Advanced Functional Materials Research Articles

Preface

The 2022 4th International Conference on Polymer Synthesis and Application (ICPSA 2022) was be held in Chengdu, China during June 24-26, 2022. ICPSA 2022 provided an enabling platform for innovative academics, engineers and industrial experts in the field of synthesis and application of polymer to exchange new ideas and present research results. This conference also promoted the establishing of business or research relations among global partners for future collaboration. We hope that this conference could make significant contribution to the update of knowledge about these latest scientific field.The conference model was divided into three sessions, including oral presentations, keynote speeches and invited speeches. In the first part, some scholars, whose submissions were selected as the excellent papers, were given 15 minutes to perform their oral presentations one by one. Then in the second and three parts, keynote speakers and invited speakers were each allocated 30-45 minutes to hold their speeches.More than 50 participants attended the conference. We are greatly honored to have invited Prof. Shahid Hussain, from School of Materials Science and Engineering, Jiangsu University, China to serve as our Conference Chair. On this conference, two keynote speakers and four invited speakers delivered their research works in area of Polymer Synthesis and Application. The first keynote speakers, Prof. Wenbin Yang, Southwest University of Science and Technology, China. He delivered a wonderful speech: Study on functional polymer composites based on phase change microcapsules. The next keynote speakers were Prof. Jinming Hu, University of Science and Technology of China, China. In the invited speech part, we were glad to invited Prof. Yagang Zhang, School of Materials and Energy University of Electronic Science and Technology of China, China. His research focused on developing advanced functional materials, polymer composite, bio-based materials, fine chemicals based on molecular recognition and molecular imprinting. Others invited speakers were Dr. Hemin Zhang, Sichuan University, China; Prof. Umapada Pal, Benemérita Universidad Autónoma de Puebla, Mexico; Prof. Xin Wu, Sun Yat-sen University, China. We would like to especially thank all the speakers who shared their latest research results with the audience.ICPSA 2022 is to bring together innovative academics and industrial experts in the field of Polymer Synthesis and Application to a common forum. Therefore, we compiled a lot of excellent papers featuring the latest advanced studies on the following topics: Research trends of polymer science, Synthesis and reaction of polymer materials, Functional polymers, Preparation and testing of fine polymer materials and other related topics. All the papers have been through rigorous review and process to meet the requirements of international publication standard.We would like to acknowledge all of those who have supported ICPSA 2022. Each individual and institutional help were very important for the success of this conference. Especially we would like to thank the organizing committee for their valuable advices in the organization and helpful peer review of the papers.The Committee of ICPSA 2022List of Committee member is available in the pdf.

Poly(N-isopropylacrylamide)-Based Hydrogels for Biomedical Applications: A Review of the State-of-the-Art.

A prominent research topic in contemporary advanced functional materials science is the production of smart materials based on polymers that may independently adjust their physical and/or chemical characteristics when subjected to external stimuli. Smart hydrogels based on poly(N-isopropylacrylamide) (PNIPAM) demonstrate distinct thermoresponsive features close to a lower critical solution temperature (LCST) that enhance their capability in various biomedical applications such as drug delivery, tissue engineering, and wound dressings. Nevertheless, they have intrinsic shortcomings such as poor mechanical properties, limited loading capacity of actives, and poor biodegradability. Formulation of PNIPAM with diverse functional constituents to develop hydrogel composites is an efficient scheme to overcome these defects, which can significantly help for practicable application. This review reports on the latest developments in functional PNIPAM-based smart hydrogels for various biomedical applications. The first section describes the properties of PNIPAM-based hydrogels, followed by potential applications in diverse fields. Ultimately, this review summarizes the challenges and opportunities in this emerging area of research and development concerning this fascinating polymer-based system deep-rooted in chemistry and material science.

A universal design for triggering the precise micro-structure reconstruction through in-situ electro-regulating to boost the pseudocapacitance of MnO2

Developing a precise controllable strategy for modulating the micro-morphology, atom coordination environment, and electronic structure of electrode materials is crucial for the performance in the field of energy storage, yet still a tremendous challenge. Herein, a facile and universal in-situ electrochemical self-optimization design, electro-regulating, is designed to controllably produce electrode materials with abundant defects. Through detailed characterization studies, the microstructure of MnO2 is reconstructed after electro-regulating, which exhibits a structure of small fragments with numerous holes due to the partial self-dissolution of acidic oxides under an alkaline operating environment. Furthermore, the electro-regulating strategy not only presents the formation steps of numerous holes but is also accompanies by a number of O vacancies generation process due to the activation of an external electric field. This study provides a new inspiration for reasonably designing advanced functional electrode materials for various electrochemical applications and beyond.

