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Best Materials Chemistry Frontiers Covers of 2021

We are delighted to announce the Best Materials Chemistry Frontiers Covers of 2021!

Read below the scientific papers.

Achieving metal-free phosphorescence in dilute solutions for imaging hypoxia in cells and tumors

Peng Li, Yurong Guo, Yan Jia, Hongwei Guan, Chao Wang, Zibo Wu, Shuqing Sun, Zongjin Qu, Panwang Zhou and Guangjiu Zhao

Mater. Chem. Front., 2021, 5, 7170-7175

https://doi.org/10.1039/D1QM00733E

Issue 19 Vol. 5 Outside Front Cover

Biologically-derived nanoparticles for chemo-ferroptosis combination therapy

Haifeng Sun, Zhonghe Zhang, Xiaoyu Kang, Qiong Dai, Aixin Song, Jingcheng Hao and Jiwei Cui

Mater. Chem. Front., 2021, 5, 3813-3822

https://doi.org/10.1039/D1QM00295C

Issue 10 Vol. 5 Outside Front Cover

Synergistic improvements in the performance and stability of inverted planar MAPbI3-based perovskite solar cells incorporating benzylammonium halide salt additives

Hung-Cheng Chen, Jie-Min Lan, Hsiang-Lin Hsu, Chia-Wei Li, Tien-Shou Shieh, Ken-Tsung Wong and Chih-Ping Chen

Mater. Chem. Front., 2021, 5, 3378-3387

https://doi.org/10.1039/D0QM00983K

Issue 08 Vol. 5 Outside Front Cover

Congratulations to the winners of Best Materials Chemistry Frontiers Covers of 2021!

We expressed our sincere appreciation for all the support and contributions from our authors, reviewers, and readers in the past 2021.

Looking forward to receiving your high-quality work in 2022.

Happy Lunar New Year!

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Dispiroacridine-indacenobisthiophenes positional isomers: Impact of the bridge on the physicochemical properties

In the emerging technologies of organic electronics, positional isomerism has appeared in recent years as an efficient molecular tool to tune the electronic and physical properties of organic semi-con­­ductors (OSCs), which are at the heart of the devices. For example, modifying the position of the linkages (ortho, meta, para), allows to extend or restrict the π-con­jugation between two molecular fragments and, all the key electronic parameters of an OSC can be easily modified (HOMO / LUMO energy levels, single and triplet state energies, charge carriers mobilities…) leading to substantial different performances in electronic devices.

The indacenobisthiophene (IDT) fragment, which is an association of two thienyl cores to a central phe­nyl ring, has appeared in the last ten years as an important building unit to construct efficient or­ganic materials mainly for organic photovoltaics but also for Organic Field-Effect Transistors (OFETs). However, with a few exceptions, nearly all the IDT-based molecules described to date in the literature are cons­tructed on a central para-linked phenyl ring with the two thienyl sulfur atoms in an anti-configuration (see para-IDT core in pink in Chart 1). Re­cent­ly, the study of IDT positional isomers possessing a central meta-linked phenyl unit with the two sulfur atoms in a syn configuration (see meta-IDT core in blue in Chart 1) has allowed to show the impact of positional isomerism on this family of compounds.

Continuing this systematic approach, the authors investigate herein the incorporation of the widely known electron rich phe­nyl­­acridine (PA) fragment spiro-linked to the meta- or para-IDT core. Thus, Di­Spiro­Phe­nyl­A­cri­dine-IDT isomers, para-DSPA-IDT and meta-DSPA-IDT, constructed on the so-called “3π-2spiro” ar­chi­te­ctu­re, have been investigated through a detailed structure-properties relationship study.

Chart 1. Positional isomers investigated (para-DSPA-IDT and meta-DSPA-IDT)

In the present work, the group of Prof Cyril Poriel and Prof Joëlle Rault-Berthelot (Institut des Sciences Chimiques de Rennes- UMR 6226, Rennes) reports that the phenylacridine fragment significantly modifies the elec­tronic, physical and charge transport properties compared to structurally related DiSpiro­Fluo­­re­ne-IDT analogues (para-DSF-IDT, meta-DSF-IDT). This finding is different to what was reported in literature for other couples of IDT-based isomers and shows the key role played by the spiro-connected frag­ments on the charge transport properties of these molecular systems and open new avenues for meta-substituted oligomers.

Despite that the properties are mainly driven by the IDT core, this work shows that the bridges (herein spiro-connected phenylacridine) allow a fine tuning of all the properties. Particularly, the electrochemical studies have revealed the strong differences observed in the oxidation of the two isomers.

Figure 1. Left, CVs of para-DSPA-IDT (1.5 × 10-3 M) and of meta-DSPA-IDT (2.15 × 10-3 M) recorded between 0.25 and 1.8 V, sweep-rate 100 mV.s-1. Right: DPVs normalized on the first oxidation wave for para-DSPA-IDT and on the second oxidation wave for meta-DSPA-IDT. Pulse Height: 25 mV, sweep-rate 50 mV.s-1, t: 50 ms. Working platinum disk electrode (Ø 1 mm).

This work also shows that the mobilities of charge carriers are higher for the meta isomer than for the para isomer. This finding is different to what was reported in literature for other couples of IDT-based isomers and shows the key role played by the spiro-connected frag­ments on the charge transport properties of these molecular systems.

Figure 2. Thickness-scaled current-voltage characteristic of the para and meta-DSPA-IDT and para and meta-DSF-IDT hole-only SCLC devices (Left), SCLC mobility and SCLC device (right). In left, the dotted lines indicate the SCLC regime and the continuous ones the Ohmic regime.

