophylline residues, adsorption experiments involving the adsorption of palladium(II), copper(II) and platinum(IV) from acidic chloride media under both individual and mixed conditions were carried out and it was found that the μ-T2 microspheres exhibited excellent adsorption selectivity for palladium(II) over copper(II) and platinum(IV). It was also revealed that thiourea or ammonia solutions are the most effective in desorbing palladium ions from the microspheres. Despite being used in four adsorption–desorption cycles, the μ-T2 microspheres were still able to strongly adsorb palladium ions, with an adsorption of over 85%. In addition, the μ-T2 microspheres also showed palladium capturing ability even in very dilute palladium solutions (below 1.0 ppm). Interestingly, the μ-T2 microsphere-adsorbed palladium ions exhibited excellent catalytic activity in the Suzuki–Miyaura coupling reaction of bromobenzene and phenylboronic acid, yielding biphenyl in 100% under the conditions within 1 hour at 50 °C in water.

Chiral SiO2 nanofibres associated with polyamines on their surfaces could promote polymerization between resorcinol and formaldehyde on the silica surface to give phenolic resins (RF). In this process, the chiral information was effectively transferred from SiO2 to the final phenolic resins forming double chiral hybrid.

In this work, we synthesized free-standing disk-shaped gels (FGPEI) from the chemical cross-linking of linear polyethyleneimine (LPEI), and investigated their crystalline features in gel state and templating function in mineralizations of silica and titania. It was found that the FGPEIs with different cross-linkers and different cross-linking degrees showed remarkable crystalline properties in water containing state but became amorphous in the swollen state in methanol. This is reversible by alternating the medium of water and methanol. The crystalline domains in the FGPEI were estimated by XRD as in the ranges of 3.0~11 nm. Immersion of the disk-shaped FGPEIs in tetramethoxysilane (TMOS) solutions spontaneously resulted in the corresponding hybrids SiO2/FGPEIs keeping the same disk shape with silica content of 63%. Calcinating the hybrids could tune them into monolith silica with mesoporous structure consisting of nanoparticle (ca. 20 nm) agglomeration. On the other hand, immersion of the FGPEI in tetraisopropyloxy titanium solution offered hybrid of TiO2/FGPEI but only with ca. 14% content of TiO2. However, calcination of this hybrid at different temperatures could result in monolith titania possessing mesopore and/or macropore structures inside with agglomeration of anatase- and/or rutile-type nanoparticles.

In this work, we synthesized a new comb-like copolymer (c-iMP) possessing amphiphilic diblock side chains consisting of poly(methyloxazoline) (PMOZ) and poly(phenyloxazoline) (PPOZ) via reversible addition-fragmentation chain-transfer (RAFT) polymerization of p-choloromethylstyene (CMS) and cationic ring-opening polymerization (CROP) of 2-methyl-2-oxazoline (MOZ) and 2-phenyl-2-oxazoline (POZ). Then, by performing selective hydrolysis of the hydrophilic PMOZ block, the PMOZ block was transformed into PEI (polyethylenimine) from which comb-like copolymers (c-iEP) possessing two blocks of PEI (E) and PPOZ (P) were produced. The comb-copolymers c-iEP showed unique self-assembling behavior in water to give an unusual polymersome covered by a loop-cluster polyamine corona. The polymersome showed extreme toughness and stability without collapse and fusion even at dry conditions and could be transformed into capsules. This is the first example of polymesome without free-ends on the vesicle wall which could include Ag ions inside and could deposit silica around the wall to form hybrid hollow spheres.