Detection of Proton Carriers in Tyrosine-Rich Peptide Thin Film

Traditional Von Neumann structure, where memory and computational units are separated, is now facing significant difficulties in terms of power consumption and computing speed in big data era. Therefore, human brain-like computing architecture is now paid attention in research field owing to its high parallelism, fault tolerance and robustness1-2. In this biological system, synaptic weight which plays crucial role in memory and learning is modulated by ionic species, especially protons transmitted between synapses. Here, we focused on short length peptide Y7C (YYACAYY) thin film which induces proton coupled electron transfer (PCET) due to its Tyrosine-rich structure. The Y7C film has shown an interesting behavior in which electrical conductivity varies with humidity3-4. By this modulation, bimodal memristor using both of voltage and humidity5 input and synaptic transistor which shows dynamic reponses through humidity have been demonstrated, but direct relation between current and proton conduction is still ambiguous. Therefore, we measured transient current flow between Pd and Au electrode and detected proton conduction of Y7C film.In previous studies, voltage & humidity controlled Y7C bimodal memristor has been reported. However, since the current regulation through humidity showed insufficient response than that through voltage, a definite relationship between moisture and current needs to be defined. To achieve that, thin film of the peptide material dissolved in Trifluoroacetic acid (TFA) 99% solution was spin coated on SiO2/Si substrate. By measuring the transient current of the Y7C film, presence of temporary charge carriers was observed. Also, the electrical impedance spectroscopy (EIS) of peptide layer showed a semicircle and a nonvertical tail, which indicate ionic conduction through the film. Lastly, film characterization of Y7C thin layer unveiled that the corresponding ions are protons as originally targeted. This research has showed principles of peptide thin film’s current increment driven by both of humidity and voltage through electrochemical reaction. Fig.1. Transient charge flowing through Y7C thin film measured in various atmospheric conditions and electrodes Acknowledgment This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020R1A2C2004864). References Pakkenberg B, Pelvig D, Marner L, Bundgaard M J, Gundersen H J G, Nyengaard J R and Regeur L 2003 Exp. Gerontol. 38 95Abbott L F and Nelson S B 2000 Nat. Neurosci. 3 1178Lee, Jaehun, et al. "Proton conduction in a tyrosine‐rich peptide/manganese oxide hybrid nanofilm." Advanced Functional Materials 27.35 (2017): 1702185.Sung, Taehoon, et al. "Effects of proton conduction on dielectric properties of peptides." RSC advances 8.59 (2018): 34047-34055.Song, Min-Kyu, et al. "Proton-enabled activation of peptide materials for biological bimodal memory." Nature Communications 11.1 (2020): 1-8. Figure 1

Electrical Detection of Gaseous Pollutants Using Nanoporous-Based Gas Sensors

The advanced in situ detection of gaseous pollutants, such as NOx or SOx, is of great interest in many applications, such as the automotive and coal industries. We will discuss the continued advancement of our low power sensors for these pollutants, leveraging the previous successful development of impedance spectroscopy-based sensors for the detection of gaseous I2.1-3 The sensors, composed of Pt interdigitated electrodes (IDEs) with a nanoporous adsorbent layer, can be tuned to selectively adsorb gases of interest through judicious material selection, and the electrical response directly correlated to gas concentration. The current work is focused on exploring these nanoporous phases (metal-organic frameworks (MOFs), zeolites, etc.) for the real-time detection of NOx. The sensors have been successfully demonstrated for detection of trace NO2 (0.5 – 5 ppm),4 and experimental results, collected at relatively low temperature (25-50°C), will be discussed. Other recent work exploring the direct growth of crystalline MOF membranes, through the chemical functionalization of the surface of interdigitated electrodes will also be discussed.5 Direct growth of thin MOF films on surface functionalized IDEs has been shown to result in increased sensor sensitivity and a faster response time. Lastly, we will present initial results for the use of the sensors in the selective detection of NO2 in complex environments (e.g. presence of H2O, CO2, etc.).6 Acknowledgements Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. References Small, L.J and Nenoff, T.M., ACS Appl. Mater. Interfaces, 2017, 9 (51), 44649.Small, L.J.; Krumhansl, J.L.; Rademacher, D.X.; Nenoff, T.M. Meso. Mater., 2019, 280, 82.Small, L.J.; Hill, R. C.; Krumhansl, J. L.; Schindelholz, M. E.; Chen, Z.; Chapman, K.W.; Zhang, X.; Yang, S.; Schroder, M.; Nenoff, T.M., ACS Applied Materials and Interfaces, 2019, 11 (31), 27982.Small, L.J.; Henkelis, S.E; Rademacher, D.X.; Schindelholz, M. E.; Krumhansl, J. L.; Vogel, D.J.; Nenoff, T.M, Advanced Functional Materials, 2020, 30 (50), 2006598.Henkelis, S.E; Percival, S.J.; Small, L.J; Rademacher, D.X.; Nenoff, T.M, Membranes, 2021, 11 (3), 176.Percival, S.J.; Henkelis, S.E; Li, M.; Schindelholz, M.E.; Krumhansl, J. L.; Small, L.J.; Lobo, R.F.; Nenoff, T.M., I Eng. Chem. Res., 2021, 60 (40), 14371.

(Invited, Digital Presentation) Macroscopically Aligned Carbon Nanotubes for Photonics, Electronics, and Thermoelectrics

