Nanoscale Morphology Research Articles

Probing Molecular Chirality on the Self-Assembly and Gelation of Naphthalimide-Conjugated Dipeptides.

In this work, 1,8-naphthalimide (NMI)-conjugated three hybrid dipeptides constituted of a β-amino acid and an α-amino acid have been designed, synthesized, and purified. Here, in the design, the chirality of the α-amino acid was varied to study the effect of molecular chirality on the supramolecular assembly. Self-assembly and gelation of three NMI conjugates were studied in mixed solvent systems [water and dimethyl sulphoxide (DMSO)]. Interestingly, chiral NMI derivatives [NMI-βAla-lVal-OMe (NLV) and NMI-βAla-dVal-OMe (NDV)] formed self-supported gels, while the achiral NMI derivative [NMI-βAla-Aib-OMe, (NAA)] failed to form any kind of gel at 1 mM concentration and in a mixed solvent (70% water in DMSO medium). Self-assembly processes were thoroughly investigated using UV-vis spectroscopy, nuclear magnetic resonance (NMR), fluorescence, and circular dichroism (CD) spectroscopy. A J-type molecular assembly was observed in the mixed solvent system. The CD study indicated the formation of chiral assembled structures for NLV and NDV, which were mirror images of one another, and the self-assembled state by NAA was CD-silent. The nanoscale morphology of the three derivatives was studied using scanning electron microscopy (SEM). In the case of NLV and NDV, left- and right-handed fibrilar morphologies were observed, respectively. In contrast, a flake-like morphology was noticed for NAA. The DFT study indicated that the chirality of the α-amino acid influenced the orientation of π-π stacking interactions of naphthalimide units in the self-assembled structure that in turn regulated the helicity. This is a unique work where molecular chirality controls the nanoscale assembly as well as the macroscopic self-assembled state.

Anticancer potentiality of green synthesized Mg-Co ferrites nanoparticles against human breast cancer MCF-7 cells

Inherent magnetic features of engineered nanomaterials are quite important parameters for biomedical applications and cancer treatments. In this study, cobalt ferrite (CF-NPs) and magnesium-cobalt ferrite (MCF-NPs) magnetic nanoparticles were synthesized by aqueous extract of turmeric, characterized by various instruments, and utilized for anticancer activity. These are characterized with TG-DTG, XRD, SEM, BET, FTIR, and UV–Vis sophisticated techniques. The results revealed that they have inverse cubic spinel structure, optically active and nanoscale spherical morphology. The particle size was calculated by the Scherrer formula and was found to be 24.78 nm for CF-NPs and 27.48 nm for MCF-NPs, respectively. Moreover, MTT method was used to find out anticancer activity of the fabricated CF-NPs and MCF-NPs using the human breast cancer cells (MCF-7) and data discloses that cytotoxicity effects of CF-NPs are higher than MCF-NPs, and dose dependent. At high dose (100 μg/ml), CF-NPs shows 45.76% and 61.57% in CF-NPs and MCF-NPs cell viability, respectively. Similarly, cellular ROS generation was found to be higher in CF-NPs (183 %) as compared to MCF-NPs (159% in at 100 μg/ml). By the obtained results it can be claimed that ferrites will be useful model for cancer treatments if they are explored at advance level.

Facile synthesis of N-doped TiO2 nanosheets with enhanced photocatalytic activity

Titanium dioxide is a widely used photocatalyst for photodegradation of water pollutants. There has been a growing interest to improve the photocatalytic performance by using nanoscale forms of titania due to increased specific surface area of catalyst. Among the various nanoscale morphologies, nanosheets hold a remarkable distinction due to their higher specific surface area and lower crystalline defects in comparison the spherical particles. The performance of a photocatalyst can be further enhanced by using certain dopants and modifiers. In the present work, titanium dioxide nanosheets were doped with nitrogen using two nitrogen sources (Urea and Ammonia). X-ray diffraction and Field emission scanning electron microscopy were used to characterise the synthesized nanosheets. Dye degradation experiments were conducted to analyse the enhancement of photocatalytic activity.

Highly Ordered Supramolecular Materials of Phase-Separated Block Molecules for Long-Range Exciton Transport.