Systems that show circularly polarized luminescence (CPL) are usually constructed in one of two possible ways: either covalently binding the chiral moieties (usually organic compounds) to luminophores (inorganic or organic compounds) or associating the luminophores as guests with chiral hosts (usually organic compounds). Herein, we propose inorganic-based CPL-active systems constructed by the "chiral host-luminescent guest" strategy, in which silica acts as a chiral host to endow various luminescent guests with CPL. The chiral silica was modified by silane coupling with amino or phenyl groups to allow interaction with luminescent guests, and then used in combination with acidic achiral dyes, lead-halide type perovskites, and aggregation-induced emission luminogens (AIEgens). Interestingly, when these achiral guests were noncovalently confined in surface-modified chiral silica, the guests showed chiroptical behavior in the circular dichroism (CD) spectra, and thus became CPL active, even though they are not inherently chiral. The surface functional groups on the silica play very important roles in transferring the chiral information from the silica to the guests. This work provides a new concept for constructing CPL-active systems using inorganic materials as a chiral source.

Most of the chemical hydrogels are stretchable, and deformed hydrogels may be recovered when the strain is removed. Such a hydrogel with viscoelastic property cannot be remolded under mild conditions. Here, we demonstrated that a combination of dual reversible cross-linking with different relaxation time scales could be used to develop a remoldable hydrogel responding to mild external stress. We fabricated the hydrogel with the surface-primary amine-rich silica nanodots (ca. 2.0 nm) and benzaldehyde-terminated poly(ethylene oxide)-poly(propylene oxide) (PPO)-poly(ethylene oxide) triblock copolymers (BAF127) at low temperature (10 °C) to form the chemical cross-linking by Schiff-base bonding. Increasing temperature (15 °C) induced the formation of physical cross-linking between the hydrophobic PPO segments. The latter network is weak and shows fast relaxation, whereas the former shows slow relaxation. The unique structural characteristics provides this hydrogel high stretchability and self-healability, as well as moldability. In particular, we demonstrated that this transparent hydrogel can keep the fine three-dimensional patterns of a fingerprint, which may be applied for collecting digital information of fingerprints for identification.

Herein, sub-5 μm microballs, with unusual forest-like structures consisting of a polystyrene network and forest-like poly(2-methyl-2-oxazoline) (PMOZ) and/or linear polyethyleneimine (LPEI) side chains, were synthesized by combining two isolated processes. The first process is the dispersion radical polymerization of 4-chloromethylstyrene (CMS) and divinylbenzene (DVB) in the presence of a stabilizer, polyvinylpyrrolidone (PVP), using 2,2′-azobis(isobutyronitrile) (AIBN) as an initiator, which produces a poly(4-chloromethylstyrene) type microgel (μ-PStCl). The second process is the cationic ring-opening polymerization of 2-methyl-2-oxazoline (MOZ) using μ-PStCl as a solid initiator, which produces poly(2-methyl-2-oxazoline)-grafted microballs (μ-PSt-g-PMOZ). The latter, possessing PMOZ side chains, was transformed into poly(ethyleneimine)-grafted microballs (μ-PSt-g-PEI) via treatment with HCl (aq). Moreover, the three types of microballs μ-PStCl, μ-PSt-g-PMOZ, and μ-PSt-g-PEI of 1–3 micrometer in diameter were characterized by FT-IR, 13C CP/MAS NMR, elemental analysis, XRD, and SEM. Both the microballs μ-PSt-g-PMOZ and μ-PSt-g-PEI, which resembled the assemblies of hydrophilic comb polymers in their chemical structure, exhibited good wettability in an aqueous phase. In particular, the μ-PSt-g-PEI microballs, which have forest-like basic polyamine chains throughout the microballs, act as catalytic templates in the hydrolytic polycondensation of tetramethoxysilane (TMOS) at room temperature to produce polymer/silica hybrid microballs of μ-PSt-g-PEI@SiO2 with 2.5–3.5 μm diameter and 35–70 wt% silica content depending upon the mediation conditions. Calcination of the μ-PSt-g-PEI@SiO2 hybrid microballs at 700, 800, and 900 °C resulted in silica microballs possessing 2–4 nm mesopores with reduced diameter from 3.5 to 1.2 μm and reduced BET surface area from 582 to 189 m2 g−1. It was confirmed that the sub-5 μm microballs of μ-PSt-g-PEI were very effective catalytic templates for the construction of silica microballs of different sizes (1–4 μm), different surface areas, and different (large hollow or co-continuous) internal structures.