BIOGRAPHICAL INFORMATIONS

Cyril Poriel received his PhD in 2003 from the University of Rennes 1. After a postdoctoral stay at the University of Exeter (UK), he joined the CNRS (Institut des Sciences Chimiques de Rennes) in 2005, where he is currently CNRS Research Director. His main research interest deals with the design of π-conjugated architectures for Organic Electronics. He is author/co-author of more than 120 publications, reviews and book chapters.

Joëlle Rault-Berthelot received her PhD in 1986 from the University of Rennes 1, where she is currently CNRS research director (Institut des Sciences Chimiques de Rennes). She has been working for 40 years in electrochemistry. Since 2005, she is involved in the design of π-conjugated systems for Organic Electronics and is author/co-author of more than 160 publications, reviews and book chapters.

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Amphiphilic-like carbon dots as antitumoral drug vehicles and phototherapeutical agents

Carbon dots (CDs) are nanosized carbon particles that have attracted the attention of researchers from different fields for their potential applications due to their high photostability, tunable excitation and emission, low toxicity and high biocompatibility. Reports on CDs that are soluble in non-aqueous solutions are still scarce, despite being recognized as promising materials and their compatibility with biological membranes facilitates their traversing. This feature is attractive for biomedical applications, in particular in cancer, where drug resistance and low specificity (i.e. side effects) urge the development of new drugs whose fate may be compromised by solubility, stability and clearance rate.

Recently the group of Prof. Santoyo and collaborators at Universidad of Granada (Spain) have demonstrated that the thermolysis of citric acid in DMSO and then reaction with alkyl amines yields CDs (LCDs) that bear both hydrophobic alkyl chains and carboxylic groups, and that the former make them suitable for hosting hydrophobic guests and the latter allow the modulation of their hydrosolubility. As a proof of concept the hydrophobic drug camptothecin (CPT) and the NIR fluorescent hydrophobic dye IR780 were assayed. The clinical implementation of both molecules is limited by their poor solubility, although CPT is a potent chemotherapeutic agent and IR786, besides the emission in the 807–823 nm wavelength range that makes it suitable for bioimaging, shows an absorption peak at 792 nm that yields a temperature increase and a production of ROS upon illumination with NIR light, enabling its use in photothermal and photodynamic therapies.

When LCD-2Na was loaded with CPT to yield LCD-2Na@CPT and the toxicity on a battery of cell lines was compared with an equivalent amount of free fresh CPT (Fig. 1), results demonstrated that the interaction between LCD-2Na and CPT is reversible and that the released drug is functional, despite it underwent a processing incompatible with the stability of free CPT.

Fig.1 Comparison of the cytotoxicity of LCD-2Na@CPT (green) and free CPT (red) on different cancer cell lines at different equivalent concentrations of CPT. Cell lines were incubated for 24 h with suitable amounts of either free CPT or LCD-2Na@CPT and cytotoxicity was assayed by the MTT method. Results are means ±1 standard deviation.

Additionally, the system LCD-2Na@IR780 was found to provoke an increase in the temperature of the solution up to 68℃ upon illumination with a 808 nm laser and yielded the formation of oxygen singlet with the concomitant destruction of IR780. At this point, it is important to recall that temperatures above 48℃ for minutes provoke irreversible injury that is enhanced by the reactive species produced during the destruction of IR780 by the laser.

Fig. 2 Temperature increase as a function of time of 200 μL of a water solutions containing 133 μM IR783 (red), 72 μM LCD-2Na@IR780 (blue) and 285 μM LCD-2Na@IR780 (magenta) irradiated with a 808 nm NIR laser at a power of 1.2 W cm−2 for 5 min (A) or 10 min (B). Inset B: Thermal image of the epperdorf containing the LCD-2Na@IR780 solution and the sample holder during the illumination. The temperature was recorded in real time with a high-resolution infrared camera.

It is important to highlight that LCDs are well tolerated by cells and, using a suitable length of the alkyl chains, they form inclusion complexes with hydrophobic guests of complementary size. The values of log P and the results obtained from the model molecules CPT and IR780 support the biotechnological potential of LCDs as drug carriers and in photothermal therapy.

Francisco Santoyo-Gonzalez is a Full Professor in Organic Chemistry at Universidad de Granada (Spain), full member of the Academy of Mathematics, Physical-Chemistry and Natural Sciences and  founder and leader of the group Glycochemistry & Bioconjugation. His research focuses on the development of new synthetic methodologies, with a particular emphasis in those related with the click-chemistry concept, and their application in a variety of diverse (bio)fields including cyclodextrins, glycochemistry, bioconjugation, non catalytic and catalytic hybrid-materials, nano-materials, targeted drug delivery, gene-transfection and (bio)sensors.

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Enhance of an efficient sensitivity for the diclhovors detection by a low-weighted gelator based bolaamphiphile amino acid derivatives decorated with a hybrid graphene quantum dots/enzyme/ hydrogel

Supramolecular hydrogels arise from the self-assembly of low molecular weight gelators (LMWG) and a large amount of water (typically higher than 99% by mass) using non-covalent interactions.  Bolaamphiphilic molecules comprise of at least two parts including a hydrophobic skeleton such as alkyl chains, a steroid, or a porphyrin, and two hydrophilic groups on both ends which to give either symmetric or asymmetric end groups.  Such bolaamphiphiles with hydrophobic spacers can act as low molecular mass gelators.

Non-chemically crosslinked hydrogels have been extensively studied in the context of enzyme encapsulation and stabilization. However, a flexible and porous structure is required to facilitate full penetration of the enzyme into the substrate.  The immobilization of amphiphilic graphene quantum dots (GQDs) and enzymes into hydrogels remains of great interest for amplifying a signal to give high sensitivity for sensing applications and maintaining enzymatic activity in biological applications.

