High Ammonia Yield Rate from Dilute Nitrate Solutions Using a Cu(100)-Rich Foil: A Step Closer to Large-Scale Production.

The electrochemical reduction of nitrate (NO3-) ions to ammonia (NH3) provides an alternative method to eliminate harmful NO3- pollutants in water as well as to produce highly valuable NH3 chemicals. The NH3 yield rate however is still limited to the µmol h-1 cm-2 range when dealing with dilute NO3- concentrations found in waste streams. Copper (Cu) has attracted much attention because of its unique ability to effectively convert NO3- to NH3. We have reported a simple and scalable electrochemical method to produce a Cu foil having its surface covered with a porous Cu nanostructure enriched with (100) facets, which efficiently catalyzes NO3- to NH3. The Cu(100)-rich electrocatalyst showed a very high NH3 production rate of 1.1 mmol h-1 cm-2 in NO3- concentration as low as 14 mM NO3-, which is 4-5 times higher than the best-reported values. Increasing the NO3- concentration (140 mM) resulted in an NH3 production yield rate of 3.34 mmol h-1 cm-2. The durability test conducted for this catalyst foil in a flow cell system showed greater than 100 h stability with a Faradaic efficiency greater than 98%, demonstrating its potential to be used on an industrially relevant scale. Further, density functional theory (DFT) calculations have been performed to understand the better catalytic activity of Cu(100) compared to Cu(111) facets toward NO3-RR.

Dysregulated expression of cholesterol biosynthetic genes in Alzheimer's disease alters epigenomic signatures of hippocampal neurons.

Aging is the main risk factor of cognitive neurodegenerative diseases such as Alzheimer's disease, with epigenome alterations as a contributing factor. Here, we compared transcriptomic/epigenomic changes in the hippocampus, modified by aging and by tauopathy, an AD-related feature. We show that the cholesterol biosynthesis pathway is severely impaired in hippocampal neurons of tauopathic but not of aged mice pointing to vulnerability of these neurons in the disease. At the epigenomic level, histone hyperacetylation was observed at neuronal enhancers associated with glutamatergic regulations only in the tauopathy. Lastly, a treatment of tau mice with the CSP-TTK21 epi-drug that restored expression of key cholesterol biosynthesis genes counteracted hyperacetylation at neuronal enhancers and restored object memory. As acetyl-CoA is the primary substrate of both pathways, these data suggest that the rate of the cholesterol biosynthesis in hippocampal neurons may trigger epigenetic-driven changes, that may compromise the functions of hippocampal neurons in pathological conditions.

Highly Efficient Electrochemical Hydrogen Evolution with Ultra-Low Loading of Strongly Adhered Pt Nanoparticles on Carbon.

The development of robust electrocatalysts with low platinum content for acidic hydrogen evolution reaction (HER) is paramount for large scale commercialization of proton exchange membrane electrolyzers. Herein, a simple strategy is reported to synthesize a well anchored, low Pt containing Vulcan carbon catalyst using ZnO as a sacrificial template. Pt containing ZnO (PZ) is prepared by a simultaneous borohydride reduction. PZ is then loaded onto Vulcan carbon to produce a very low Pt content electrocatalyst, PZ@VC. PZ@VC with 2 wt.% Pt shows excellent performance for acidic HER in comparison to the commercial Pt/C (20 wt.%) catalyst. PZ@VC with a very low Pt loading shows significantly low η10 and η100 values (15 and 46 mV, respectively). PZ@VC on coating with Nafion (PZ@VC-N) shows further improvement in its performance (η10 of 7 mV, η100 of 28 mV) with ≈300 h of stability (≈10 mA cm-2 ) with only 4 µgPt cm-2 . PZ@VC-N shows a record high mass activity of 71 A mgPt -1 (32 times larger than Pt/C (20 wt.%) at 50 mV of overpotential. Post reaction characterizations reveal Pt nanoparticles are embedded onto VC with no traces of zinc, suggestive of a strong metal-support interaction leading to this high stability at low Pt loading.

CBP/p300 activation promotes axon growth, sprouting, and synaptic plasticity in chronic experimental spinal cord injury with severe disability.

