Cover Picture: A Diagonal Approach to Chemical Recycling of Carbon Dioxide: Organocatalytic Transformation for the Reductive Functionalization of CO2 (Angew. Chem. Int. Ed. 1/2012)

Robust, transparent, self-healable, recyclable all-starch-based gel with thermoelectric capability for wearable sensor

Conventional all-starch-based (ASB) gels are weak and lack ductility. The preparation of a robust ASB gel with multi-functionalities e.g., self-healing, anti-freezing, conductivity, and so forth, is highly desirable but challenging. Herein, a new kind of ASB gel was prepared by gelatinizing starch in urea and choline chloride solution (UC) with the aid of water. Its tensile strength was up to 1.08 MPa with a tensile strain of 313 %, and this value hardly changed after 10 days ageing. A high healing efficiency of 98 % can be achieved after 1 h of healing at room temperature, and the healed tensile strength reaches up to ca. 1.06 MPa, which is almost the highest value for ASB gel. The resultant ASB gel can surfer from bending and twisting at -80 °C. Moreover, ASB gel also exhibits excellent biocompatibility and biodegradability. In addition, UC endowed the ASB gel with ion conductivity, allowing it to be used as a flexible strain sensor to monitor human movement. The ion-conductive ASB gel also exhibited thermoelectric ability with a Seebeck coefficient of 2.5 mV K-1, which can be further improved to 5 mV K-1 with a maximum output voltage of 252 mV by introducing a gradient of ionic concentration.

Recent applications of nanoparticles in organic transformations

A variation in the size of metal nanoparticles leads to a difference in their properties. As the size of metal nanoparticles decreases, the surface area increases which leads to an increase in the reactivity of metal nanoparticles. Metals like Au, Ag, Pd, and Pt have interesting properties when used in nanometric dimensions. They function efficiently in significant industrial processes as electrocatalysts and photocatalysts in various organic reactions. Recently, the green biosynthesis of nanoparticles has attracted the attention of researchers. With environmental pollution rising over the past few decades, metal nanoparticle catalysts could be the key to subdue the toxic effects. Being versatile, they can be used to degrade pollutants, develop solar cells, convert toxic nitroaromatic compounds, significantly reduce CO₂ emissions per unit of energy, and many more. Owing to their unique properties, nanoparticles have wide applications in biomedicine, for example, gold cages are promising agents for cancer diagnosis and therapy. Transition metal-oxide nanoparticles have been considered one of the best supercapacitor electrodes with high electrochemical performance. In this review, we have summarised fundamental concepts of metal nanoparticles over the last decade's main emphasis from 2010 to 2021. It focuses on the exceptional use of these nanocatalysts in various organic reactions. Additionally, we have also discussed the utility of these reactions and their crucial role in solving the problems of today. Through this article, we hope to provide the necessary framework needed to further advance the applications of metal nanoparticles as catalysts.

Gel scaffolds and emerging applications in biomedicine

Nowadays, gels are formed by small molecules self-assembling under the influence of various non-covalent interactions. They can be easily perturbed, which allows for the careful tweaking of their properties. They are kinetically confined, and following production, they usually do not demonstrate time-variable changes in material properties. When exposed to external stimuli such as temperature, pH, light, enzymes, redox, and chemical analytes, such materials may become switchable, leading to the reconfiguration of the gel matrix into a different type of network. The transformations allow gel-to-gel transitions, while the changes in the molecular aggregation result in the alteration of the physical and chemical properties of the gel with time. Here, we discuss various methods used to achieve gel-to-gel transitions by modifying a pre-formed gel material through external perturbation. The dynamic modification of gels allows the construction of an array of gels with various properties from a single material, which eventually extends the limit of application of the gels.