Graphene quantum dot nanozymes (GQDzymes) with peroxidase mimic catalytic activity for analytical and biomedical applications, for example of glucose, organophosphate detection, are of great interest.  Graphene quantum dots embedded within porous hydrogels exhibit useful physical properties. For instance, mediated through hydrogel encapsulation they show advantageous high fluorescent intensity compared to those in solution. This can result in high sensitivity for fluorescent sensing applications.

Recently, the groups of Boosayarat Tomapatanaget (Chulalongkorn University, Thailand) and Jonathan W. Steed (Durham University, UK) have collaborated to design novel fluorescent hybrid materials comprising graphene quantum dots and enzymes supported in Lphenylalanine derived bis(urea) supramolecular hydrogels (GQDs/Enz/Gels) for detection of organophosphates such as pesticides. Determination of organophosphates (OPs) using this hybrid material arises from the turn-on photoluminescent responses observed in the presence of the pesticide and is caused by inhibition of the enzymatic production of hydrogen peroxide, which quenches luminescence as shown in Scheme 1.

Scheme 1. Hybrid hydrogels of GQDs/Enz/Gels and proposed mechanism of organophosphate pesticide detection.

The enzyme-loaded photoluminescent sensing hybrid gel materials (GQD/Enz/Gel) were prepared in two stages (Figure 2, S1 – S2). The microstructures of materials were examined by SEM with the comparison of GQDs/Gels and GQDs/Enz/Gels with different gelation time. Moreover, the rheological properties of gels demonstrated large G¢ values by the addition of GQDs or by using phosphate buffer as the solvent. GQD/Enz/Gel materials have been investigated for their organophosphate sensing ability. Gratifyingly, the visual changes showed that the photoluminescence intensity of the GQDs/Enz/Gels depended on the concentration of organophosphate pesticide dichlorvos, which inhibited the activity of the acetylcholine esterase enzyme (AChE) in the hybrid hydrogels.  The inhibition efficiency of AChE by OPs in oxo-form of the phosphate group (methyl-paraoxon and dichlorvos) are higher than those of OPs in thio-form (malathion and parathion).  Interestingly, the naked-eye fluorescence images obtained by the GQDs/Enz/Gels with dichlorvos, under UV irradiation at 365 nm displayed a significant brightness change upon increasing the analyte concentration.

Figure 2. (A1) Preparation of partial GQDs/Gels (stage1) and GQDs/Enz/Gels hybrid hydrogels (stage2). (A2) SEM images of the dried partial gels (xerogels) from stage 1 prepared for 1 min and the hybrid hydrogels from stage 2 prepared for 30 min followed by drying under ambient conditions for 2 days. (B) frequency-sweep rheology of gelator 4b and GQDs/Gels from 4b in different conditions. (C1) visual changes of GQDs/Enz/Gels with various number of OPs and ACh. (C2) Comparison of inhibition efficiency (%) of AChE in hybrid hydrogels after incubation in 1.25 x10-6 and 12.5 x10-6 M of four organophosphate pesticides. (D) Photographs of hybrid GQDs/Enz/Gels sensory chips (Glass slide 7.6 x 2.6 cm and circle with diameter of 0.5 cm) in the presence of various concentration of dichlorvos (DV) and time of measurement.

This work also provides new insight into improving the performance of low molecular weight hybrid hydrogels through combination with GQDs, enzyme and phosphate buffer. The result is a highly effective and potentially versatile sensing system, with a high sensitivity and stability.  This is the candidate sensing system regarding to the enzymatic turn-on sensing in a small molecule gel medium. This efficient enzymatic sensing candidate offers opportunities for the development of a myriad of specific and highly sensitive hybrid nanomaterial-based (bio)sensors.

Prof. Jonathan W. Steed
University of Durham

Assoc. Prof. Boosayarat Tomapatanaget
Chulalongkorn University

Jonathan W. Steed obtained his B.Sc. and Ph.D. degrees at University College London, working with Derek Tocher on organometallic and coordination chemistry. He graduated in 1993 winning the Ramsay Medal for his Ph.D. work. Between 1993 and 1995 he was a NATO postdoctoral fellow at the University of Alabama and University of Missouri, working with Jerry Atwood. In 1995 he was appointed as a Lecturer at King’s College London. In 2004 he joined Durham University where he is currently Professor of Inorganic Chemistry. Professor Steed is co-author of the textbooks Supramolecular Chemistry (2000, 2009 & 2021) Core Concepts in Supramolecular Chemistry and Nanochemistry (2007) and around 350 research papers. He has edited various books including the 8-volume Supramolecular Chemistry from Molecules to Nanomaterials (2012). He is the recipient of a number of awards, most recently the 2021 RSC Tilden Prize. He is Editor-in-Chief of the American Chemical Society journal Crystal Growth & Design. His interests are in crystallization, supramolecular gels and crystalline solids particularly pharmaceutical solids, co-crystals and hydrates. See personal web pages for full details.

Boosayarat Tomapatanaget is associate professor in the Department of Chemistry, Faculty of Science, Chulalongkorn University (Thailand). She received her PhD in Chemistry at the Faculty of Science, Chulalongkorn University in 2003. The research field of Professor Boosayarat Tomapatanaget encompasses many aspects of supramolecular chemistry, particularly in applications such as the design and synthesis of chemosensors. The molecular recognition of biological targets has formed a major part of host-guest chemistry including the hybrid organic/inorganic based on nanomaterials for sensing purpose.