The remarkable flexibility, stable chemical structure, and extraordinary thermal, electrical, and optical properties of carbon nanotubes (CNTs) are promising for a variety of applications in flexible and/or high-temperature electronics, optoelectronics, and thermoelectrics, including wearables, refractory photonics, and waste heat harvesting [1]. However, the long-standing goal in the preparation of CNT ensembles is how to maintain the extraordinary properties of individual CNTs on a macroscopic scale. The polydispersity and randomness remain two main challenges.Here, we will discuss different methods for creating macroscopically aligned CNTs, including spontaneous formation of wafer-scale aligned CNT films via controlled vacuum filtration [2-4] and production of ultrahigh-conductivity CNT fibers and films through solution spinning and coating [5,6]. We will then describe the optical [2,7-11], dc and ac electrical [2,12-17], thermal [18], and thermoelectric [19-21] properties of these materials. These results are promising for device applications in various fields such as flexible CNT broadband detectors [22-26], spectrally selective thermal emitters [11], and thermoelectric devices [20,21]. W. Gao et al., “Macroscopically Aligned Carbon Nanotubes for Flexible and High-Temperature Electronics, Optoelectronics, and Thermoelectrics,” Journal of Physics D: Applied Physics 53, 063001 (2020).X. He et al., “Wafer-Scale Monodomain Films of Spontaneously Aligned Single-Walled Carbon Nanotubes,” Nature Nanotechnology 11, 633 (2016).W. Gao and J. Kono, “Science and Applications of Wafer-Scale Crystalline Carbon Nanotube Films Prepared through Controlled Vacuum Filtration,” Royal Society Open Science 6, 181605 (2019).N. Komatsu et al., “Groove-Assisted Global Spontaneous Alignment of Carbon Nanotubes in Vacuum Filtration,” Nano Letters 20, 2332 (2020).N. Behabtu et al., “Strong, Light, Multifunctional Fibers of Carbon Nanotubes with Ultrahigh Conductivity,” Science 339, 182 (2013).L. W. Taylor et al., “Improved Properties, Increased Production, and the Path to Broad Adoption of Carbon Nanotube Fibers,” Carbon 171, 689 (2021).K. Yanagi et al., “Intersubband Plasmons in the Quantum Limit in Gated and Aligned Carbon Nanotubes,” Nature Communications 9, 1121 (2018).W. Gao et al., “Continuous Transition between Weak and Ultrastrong Coupling through Exceptional Points in Carbon Nanotube Microcavity Exciton–Polaritons,” Nature Photonics 12, 362 (2018).M. E. Green et al., “Bright and Ultrafast Photoelectron Emission from Aligned Single-Wall Carbon Nanotubes through Multiphoton Exciton Resonance,” Nano Letters 19, 158 (2019).F. Katsutani et al., “Direct Observation of Cross-Polarized Excitons in Aligned Single-Chirality Single-Wall Carbon Nanotubes,” Physical Review B 99, 035426 (2019).W. Gao et al., “Macroscopically Aligned Carbon Nanotubes as a Refractory Platform for Hyperbolic Thermal Emitters,” ACS Photonics 6, 1602 (2019).X. Wang et al., “High-Ampacity Power Cables of Tightly-Packed and Aligned Carbon Nanotubes,” Advanced Functional Materials 24, 3241 (2014).A. Zubair et al., “Carbon Nanotube Fiber Terahertz Polarizer,” Applied Physics Letters 108, 141107 (2016).D. Tristant et al., “Enlightening the Ultrahigh Electrical Conductivities of Doped Double-Wall Carbon Nanotube Fibers by Raman Spectroscopy and First-Principles Calculations,” Nanoscale 18, 19668 (2016).N. Komatsu et al., “Modulation-Doped Multiple Quantum Wells of Aligned Single-Wall Carbon Nanotubes,” Advanced Functional Materials 27, 1606022 (2017).F. R. G. Bagsican et al., “Terahertz Excitonics in Carbon Nanotubes: Exciton Autoionization and Multiplication,” Nano Letters 20, 3098 (2020).A. Baydin et al., “Giant Terahertz Polarization Rotation in Ultrathin Films of Aligned Carbon Nanotubes,” Optica 8, 760 (2021).S. Yamaguchi et al., “One-Directional Thermal Transport in Densely Aligned Single-Wall Carbon Nanotube Films,” Applied Physics Letters 115, 223104 (2019).K. Fukuhara et al., “Isotropic Seebeck Coefficient of Aligned Single-Wall Carbon Nanotube Films,” Applied Physics Letters 113, 243105 (2018).Y. Ichinose et al., “Solving the Thermoelectric Trade-Off Problem with Metallic Carbon Nanotubes,” Nano Letters 19, 7370 (2019).N. Komatsu et al., “Macroscopic Weavable Fibers of Carbon Nanotubes with Giant Thermoelectric Power Factor,” Nature Communications 12, 4931 (2021).S. Nanot et al., “Broadband, Polarization-Sensitive Photodetector Based on Optically-Thick Films of Macroscopically Long, Dense, and Aligned Carbon Nanotubes,” Scientific Reports 3, 1335 (2013).X. He et al., “Photothermoelectric p-n Junction Photodetector with Intrinsic Broadband Polarimetry Based on Macroscopic Carbon Nanotube Films,” ACS Nano 7, 7271 (2013).X. He et al., “Carbon Nanotube Terahertz Detector,” Nano Letters 14, 3953 (2014).X. He, F. Léonard, and J. Kono, “Uncooled Carbon Nanotube Photodetectors,” Advanced Optical Materials 3, 989 (2015).A. Zubair et al., “Carbon Nanotube Woven Textile Photodetector,” Physical Review Materials 2, 015201 (2018).