The Intracellular and Extracellular Microenvironment of Tumor Site: The Trigger of Stimuli-Responsive Drug Delivery Systems

The tumor microenvironment (TME), including intracellular and extracellular microenvironment, contains many biochemical indicators (such as acidity/alkalinity, oxygen content, and enzymatic activity) that are different from the normal physiological environment. These abnormal biochemical indicators can accelerate the heterogeneity of tumors, but on the other hand, they also provide opportunities for the design of intelligent drug delivery systems (DDSs). The TME-responsive DDSs have shown great potential in reducing the side effects of chemotherapy and improving the curative effect of tumors. In this review, the abnormal biochemical indicators of TME are introduced in detail from both the extracellular and intracellular aspects. In view of the various physiological barriers encountered during drug delivery, the strategy of constructing TME-responsive DDSs is discussed. By summarizing the typical research progress, the authors prospect the development of TME-responsive DDS in the future.

Fluorescent supramolecular polymers of barbiturate dyes with thiophene-cored twisted π-systems

Because supramolecular polymerization of emissive π-conjugated molecules depends strongly on π-π stacking interaction, the formation of well-defined one-dimensional nanostructures often results in a decrease or only a small increase of emission efficiency. This is also true for our barbiturate-based supramolecular polymers wherein hydrogen-bonded rosettes of barbiturates stack quasi-one-dimensionally through π-π stacking interaction. Herein we report supramolecular polymerization-induced emission of two regioisomeric 2,3-diphenylthiophene derivatives functionalized with barbituric acid and tri(dodecyloxy)benzyl wedge units. In CHCl3, both compounds are molecularly dissolved and accordingly poorly emissive due to a torsion-induced non-radiative decay. In methylcyclohexane-rich conditions, these barbiturates self-assemble to form crystalline nanofibers and exhibit strongly enhanced emission through supramolecular polymerization driven by hydrogen-bonding. Our structural analysis suggests that the barbiturates form a tape-like hydrogen-bonding motif, which is rationalized by considering that the twisted geometries of 2,3-diphenylthiophene cores prevend the competing rosettes from stacking into columnar supramolecular polymers. We also found that a small difference in the molecular polarity originating from the substitutional position of the thiophene core influences interchain association of the supramolecular polymers, affording different luminescent soft materials, gel and nanosheet.

Unusual hydrogen implanted gold with lattice contraction at increased hydrogen content

The experimental evidence for the contraction of volume of gold implanted with hydrogen at low doses is presented. The contraction of lattice upon the addition of other elements is very rare and extraordinary in the solid-state, not only for gold but also for many other solids. To explain the underlying physics, the pure kinetic theory of absorption is not adequate and the detailed interaction of hydrogen in the lattice needs to be clarified. Our analysis points to the importance of the formation of hydride bonds in a dynamic manner and explains why these bonds become weak at higher doses, leading to the inverse process of volume expansion frequently seen in metallic hydrogen containers.

Recent advances and prospects in the Zn-catalysed Mannich reaction

Zn-catalysed reactions are ubiquitously important due to their inexpensive, generally less toxic and atom-economic nature. According to the modern criteria of sustainability, their use in a catalytic manner is a highly desirable goal, especially when using chiral ligands. Considering the relevance of well-established zinc-mediated C-C bond formation reactions, it is relatively surprising that the use of Zn as a catalyst is still underdeveloped, especially in comparison with other transition metals. The vast majority of natural molecules, including proteins, nucleic acids and most biologically active compounds, contain nitrogen. Consequently, developing new synthetic methods for the construction of nitrogenous molecules receives great attention from organic chemists. The Mannich reaction is a very basic and very useful platform for the development of several such nitrogen-containing molecules. In this review, we summarise the recent advancements in the Zn-catalysed Mannich reaction, covering the literature from 2011 to 2020.

Metal-free catalytic hydrocarboxylation of hexafluorobut-2-yne

An efficient method for stereoselective synthesis of trifluorinated enol esters catalyzed by base was introduced.

Pd(ii)-Based polyoxometalate polymers as highly efficient heterogeneous catalysts for Suzuki–Miyaura reactions

Five Pd(ii)/polyoxometalate catalysts with a unique atomic arrangement and high Pd loading were synthesized under solvothermal conditions, and their structures were determined by single crystal X-ray diffraction.

Graphene-based frustrated Lewis pairs as bifunctional catalysts for CO2 reduction via the dissociative chemisorption of molecular H2: a periodic density functional perspective

Nanocarbon-based frustrated Lewis pair (FLP) bifunctional catalysts, on account of their unquenched electron transfer property, are becoming increasingly attractive as catalysts for the CO₂ reduction reaction via the dissociative chemisorption of H₂.