Biomimetic synthesis of shaped functional inorganic materials is still a hot issue. In this work, we investigated the influence of crystallization conditions on formation of crystalline aggregates from comb-like polyethyleneimine (cPEI). A range of well-controlled polymeric aggregates rich in basic amine groups were prepared through a crystallization-driven self-assembly of cPEI under varied conditions such as different crystallization media (including solvent type and composition) and temperature, as well as the presence of metal cations of different valence. Meanwhile, these crystalline aggregates were applied as catalytic templates to replicate silica with corresponding structures and shapes. The cPEI templates and the templated silica products were mainly subjected to scanning electron microscope (SEM) observation, Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) measurements. The results indicated that cPEI was a very effective template component for the construction of specially structured silica materials being due to the special crystallites growing behavior of cPEI.

Amphiphilic block copolymers have attracted a considerable amount of attention in the past two decades because of their ability to self-organize into various complex nanostructures. Most of these studies concentrated on linear amphiphilic block copolymers. In this work, we focused our attention on two type unique comb-like copolymers which grafting amphiphilic diblocked side chains onto main chain of polystyrenic backbone. One is Type-I in which a block of hydrophilic polymers is located inside near to the backbone while other block of hydrophobic poly (phenyl-2-oxazoline) [PPOZ] is in outside far away the backbone. The other one is Type-O in which the hydrophobic block of PPOZ is grafted (inside) onto the main chain backbone then the hydrophilic block is joined (outside) on the PPOZ. A series of five kinds of Type-I and five kinds of Type-O comb-like block copolymers with different components of the amphiphiles were prepared. We performed self-assembly of them in a DMF/water or methanol/water (v/v, 1/9) media. All of Type-O comb-like block copolymers formed micelle. In contrast, in the case of Type-I, interestingly, the comb-like block copolymers possessing hydrophilic blocks with crystalline feature formed loop-cluster covered vesicles, while the others having non-crystalline hydrophilic blocks formed flower-like micelle. We proposed the self-organizing mechanism of these two types comb-like block copolymers and provides new molecular design strategy for the site-selective fabrication of vesicle/micelle possessing special surface structures.

Silica is abundant in the Earth's crust, and silicate materials are used on the global scale, from industrial products for architecture, vehicles, electronics, and optics to consumption as foods, medicines, supplements, and cosmetics. Silica has become increasingly important in current science and technology, as seen in the components of advanced materials. The characteristic formula of silica is very simply often expressed as SiO2 . However, it is difficult to draw silica precisely owing to its intricate chemical structures. We need to make a greater effort in understanding silica, even though silica chemistry has existed for over 200 years. Similar to the homochirality observed in natural amino acids, natural silica of quartz is chiral, and in some sense, the origin of life with chirality might be partly related to quartz-like silica chirality. This review focuses on the asymmetry of silica from the view of the formation of irregular tetrahedron structures of SiO4 . Silica is composed of several repeated tetrahedron units of SiO4 , leading to the formation of inorganic polymers with divergently expanded 3D structures. In this large polymeric skeleton, not every unit of SiO4 can maintain an ideal tetrahedron, and thus, it becomes twisted. The twisting results in an asymmetric point on the Si atom, leading silica to become racemic in the stereochemical sense. Therefore, enantioselective preparation of silica should endow silica with chirality through the silica skeleton. Some recent achievements exhibit that silica is an effective chiral material and has great potential for transferring chirality from silica to other matter.

