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.
Asymmetric silica: The CABCD labeling rule for the judgment of asymmetry in tetrahedral carbon materials is not suitable in the case of silicate materials. The structure of silica based on the accumulation of SiO4 tetrahedrons is practically asymmetric owing to the formation of irregular tetrahedrons with different bond lengths and bond angles on Si−O, and thus, the protocol of enantioselective synthesis is applicable in the preparation of chiral silica.
Poly(N‐isopropylacrylamide) (PNIPAM) having lower critical solution temperature (LCST) behavior in aqueous solutions has been actively studied for various applications in nanotechnology and ...controlled drug delivery. In this work, a comb‐coil block copolymer is synthesized with PNIPAM coil and polyethyleneimine brushes. Self‐organization of the copolymer into micelle by heating and subsequent cross‐linking of the part of PEI corona resulted in a unique nanocapsule (i‐CLM) with hydrophilic cross‐linked PEI outer shell and thermo‐responsive PNIPAM inner brush. The nanocapsule appears as a vesicle‐like hollow at room temperature but did into micelle‐like spheres when heated. From dynamic light scattering measurement, it is revealed apparently that the nanocapsule exhibited well the swelling and the shrinking reversibly under heating and cooling and the feature is cycled repeatedly with gradual fashion under wide‐range of temperature responding. The carrier property of the nanocapsule is investigated by using hydrophobic fluorophore of Nile red (NR) as a probe and it is found that the hollow of the nanocapsule is a good nano pocket to promote the growth of nanocrystals of NR.
A thermo‐responsive water‐soluble comb−coil block copolymer can be self‐assembled into the core‐corona polymeric micelle under heating. The micelle is successively transformed into a unique nano‐capsule possessing thermo‐responding inner surface.
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.
Generous hosts: Systems that show circularly polarized luminescence (CPL) and are based on chiral silica hosts and luminescent guests such as achiral dyes, lead halide perovskites, aggregation‐induced emission luminogens were constructed. All the achiral luminophores trapped in the silica showed remarkable CPL activity.
In this work, chiroptical crystalline complexes of PEI/Tart (P/T) consisting of linear poly(ethylemeimine) (PEI) and an enantiomeric excess (ee) of tartaric acid (Tart) were used as chiral catalytic ...templates in the hydrolytic condensation of titanium bislactates and co-condensation of titanium bislactates and tetramethoxysilane for the preparation of chiral titania (TiO
2
) and chiral titania/silica (TiO
2
/SiO
2
) hybrid. Different from the general case of enantiopure templates excelling in chiral transformation when compared to enantiomeric excess ones, P/T systems with different enantiomer ratios exhibited each activity in the transformation of their chiral information to the resulting minerals titania and titania/silica. Especially, the P/T complexes with ee only by ±4% (
d
/
l
= 52/48 or 48/52), which is near the racemic state (
d
/
l
= 50/50), served as excellent chiral catalytic templates to generate chiroptical titania and titania/silica with mirror relation of the CD signals. By means of DSC, XRD, SEM and DRCD techniques, the crystalline complexes of PEI/Tart (P/T), the as-prepared TiO
2
@P/T and TiO
2
/SiO
2
@P/T, and the calcined TiO
2
and TiO
2
/SiO
2
were thoroughly investigated and the mechanism of the chiral transformation from the enantiomeric excess of P/T to minerals was proposed.
Crystalline aggregates (P/T) self-organized from polyethyleneimine (P) and enantiomeric excess (ee = ±4%,
d
/
l
= 52/48 and 48/52) of tartaric acid (T) could serve as chiral catalytic templates to effectively give chiroptical hybrids of TiO
2
/SiO
2
.
Chiral polymers are often prepared by two ways depending upon chiral monomers, chiral catalysts, and chiral auxiliaries which always come from organics: one is the enantio‐selective polymerization of ...prochiral or racemic monomers or polymerization of optically active monomers; and the other one is the molecular imprinting technique, which creates chiral recognition sites inside a densely cross‐linked polymer gel. Herein, a unique method for the synthesis of chiroptical cross‐linked polymers via radical polymerization of achiral divinyl monomers in the mediation of the inorganic chiral nanosilica is reported. The monomers that are cross‐linkable such as divinylbenzene (DVB) and N,N′ ‐methylenebisacrylamide (MBA) are physically adsorbed onto chiral silica bundles and then polymerized by dispersion of those monomers/silica bundles in the presence of radical initiators. The products are characterized by SEM, FT‐IR, solid‐state 13C NMR, TGA, and CD. Very interestingly, the cross‐linked polymers themselves obtained via final removal of the chiral silica show remarkable chiroptical activity with mirror relationship and can make achiral guest of porphyrin adsorbed on the polymers become optically active.
Chiroptical cross‐linked polymers via radical polymerization of achiral divinyl monomers are produced in the mediation of the inorganic chiral silica. In this process, chiral information is transferred from the silica to the resulting networked polymers while the polymers can further induce chiral activity of guest molecules adsorbed on them.