Nucleobase-monofunctionalized supramolecular poly(l-lactide): controlled synthesis, competitive crystallization, and structural organization

Controlled synthesis, competitive crystallization, and crystallization-driven structural organization of thymine-monofunctionalized supramolecular poly(l-lactide).

PtPd nanoframes derived from Pd@PdPt core–shell rhombic dodecahedrals with excellent catalytic performance toward methanol oxidation

PtPd nanoframes with excellent catalytic properties were obtained by etching Pd@PdPt core–shell RDs with Fe³⁺ in an acid environment.

"Luminescent carbon nanodots: Current prospects on synthesis, properties and sensing applications"

"Nanocarbon science" ignited interest owing to its substantial scope in biomedicine, energy and environment-beneficial applications. Carbon dots (C-dots), a multi-faceted nanocarbon material, emerged as a homologue to graphene and henceforth geared extensive investigation both on its properties and applications. Eximious properties like excitation-wavelength tunable fluorescence emission, up-converted photoluminescence, photon-induced electron transfer, low cytotoxicity, chiroptical behavior, high chemical and photostability set the ground for astounding applications of carbon dots. Abundant availability of raw "green" precursors complementary to other molecular/graphitic precursors make them environmentally benign, inexpensive and ultimately "nanomaterials of the current decade". This review focuses on the synthesis of carbon dots not only from natural sources but also from other carbonaceous precursors and contemplates the inherent but controversial properties. We also aim to garner the attention of readers to the recent progress achieved by C-dots in one of its prestantious area of applications as nanosensors.

Recent advances in the global ring functionalization of 7-azaindoles

The 7-azaindole building block has attracted considerable interest in the field of drug discovery in the current portfolio. Because of their powerful medicinal properties, the development of synthetic, elegant techniques for the functionalization of 7-azaindoles continues to be an active area of research. Advances in metal-catalyzed chemistry have recently supported the successful development of a number of novel and effective methods for functionalization of the 7-azaindole template. This review reports state-of-the-art functionalization chemistry of 7-azaindoles with an aspiration to highlight the global ring functionalization of 7-azaindoles that are potential as pharmacophores for various therapeutic targets. Other relevant reviews focused on 7-azaindole synthesis, properties and applications have also been reported. However, none of these reviews have been dedicated to the results achieved in the field of metal-catalyzed cross-coupling/C-H bond functionalized reactions. So we wish to discuss and summarize the advances made since 2011 in this field toward 7-azaindole functionalization.

Palladium-Catalyzed Intramolecular Alder-Ene Type Cycloisomerization Reactions

An overview of the recent literature on palladium-catalyzed intramolecular Alder-ene (IMAE) reaction of a variety of 1,n-unsaturated systems is presented. The reaction which was first reported by Trost and Lautens provided an efficient alternative to the thermal or Lewis acid catalyzed cycloisomerizations involving ene-type reaction. The IMAE cyclization of enynes and dienes has emerged as an important area and found significant applications in building up of complex molecular architectures and in the synthesis of several bioactive natural products. Since highly impactful reviews on this subject have covered the literature till 2015, this article focuses on summarizing the works subsequent to 2015.

Smart Nanocarriers for the Delivery of Nucleic Acid-Based Therapeutics: A Comprehensive Review

Nucleic acid-based therapies are promising therapeutics for the treatment of several systemic disorders, and they offer an exciting opportunity to address emerging biological challenges. The scope of nucleic acid-based therapeutics in the treatment of multiple disease states including cancers has been widened by recent progress in Ribonucleic acids (RNA) biology. However, cascades of systemic and intracellular barriers, including rapid degradation, renal clearance, and poor cellular uptake, hinder the clinical effectiveness of nucleic acid-based therapies. These barriers can be circumvented by utilizing advanced smart nanocarriers that efficiently deliver and release the encapsulated nucleic acids into the target tissues. This review describes the current status of clinical trials on nucleic acid-based therapeutics and highlights representative examples that provide an overview on the current and emerging trends in nucleic acid-based therapies. A better understanding of the design of advanced nanocarriers is essential to promote the translation of therapeutic nucleic acids into a clinical reality.