Transfer of chirality from chiral organic molecules to metallic nanoparticles (NPs) is a very attractive field of research and some unique approaches to obtaining chiral metallic NPs have been developed. However, to date, there has been no report in the literature that the chiral information of silica can be transferred into metallic NPs. In this work, a new chirality transfer system to metallic NPs from chiral silica has been achieved. The chiral transfer was performed by simple two steps: (1) trapping metal cations of silver (Ag) and gold (Au) in chiral silica of nano fibrous bundles embedding poly(ethyleneimine) inside and (2) thermoreducing the metal ions into metallic NPs. The metallic NPs of Au and Ag grown around a silica frame, using a thermo-reduction (calcination) process, showed a spherical shape with a size of about 30 nm. Interestingly, the metallic NPs detached or isolated from the silica via crushing and/or hydrolysis of the silica showed remarkable circular dichroism activity in their plasmon absorption band with an exciton coupling feature. Using an atomic resolution scanning transmission protocol, it was found that the chiral metallic NPs have a definite distortion in the atomic array in their crystal lattice structures. In comparison, achiral metallic NPs, which were prepared using a similar method around achiral silica bundles, showed a precisely ordered atomic line without distortion.

Polyethyleneimine (PEI) complexed with chiral D- (or L-) tartaric acid (tart) in water can self-organize into chiral and crystalline PEI/tart assemblies. It has been previously confirmed that the complexes of PEI/tart could work as catalytic/chiral templates to induce the deposition of SiO2 nanofibres with optical activity but without outwards shape chirality such as helices. In this work, we found that the templating functions of PEI/tart were still effective to prompt the deposition of TiO2 to form chiral PEI/tart@TiO2 hybrid nanofibres under aqueous and room temperature conditions within two hours. Furthermore, the co-deposition of TiO2 and SiO2 was also fulfilled to yield chiral PEI/tart@TiO2/SiO2 nanofibres. These TiO2-containing hybrid nanofibres showed non-helical shapes on the length scale; however, chiroptical signals with mirror relation around the UV-Vis absorption band of TiO2 remarkably appeared on their circular dichroism (CD) spectra. By means of the protocols of XRD, TEM, SEM, UV-Vis, CD and XPS, structural features and thermoproperties of the chiral TiO2 and SiO2/TiO2 were investigated.

In this paper, we firstly synthesized comb polymers with crystallizable poly(ethyleneimine) (PEI) side chains via a combination of reversible addition–fragmentation chain-transfer (RAFT) polymerization, cationic ring-opening polymerization (CROP), and further hydrolysis. At first, poly(4-chloromethylstyrene) (PCMS) and poly(4-chloromethylstyrene)-block-polystyrene (PCMS-b-PSt) as macroinitiators were synthesized by employing cumyl dithiobenzoate-mediated RAFT polymerization. Then, comb polymers with poly(2-methyloxyzoline) (PMOZ) side chains were prepared using PCMS and PCMS-b-PSt as macroinitiators in the presence of an excess of potassium iodide in benzonitrile, and the PMOZ side chains on the comb polymers were subsequently hydrolyzed into PEI. Furthermore, we demonstrated that the crystalline aggregates of these PEI-bearing comb polymers (i.e., comb-like PEI and comb-like PEI block with a PSt block) formed via crystallization-driven self-assembly in different aqueous media such as water, water/methanol, water/acetone and water/DMF could act as catalytic templates in silicification to give silica with well-controlled morphologies.

A general approach to fabricate a series of silica nanoobjects with sheet-like, tubular and hollow spherical shapes was reported. These silica nanoobjects were prepared by using water-dispersed diblock copolymer nanoobjects with glassy polystyrene cores and densely grafted poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA) shells as templates as well as catalysts. A sol–gel reaction of tetramethoxysilane (TMOS) was subsequently induced by PDMAEMA shells of shaped nanoobjects in water dispersions at near-neutral pH and under ambient conditions, and thus the shaped polymer@silica hybrids with a high silica content (around 70 wt% silica in hybrids) were obtained. Then silica nanoobjects of three different dimensions were further prepared by calcination at 650 °C to remove the organic components. The spherical and cylindrical silicas have a hollow structure. Formation of diblock copolymers, polymer nanoobjects, polymer@silica hybrids, and silica nanoobjects was characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), solid state 29Si CPMAS NMR analysis, N2 adsorption–desorption measurements, and Fourier-transform infrared spectroscopy (FT-IR). This methodology could be a general approach to fabricate various inorganic nanoparticles with different geometric shapes.