Efficient energy transport over long distances is essential for optoelectronic and light-harvesting devices. Although self-assembled nanofibers of organic molecules have been shown to exhibit long exciton diffusion lengths, alignment of these nanofibers into films with large, organized domains with similar properties remains a challenge. Here, we show how the functionalization of C3 -symmetric carbonyl-bridged triarylamine trisamide (CBT) oligodimethylsiloxane (oDMS) sidechains with discrete length leads to fully covered surfaces with aligned domains up to 125 × 70 μm2 in which long-range exciton transport takes place. The nanoscale morphology within the domains consists of highly ordered nanofibers with discrete intercolumnar spacings within a soft amorphous oDMS matrix. The oDMS prevents bundling of the CBT fibers, reducing the number of defects within the CBT columns. As a result, the columns have a high degree of coherence, leading to exciton diffusion lengths of a few hundred nanometers with exciton diffusivities (∼0.05 cm2 s-1 ) that are comparable to those of a crystalline tetracene. These findings represent the next step towards fully covered surfaces of highly aligned nanofibers through functionalization with oDMS. This article is protected by copyright. All rights reserved.

Enhanced cutting performance of electrosurgical units by oil-infused laser-textured surfaces

To enhance the cutting performance of electrosurgical units, urgent demands have been put forward for their work terminal, including an antiadhesion property and less thermal damage. Herein, an oil-infused surface (OIS) was fabricated by nanosecond laser texturing and spin-coating of medical olive oil and then applied to a work terminal (a scalpel). The effects of four laser scanning paths on the morphology of microdimples used for oil storage were investigated. Then, an array of 0° microdimples with vertical wall and symmetry features was selected to create OISs. The fabricated microdimples contained a nanoscale sponge-like morphology, which improved the oil storage capacity. From the point of view of experimental and theoretical analysis, we verified the autonomous sliding behaviour of plasma droplets on the inclined OIS, and the analysis of the viscosities of the oil film and a plasma droplet showed that the sliding velocity of the droplet decreased with increasing microdimple spacing. Cutting experiments proved that the OIS scalpel has excellent antiadhesion properties for multiple biological tissues. In particular, the OIS scalpel can reduce the cutting force by 19.0% and the tissue thermal damage by 30.8% when cutting pork tenderloin compared to the pristine scalpel. During the cutting process, the introduction of an oil film shifts the interfacial separation from within the tissue to the oil film itself, and the film acts as a thermal barrier to reduce tissue damage, thus greatly improving the cutting performance. The present study highlights the practical application of the OIS as an effective tool in the field of electrosurgical units.

Nanoscale morphology tailoring in plasma deposited CN x layers

Magnetron discharge plasma was applied for the synthesis of CN x thin layers using methane and nitrogen gas precursors. The incorporation of nitrogen in the carbon network resulted in the dramatic evolution of growth morphology: from a ‘buried’ porous layer observed at low nitrogen incorporation to aligned bundles of nanorods grown perpendicular to the substrate surface at maximum discharge power and nitrogen flow. The films deposited at the low discharge power and high nitrogen incorporation exhibited a mesoporous sponge-like morphology after vacuum annealing. Relevant physical mechanisms responsible for the formation of nano- and mesoshaped morphology are discussed in terms of the effects of internal mechanical stresses and plasma etching. In addition, the sensing properties of the sponge-like layer were preliminarily examined in water vapor and ammonia ambients. The CN x films showed enhanced sensitivity to ammonia and reverse electrical response to moisture in comparison with a nitrogen-free nanoporous carbon film, which were assigned to modification of the electronic properties of the nitridated surface.

Molecular mobility of liquid crystalline polyurethanes modified by polyhedral oligomeric silsesquioxanes

Molecular mobility and liquid crystalline order formation of liquid crystalline polyurethanes (LCPU) modified by trisilanolphenyl-POSS was investigated by using dielectric spectroscopy (DRS), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Hybrid materials with 2, 4 and 6 wt% of POSS load were studied. Small-angle X-ray scattering (SAXS) results suggested that the nanoscale morphology was not significantly altered by the introduction of POSS into the LCPU matrix. The presence of liquid crystal phase transitions was confirmed by both DRS and DSC measurements. Dielectric study showed changes in relaxation steps and conductivity in the LC transitions region due to a shift in phase order. Using partially cross-linked POSS particles, an enhancement of the material's rubber modulus was observed in the DMA measurement. Deterioration in charge transfer was observed for the composites, which was attributed to the crosslinking nature of the silsesquioxane used. Further, dynamic calorimetric studies in different cooling rates were performed for detailed study of liquid crystalline transitions. In summary, it was found that the addition of POSS causes a nucleation effect and does not impair LC phase formation.