Strain Evolution in Pt-Ni Alloy Nanoparticles during Electrochemical Ni Leaching Revealed By Bragg Coherent Diffraction Imaging

Alloy catalysts such as Pt-M (M: other metal elements) have been extensively developed to improve the sluggish oxygen reduction reaction (ORR) that limits the efficiencies of fuel cells and metal-air batteries. Their catalytic activity is potentially enhanced by strain induced in a nearly pure Pt "shell" formed by dissolving the alloyed metal (M) from the surface. It is, therefore, of great importance to reveal the strain distribution on the Pt shell in situ so that we can exploit this mechanism to design new alloy catalysts. Yet, it has been challenging to analyze the strain on the shell because it inevitably requires a technique that can image the strain field of the nanoparticles with high spatial resolution.In this study,1 we successfully revealed the strain of the exemplary Pt-Ni alloy nanoparticles in detail from the 3D images obtained by using a novel synchrotron technique, “Bragg Coherent X-ray Diffraction Imaging” (BCDI), which can directly image minute atomic displacement field owing to the X-ray coherence. Pt-Ni nanoparticles with compositions of Pt2Ni3 (Ni rich), Pt1Ni1 (moderate Ni), and Pt3Ni2 (Ni poor) were observed by BCDI during cyclic voltammetry cycles, in which the less noble metal Ni electrochemically leached from the alloy. This cycling induced tensile strain inside particles in all the compositions, implying that the formation of a Pt shell on the surface strained the core of the particle because of the lattice mismatch between the Pt-Ni alloys and Pt. The strain in the shell was evaluated from a core-shell elastic model using the parameters obtained in the 3D images.A compressive circumferential strain in the shell was observed in all the compositions, and the Pt1Ni1 particle showed the largest compressive circumferential strain of 5%. Since the compressive strain is reported to facilitate the enhanced ORR,2 the compositional dependence of the strain magnitude observed in this study was in excellent agreement with the previous study performed with nm-size particles where Pt1Ni1 exhibits the highest activity among a wide range of compositions.3 A similar strain-activity relation was also inferred in a powder X-ray diffraction studies of core-shell Pt x Co1-x alloys,4 suggesting it is a widely applicable phenomenon. The present study demonstrated that the strain on alloy nanoparticles can be quantitatively determined by BCDI during electrochemical reactions, which enables us to exploit surface strain in designing a wide range of electrocatalysts. T. Kawaguchi et al., Nano Letters, 21, 5945–5951 (2021).H. Wang et al., Science, 354, 1031–1036 (2016).C. Wang et al., Advanced Functional Materials, 21, 147–152 (2011).D. Wang et al., Nature Materials, 12, 81–87 (2013).

(Digital Presentation) ORR/OER Activity and Rechargeable Zinc-Air Battery Performance of B Site Doped Double Perovskite NdBaCoXO5+δ (X= Fe, Ni, Mn)

Renewable energy systems and designing economically viable electrochemical energy storage systems is essential to decrease environmental pollution concerns while meeting the growing energy demand. Among the various energy storage devices, rechargeable zinc-air batteries (RZAB) have attracted great attention due to their relatively high specific energy (1218 W.h/kg), and volumetric energy density (6136 W.h/L) cost-effectiveness, and environmental friendliness, comparable to that of lithium–air batteries [1]. However, the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during the discharge and recharge process of the air cathode on RZAB prevents large-scale application. So far noble metals (Pt, Ru, Ir) and their alloys (Pt-Ru/C) are used as bifuctional oxygen electrocatalysts in commercial rechargeable RZAB, yet they are too expensive to be viable for large-scale commercial applications. Therefore, designing robust and cost-effective bifunctional oxygen electrocatalysts is prime of importance for RZAB to be commercialized [2]. One of the most promising oxygen bifunctional catalyst are perovskite oxides due to their structural and compositional flexibility [3]. Moreover, the electronic structure of perovskite oxides can be tuned by varying the transition metals at the B site and thus their electrocatalytic performance [4-5].In this work, first we will demonstrate phase pure fabrication of double perovskite oxide series of NdBaCoXO5+δ (X= Fe, Ni, Mn). Second, OER and ORR performances of the series of NdBaCoXO5+δ (X= Fe, Ni, Mn) will be explained in relation with their electronic structure and work function. Here, we applied NdBaCoMnO6 on a home-made RZAB as air cathode, according to its bifunctional index. Therefore, we will finally present charge-discharge performance of RZAB with NdBaCoMnO6 as air cathode. J. Fu, Z. P. Cano, M.G. Park, A. Yu, M. Fowler, Z. Chen, Advanced Materials, 29, 1604685 (2016).Y. Tong, J. Wu, P. Chen, H. Liu, W. Chu, C. Wu, Y. Xie, Journal of the American Chemical Society, 140, 11165-11169 (2018).W. Yin, B. Weng, J. Ge, Q. Sun, Z. Li, Y. Yan, Energy & Environmental Science, 12, 442-462 (2019).J. Ahmed, N. Alhokbany, M. Ubaidullah, S. Mutehri, M. M. Khan, S. M. Alshehri, Ceramics International, 46, 20038-20044 (2020).A. Mulder, N. Benedek, J. Rondinelli and C. Fennie, Advanced Functional Materials, n/a-n/a (2013).