 

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Quinolinophenothiazine as Electron Rich Fragment for RGB Single-Layer Phosphorescent Organic Light-Emitting Diodes

The development of efficient organic host matrices for the emissive layer of Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) is at the origin of the fantastic progresses made by this technology in the last twenty years. The role played by the host matrix is crucial as it should prevent energy back transfers from the guest emitter to the host and favour the confinement of excitons. The rational design of host materials for guest phosphors has allowed to reach very high-efficiency red, green and blue PhOLEDs (with external quantum efficiency EQE>25%). However, all these devices are multi-layer PhOLEDs, which are constituted of a stack of organic layers in order to improve the injection, transport and recombination of charges within the emissive layer. To reduce the cost and the environmental footprint of the OLED technology, simplifying the multi-layer structure is one interesting direction for the future. The so-called Single-Layer PhOLEDs (SL-PhOLEDs, Figure 1), the simplest device only made of the electrodes and the emissive layer, have thus stimulated a strong interest for the last fifteen years. However, high efficiency SL-PhOLEDs (especially for the blue emission) are very rarely reported in literature due to the difficulty to design an efficient host material. To reach high-performance SL-PhOLEDs, the host material should fulfil several precise criteria: (i) a high triplet state energy ET˃ 2.7 eV to confine the triplet excitons within phosphorescent guest, (ii) HOMO/LUMO energy levels well adapted to the electrode Fermi levels allowing efficient charge injection, (iii) good and well balanced mobilities of electrons and holes (ambipolar character) in order to compensate for the absence of electron/hole transporting layers, and (iv) thermal and morphological stabilities to extend the lifetime of the devicesThese four criteria can be fulfilled by the careful association of an electron-rich and an electron-deficient unit within a single molecule. 

Figure 1. Schematic representation of the architecture of a Single-Layer PhOLED (Left) and a Multi-Layer PhOLED (Right). Hole injection layer (HIL), hole transporting layer (HTL), electron injection layer (EIL), electron transporting layer (ETL), hole blocking layer (HBL), electron blocking layer (EBL), Emissive Layer (EML).

In the present work, the group of Prof Cyril Poriel (Institut des Sciences Chimiques de Rennes- UMR 6226, Rennes) reports a high-efficiency host material constructed on a barely studied electron rich fragment, namely quinolinophenothiazine (QPTZ). The QPTZ fragment is a phenylacridine bridged by a sulphur atom, Figure 2. Despite appealing properties induced by this bridging (e.g. strong electron rich character), this fragment remains almost unexplored to date in organic electronics. Herein, the strong potential of the QPTZ fragment as host for the new generation of simplified SL-PhOLEDs is demonstrated. Red, green and blue SL-PhOLEDs were successfully fabricated and yielded an average external quantum efficiency of ca 10% (Figure 3). High luminances of ca 10000 cd/m2 for red and blue devices and 40000 cd/m2 for green devices were obtained. These luminances are higher than the best reported to date with structurally related analogues and highlight the strong interest of the QPTZ fragment in such devices. Thanks to its high HOMO energy level, the QPTZ unit also allows to decrease the threshold voltage of the corresponding devices, which is a key point in ‘single-layer’ technology.

Figure 2. Phenylacridine and Quinolinophenothiazine molecular fragment

This work demonstrates the potential of the QPTZ fragment in the design of host materials for high performance single-layer PhOLEDs. QPTZ appears as a promising building unit and can advance the field of organic semi-conducting materials. We are convinced that the future development of QPTZ-based materials would also be appealing for other organic devices.

Figure 3. SL-PhOLEDs characteristics using SQPTZ-2,7-F(POPh2)2 as host material. A) Current density (mA/cm²) and luminance (cd/m²) as a function of the voltage; B) Current efficiency (cd/A, filled symbols) and power efficiency (lm/W, empty symbol) as a function of the current density (mA/cm²) and C) Normalized EL spectra.

BIOGRAPHICAL INFORMATIONS

Cyril Poriel received his PhD in 2003 from the University of Rennes 1. After a postdoctoral stay at the University of Exeter (UK), he joined the CNRS (Institut des Sciences Chimiques de Rennes) in 2005, where he is currently CNRS Research Director. His main research interest deals with the design of π-conjugated architectures for Organic Electronics. He is author/co-author of more than 120 publications, reviews and book chapters. twitter: @CyrilPoriel

 

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Silk fibroin microspheres as optical resonators for wide-range humidity sensing and biodegradable lasers

Silk fibroin (SF) is a biopolymer from Bombyx mori mulberry silkworm that has been utilized as textile for millennia. Recent advancement has emphasized to the biodegradation and biocompatibility of silk for medical applications. 

Due to the hydrogen bonding in silk fibroin, SF interacts with water molecules through the random coil conformation, while the β-sheet conformation provides mechanical strength to the entire spherical structure. 

Figure 1. Optical (a), fluorescence (b), and SEM (c) images of the SF microspheres. Scale bars: 5 µm. (d) PL spectra of a single SF microsphere upon excitation with cw laser (λex = 450 nm). Each WGM peak is assigned as shown on the bottom. (e) PL spectra of a single SF microsphere upon excitation with fs pulsed laser.

Recently, the group of Prof. Yohei Yamamoto and collaborators of University of Tsukuba have demonstrated that self-assembled SF microspheres, doped with ionic fluorescent dye, display resonant luminescence, which shifts in response to the humidity change. The resonant peaks result from the total internal reflection of the fluorescence, causing interference at the circumference of the microspheres. The SF microspheres display lasing property upon femto-second laser pumping (Figure 1).