Crystallinity and phase separation induced morphological modulation for efficient ternary all-polymer solar cells

All-polymer solar cells (all-PSCs) have attracted enormous attention and achieved significant progress in recent years due to their long-term stability and excellent film stretchability. However, the problem of morphology control in bulk-heterojunction (BHJ) films due to highly entangled polymeric chains hinders the further improvement of device performance. In this work, we obtained fine-tuned photoactive layer morphology through reconstructed microstructure induced by steric effects to realize an improved device performance in ternary all-PSCs. The large tetrahexylphenyl substituents on the backbone of naphthalene diimide–indacenodithienothiophene based copolymer acceptor BL-102 bring forth the steric-hindrance effect and influence intermolecular interactions. Therefore, the copolymer BL-102 delivers the property of suppressed self-aggregation, causing reconstructed crystalline features and morphology in blending films. The ternary devices tended to reduce the excessive phase separation by suppressing the aggregation of original polymers but to promote intermixing behaviors. Therefore, the optimal BHJ film manifested a well-formed bi-continuous interpenetrating nanoscale network with a larger π–π stacking coherence length and ordered face-on molecular orientation. Hence, a faster electron transfer (ET) and hole transfer (HT) process combined with balanced charge carrier mobilities can be achieved to enhance the overall device performance. This work provides an effective method to regulate the photoactive layer morphology of all-PSCs through structurally steric hindrance effects and demonstrate the significance of ternary-blending strategy induced nanoscale morphology modulation for fabricating highly efficient all-PSCs.

Shaping Copper Oxide Layers on Gold Nanoparticle Ensembles by Controlled Electrodeposition with Single Particle Scatterometry.

Electrodeposition of copper on gold nanoelectrode ensembles result in the formation of uniform copper oxide layers on individual nanoparticles. A linear sweep of voltammetric change induces three distinct morphologies dependent upon particle density. Ex situ imaging and in situ scatterometry at a single-particle level identifies multi-step electrochemical growth sequences that deviated from classical nucleation and growth pathways. In addition, the study demonstrated the possibility of synthesizing sophisticated structures based on the symmetry of nanoelectrodes. This result guides the nanoscale morphology control of electrode ensembles with potential application in electrocatalysis and sensing.

Structural Anisotropy Governs the Kink Formation in Cellulose Nanocrystals

Understanding the defect structure is fundamental to correlating the structure and properties of materials. However, little is known about the defects of soft matter at the nanoscale beyond their external morphology. We report here on the molecular-level structural details of kink defects of cellulose nanocrystals (CNCs) based on a combination of experimental and theoretical methods. Low-dose scanning nanobeam electron diffraction analysis allowed for correlation of the local crystallographic information and nanoscale morphology and revealed that the structural anisotropy governed the kink formation of CNCs. We identified two bending modes along different crystallographic directions with distinct disordered structures at kink points. The drying strongly affected the external morphology of the kinks, resulting in underestimating the kink population in the standard dry observation conditions. These detailed defect analyses improve our understanding of the structural heterogeneity of nanocelluloses and contribute to the future exploitation of soft matter defects.

Controlling the Structure and Morphology of Organic Nanofilaments Using External Stimuli.

In our continuing pursuit to generate, understand, and control the morphology of organic nanofilaments formed by molecules with a bent molecular shape, we here report on two bent-core molecules specifically designed to permit a phase or morphology change upon exposure to an applied electric field or irradiation with UV light. To trigger a response to an applied electric field, conformationally rigid chiral (S,S)-2,3-difluorooctyloxy side chains were introduced, and to cause a response to UV light, an azobenzene core was incorporated into one of the arms of the rigid bent core. The phase behavior as well as structure and morphology of the formed phases and nanofilaments were analyzed using differential scanning calorimetry, cross-polarized optical microscopy, circular dichroism spectropolarimetry, scanning and transmission electron microscopy, UV-vis spectrophotometry, as well as X-ray diffraction experiments. Both bent-core molecules were characterized by the coexistence of two nanoscale morphologies, specifically helical nanofilaments (HNFs) and layered nanocylinders, prior to exposure to an external stimulus and independent of the cooling rate from the isotropic liquid. The application of an electric field triggers the disappearance of crystalline nanofilaments and instead leads to the formation of a tilted smectic liquid crystal phase for the material featuring chiral difluorinated side chains, whereas irradiation with UV light results in the disappearance of the nanocylinders and the sole formation of HNFs for the azobenzene-containing material. Combined results of this experimental study reveal that in addition to controlling the rate of cooling, applied electric fields and UV irradiation can be used to expand the toolkit for structural and morphological control of suitably designed bent-core molecule-based structures at the nanoscale.