A novel geometric structure of a nanocluster with an irregular kernel: Ag30Cu14(TPP)4(SR)28

Here, we report a bi-ligand protected bimetallic nanocluster Ag₃₀Cu₁₄(TPP)₄(SR)₂₈. It is composed of an Ag₂₇ kernel and Ag₃Cu₁₄(TPP)₄(SR)₂₈ shell. Typically, the metal atoms are arranged irregularly. Both the core and shell exhibit the characteristics of C₂-symmetry.

An electron-rich small AIEgen as a solid platform for the selective and ultrasensitive on-site visual detection of TNT in the solid, solution and vapor states

Promising research on AIEgen (aggregation-induced emission active fluorogens)-based sensors for the detection of explosives (mostly picric acid) is primarily dominated by polymeric molecules. However, herein, we report the ability of a recently developed anthracene-based electron-rich π-conjugate as a small and suitable AIEgen for the selective and sensitive detection of 2,4,6-trinitrotoluene (TNT) through fluorescence (PL) quenching. This fluorophore consists of trimethoxybenzene-linked anthranyl-π-phenothiazine, which is recognized as a significantly electron-rich AIEgen suitable for the selective detection of TNT detection. The detection of TNT was performed in the solid, liquid and vapor states using this AIEgen in the aggregate or solid-state. The detection limit in the solution state was measured to be 3.2 × 10-9 M. When this fluorophore was impregnated on a paper strip for on-site visual detection, TNT was detected up to the 10-14 M level by the naked eye using a 365 nm UV-torch. The paper strip was also successfully used to detect TNT in the vapour state. This application was further extended to detect TNT in field soil. The detection of TNT by replacing trimethoxybenzene in the fluorophore with dimethoxy or monomethoxy was a failure, indicating the requirement of an adequate electron-rich system. Unlike the previous report with static quenching as the main reason for TNT detection, our experimental observations demonstrated the participation of favorable photo-induced electron transfer (PET) between TNT and the fluorophore as the origin of the PL quenching.

Synthesis of nanoparticle-assembled Zn3(VO4)2 porous networks via a facile coprecipitation method for high-rate and long-life lithium-ion storage

A simple coprecipitation route followed by a calcination process was developed to prepare 2D hierarchical Zn₃(VO₄)₂ porous networks formed by the crosslinkage of monolayered nanoparticles. As a promising anode for lithium ion batteries, the electrochemical performance of Zn₃(VO₄)₂ was investigated. At a current density of 1.0 A g^-1, the Zn₃(VO₄)₂ porous networks could register a high reversible discharge capacity of 773 mA h g^-1 and the capacity retention was 94% after 700 cycles. Moreover, a remarkable reversible discharge capacity of 445 mA h g^-1 was achieved at a current density of 5 A g^-1 after 1200 cycles. Even at a higher current density of 10.0 A g^-1, a high reversible capacity of 527 mA h g^-1 could be delivered, which still remained at 163 mA h g^-1 after 1200 cycles. This superior performance is attributed to the unique 2D porous networks with a stable structure. This work shows a new avenue for facile, cheap, green, and mass production of zinc vanadate oxides with 2D porous hierarchical networks for next-generation energy conversion and storage devices.

Pt-Substituted polyoxometalate modification on the surface of low-cost TiO2 with highly efficient H2 evolution performance

In this study, Pt-substituted polyoxometalate was first modified on the surface of commercially available TiO₂, forming an efficient photocatalyst with high reactivity for hydrogen evolution. During the photocatalytic process, Pt-polyoxometalates not only increase the mobility rate of electrons but also improve the separation efficiency of photoinduced electrons and holes. After photoreduction, the in situ generated Pt⁰ species are anchored on the surface of polyoxometalate anion, which prevents further agglomeration. Then, the in situ formed Pt⁰ species and polyoxometalates synergistically promote the efficiency of photoinduced electron transfer from TiO₂ to the protons adsorbed on the Pt⁰ surface. Although the content of Pt⁰ in the nanocomposite is only 0.6%, the photocatalytic hydrogen production rate reaches 5.6 mmol g^-1 h^-1 and remains stable at 4.5 mmol g^-1 h^-1 after the continuous catalytic process. Due to the modification of TiO₂ by Pt-substituted polyoxometalate, this nanocomposite represents a practical model that possesses highly efficient photoelectric conversion performance. The presented work not only extends the family of new TiO₂-polyoxometalate-based materials but also takes a further step toward the practical application of commercial TiO₂ in photocatalytic hydrogen production.