The WGM peaks respond to the change of the ambient humidity. When the humidity is low, SF microsphere release water molecules, leading to shrinkage of the SF microsphere and thereby causing the WGM peaks shift to the lower wavelength. In the reversal process where ambient humidity is high, SF microsphere is hydrated, causing the shift WGM of the WGM peaks to the higher wavelength (Figure 2).

Figure 2. (a) Humidity-dependent PL spectra of a single SF microsphere upon excitation with cw laser (λex = 450 nm). (b) Plot of the wavelength of the resonant peak of TE26 upon increasing (filled circle) and decreasing (open circle) the surrounding humidity. (c) Plot of the wavelength of the resonant peak of TE26 upon 6 cycles of hydration (red) and dehydration (blue) between 93 and 25 %RH.

It is interesting to highlight the secondary structure of silk fibroin. Upon treated with alcohol, β-sheet conformation is increased, providing rigid structure for the SF microspheres while the remaining random coil structure in the SF microspheres is interacting with ambient moisture. This combination contributes to the SF microsphere for obtaining a high responsivity and high sensing range toward humidity.

These properties have given a new prospect or direction for designing next generation microresonators for optical sensing or lasing applications.

Prof. Yohei Yamamoto, University of Tsukuba

Yohei Yamamoto is a professor in the department of materials Science, faculty of Pure and applied sciences, University of Tsukuba. He received his doctor degree in 2003 from Osaka University. After post-doctoral researcher term, he was appointed as an associate professor in University of Tsukuba at 2010. on 2018, he promoted to full professor in University of Tsukuba. His research interests are self-assembly of π-conjugated molecules, polymers and biomolecules to construct electronically and optically active nano/micrometer-scale materials. He is the author of more than 90 articles and cited more than 2900 times with an index H = 28.

https://publons.com/researcher/1757952//

 

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Dual-Template Approach to Hierarchically Porous Polymer Membranes

Polymer membranes are an important class of materials that find use in a wide variety of fields. The suitability of a polymer membrane often requires careful tuning of their properties to the target application. This must be balanced with the cost of any modification. Hence the non-solvent induced phase separation method (NIPS) is a common route of manufacture for polymer membranes, as it is easy to accomplish on a commercial scale at low-cost.’

In the NIPS method, the polymer of choice is first dissolved in a good solvent, along with any additives, before its immersion in a non-solvent to produce the membrane morphology. This morphology typically shows a dense skin-layer with smaller pores above a layer of larger finger-like vertical pores. By careful choice of additive, some of the membrane properties, including hydrophilicity and microstructure, can be modified.

Poly(ethersulfone) (PES) is a material commonly used for water filtration membranes, chosen for its good mechanical, thermal and chemical properties. Use of an amphiphilic surfactant additive has been shown to produce a membrane with a larger and more well-defined microstructure in the larger finger-like pore regime, as well as increasing the surface hydrophilicity, a key requirement for reduction in biological fouling.

This work by Southern and Evans of the University of Cambridge introduces an additional level of structural hierarchy by the use of a second template molecule, 4-(phenylazo)benzoic acid (PABA), as well as the surfactant Pluronic® F127 (F127) to allow templating of both the dense skin layer and the larger pores. This addition of PABA leads to a more fibrous structure at the 1μm level, leading to higher pore connectivity and permeability, compared to membranes templated only with F127 (Figure 1).

Figure 1a. shows the poor connectivity of the skin layer of a membrane templated with only F127, compared to the fibrous structure of a membrane templated with both F127 and PABA shown in Figure 1b.

Their work demonstrates that this fibrous structure leads to a remarkable increase in flow rate that is improved further by the subsequent removal of the PABA. Extraction using ethanol is shown to provide an excellent approach for removal. This extraction method also allows recycling of the PABA for further membrane manufacture.

This dual-template approach, as part of the NIPS process, can be used to easily modify membrane manufacture, producing membranes exhibiting a hierarchical structure with improved pore connectivity, which could find use as energy materials or in water filtration.

Authors:

Dr Rachel C. Evans

Dr Rachel Evans obtained her MChem and PhD in Physical Chemistry from Swansea University. She was a Marie Curie Postdoctoral Fellow at the Université Paris-Sud, France and subsequently held an FCT research fellowship between the University of Coimbra and the University of Aveiro, Portugal. From 2009-2016, she was an Assistant, then Associate Professor in Physical Chemistry at Trinity College Dublin (TCD). In 2017, Rachel moved back to the UK to take up a University Lectureship at the University of Cambridge in the Department of Materials Science and Metallurgy. Rachel’s research is multidisciplinary and involves polymer, colloid and photophysical chemistry. Her current work is focused on the development of photoactive polymer-hybrid materials for luminescent solar devices, organic photovoltaics and stimuli-responsive membranes. She is a Fellow of the Royal Society of Chemistry and the Institute of Materials, Minerals and Mining and. In 2017, she was awarded the Dillwyn Medal for STEMM from the Learned Society of Wales and the MacroGroup UK Young Researcher’s Medal.

Thomas Southern graduated from the University of Cambridge with an MSci and B.A. in Materials Science. In 2017, Thomas began his PhD as part of the Functional Photoactive Materials group at the Department of Materials Science and Metallurgy, within the University of Cambridge. Thomas’ work, funded by an EPSRC studentship, focuses on hierarchically porous membranes for environmental remediation.