Crystalline and chiral supramolecular complexes can be self‐assembled from linear polyethyleneimine and D‐ or L‐tartaric acid. These complexes act as templates to direct nanofiber‐based chiral ...silica, which showed remarkable chiraoptical properties and remained chiral even after sintering at ultrahigh temperatures. Achiral molecules and gold nanoparticles bound to the chiral silica became active in CD spectra owing to induced chirality.
Recently, circularly polarized luminescence (CPL)‐active systems have become a very hot and interesting subject in chirality‐ and optics‐related areas. The CPL‐active systems are usually available by ...two approaches: covalently combining a luminescent centre to chiral motif or associating the guest of luminescent probe to a chiral host. However, all the chiral components in CPL materials were organic, although the luminescent components were alternatively organics or inorganics. Herein, the first totally inorganic CPL‐active system by “luminescent guest–chiral host” strategy is proposed. Luminescent sub‐10 nm lanthanide oxides (Eu2O3 or Tb2O3) nanoparticles (guests) were encapsulated into chiral non‐helical SiO2 nanofibres (host) through calcination of chiral SiO2 hybrid nanofibres, trapping Eu3+ (or Tb3+). These lanthanide oxides display circular dichroism (CD) optical activity in the ultraviolet wavelength and CPL signals around at 615 nm for Eu3+ and 545 nm for Tb3+. This work has implications for inorganic‐based CPL‐active systems by incorporation of various luminescent guests within chiral inorganic hosts.
Sand in the tartan kilt? Inorganic materials assembled with chiral silica hosts and luminescent oxide guests were synthesized by entrapping lanthanide ions into chiral silica loaded with polyethyleneimine/tartaric acid and subsequently calcined at 900 °C. The lanthanide oxide nanoparticles of Eu2O3 and Tb2O3 formed in the restricted space of the chiral d‐ and l‐silica hosts displayed chiral signals both in circular dichroism (CD) and circularly polarized luminescence (CPL).
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 PdCl
2
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.
Bis-theophylline-palladium complex exhibit high catalytic activity in the C-C coupling reaction with excellent recyclability in the presence of NaCl.
One of frequent uses of palladium as catalyst is in the Suzuki-Miyaura cross-coupling reaction, which is one of key reactions in the synthesis of pharmaceuticals, fine chemicals, and electronic ...device materials. In this work, we explored a unique circulation reactor system for Suzuki-Miyaura CC coupling reaction, in which a robust microflower self-assembled from bistheophyllines heptane (PdBTC7) and PdCl2 were packed in column. Injection of the reactants of bromobenzene and phenylboronic acid 51 times in definite interval in the eluent of water/NaCl/ethanol could give continuously biphenyl product, showing the performance of catalyst in 4498 of TON and 8996 h−1 of TOF.
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•A circulation cross-coupling reaction system with column reactor was constructed.•The column was packed with trace amount of flower-like complex of Pd/Theophylline.•51 times injections made TON and TOF to reach 4498 and 8996 h−1, respectively.•Presence of NaCl enhanced greatly catalytic lifetime.
Targeting protein for Xenopus kinesin‐like protein 2 (TPX2) is a microtubule‐associated protein that plays a pivotal part in the formation of spindles. There is accumulating evidence that the ...expression of TPX2 is upregulated in many kinds of human cancers and that this protein is involved in the occurrence and progression of tumors. The purpose of this meta‐analysis was to investigate the relationship between the overexpression of TPX2 and poor prognosis in cancer patients. A total of 18 eligible studies encompassing 3115 patients were included by searching relevant databases. Hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (CIs) were pooled under random‐/fixed‐effect models. After calculation, the results showed that patients with increased TPX2 expression had a significantly shorter overall survival (HR = 2.21; 95% CI: 1.70–2.86), and disease‐free survival (HR = 2.10; 95% CI: 1.67–2.64). In addition, it was found that increased TPX2 expression was significantly associated with TNM stage (OR = 2.17; 95% CI:1.42–3.32), lymph node metastasis (OR = 2.98; 95% CI: 2.28–3.89), distant metastasis (OR = 2.25; 95% CI:1.03–4.92), and vascular invasion (OR = 2.22; 95% CI:1.26–3.91). Nevertheless, there was no significant correlation between increased expression of TPX2 and either gender, tumor differentiation, or tumor size. Thus, we can come to the conclusion that the overexpression of TPX2 is related to poor clinical outcomes and can be used as a biomarker for the prognosis of patients with cancer.
The results showed that patients with increased Xenopus kinesin‐like protein 2 (TPX2) expression had significantly shorter overall survival (hazards ratio HR = 2.21; 95% confidence interval CI: 1.70–2.86) and disease‐free survival (HR = 2.10, 95% CI: 1.67–2.64). In addition, it was found that increased TPX2 expression was significantly associated with TNM stage (OR odds ratio = 2.17; 95% CI:1.42–3.32), lymph node metastasis (OR = 2.98; 95% CI: 2.28–3.89), distant metastasis (OR = 2.25; 95% CI:1.03–4.92) and vascular invasion (OR = 2.22; 95% CI: 1.26–3.91). Therefore we can conclude that overexpression of TPX2 is related to poor clinical outcomes and can be used as a biomarker for the prognosis of cancer patients.
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