In-Situ Raman Spectroscopy of Lithium-Sulfur Cells

With the increasing demand for higher capacity and energy density, new batteries are being developed to meet these demands. Among the most promising chemistries, Lithium-Sulfur (Li-S) is one of the most popular. This is because of its excellent theoretical energy density (2600 Wh/kg, active materials) [1]. There are challenges that prevent Li-S cells from being commercialized, including adverse impact on cell performance due to lithium polysulfide (PS) formation/dissolution, volume changes during cycling and lithium dendrite formation. The issue that retains the focus of many researchers is the formation and shuttling of PSs as it directly impacts the practicality of the cell in terms of longevity and efficiency. There have been various approaches to mitigate PS shuttling including the use of specially designed cathode materials. One such material is sulfur-polyacrylonitrile (S-PAN) where PAN acts as a backbone [1, 2, 3]. The structure of this material supports the full reduction of elemental sulfur to Li2S upon discharging. This full reduction prevents the formation of intermediate PSs and loss of sulfur through PS shuttling, thus improving the sulfur utilization of S-PAN cathodes. The hypothesis is that there are little to no intermediate PSs present in S-PAN cathodes. To prove this, we used Raman spectroscopy to compare the quantitative results between the S-PAN electrode and conventional sulfur electrode. Specifically, with Raman spectroscopy, the features of the spectra that we are comparing are the Raman peaks of intermediate PSs that may be present in the samples [4, 5]. If the hypothesis is correct, the intensities of the Raman peaks for intermediate PSs for S-PAN should be less pronounced than conventional sulfur. In other words, the S-PAN electrode should exhibit significantly fewer intermediate polysulfides than the conventional sulfur electrode. The test is conducted by discharging the Raman cell to a set of incremental potentials where Raman spectra are taken at each potential. This will allow for the comparison of the polysulfide compositions and concentrations at different potential levels.We will present the effect of S-PAN on the charge-discharge cycle and compare it to a conventional Li-S cell. We will also utilize Raman Spectroscopy and in-situ Raman cells to characterize and compare PS species in both S-PAN and conventional S based cells. References Mukkabla, R.; Buchmeiser, M. R., Cathode materials for lithium–sulfur batteries based on sulfur covalently bound to a polymeric backbone. Journal of Materials Chemistry A, 2020, 8 (11), 5379-5394.Wang, J.; Yang, J.; Wan, C.; Du, K.; Xie, J.; Xu, N., Sulfur Composite Cathode Materials for Rechargeable Lithium Batteries. Advanced Functional Materials, 2003, 13 (6), 487-492.Warneke, S.; Eusterholz, M.; Zenn, R. K.; Hintennach, A.; Dinnebier, R. E.; Buchmeiser, M. R., Differences in Electrochemistry between Fibrous SPAN and Fibrous S/C Cathodes Relevant to Cycle Stability and Capacity. Journal of The Electrochemical Society, 2018, 165 (1), A6017-A6020.Zhang, L.; Qian, T.; Zhu, X.; Hu, Z.; Wang, M.; Zhang, L.; Jiang, T.; Tian, J.-H.; Yan, C., In situ optical spectroscopy characterization for optimal design of lithium–sulfur batteries. Chemical Society Reviews, 2019, 48 (22), 5432-5453.McBrayer, J. D.; Beechem, T. E.; Perdue, B. R.; Apblett, C. A.; Garzon, F. H. Polysulfide Speciation in the Bulk Electrolyte of a Lithium SULFUR BATTERY. Journal of The Electrochemical Society, 2018, 165 (5). Acknowledgement This work was supported in part by the U.S. Department of Energy, Office of Science, Office Workforce Development for Teachers and Scientists (WDTS) under the Science Community College Internship (CCI) Program as well as the Office of Energy Efficiency and Renewable Energy, Energy Storage Graduate Internship Program at the National Renewable Energy Laboratory.

(Invited, Digital Presentation) Exploring New Applications of Luminescent Silicon Nanocrystals

The luminescence of silicon nanocrystals (Si NCs) has been traditionally studied for various applications such as light-emitting diodes, solar cells and bioimaging[1]. In the past few years we have started exploring the use of Si NCs for emerging optoelectronic synaptic devices[2,3]. As an important type of optoelectronic synaptic devices, electroluminescent synaptic devices have been fabricated by using Si NCs[4,5]. Under the stimulation of electrical spikes these devices give out electroluminescence that decays in the timeframe of tens of microseconds, enabling a series of synaptic functionalities and logic functions. In addition, we have synthesized Er-hyperdoped Si NCs, which emit light simultaneously at the wavelengths of 830 and 1540 nm. It is found that Er-hyperdoped Si NCs are a powerful ratiometric near-infrared fluorescent platform. The rationmetric near-infrared fluorescence may be well used for temperature sensing, which further enables the construction of logic gates[6].[1] Z. Y. Ni, et al., Materials Science & Engineering R 138, 85-117 (2019).[2] L. Yin, et al., Nano Letters 20, 5, 3378–3387 (2020).[3] Y. Wang, et al., Advanced Functional Materials 2107973 (2021).[4] S. Y. Zhao, et al., Nano Energy 54, 383-389 (2018)[5] S. Y. Zhao, et al., Science China Materials 62, 1470-1478 (2019)[6] K. Wang, et al., to be submitted.