Article information:

Dual-template approach to hierarchically porous polymer membranes
Thomas J. F. Southern and Rachel C. Evans
Mater. Chem. Front., 2021, Advance Article
https://doi.org/10.1039/D0QM00610F

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Life science nanoarchitectonics at interfaces

Nanotechnology is an indispensable item in advanced bio-related and life sciences, but a novel concept is necessary to bridge gaps between nanotechnology and biology/materials chemistry. The most suitable concept for this task would be nanoarchitectonics. In this short review article, our recent accomplishments of nanoarchitectonics approaches on cell functions including gene delivery and controlled differentiation are summarized. Regulations of cell activities by nanoarchitected materials are carried out through their interfacial contacts. Our accomplishments are here described according to types of material structural motif, (i) nanotopography, (ii) self-assembled structures, and (iii) composite materials. Finally, several challenging approaches are introduced as frontiers of cell fate regulation at the interfacial media. Developments of artificial materials and systems to regulate bio-organizations including living cells will give intuitions and ideas even to the design of general functional systems. Interfacial nanoarchitectonics could be an important key concept for future advanced life technologies as well as currently required biomedical applications.

 

Figure 1. Outline of nanoarchitectonics and application to life science at interfaces.

 

Interfacial structures with various topological and mechanical features affect significantly cell behaviours including cell fates. At insides of living cells, sophisticated mechanisms are working upon relays of functional elements, and these mechanisms can be triggered by the input of external stimuli at the surfaces of cells. Control of surface contact can lead to the regulation of complicated cell functions. Interfacial nanoarchitectonics would be an important key concept for cell regulations for biomedical applications and life sciences.

 

Article Information

Life science nanoarchitectonics at interfaces
Katsuhiko Ariga, Kun-Che Tsai, Lok Kumar Shrestha and Shan-hui Hsu
Mater. Chem. Front., 2020, Accepted Manuscript
https://doi.org/10.1039/D0QM00615G

 

Authors Information

Katsuhiko Ariga

National Institute for Materials Science & University of Tokyo

Katsuhiko Ariga received his Ph.D. from Tokyo Institute of Technology in 1990. He is currently the Leader of the Supermolecules Group and Principal Investigator at the World Premier International Research Centre for Materials Nanoarchitectonics, NIMS. He has also been appointed as Professor at the University of Tokyo. He is the author of more than 700 articles indexed by SCI and cited more than 40000 times with an index H = 106 (Sept., 2020)

https://publons.com/researcher/2767466/katsuhiko-ariga/

 

Shan-hui Hsu

National Taiwan University

Shan-hui Hsu received her Ph.D. degree from Case Western Reserve University (USA) in 1992. She is now the Director for the Doctoral Program of Green Sustainable Materials and Precision Devices and Distinguished Professor at the Institute of Polymer Science and Engineering, National Taiwan University.

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Manganese as a Superior Dopant for Oxide Nanosheets in Water Oxidation

The efficiency of water splitting is severely limited by the oxygen evolution reaction (OER), due to sluggish kinetics and a substantial overpotential. To overcome this challenge, precious-metal based catalysts, such as IrO2 and RuO2, have been investigated and confirmed to exhibit good OER performance. However, the scarcity and high cost of these materials restrict their large-scale application.

 

Recently, the group of Derek Ho and collaborators of the City University of Hong Kong have demonstrated a one-step method for the synthesis of Mn doped ultrathin nickel-iron oxide (Mn-Ni-Fe-O) nanosheets, which simultaneously achieves an abundance of oxygen vacancies and high valance Ni3+ catalytic sites (Fig. 1). The Mn dopant exists in the form of mixed-valence Mn cations, which contributes to tailoring the electronic structure of the Ni and Fe sites, leading to outstanding OER catalytic performance.

Figure 1. Schematic of the preparation procedure of Mn-Ni-Fe-O nanosheets.

 

 

SEM and TEM images of the Mn-Ni-Fe-O hybrid shows 100 – 300 nm interconnected nanosheet structures, having an ultrathin and veil-like morphology (Fig. 2). AFM images show a nanosheet thickness of approximately 3.2 nm. EDX mapping presents that Ni, Fe, Mn, and O elements are uniformly dispersed throughout the nanosheets.

 

Figure 2. (a) SEM image, (b, c) TEM images and the inset in (c) is the corresponding SAED patterns, (d) HRTEM image, (e) AFM image and the corresponding thickness curve, (f) STEM image and the corresponding element mapping, and (g) EDX spectrum of the Mn-Ni-Fe-O nanosheets.

 

 

XRD, XPS, CV, and EPR are also performed (Fig. 3). From XPS, after Mn doping, the Fe 2p3/2 XPS peak of the Mn-Ni-Fe-O nanosheets shifts to a higher binding energy as compared to that of undoped Ni-Fe-O nanosheets, suggesting that Mn dopant can modulate the charge density of Fe atom sites. Compared to the Ni 2p XPS spectrum of pristine Ni-Fe-O, the Ni 2p XPS spectrum of Mn-Ni-Fe-O nanosheets exhibits an obvious positive shift of 0.3 eV in binding energy, which is attributed to Mn incorporation. From CV curves, the Ni2+ oxidation peaks appear at 1.40 and 1.36 V versus RHE for the undoped and doped samples, respectively, indicating the oxidation of Ni species is enhanced upon Mn doping. Also, the O2 ratio (51.0 %) for the Mn-Ni-Fe-O nanosheets is higher than that of the Ni-Fe-O nanosheets (41.9 %), which indicates that Mn dopants can create an enhanced oxygen vacancies concentration.

Figure 3. Characterization data of the Mn-Ni-Fe-O and Ni-Fe-O: (a) XRD patterns, (b) XPS survey spectra, (c) high-resolution XPS spectra for Mn 2p region for Mn-Ni-Fe-O, (d) XPS for the Fe 2p region, (e) XPS for the Ni 2p region, CV curves (scan rate of 50 mV s-1) of (f) Ni-Fe-O  and (g) Mn-Ni-Fe-O, (h) XPS for the O 1s region, and (i) electron paramagnetic resonance (EPR) spectra of Mn-Ni-Fe-O (2 wt%).