Synthesis of SnO2 nanoparticles coated ZnO–g–C3N4 composite nanostructures with novel antibacterial activity

Abstract In this work, composite nanostructures (CNs) of SnO2–ZnO–g–C3N4 have been prepared by a soft chemical method and investigated for their potential application in photocatalytic remediation of organics in water and antibacterial agents. Structural study revealed the presence of three phases related to hexagonal wurtzite phase of ZnO, tetragonal phase of SnO2 and monoclinic phase of g–C3N4 having nanocrystalline nature which confirms the formation of CNs. Formation of nanoscale morphology along with elemental composition of the CNs have been validated through scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) spectroscopy. The presence of only A 1g mode of SnO2 in Raman spectrum of ternary CNs suggested that SnO2 nanoparticles have been coated on the surfaces of ZnO and g–C3N4 which is also evident from SEM results. SnO2–ZnO–g–C3N4 CNs have shown much higher photocatalytic degradation efficiency and produced 7 mm greater zone of inhibition (ZOI) against Gram-positive S. Aureus bacteria as compared to pure ZnO which is quite significant result when compared to previously reported results for SnO2–ZnO CNs. These synthesized CNs may have potential uses in healthcare technology and treatment of organics in water.

Fotovoltaik Hücrelerin Yüzey Morfolojisi ve Verimliliği Üzerinde Termal Tavlama Etkisi

Photovoltaics convert solar radiation into electrical current. For the present study, blends containing electron donor and acceptor are used instead of materials made with silicon. Carbon-based organic semiconductors are easy to process and have low fabrication costs. There are several fabrication steps playing important role in the photovoltaic device performance such as, substrate preparation, polymer-acceptor ratios in the blend, thermal annealing of the active layer and top electrode deposition. It has been shown that nanoscale morphology of the blend can be altered via thermal annealing treatment. As a result, efficiency is affected by surface roughness. The blend of P3HT: PCBM as donor: acceptor was used to fabricate thin films and photovoltaic cells. The power conversion efficiencies and surface morphologies of the devices annealed at various times were measured. Atomic force microscopy (AFM) images revealed that the surface roughness of the active layer is mainly affected by the annealing time, and the film with the roughest surface results in the most efficient solar cell.

Insights into the Photoelectrocatalytic Behavior of gCN-Based Anode Materials Supported on Ni Foams.

Graphitic carbon nitride (gCN) is a promising n-type semiconductor widely investigated for photo-assisted water splitting, but less studied for the (photo)electrochemical degradation of aqueous organic pollutants. In these fields, attractive perspectives for advancements are offered by a proper engineering of the material properties, e.g., by depositing gCN onto conductive and porous scaffolds, tailoring its nanoscale morphology, and functionalizing it with suitable cocatalysts. The present study reports on a simple and easily controllable synthesis of gCN flakes on Ni foam substrates by electrophoretic deposition (EPD), and on their eventual decoration with Co-based cocatalysts [CoO, CoFe2O4, cobalt phosphate (CoPi)] via radio frequency (RF)-sputtering or electrodeposition. After examining the influence of processing conditions on the material characteristics, the developed systems are comparatively investigated as (photo)anodes for water splitting and photoelectrocatalysts for the degradation of a recalcitrant water pollutant [potassium hydrogen phthalate (KHP)]. The obtained results highlight that while gCN decoration with Co-based cocatalysts boosts water splitting performances, bare gCN as such is more efficient in KHP abatement, due to the occurrence of a different reaction mechanism. The related insights, provided by a multi-technique characterization, may provide valuable guidelines for the implementation of active nanomaterials in environmental remediation and sustainable solar-to-chemical energy conversion.

Fluid Flow Templating of Polymeric Soft Matter with Diverse Morphologies.