Methods to Tune the Optical Response of Porous Photonic Crystal Structures

Photonic crystals are periodic dielectric structures which selectively tune the wavelengths of light propagating through the material1 2. The highly ordered, repeating structural lattice induces a photonic bandgap or stopband which inhibits or partially attenuates certain frequencies of light, similar to the electronic bandgap with forbidden energies present in semiconductor materials3. These forbidden frequencies are blocked in transmission and reflected from the material surface. The inherent sensitivity of this photonic response to repeating lattice size dimensions and the magnitude of the refractive index contrast between the constituent materials allows for tailored optical behaviour by adjusting the photonic crystal structural parameters or environment4 5.A range of interesting applications using both the photonic bandgap and material porosity have emerged, predicated on the ability to accurately forecast the wavelength position of the photonic response. Colorimetric sensors6 7, photocatalysts8 9 and solar cells10 are prime examples of these types of applications; the porosity of the photonic crystal facilitates greater material infiltration and reactions, while the photonic bandgap acts to enhance the optical component of the process. Critically, the use of these structures is tied to our ability to predict and interpret the signature optical response.Here, we examine several techniques which can be used modify the photonic bandgap/stopband for photonic crystal structures. For TiO2 and SnO2 inverse opal photonic crystals, we explore how solvent infiltration into the highly porous network red-shifts the observed photonic response. Using solvents with different refractive indices, we apply the shifted photonic stopband data to determine the fill fraction of solid material comprising the photonic crystal network. We also examine functionalization of artificial opal and inverse opal photonic crystals with metal films. We detail the emergence of a consistent photonic stopband blue-shift with increasing metal content and propose a reduction in the effective refractive index of the entire photonic crystal introduced by the specific properties of the metal film. Importantly, the effects investigated here are broadly applicable to a range of realistic operating conditions across many disciplines where an understanding of the photonic stopband is paramount to the application. References Yablonovitch, E., Inhibited Spontaneous Emission in Solid-State Physics and Electronics. Physical Review Letters 1987, 58 (20), 2059-2062.John, S., Strong localization of photons in certain disordered dielectric superlattices. Physical Review Letters 1987, 58 (23), 2486-2489.Joannopoulos, J. D.; Villeneuve, P. R.; Fan, S., Photonic crystals: putting a new twist on light. Nature 1997, 386 (6621), 143-149.Blanford, C. F.; Schroden, R. C.; Al-Daous, M.; Stein, A., Tuning Solvent-Dependent Color Changes of Three-Dimensionally Ordered Macroporous (3DOM) Materials Through Compositional and Geometric Modifications. Advanced Materials 2001, 13 (1), 26-29.Aguirre, C. I.; Reguera, E.; Stein, A., Tunable Colors in Opals and Inverse Opal Photonic Crystals. Advanced Functional Materials 2010, 20 (16), 2565-2578.Zhang, Y.; Qiu, J.; Hu, R.; Li, P.; Gao, L.; Heng, L.; Tang, B. Z.; Jiang, L., A visual and organic vapor sensitive photonic crystal sensor consisting of polymer-infiltrated SiO2 inverse opal. Physical Chemistry Chemical Physics 2015, 17 (15), 9651-9658.Li, H.; Chang, L.; Wang, J.; Yang, L.; Song, Y., A colorful oil-sensitive carbon inverse opal. Journal of Materials Chemistry 2008, 18 (42), 5098-5103.Chen, J. I. L.; von Freymann, G.; Choi, S. Y.; Kitaev, V.; Ozin, G. A., Amplified Photochemistry with Slow Photons. Advanced Materials 2006, 18 (14), 1915-1919.Collins, G.; Lonergan, A.; McNulty, D.; Glynn, C.; Buckley, D.; Hu, C.; O'Dwyer, C., Semiconducting Metal Oxide Photonic Crystal Plasmonic Photocatalysts. Advanced Materials Interfaces 2020, 7 (8), 1901805.Liu, L.; Karuturi, S. K.; Su, L. T.; Tok, A. I. Y., TiO2 inverse-opal electrode fabricated by atomic layer deposition for dye-sensitized solar cell applications. Energy & Environmental Science 2011, 4 (1), 209-215. Figure 1 SEM images and optical transmission spectra for (a) TiO2 and (b) SnO2 inverse opals. In each case the wavelength position of the photonic stopband is red-shifted significantly when a solvent infiltrates the porous photonic crystal network. SEM images and optical transmission spectra for (c) artificial polystyrene opals coated with a gold film and (d) TiO2 inverse opals coated with a copper film. Metal film incorporation into the photonic crystal network acts to consistent blue-shift the observed photonic stopband. Figure 1

Thermal Conductivity of Semicrystalline Polymer Networks: Crystallinity or Cross-Linking?

Understanding the heat flow in polymers is at the onset of many developments in designing advanced functional materials. Here, however, amorphous linear polymers usually exhibit a very low thermal conductivity κ, often hindering their broad applications. In this context, two common routes to increase κ are via semicrystallinity and cross-linking. It can therefore be inferred that the combination of these two effects may result in a further increase of κ with respect to the systems where only one of these two effects is important. Using molecular dynamics simulations, we investigate κ in semicrystalline polymer networks. Contrary to a priori understanding, we show that a combination of cross-linking and crystallinity does not always increase κ. Instead, a delicate competition between the lattice periodicity, the cross-linker types, and the bond density dictates the tunability of κ in these complex macromolecular systems. These results are also compared with the existing experiments.

Bio-inspired membranes for adsorption of arsenic via immobilized L-Cysteine in highly hydrophilic electrospun nanofibers

Arsenic is a concern for its ubiquity in the environment and its accumulative and toxic properties. Water is often contaminated with this chemical, so developing simple, scalable, and green water treatment technologies is urgently needed. We show here that the ability of the L-Cysteine biomolecule to form complexes with arsenic inspires its use as a natural bio-inspired sorbent to develop advanced functional materials. We establish for the first time a way to chemically anchor L-Cysteine (L-Cys) inside highly hydrophilic nanofibers to create a membrane capable of lowering As(V) concentration below the WHO limit of 10 μg/L. A homogeneous precursor mixture of an aqueous solution of PVA and L-Cys (5 wt% and 10 wt% of L-Cys with respect to PVA) was electrospun to obtain a nanofibrous membrane. Successful immobilization of L-Cys within PVA nanofibers is achieved during heat treatment at 190 °C. It occurs through esterification reactions between the hydroxyl group on the PVA chain and the carboxylic acid on L-Cys. Arsenic sorption (as As(V)) was assessed by batch experiments in aqueous media and at a controlled pH range. The maximum removal efficiency was achieved at pH 7, supporting the formation of thiolate complexes as the primary mechanism for arsenic sorption. We show that L-Cys confinement makes arsenic diffusion inside the nanofibers a rate-limiting process in adsorption kinetics, following the pseudo first order equation. Overall, this work establishes a novel arsenic remediation strategy and encourages the research of nature-mimicking adsorbents and biodegradable polymers to develop functional materials in water remediation.