 

 

OER electrochemical performance has been investigated in an O2-saturated KOH (1 M) solution. Upon doping of Mn, polarization curves show an OER overpotential of only 225 mV (vs. undoped at 250 mV) (Fig. 4). Remarkably, these two as-prepared ultrathin nanosheets, with or without Mn doping, exhibit faster OER than the commercial RuO2. The Mn doped nanosheets exhibit a turnover frequency (TOF) of 0.063 s−1 at the overpotential of 300 mV, which is 3.5 and 12 times higher than that of the undoped sample and commercial RuO2, respectively. The Tafel slope is 38.2 mV dec-1 (vs. 65.8 mV dec-1 undoped and 72.0 mV dec-1 from RuO2). Electrochemical impedance spectroscopy (EIS) reveals that the Mn dopants can effectively improve the electrical conductivity.

Figure 4. (a) Polarization curves, (b) TOF, and (c) Tafel slope of Mn-Ni-Fe-O, Ni-Fe-O, and RuO2. (d) Nyquist slopes of Ni-Fe-O and Mn-Ni-Fe-O, (e) overpotential at 10 mA cm-2 and Tafel slope of Ni-Fe-O nanosheets with different Mn doping levels, and (f) chronopotentiometry curves of Mn-Ni-Fe-O nanosheets at 30 mA cm-2.

 

 

This work demonstrated a facile method in synthesizing ultrathin Mn-Ni-Fe-O nanosheets that achieve highly efficient OER catalytic performance, providing a sound strategy for the design and synthesis of multi-metallic, atomically-thin oxides nanosheets to mitigate the catalytic limitation of OER, thereby rendering the electrolysis of water a practical form of alternative fuel production.

 

Information on Corresponding Author

 

Derek Ho

City University of Hong Kong

Derek Ho is currently an associate professor at the Department of Materials Science and Engineering at City University of Hong Kong. He directs the Atoms to Systems Laboratory. He received his B.A.Sc. (first class) and M.A.Sc. in Electrical and Computer Engineering from the University of British Columbia (UBC), Vancouver, Canada, in 2005 and 2007 respectively. At UBC, he focused his study on microelectronics. He received his Ph.D. in Electrical and Computer Engineering from the University of Toronto, Toronto, Canada in 2013, where he worked on sensors incorporating nanomaterials and CMOS electronics for chemical detection and DNA biosensing applications. Professor Ho’s research interest is in the synthesis of electronic nanomaterials and fabrication of advanced devices. His current research focuses on sensing and energy applications, mainly in the form of stretchable and healable electronics. www.atomstosystems.com

 

Article information:

Mn dopant induced high-valence Ni3+ sites and oxygen vacancies for enhanced water oxidation

Yu Zhang, Zhiyuan Zeng and Derek Ho

Mater. Chem. Front., 2020, Advance Article

https://doi.org/10.1039/D0QM00300J

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Functional conjugated organic molecules – A collection of articles from Frontiers Journals

We are delighted to share with you a collection of articles from Materials Chemistry Frontiers and Organic Chemistry Frontiers to showcase the key findings and breakthroughs in the field of functional conjugated organic molecules, including the synthesis of the conjugated systems, their properties and applications. This collection is free to access till Jun 19th 2020.

Reviews


Figuration of bowl-shaped π-conjugated molecules: properties and functions
Masaichi Saito, Hiroshi Shinokubo and Hidehiro Sakurai
Mater. Chem. Front., 2018,2, 635-661
https://doi.org/10.1039/C7QM00593H

Design strategies of n-type conjugated polymers for organic thin-film transistors
Ying Sui, Yunfeng Deng, Tian Du, Yibo Shi and Yanhou Geng
Mater. Chem. Front., 2019,3, 1932-1951
https://doi.org/10.1039/C9QM00382G

Research articles


Modulation of luminescence chromic behaviors and environment-responsive intensity changes by substituents in bis-o-carborane-substituted conjugated molecules
Hiroki Mori, Kenta Nishino, Keisuke Wada, Yasuhiro Morisaki, Kazuo Tanaka and Yoshiki Chujo
Mater. Chem. Front., 2018,2, 573-579
https://doi.org/10.1039/C7QM00486A

Enhancement of intra- and inter-molecular π-conjugated effects for a non-fullerene acceptor to achieve high-efficiency organic solar cells with an extended photoresponse range and optimized morphology
Ning Wang, Lingling Zhan, Shuixing Li, Minmin Shi, Tsz-Ki Lau, Xinhui Lu, Rafi Shikler, Chang-Zhi Li and Hongzheng Chen
Mater. Chem. Front., 2018,2, 2006-2012
https://doi.org/10.1039/C8QM00318A

One-step rapid synthesis of π-conjugated large oligomers via C–H activation coupling
Shi-Yong Liu, Di-Gang Wang, Ai-Guo Zhong and He-Rui Wen
Org. Chem. Front., 2018,5, 653-661
https://doi.org/10.1039/C7QO00960G

Folate-conjugated and pH-triggered doxorubicin and paclitaxel co-delivery micellar system for targeted anticancer drug delivery
Lijing Niu, Feiyan Zhu, Bowen Li, Lingling Zhao, Hongze Liang, Yinghua Yan and Hui Tan
Mater. Chem. Front., 2018,2, 1529-1538
https://doi.org/10.1039/C8QM00217G