Organic molecules with accompanying self-organization have been a great subject in chemistry, material science and nanotechnology in the past two decades. One of the most important roles of organized organic molecules is the capability of templating complexly structured inorganic materials. The focus of this Minireview is on nanostructured silica with divergent morphologies and/or integrated chirality directed by organic templates of self-assembled polyamine/polypeptides/block copolymers, chiral organogels, self-organized chiral amphiphiles and chiral crystalline complexes, etc., by biomimetic silicification and conventional sol-gel reaction. Among them, biosilica (diatoms and sponges)-inspired biomimetic silicifications are particularly highlighted.

Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3 TACN) ligands. Two types of structures were confirmed by crystallography: "[(R3 TACN)FeX2 ]" complexes with relatively small R groups have ionic and dinuclear structures including a [(R3 TACN)Fe(μ-X)3 Fe(R3 TACN)](+) moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3 TACN)FeX2 ]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)3 TACN}FeBr2 ] (4 b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined.

Nanostructured silicon (Si) is a promising candidate for use in lithium ion batteries. In this work, one-dimensional SiO2 was obtained using linear polyethyleneimine (LPEI) as a biomimetic template/scaffold/catalyst, which was subsequently employed to fabricate nanostructured Si with a size of less than 10 nm in a SiO2 matrix using a solid–solid magnesiothermic reaction at a relatively low temperature of 500 °C. This procedure proved to be cost-effective and high-yielding and generated a product that could withstand a significant Si volume change during lithium insertion/extraction by combining the advantages of Si nanostructures with the buffer effect of the SiO2 matrix. In this manner, excellent cycling stability and a discharge capacity of more than 900 mAh/g were observed after 50 cycles. This work expands the structure-derived applications of bioinspired/biomimetic silica.

Poly(N-cyanoethylethyleneimine) (PCEI) obtained by Michael addition of linear poly(ethyleneimine) (LPEI) with acrylonitrile provided novel nanocrystalline entities which could serve as catalytic templates affording nanosheet-based structured silica under mild conditions.

D-glucaric acid (D-Glc) associates with linear poly(ethyleneimine) (PEI) through hydrogen bonding and electrostatic interactions in aqueous media to form nanostructured crystalline PEI/D-Glc/H2O complexes with PEI/D-Glc/H2O ratios of 2:1:2. These complexes can serve as templates for silica depositions from hydrolytic condensation of tetramethoxysilane to guide morphologically duplicated silica under very mild conditions. Their microscale morphologies are tunable by use of the crystalline complexes regulated in the different pH of the PEI/D-Glc solutions. It was also found that some metal ions added in the PEI/D-Glc complexation process could have a synergistic effect under a certain pH regimes, bringing about remarkable changes in the hierarchy of the resulting complexes. Especially, the complexes formed through fine-tuning of the complexation conditions could direct torsionally stacked silica nanosheets, in which the nanosheets are composed of orderly-bundled nanofibrils. Final elimination of organic components of the templates afforded chiral inorganic silica while retaining the morphologically higher-order structures. The chirality of the silica, which was obtained after calcination at 600 °C, was characterized by means of diffused reflectance circular dichroism (DRCD) spectroscopy with a remote confirmation of the appearance of induced-CD (ICD) signals of achiral or racemic chromophores covalently linked on the silica frames. Interestingly, the shapes and signs of these ICD signals are dramatically changed depending on the pH-tuned templates used in silicification and are strongly correlated to that of the CD signals of the complex templates, indicating that the chiral transcription proceeds accurately with imprinting the higher-order chirality of the complexes on the morphologically structured silica networks.