A Bibliometric and Visual Analysis of Nanocomposite Hydrogels Based on VOSviewer From 2010 to 2022.

Background: Nanocomposite hydrogels (NHs) are stable composite materials formed by dispersing nanomaterials in hydrogels and have broad development prospects in the biomedical field. In this study, we aimed to systematically and comprehensively evaluate the trends and hot spots of biomedical applications of NHs from 2010 to 2022. Methods: In total, 713 articles and reviews related to NH applications in the biomedical field from 2010 to 2022 were retrieved from the Web of Science Core Collection (WOSCC). Two scientometric software programs, VOSviewer and Microsoft Excel 2019, were used to visually perform bibliometric analysis in terms of research trends, sources, the contribution of journals, co-citation, and the co-occurrence of keywords. Results: From 1 January 2010 to 3 February 2022, the number of annual scientific publications about NHs exhibited an upward trend, and research articles were published in a larger proportion (more than 77%). The top three countries in NH research were China, the United States, and India. Meanwhile, Tabriz University of Medical Sciences, the Chinese Academy of Sciences, and Tshwane University of Technology were the most active and contributive. In the contribution of journals, the journal Advanced Functional Materials had the highest number of publications, and the journal Int J Biol Macro had the most citations. Varaprasad K was the most prolific author, and Haraguchi K ranked first among co-cited authors. In the ranking of frequency in the co-cited references, Nanocomposite Hydrogels for Biomedical Applications, published by Gaharwar AK, was the most frequently cited reference. The keyword with the highest frequency was “drug delivery.” Conclusion: This study performed a full overview of NHs using bibliometrics and identified current trends and hot spots. This information may help researchers focusing on NHs to identify developments in this field.

Insights into the anisotropic, electronic and magnetism properties of ternary TM2Si2Ys (TM = Cr, Fe, Co, Ni) silicides from the first-principles calculations

In recent years, the transition metal silicides are promising advanced functional materials. However, the relevant physical properties of TM2Si2Ys are not well understood. In this work, the electronic, anisotropic and magnetic properties of SiY, Si2Y, Si3Y5 and TM2Si2Ys (TM = Cr, Fe, Co, Ni) were investigated using the first-principles calculations. The results show that these ternary TM2Si2Y silicides are thermodynamically stable. The elastic properties confirm that these compounds exhibit mechanically stable. According to the elastic constants and elastic modulus results, Co2Si2Y shows the stronger deformation resistance and the brittle behavior. The elastic anisotropy was characterized by the three-dimensional (3D) surface constructions and 2D projections. The band structure, density of states and electron density difference were systematically studied. In addition, the electronic structures explain the magnetic properties for TM2Si2Ys (TM = Cr, Fe, Co, Ni).

Valuable aramid/cellulose nanofibers derived from recycled resources for reinforcing carbon fiber/phenolic composites

The scale-up preparation of aramid nanofiber (ANF) and cellulose nanofiber (CNF), still faces serious challenges such as extreme production cost and lengthy preparation cycle. Herein, a feasible top-down strategy was proposed to achieve the efficient reclamation of waste resources, further realizing the large-scale production of high value-added nanofibers. The ANF/CNF as nanoscale building blocks and their reinforcement effects on the mechanical performances of carbon fiber/phenolic composites were investigated. Related strength and modulus of ANF/CNF-enhanced composites in the tensile, bending, shear and nano indentation tests, increased by 118.1% (tensile strength), 141.2% (tensile modulus), 142.2% (flexural strength), 354.4% (flexural modulus), 38.8% (shear strength) and 94.4% (elastic modulus), respectively. Our work offers a valuable reference in the fabrication of low-cost ANF/CNF derived from waste resources, which would facilitate the wide application of nanofibers in fabricating high-performance advanced functional materials.

High entropy fluorides as conversion cathodes with tailorable electrochemical performance

With the recent development of high entropy materials, an alternative approach to develop advanced functional materials with distinctive properties that show improved values compared to conventional materials has been provided. The high entropy concept was later successfully transferred to metal fluorides and high entropy fluorides (HEFs) were successfully synthesized. Owing to their high theoretical specific capacities in energy storage applications, HEFs were utilized as cathode materials for lithium-ion batteries (LIBs) and their underlying storage mechanisms were investigated. Instead of a step-by-step reduction of each individual metal cation, the HEFs seem to exhibit a single-step reduction process, indicating a solid solution compound instead of merely a mixture of different metal fluorides. It was also observed that the electrochemical behavior of the HEFs depends on each individual incorporated element. Therefore, by altering the elemental composition, new materials that exhibit improved electrochemical properties can be designed. Remarkably, HEFs with seven incorporated metal elements exhibited a better cycling stability as well as a lower hysteresis compared to binary metal fluorides. These findings offer new guidelines for material design and tailoring towards high performance LIBs.