Influence of catalytic systems in Stille polymerization on the electrochromic performance of diketopyrrolopyrrole-based conjugated polymers
Wei Teng Neo, Qun Ye, Zugui Shi, Soo-Jin Chua and Jianwei Xu
Mater. Chem. Front., 2018,2, 331-337
https://doi.org/10.1039/C7QM00377C

Highly efficient transformation of linear poly(phenylene ethynylene)s into zigzag-shaped π-conjugated microporous polymers through boron-mediated alkyne benzannulation
Yoshiaki Shoji, Minsu Hwang, Haruka Sugiyama, Fumitaka Ishiwari, Kumiko Takenouchi, Ryota Osuga, Junko N. Kondo, Shigenori Fujikawa and Takanori Fukushima
Mater. Chem. Front., 2018,2, 807-814
https://doi.org/10.1039/C7QM00582B

Conjugated molecular dyads with diketopyrrolopyrrole-based conjugated backbones for single-component organic solar cells
Dongdong Xia, Fan Yang, Junyu Li, Cheng Li and Weiwei Li
Mater. Chem. Front., 2019,3, 1565-1573
https://doi.org/10.1039/C9QM00238C

Preparation of bright-emissive hybrid materials based on light-harvesting POSS having radially integrated luminophores and commercial π-conjugated polymers
Masayuki Gon, Keita Sato, Keigo Kato, Kazuo Tanaka and Yoshiki Chujo
Mater. Chem. Front., 2019,3, 314-320
https://doi.org/10.1039/C8QM00518D

Fused donor–acceptor π-conjugated diazatruxenones: synthesis and electronic properties
Angela Benito-Hernández, Mardia T. El-Sayed, Juan T. López Navarrete, M. Carmen Ruiz Delgado and Berta Gómez-Lor
Org. Chem. Front., 2018,5, 1748-1755
https://doi.org/10.1039/C8QO00122G

Orthogonally arranged tripyrrin–BODIPY conjugates with an “edge to plane” mode
Chun-Liang Hou, Yuhang Yao, Da Wang, Jing Zhang and Jun-Long Zhang
Org. Chem. Front., 2019,6, 2266-2274
https://doi.org/10.1039/C9QO00445A

Near-infrared light-induced shape memory, self-healable and anti-bacterial elastomers prepared by incorporation of a diketopyrrolopyrrole-based conjugated polymer
Yaling Zhang, Shiwei Zhou, Kok Chan Chong, Shaowei Wang and Bin Liu
Mater. Chem. Front., 2019,3, 836-841
https://doi.org/10.1039/C9QM00104B

Increased conjugated backbone twisting to improve carbonylated-functionalized polymer photovoltaic performance
Tao Zhang, Cunbin An, Kangqiao Ma, Kaihu Xian, Changguo Xue, Shaoqing Zhang, Bowei Xu and Jianhui Hou
Org. Chem. Front., 2020,7, 261-266
https://doi.org/10.1039/C9QO01251F

Pyridine-terminated low gap π-conjugated oligomers: design, synthesis, and photophysical response to protonation and metalation
Asmerom O. Weldeab, Lei Li, Seda Cekli, Khalil A. Abboud, Kirk S. Schanze and Ronald K. Castellano
Org. Chem. Front., 2018,5, 3170-3177
https://doi.org/10.1039/C8QO00963E

Molecular modulation of fluorene-dibenzothiophene-S,S-dioxide-based conjugated polymers for enhanced photoelectrochemical water oxidation under visible light
Chunhui Dai, Xuezhong Gong, Xianglin Zhu, Can Xue and Bin Liu
Mater. Chem. Front., 2018,2, 2021-2025
https://doi.org/10.1039/C8QM00275D

Helicene-derived aggregation-induced emission conjugates with highly tunable circularly polarized luminescence
Chengshuo Shen, Fuwei Gan, Guoli Zhang, Yongle Ding, Jinghao Wang, Ruibin Wang, Jeanne Crassous and Huibin Qiu
Mater. Chem. Front., 2020,4, 837-844
https://doi.org/10.1039/C9QM00652D

Electrochemical doping engineering tuning of the thermoelectric performance of a π-conjugated free-standing poly(thiophene-furan) thin-film
Wenqian Yao, Lanlan Shen, Peipei Liu, Congcong Liu, Jingkun Xu, Qinglin Jiang, Guoqiang Liu, Guangming Nie and Fengxing Jiang
Mater. Chem. Front., 2020,4, 597-604
https://doi.org/10.1039/C9QM00542K

Conjugated oligomers with alternating heterocycles from a single monomer: synthesis and demonstration of electroluminescence
Sara Urrego-Riveros, Matthias Bremer, Jonas Hoffmann, Anne Heitmann, Thibault Reynaldo, Janek Buhl, Paul J. Gates, Frank D. Sönnichsen, Muriel Hissler, Martina Gerken and Anne Staubitz
Org. Chem. Front., 2019,6, 3636-3643
https://doi.org/10.1039/C9QO00947G

The synthesis and properties of a new class of π-expanded diketopyrrolopyrrole analogs and conjugated polymers
Yazhou Wang, Yuchun Xu, Mahesh Kumar Ravva, Yaping Yu, Mingfei Xiao, Xiang Xue, Xinru Yang, Yongming Chen, Zhengke Li and Wan Yue
Org. Chem. Front., 2019,6, 2974-2980
https://doi.org/10.1039/C9QO00645A

Wave-packet multi-scale simulations based on a non-linear tight-binding Hamiltonian for carrier transport in π-conjugated polymers
Tomofumi Tada
Mater. Chem. Front., 2018,2, 1351-1359
https://doi.org/10.1039/C7QM00591A

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