It is challengingto find a conventional nanofabrication technique that can consistently produce soft polymeric matter of high surface area and nanoscale morphology in a way that is scalable, versatile, and easily tunable. Here, the capabilities of a universal method for fabricating diverse nano- and micro-scale morphologies based on polymer precipitation templated by the fluid streamlines in multiphasic flow are explored. It is shown that while the procedure is operationally simple, various combinations of its intertwined mechanisms can controllably and reproducibly lead to the formation of an extraordinary wide range of colloidal morphologies. By systematically investigating the process conditions, 12distinct classes of polymer micro- and nano-structures including particles, rods, ribbons, nanosheets, and soft dendritic colloids (dendricolloids) are identified. The outcomes are interpreted by delineating the physical processes into three stages: hydrodynamic shear, capillary and mechanical breakup, and polymer precipitation rate. The insights into the underlying fundamental mechanisms provide guidance toward developing a versatile and scalable nanofabrication platform. It is verified that the liquid shear-based technique is versatile and works well with many chemically diverse polymers and biopolymers, showing potential as a universal tool for simple and scalable nanofabrication of many morphologically distinct soft matter classes.

Enhanced luminescence sensing performance and increased intrachain order in blended films of P3HT and cellulose nanocrystals

Blended films comprising poly(butyl acrylate) (PBA)-grafted cellulose nanocrystals (CNCs) and poly(3-hexylthiophene) (P3HT), exhibited more intense photoluminescence (PL) and longer PL emission lifetimes compared to pristine P3HT films. Optical absorption and photoluminescence spectra indicated reduced torsional disorder i.e. enhanced backbone planarity in the P3HT@CNC blended composites compared to the bare P3HT. Such molecule-level geometrical modification resulted in both smaller interchain and higher intrachain exciton bandwidth in the blended composites compared to the bare P3HT, because of reduced interchain interactions and enhanced intrachain order. These results indicate a potential switch of the aggregation behavior from dominant H-aggregates to J-aggregates, supported by Raman spectroscopy. The reorganization of micromolecular structure and concomitant macroscopic aggregation of the conjugated polymer chains resulted in a longer conjugation length for the P3HT@CNC blended composites compared to the bare P3HT. Additionally, this nanoscale morphological change produced a reduction in the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap of the blends, evidenced from optical absorption spectra. Classical molecular dynamics simulation studies predicted the probability of enhanced planarity in the polymer backbone following interactions with CNC surfaces. Theoretical results from density functional theory calculations corroborate the experimentally observed reduction of optical bandgap in the blends compared to bare P3HT. The blended composite outperformed the bare P3HT in nitro-group PL sensing tests with a pronounced difference in the reaction kinetics. While the PL quenching dynamics for bare P3HT followed Stern–Volmer kinetics, the P3HT@CNC blended composite exhibited a drastic deviation from the same. This work shows the potential of a functionalized rod-like biopolymer in tuning the optoelectronic properties of a technologically important polymeric organic semiconductor through control of the nanoscale morphology.

Surface modification of hybrid composite multilayers spin cold spraying for biomedical duplex stainless steel

The performance of biomaterials in biological systems is of critical significance for advancing biomedical implants. Duplex Stainless Steel alloys are the major biomaterials due to their significant characteristics. Many functional coatings are deposited on DSS alloy surfaces utilizing numerous surface coating techniques to improve their bioactivity and protect them from corrosion degradations. Coatings of titanium dioxide (TiO2), Hydroxyapatite (HA), and zinc oxide (ZnO) have received considerable attention in the field of surface bioactive modification of DSS alloy implants. The coating techniques play a key role in increasing the required biological characteristics of DSS alloys, such as biocompatibility, mechanical properties, and corrosion resistance. In this regard, HA-ZnO, HA-TiO2, and TiO2–ZnO from each coating group are divided into single, double, and triple layers. These coatings were prepared by cold spray and deposited on the surface of the DSS alloy, followed by a heat treatment at 250 °C. The surface morphology of coated surfaces was analyzed utilizing field emission scanning electron microscopy (FESEM), atomic force microscopic (AFM), microhardness test, corrosion test in Ringer solution, and antibacterial test. The coatings showed nano-scale surface morphology with advanced crystallization and homogeneous structures; in the corrosion characteristics utilizing potentiodynamic polarization, triple layers of HA-ZnO coatings displayed advanced nanostructures with higher hardness values (514.75HV). The antibacterial test showed the triple layers of HA-TiO2 and two layers of TiO2–ZnO sensitivity to positive bacteria.