The interruption of spinal circuitry following spinal cord injury (SCI) disrupts neural activity and is followed by a failure to mount an effective regenerative response resulting in permanent neurological disability. Functional recovery requires the enhancement of axonal and synaptic plasticity of spared as well as injured fibres, which need to sprout and/or regenerate to form new connections. Here, we have investigated whether the epigenetic stimulation of the regenerative gene expression program can overcome the current inability to promote neurological recovery in chronic SCI with severe disability. We delivered the CBP/p300 activator CSP-TTK21 or vehicle CSP weekly between week 12 and 22 following a transection model of SCI in mice housed in an enriched environment. Data analysis showed that CSP-TTK21 enhanced classical regenerative signalling in dorsal root ganglia sensory but not cortical motor neurons, stimulated motor and sensory axon growth, sprouting, and synaptic plasticity, but failed to promote neurological sensorimotor recovery. This work provides direct evidence that clinically suitable pharmacological CBP/p300 activation can promote the expression of regeneration-associated genes and axonal growth in a chronic SCI with severe neurological disability.

Glucose derived carbon nanosphere (CSP) conjugated TTK21, an activator of the histone acetyltransferases CBP/p300, ameliorates amyloid-beta 1-42 induced deficits in plasticity and associativity in hippocampal CA1 pyramidal neurons.

The master epigenetic regulator lysine acetyltransferase (KAT) p300/CBP plays a pivotal role in neuroplasticity and cognitive functions. Recent evidence has shown that in several neurodegenerative diseases, including Alzheimer's disease (AD), the expression level and function of p300/CBP are severely compromised, leading to altered gene expression causing pathological conditions. Here, we show that p300/CBP activation by a small-molecule TTK21, conjugated to carbon nanosphere (CSP) ameliorates Aß-impaired long-term potentiation (LTP) induced by high-frequency stimulation, theta burst stimulation, and synaptic tagging/capture (STC). This functional rescue was correlated with CSP-TTK21-induced changes in transcription and translation. Mechanistically, we observed that the expression of a large number of synaptic plasticity- and memory-related genes was rescued, presumably by the restoration of p300/CBP mediated acetylation. Collectively, these results suggest that small-molecule activators of p300/CBP could be a potential therapeutic molecule for neurodegenerative diseases like AD.

Electrochemical Nitrogen Reduction to Ammonia Under Ambient Conditions: Stakes and Challenges.

Aqueous electrochemical nitrogen reduction (ENR) to ammonia (NH3 ) under ambient conditions is considered as an alternative to the energy-intensive Haber-Bosch process for ammonia production. Many metal, non-metal, carbon-based materials along with metal-chalcogenides, metal-nitrides have been explored for their ENR activity. The reported NH3 production through ENR is still in the micro-gram level and often falls in the range of NH3 and NOx contaminations from the surrounding. The quantification of NH3 at very low concentration possess enormous challenge in this field and thus many reported ENR electrocatalysts suffer from reproducibility issue. This review highlights in detail the challenges associated with ENR in aqueous medium and necessitates standardization of protocols to quantify the low concentration of NH3 free of false-positives. It concludes the prospects of electrochemical NH3 production through lithium-mediated N2 reduction.

Improvement in Oxygen Evolution Performance of NiFe Layered Double Hydroxide Grown in the Presence of 1T-Rich MoS2.

NiFe layered double hydroxide (NiFe LDH) grown in the presence of MoS2 (rich in 1T phase) shows exceptional performance metrics for alkaline oxygen evolution reaction (OER) in this class of composites. The as-prepared NiFe LDH/MoS2 composite (abbreviated as MNF) exhibits a low overpotential (η10) of 190 mV; a low Tafel slope of 31 mV dec-1; and more importantly, a high stability in its performance manifested by the delivery of current output for 45 h. It is important to note that this could be achieved with an exceedingly low loading of 0.14 mg cm-2. The mass activity of this composite (97 A g-1) is about 14 times greater than that of the conventional RuO2 (7 A g-1) at η = 200 mV. When normalized with respect to the total metal content, a mass activity of 1000 A g-1 (η = 300 mV) was achieved. Impedance analysis further reveals that the significant reduction in charge-transfer resistance and hence high current density (5 times greater as compared to NiFe LDH at η = 300 mV) observed for MNF is associated with interfacial adsorption kinetics of intermediates (R1). Significant enhancement in the intrinsic activity of MNF over LDH has been observed through normalization of current with the electrochemically active surface area. Computational studies suggest that the Ni centers in the composite act as the active sites for OER, which is well-corroborated with the observed postreaction appearance of Ni3+ species.

Facts or Artifacts: Pitfalls in Quantifying Sub-ppm Levels of Ammonia Produced from Electrochemical Nitrogen Reduction.