Reactive oxygen species (ROS)-responsive ferrocene-polymer-based nanoparticles for controlled release of drugs

Ferrocene-containing nanoparticles show reversible redox activity that could trigger drug release mediated by reactive oxygen species (ROS).

A new ratiometric fluorescence assay based on resonance energy transfer between biomass quantum dots and organic dye for the detection of sulfur dioxide derivatives

Sulfur dioxide (SO2) is considered as the fourth gas signal molecule after nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S). It plays important roles in several physiological processes. Therefore, the design and synthesis of nanoprobes for the detection of SO2 derivatives in cells is of great significance. Herein, we report a new ratiometric fluorescence nanoprobe based on resonance energy transfer (RET) between biomass quantum dots (BQDs) and organic dye (DMI) for the detection of SO2 derivatives. The proposed ratiometric fluorescence assay allows the determination of HSO3 - in the range of 1.0 to 225 μM with a detection limit of 0.5 μM. Importantly, the proposed ratiometric fluorescence nanoprobe exhibits a high photostability and good selectivity for HSO3 - over other chemical species including H2S and biological mercaptans. Quantitation of HSO3 - in cell lysates by using the nanoprobe is demonstrated.

A high-power lithium-ion hybrid capacitor based on a hollow N-doped carbon nanobox anode and its porous analogue cathode

Developing advanced lithium-ion hybrid capacitors (LIHCs) has a critical challenge of matching kinetics and capacity between the battery-type anode and the capacitive cathode. In this work, a novel "dual carbon" LIHC configuration is constructed to overcome such a discrepancy. Specifically, hollow nitrogen-doped carbon nanoboxes (HNCNBs) are synthesized by a simple template-assisted strategy. As an anode material (0.01-3 V vs. Li/Li⁺), the HNCNB electrode exhibits high specific capacity (850 mA h g^-1 at 0.1 A g^-1) and superior rate capability (321 mA h g^-1 at 20 A g^-1). After alkaline activation, the HNCNBs become highly porous (PHNCNBs), which offers better capacitance performance within the potential window from 2.5 to 4.5 V (vs. Li/Li⁺) than commercial activated carbon (AC). Coupling a pre-lithiated HNCNB anode with a PHNCNB cathode forms a dual-carbon LIHC. Since the similar hollow structure in both electrodes could diminish the diffusion distance, the as-prepared HNCNB//PHNCNB LIHC provides high energy densities of 148.5 and 112.1 W h kg^-1 at power densities of 250 and 25 000 W kg^-1, respectively, together with long-term cycling stability, which efficiently bridges the gap between supercapacitors and lithium ion batteries. Furthermore, the self-discharge behavior and the temperature-dependent performance are also investigated.

NHC-Stabilised Silyliumylidene Ions

Donor-stabilised silyliumylidene ions, from the parent [R-Si:]⁺ , are a class of low-valent silicon species which have received increasing research interest in the last several years. This interest began in the fundamental synthesis and characterisation of these compounds, but has since started to include more investigation into their further reactivity after several stable NHC-stabilised silyliumylidene ions were reported. This personal account briefly discusses the history of the still-young field of silyliumylidene ions followed by a more detailed discussion of published work from our group on the further development of silyliumylidene chemistry over the last four years.