Elaborate design of shell component for manipulating the sustained release behavior from core–shell nanofibres

BackgroundThe diversified combination of nanostructure and material has received considerable attention from researchers to exploit advanced functional materials. In drug delivery systems, the hydrophilicity and sustained–release drug properties are in opposition. Thus, difficulties remain in the simultaneous improve sustained–release drug properties and increase the hydrophilicity of materials.MethodsIn this work, we proposed a modified triaxial electrospinning strategy to fabricate functional core–shell fibres, which could elaborate design of shell component for manipulating the sustained-release drug. Cellulose acetate (CA) was designed as the main polymeric matrix, whereas polyethylene glycol (PEG) was added as a hydrophilic material in the middle layer. Cur, as a model drug, was stored in the inner layer.ResultsScanning electron microscopy (SEM) results and transmission electron microscopy (TEM) demonstrated that the cylindrical F2–F4 fibres had a clear core–shell structure. The model drug Cur in fibres was verified in an amorphous form during the X-ray diffraction (XRD) patterns, and Fourier transformed infrared spectroscopy (FTIR) results indicated good compatibility with the CA matrix. The water contact angle test showed that functional F2–F4 fibres had a high hydrophilic property in 120 s and the control sample F1 needed over 0.5 h to obtain hydrophilic property. In the initial stage of moisture intrusion into fibres, the quickly dissolved PEG component guided the water molecules and rapidly eroded the internal structure of functional fibres. The good hydrophilicity of F2–F4 fibres brought relatively excellent swelling rate around 4600%. Blank outer layer of functional F2 fibres with 1% PEG created an exciting opportunity for providing a 96 h sustained-release drug profile, while F3 and F4 fibres with over 3% PEG provided a 12 h modified drug release profile to eliminate tailing–off effect.ConclusionHere, the functional F2–F4 fibres had been successfully produced by using the advanced modified triaxial electrospinning nanotechnology with different polymer matrices. The simple strategy in this work has remarkable potential to manipulate hydrophilicity and sustained release of drug carriers, meantime it can also enrich the preparation approaches of functional nanomaterials.Graphical

In Situ Self-Sorting Peptide Assemblies in Living Cells for Simultaneous Organelle Targeting.

Self-sorting is a common phenomenon in eukaryotic cells and represents one of the versatile strategies for the formation of advanced functional materials; however, developing artificial self-sorting assemblies within living cells remains challenging. Here, we report on the GSH-responsive in situ self-sorting peptide assemblies within cancer cells for simultaneous organelle targeting to promote combinatorial organelle dysfunction and thereby cell death. The self-sorting system was created via the design of two peptides E3C16E6 and EVMSeO derived from lipid-inspired peptide interdigitating amphiphiles and peptide bola-amphiphiles, respectively. The distinct organization patterns of the two peptides facilitate their GSH-induced self-sorting into isolated nanofibrils as a result of cleavage of disulfide-connected hydrophilic domains or reduction of selenoxide groups. The GSH-responsive in situ self-sorting in the peptide assemblies within HeLa cells was directly characterized by super-resolution structured illumination microscopy. Incorporation of the thiol and ER-targeting groups into the self-sorted assemblies endows their simultaneous targeting of endoplasmic reticulum and Golgi apparatus, thus leading to combinatorial organelle dysfunction and cell death. Our results demonstrate the establishment of the in situ self-sorting peptide assemblies within living cells, thus providing a unique platform for drug targeting delivery and an alternative strategy for modulating biological processes in the future.

Biomimetic Swallow Nest Structure: A Lightweight and High-Strength Thermal Insulation Material.

A common method for reducing carbon emissions and the load-bearing pressure of buildings, and while also achieving improved energy conservation is to prepare porous magnesium-based lightweight composites to reduce waste and environmental hazards. However, due to internal stress, the pores of traditional lightweight composites crack easily and collapse, resulting in composites that are brittle with poor water resistance. These materials cannot achieve both low density and high strength, which limits their application in advanced functional materials. Thus, learned from nature, inspired by swallow's nest, a solution has been proposed, which is a simple and fast chemical arrangement and assembly method. Using bamboo scraps as the supporting framework and methylcellulose (MC) molecular chains as the templates, 5-phase crystals are grown and arranged on the MC. These crystals are arranged on the bamboo scraps by chemical means with MC acting as a bridge. At the same time, using the high viscosity and flexibility of the vinyl acetate/ethylene (VAE) copolymer emulsion and the formation of magnesium acetate chelate from VAE and hydration products, crystals and bamboo scraps can be assembled. Through these organic-inorganic copolymers, an intercalated and integrated biomimetic swallow nest structure is formed. The biomimetic swallow nest structure composites (BSNSC) imitated the formation process of a natural swallow nest. It is a lightweight material with a thick wall, low connectivity rate, and regular shape. Its density is 0.42 g/cm3, which is still in the density class of ultralight inorganic foam materials, and its compressive strength reaches 6.5 MPa, three times that of ordinary composites. The structure has a strength-to-weight ratio 3.5 times that of ordinary composites and a thermal conductivity much lower than of other thermal insulation materials. In the future, this type of lightweight composites with high strength, high heat insulation, and low density not only functions as a good energy-saving material for buildings but also a good thermal insulation material in the aerospace field.