Synthesis of ammonia through electrochemical nitrogen reduction (ENR) is emerging as one of the attractive research areas in recent years, notwithstanding the enormous challenges it faces in quantification of ammonia at very low concentrations. Several reports claiming high production rate are unwittingly compromised by the accuracy of analyzing a very low concentration (<1 ppm) of ammonia in the electrolyte post-ENR reaction using the indophenol method. Therefore, in this work, we have highlighted the significance of selecting and standardizing a right protocol encompassing admissible levels of oxidants and a complexing agent, citrate (to mitigate the effect of interfering metal ions), through elaborate control experiments. In addition, the importance of setting the lowest limit of ammonia concentration that can be accurately quantified by the indophenol method is also justified. Further, the experimental observations were summarized into a protocol, which was followed to re-evaluate the performance of two well-claimed electrocatalysts for ENR reported recently in the literature.

Light-Harvesting Supramolecular Phosphors: Highly Efficient Room Temperature Phosphorescence in Solution and Hydrogels.

Solution phase room-temperature phosphorescence (RTP) from organic phosphors is seldom realized. Herein we report one of the highest quantum yield solution state RTP (ca. 41.8 %) in water, from a structurally simple phthalimide phosphor, by employing an organic-inorganic supramolecular scaffolding strategy. We further use these supramolecular hybrid phosphors as a light-harvesting scaffold to achieve delayed fluorescence from orthogonally anchored Sulforhodamine acceptor dyes via an efficient triplet to singlet Förster resonance energy transfer (TS-FRET), which is rarely achieved in solution. Electrostatic cross-linking of the inorganic scaffold at higher concentrations further facilitates the formation of self-standing hydrogels with efficient RTP and energy-transfer mediated long-lived fluorescence.

Sodium Cobalt Metaphosphate as an Efficient Oxygen Evolution Reaction Catalyst in Alkaline Solution.

Sodium cobalt metaphosphate [NaCo(PO3 )3 ] has CoO octahedra (CoO6 ) and shows superior oxygen evolution reaction (OER) activity in alkaline solution, comparable with the state-of-the-art precious-metal RuO2 catalyst. OER catalysts of this metaphosphate are prepared by combustion (Cb) and solid-state (SS) methods. The combustion-assisted method offers a facile synthesis and one-step carbon composite formation. Unusually high catalytic activity was observed in NCoM-Cb-Ar and could be due to chemical coupling effects between NaCo(PO3 )3 and partially graphitized carbon. This novel electrocatalyst exhibits very small overpotential of 340 mV with high mass activity of 532 A g-1 . Good charge transfer abilities and chemical coupling between NaCo(PO3 )3 and amorphous carbon gives the OER activity in NCoM-Cb-Ar.

Dual targeting of folate receptor-expressing glioma tumor-associated macrophages and epithelial cells in the brain using a carbon nanosphere-cationic folate nanoconjugate.

Glioblastoma multiforme (GBM), the highly invasive form of glioma, exhibits the highest mortality in patients with brain malignancies. Increasing glioma patients' survivability is challenging, as targeting only tumor-associated malignant cells would not reduce the overall aggressiveness of the tumor mass. This is due to the inadequacy in countering pro-proliferative, invasive and metastatic factors released by tumor-mass associated macrophages (TAMs). Hence, strategically, dual targeting both tumor cells and TAMs is necessary for effective glioma treatment and increased survivability. Conventional FR-targeting systems can easily target cancer cells that overtly express folate receptors (FRs). However, FRs are expressed only moderately in both glioma cells and in TAMs. Hence, it is more challenging to coordinate dual targeting of glioma cells and TAMs with lower levels of FR expression. A recently developed carbon nanosphere (CSP) with effective blood-brain barrier (BBB) penetrability was modified with a new folic acid-cationic lipid conjugate (F8) as a targeting ligand. The uniqueness of the cationic lipid-folate conjugate is that it stably associates with the negatively charged CSP surface at about >22 mol% surface concentration, a concentration at least 5-fold higher than what is achieved for conventional FR-targeting delivery systems. This enabled dual uptake of the CSP on TAMs and tumor cells via FRs. A doxorubicin-associated FR-targeting formulation (CFD), in an orthotopic glioma model and in a glioma subcutaneous model, induced the maximum anticancer effect with enhanced average mice survivability twice that of untreated mice and without any systemic liver toxicity. Additionally, we observed a significant decrease of TAM-released pro-aggressive factors, TGF-ß, STAT3, invasion and migration related sICAM-1, and other cytokines indicating anti-TAM activity of the CFD. Taken together, we principally devised, to the best of our knowledge, the first FR-targeting nano-delivery system for targeting brain-associated TAMs and tumor cells as an efficient glioma therapeutic.