Spontaneous full photocatalytic water splitting on 2D MoSe2/SnSe2 and WSe2/SnSe2 vdW heterostructures

Spontaneous full photocatalytic water splitting into hydrogen and oxygen under visible light irradiation without the need for sacrificial agents is a challenging task, because suitable band gaps, low overpotentials for both half-reactions and spatially-separated catalytic sites should be fulfilled simultaneously in a photocatalytic system. Here, we propose a promising strategy to achieve this goal by constructing van der Waals (vdW) heterostructures of two-dimensional (2D) materials. Using first-principles calculations, we predict two promising photocatalysts, MoSe2/SnSe2 and WSe2/SnSe2 heterostructures, with the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) taking place separately on the MoSe2 (WSe2) and SnSe2 layers. More excitingly, the Se-vacancy of the MoSe2 (WSe2) monolayer effectively lowers the HER overpotential, making the catalytic reactions occur spontaneously under the potentials solely provided by the photo-generated electrons and holes in pure water. The unique band alignment of these hetero-structured photocatalysts leads to high solar-to-hydrogen (STH) energy conversion efficiencies up to 10.5%, which is quite promising for commercial applications. This work opens up an avenue for the design of highly-efficient photocatalysts for full water splitting.

A 96-well wax printed Prussian Blue paper for the visual determination of cholinesterase activity in human serum

In the last decades, there is a growing search for analytical strategies to ensure clinical analysis without the need of laboratory set-up and skilled personnel. Indeed, user-friendly and low-cost devices are highly valued in the era of sustainability for their capability to be applied in low-resource contexts, such as developing countries. To address this issue, herein we report a 96-well paper-based and laboratory setup-free optical platform for the detection of butyrylcholinesterase enzyme (BChE) activity in human serum. We used chromatographic paper to realize a novel analytical tool exploiting its porous structure for reagentless synthesize Prussian Blue Nanoparticles (the sensing element), as well to load all the reagents required for the measurement. The principle of BChE activity detection relies on the reaction between the enzymatic product thiocholine and Prussian Blue, giving the Prussian White with subsequently Prussian Blue's fading, detected by a common office scanner supported by ImageJ software. Using this novel paper-based optical platform, BChE activity was linearly detected in the 2-15 U/mL range with a detection limit down to 0.8 U/mL. The accuracy was successfully demonstrated by recovery study with spiked serum and by comparing the data with the gold standard method.

Biomolecule-derived quantum dots for sustainable optoelectronics

The diverse chemical functionalities and wide availability of biomolecules make them essential and cost-effective resources for the fabrication of zero-dimensional quantum dots (QDs, also known as bio-dots) with extraordinary properties, such as high photoluminescence quantum yield, tunable emission, photo and chemical stability, excellent aqueous solubility, scalability, and biocompatibility. The additional advantages of scalability, tunable optical features and presence of heteroatoms make them suitable alternatives to conventional metal-based semiconductor QDs in the field of bioimaging, biosensing, drug delivery, solar cells, photocatalysis, and light-emitting devices. Furthermore, a recent focus of the scientific community has been on QD-based sustainable optoelectronics due to the primary concern of partially mitigating the current energy demand without affecting the environment. Hence, it is noteworthy to focus on the sustainable optoelectronic applications of biomolecule-derived QDs, which have tunable optical features, biocompatibility and the scope of scalability. This review addresses the recent advances in the synthesis, properties, and optoelectronic applications of biomolecule-derived QDs (especially, carbon- and graphene-based QDs (C-QDs and G-QDs, respectively)) and discloses their merits and disadvantages, challenges and future prospects in the field of sustainable optoelectronics. In brief, the current review focuses on two major issues: (i) the advantages of two families of carbon nanomaterials (i.e. C-QDs and G-QDs) derived from biomolecules of various categories, for instance (a) plant extracts including fruits, flowers, leaves, seeds, peels, and vegetables; (b) simple sugars and polysaccharides; (c) different amino acids and proteins; (d) nucleic acids, bacteria and fungi; and (e) biomasses and their waste and (ii) their applications as light-emitting diodes (LEDs), display systems, solar cells, photocatalysts and photo detectors. This review will not only bring a new paradigm towards the construction of advanced, sustainable and environment-friendly optoelectronic devices using natural resources and waste, but also provides critical insights to inspire researchers ranging from material chemists and chemical engineers to biotechnologists to search for exciting developments of this field and consequently make an advance step towards future bio-optoelectronics.