Low temperature ductility of BA-VAc olefin polymer modified asphalt binders

Low temperature cracking is one of the main failures of asphalt pavements, specifically in cold areas. The ductility of asphalt binders at low temperature is one of the property indexes that are used to characterize cracking resistance of asphalt binders at low temperature. In order to improve the low temperature ductility of asphalt binders, butyl acrylate (BA) as soft monomer and vinyl acetate (VAc) as hard monomer were used for free radical polymerization, and the BA-VAc polymer was then used as a modifier to modify asphalt binders. The modification scheme was optimized by orthogonal test. The modified asphalt binders were mainly evaluated by ductility test and selected other properties. Atomic force microscopy (AFM) was used to investigate the nano-scaled morphology of modified asphalt binders. The results showed that 1) BA-VAc polymer could greatly improve the ductility of asphalt binders, highly depending on the type of base asphalts for their efficient. 2) The high temperature property of asphalt binder slightly decreased, but the compatibility and storage stability of the modified binders became poorly with the dose of BA-VAc polymer got larger and exceeded 6 %. 3) Ba-VAc polymer reduced the volume and number of “bee-like structures” in the 2D morphgraphic results, and also decreased the surface roughness and stiffness of modified binders. 4) The best performance of modified binders was observed for the modification scheme of a 6 % BA-VAc polymer and BA/VAc being a ratio of 6:4 which is produced at a shear temperature of 130 °C, a shear time of 5 min and a shear rate of 1000 r/min.

Structural Elucidation of a Polypeptoid Chain in a Crystalline Lattice Reveals Key Morphology-Directing Role of the N-Terminus.

The ability to engineer synthetic polymers with the same structural precision as biomacromolecules is crucial to enable the de novo design of robust nanomaterials with biomimetic function. Peptoids, poly(N-substituted) glycines, are a highly controllable bio-inspired polymer family that can assemble into a variety of functional, crystalline nanostructures over a wide range of sequences. Extensive investigation on the molecular packing in these lattices has been reported; however, many key atomic-level details of the molecular structure remain underexplored. Here, we use cryo-TEM 3D reconstruction to directly visualize the conformation of an individual polymer chain within a peptoid nanofiber lattice in real space at 3.6 Å resolution. The backbone in the N-decylglycine hydrophobic core is shown to clearly adopt an extended, all-cis-sigma strand conformation, as previously suggested in many peptoid lattice models. We also show that packing interactions (covalent and noncovalent) at the solvent-exposed N-termini have a dominant impact on the local chain ordering and hence the ability of the chains to pack into well-ordered lattices. Peptoids in pure water form fibers with limited growth in the a direction (<14 molecules in width), whereas in the presence of formamide, they grow to over microns in length in the a direction. This dependence points to the significant role of the chain terminus in determining the long-range order in the packing of peptoid lattices and provides an opportunity to modulate lattice stability and nanoscale morphology by the addition of exogenous small molecules. These findings help resolve a major challenge in the de novo structure-based design of sequence-defined biomimetic nanostructures based on crystalline domains and should accelerate the design of functional nanostructures.

Morphology Tuning via Linker Modulation: Metal-Free Covalent Organic Nanostructures with Exceptional Chemical Stability for Electrocatalytic Water Splitting.

The development of synthetic routes for the formation of robust porous organic polymers (POPs) with well-defined nanoscale morphology is fundamentally significant for their practical applications. The thermodynamic characteristics that arise from reversible covalent bonding impart intrinsic chemical instability in the polymers, thereby impeding their overall potential. Herein, a unique strategy is reported to overcome the stability issue by designing robust imidazole-linked POPs via tandem reversible/irreversible bond formation. Incorporating inherent rigidity into the secondary building units leads to robust microporous polymeric nanostructures with hollow-spherical morphologies. An in-depth analysis by extensive solid-state NMR (1D and 2D) study on 1H, 13C, and 14N nuclei elucidates the bonding and reveals the high purity of the newly designed imidazole-based POPs. The nitrogen-rich polymeric nanostructures are further used as metal-free electrocatalysts for water splitting. In particular, the rigid POPs show excellent catalytic activity toward the oxygen evolution reaction (OER) with long-term durability. Among them, the most efficient OER electrocatalyst (TAT-TFBE) requires 314mV of overpotential to drive 10 mAcm-2 current density, demonstrating its superiority over state-of-the-art catalysts (RuO2 and IrO2).