Bio-inspired temporal regulation of ion-transport in nanochannels.

Temporal regulation of mass transport across the membrane is a vital feature of biological systems. Such regulatory mechanisms rely on complex biochemical reaction networks, often operating far from equilibrium. Herein, we demonstrate biochemical reaction mediated temporal regulation of mass transport in nanochannels of mesoporous silica sphere. The rationally designed nanochannels with pH responsive electrostatic gating are fabricated through a hetero-functionalization approach utilizing propylamine and carboxylic acid moieties. At basic pH, cationic small molecules can diffuse into the nanochannels which release back to the solution at acidic pH. The transient ion transport is temporally controlled using a base as fuel along with esterase enzyme as the mediator. The slow enzymatic hydrolysis of a dormant deactivator (ethyl acetate) determines the lifetime of transient encapsulated state, which can be programmed easily by modulating the enzymatic activity of esterase. This system represents a unique approach to create autonomous artificial cellular models.

Aqueous Phase Phosphorescence: Ambient Triplet Harvesting of Purely Organic Phosphors via Supramolecular Scaffolding.

Ambient solution and amorphous state room temperature phosphorescence (RTP) from purely organic chromophores is rarely achieved. Remarkable stabilization of triplet excitons is realized to obtain deep red phosphorescence in water and in amorphous film state under ambient conditions by a unique supramolecular hybrid assembly between inorganic laponite clay and heavy atom core substituted naphthalene diimide (NDI) phosphor. Structural rigidity and oxygen tolerance of the inorganic template along with controlled molecular organization via supramolecular scaffolding are envisaged to alleviate the unprecedented aqueous phase phosphorescence.

Reinstating plasticity and memory in a tauopathy mouse model with an acetyltransferase activator.

Chromatin acetylation, a critical regulator of synaptic plasticity and memory processes, is thought to be altered in neurodegenerative diseases. Here, we demonstrate that spatial memory and plasticity (LTD, dendritic spine formation) deficits can be restored in a mouse model of tauopathy following treatment with CSP-TTK21, a small-molecule activator of CBP/p300 histone acetyltransferases (HAT). At the transcriptional level, CSP-TTK21 re-established half of the hippocampal transcriptome in learning mice, likely through increased expression of neuronal activity genes and memory enhancers. At the epigenomic level, the hippocampus of tauopathic mice showed a significant decrease in H2B but not H3K27 acetylation levels, both marks co-localizing at TSS and CBP enhancers. Importantly, CSP-TTK21 treatment increased H2B acetylation levels at decreased peaks, CBP enhancers, and TSS, including genes associated with plasticity and neuronal functions, overall providing a 95% rescue of the H2B acetylome in tauopathic mice. This study is the first to provide in vivo proof-of-concept evidence that CBP/p300 HAT activation efficiently reverses epigenetic, transcriptional, synaptic plasticity, and behavioral deficits associated with Alzheimer's disease lesions in mice.

Oxidative Dehydrogenation of Propane over a High Surface Area Boron Nitride Catalyst: Exceptional Selectivity for Olefins at High Conversion.

Developing environment-friendly active and selective catalysts for oxidative dehydrogenation of propane for on-purpose propene synthesis is challenging despite tremendous industrial potential for this reaction. Herein, we report on catalytic activity of high surface area hexagonal boron nitride, toward oxidative dehydrogenation of propane. It shows remarkable selectivity for alkenes (∼70%) at very high conversion (of ∼50%) of propane. Propene and ethene selectivities as high as 53 and 18%, respectively, were obtained at a conversion of 52%. The catalytic activity is retained continuously for 5 h. Regeneration in ammonia brings back the catalytic activity to its full potential. Oxidation of surface B-N bonds in oxygen leads to the diminishing catalytic activity after 5 h which, on heating in ammonia, reduced back to their native form, regaining the indigenous activity. Remarkably, the addition of ammonia in the reaction feed showed stable activity for more than 100 h.

In Situ Growth of Self-Assembled ZIF-8-Aminoclay Nanocomposites with Enhanced Surface Area and CO2 Uptake.

Self-assembly of metal-organic framework (MOF) nanoparticles (NPs) with a functional material can result in MOF nanocomposites having new and advanced properties along with the fabrication of new nanoscopic structures. However, such assembly of MOFs has not been realized to date. Here we report self-assembled nanocomposites of the zeolitic imidazolate framework (ZIF-8) and layered aminoclay (AC) for the first time, and the ZIF-8@AC composites exhibit significantly enhanced adsorption properties in comparison to those of pristine ZIF-8 nanoparticles. Four different composites denoted as ZIF-8@AC-1, ZIF-8@AC-2, ZIF-8@AC-3, and ZIF-8@AC-4 were synthesized by varying the clay content, and their AC contents were found to be 12.1, 18.3, 22.2, and 27.2 wt %, respectively. The composites were thoroughly characterized by PXRD, FTIR, Raman, and various microscopic techniques (FESEM, TEM, and STEM). The formation of the composites is driven by the specific interaction between unsaturated Zn(II) sites of ZIF-8 nanoparticles and NH2 groups of the aminoclay, which was validated from ζ potential and Raman spectroscopic measurements. The adsorption studies of the desolvated composites were also carried out in detail. The best performance is achieved with one of the composites, which exhibits a 42% increase in BET surface area while CO2 uptake at 298 K is doubled in comparison to the ZIF-8 nanoparticles.

Simple and Facile Approach To Create Charge Reversible Pores via Hydrophobic Anchoring of Ionic Amphiphiles.

Mesoporous silica-based charge reversal systems have gained significant attention in recent years due to a variety of applications such as drug delivery, dye adsorption, catalysis, chromatography, etc. Such systems often use covalent strategies to immobilize functional groups on the silica scaffold. However, lack of dynamism, modularity, and postsynthetic flexibility associated with covalent routes limit their wider applicability. Alternatively, supramolecular routes are gaining increased attention owing to their ability to overcome these limitations. Here, we introduce a simple and facile noncovalent design for a highly reversible assembly of charged amphiphiles within mesopores. Hexyl pendant groups were covalently attached to the surface to provide hydrophobic anchoring for charged amphiphiles to enable facile switching of surface charge of the mesoporous silica. These charge-switchable surfaces were used for fast and selective adsorption of dyes from aqueous solutions.

MOF-aminoclay composites for superior CO2 capture, separation and enhanced catalytic activity in chemical fixation of CO2.

We delineate the growth and stabilization of ultra-small (2-3 nm) {Cu3(BTC)2(H2O)2·xH2O} MOF nanoparticles on a 2D layered aminoclay template. The composite shows significant CO2 uptake (5.35 mmol g-1 at 298 K, 1 bar; 46% higher than pristine bulk MOF), superior CO2 separation efficiency from CO2/N2 and CO2/CH4 mixtures and higher catalytic proficiency for chemical fixation of CO2 into cyclic carbonates.

No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance.

An innovative technique to obtain high-surface-area mesostructured carbon (2545 m(2) g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10 min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2 wt % at 0 °C under 0.88 bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0 wt %). JNC-1 demonstrated higher H2 adsorption capacity (2.8 wt %) compared to CMK-3 (1.2 wt %) at -196 °C under 1.0 bar H2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292 F g(-1) and 182 F g(-1) at a drain rate of 1 A g(-1) and 50 A g(-1) , respectively, in 1 m H2 SO4 compared to CMK-3 and activated carbon.

Shape-directed compartmentalized delivery of a nanoparticle-conjugated small-molecule activator of an epigenetic enzyme in the brain.

Targeted drug delivery to specific subcellular compartments of brain cells is challenging despite their importance in the treatment of several brain-related diseases. Herein, we report on shape-directed intracellular compartmentalization of nanoparticles in brain cells and their ability to deliver therapeutic molecules to specific organelles. Iron oxide (Fe3O4) nanoparticles with different morphologies (spheres, spindles, biconcaves, and nanotubes) were synthesized and coated with a fluorescent carbon layer derived from glucose (Fe3O4@C). In vivo studies showed that the Fe3O4@C nanoparticles with biconcave geometry localized predominantly in the nuclei of the brain cells, whereas those with nanotube geometry were contained mostly in the cytoplasm. Remarkably, a small-molecule activator of histone acetyltransferases delivered into the nuclei of the brain cells using nanoparticles with biconcave geometry showed enhancement in enzymatic activity by a factor of three and resulted in specific gene expression (transcription) compared with that of the molecule delivered to the cytoplasm using nanotube geometry.