Folded network and structural transition in molten tin

The fundamental relationships between the structure and properties of liquids are far from being well understood. For instance, the structural origins of many liquid anomalies still remain unclear, but liquid-liquid transitions (LLT) are believed to hold a key. However, experimental demonstrations of LLTs have been rather challenging. Here, we report experimental and theoretical evidence of a second-order-like LLT in molten tin, one which favors a percolating covalent bond network at high temperatures. The observed structural transition originates from the fluctuating metallic/covalent behavior of atomic bonding, and consequently a new paradigm of liquid structure emerges. The liquid structure, described in the form of a folded network, bridges two well-established structural models for disordered systems, i.e., the random packing of hard-spheres and a continuous random network, offering a large structural midground for liquids and glasses. Our findings provide an unparalleled physical picture of the atomic arrangement for a plethora of liquids, shedding light on the thermodynamic and dynamic anomalies of liquids but also entailing far-reaching implications for studying liquid polyamorphism and dynamical transitions in liquids.

Novel Nanoparticles Based on N,O-Carboxymethyl Chitosan-Dopamine Amide Conjugate for Nose-to-Brain Delivery

A widely investigated approach to bypass the blood brain barrier is represented by the intranasal delivery of therapeutic agents exploiting the olfactory or trigeminal connections nose-brain. As for Parkinson’s disease (PD), characterized by dopaminergic midbrain neurons degeneration, currently there is no disease modifying therapy. Although several bio-nanomaterials have been evaluated for encapsulation of neurotransmitter dopamine (DA) or dopaminergic drugs in order to restore the DA content in parkinsonian patients, the premature leakage of the therapeutic agent limits this approach. To tackle this drawback, we undertook a study where the active was linked to the polymeric backbone by a covalent bond. Thus, novel nanoparticles (NPs) based on N,O-Carboxymethylchitosan-DA amide conjugate (N,O-CMCS-DA) were prepared by the nanoprecipitation method and characterized from a technological view point, cytotoxicity and uptake by Olfactory Ensheating Cells (OECs). Thermogravimetric analysis showed high chemical stability of N,O-CMCS-DA NPs and X-ray photoelectron spectroscopy evidenced the presence of amide linkages on the NPs surface. MTT test indicated their cytocompatibility with OECs, while cytofluorimetry and fluorescent microscopy revealed the internalization of labelled N,O-CMCS-DA NPs by OECs, that was increased by the presence of mucin. Altogether, these findings seem promising for further development of N,O-CMCS-DA NPs for nose-to-brain delivery application in PD.

Synthesis of Green Deep Eutectic Solvents for Pretreatment Wheat Straw: Enhance the Solubility of Typical Lignocellulose

Deep eutectic solvents (DESs), a novel and environmentally-friendly solvent, have high potential for biomass pretreatment due to its advantages of low cost, low toxicity, strong solubility, excellent selectivity and biocompatibility. Two types of DES (binary and ternary) were synthesized and characterized, and optimized ternary DES was selected to pretreat wheat straw for enhancement of the solubility of lignocellulose. Moreover, enzymatic hydrolysis was tested to verify the performance of pretreatment. In addition, the changes in surface morphology, structure and crystallinity of wheat straw pretreated by DES were analyzed to reveal the pretreatment mechanism. Experimental results indicated that viscosity exhibited little difference in different types of DESs, and a declining trend as the temperature increases in same DES. The ternary DES pretreatment efficiently enhanced the solubility of typical lignocellulose, with the optimal removal rate of lignin at approximately 69.46%. Furthermore, the total sugar concentration of the residue was about 5.1 times more than that of untreated wheat straw after the pretreated samples were hydrolyzed by the cellulase for 24 h, indicating that DES has the unique ability to selectively extract lignin and hemicellulose from wheat straw while retaining cellulose, and thus enhanced the solubility of lignocellulose. The scanning electron microscope (SEM) observation and X-ray diffraction (XRD) determination showed that the surface of wheat straw suffered from serious erosion and the crystallinity index of wheat straw increased after DES5 pretreatment. Therefore, DES cleaves the covalent bond between lignin and cellulose and hemicellulose, and reduces the intractability of lignin resulting in the lignin dissolution. It suggests that DES can be used as a promising and biocompatible pretreatment way for the cost-effective conversion of lignocellulose biomass into biofuels.

A metastable brominated nanodiamond surface enables room temperature and catalysis-free amine chemistry

Bromination of high-pressure high-temperature (HPHT) nanodiamond (ND) surfaces has not been explored and can open new avenues for increased chemical reactivity and diamond lattice covalent bond formation. The large bond dissociation energy of the diamond lattice-oxygen bond is a challenge that prevents new bonds from forming and most researchers simply use oxygen-terminated ND (alcohols and acids) as a reactive species. In this work, we transformed a tertiary alcohol-rich ND surface to an amine surface with 50% surface coverage and was limited by the initial rate of bromination. We observed that alkyl-bromide moieties are highly labile on NDs and are metastable as previously found using density functional theory. The instability of the bromine terminated ND is explained by steric hindrance and poor surface energy stabilization. The strong leaving group properties of the alkyl-bromide intermediate were found to form diamond-nitrogen bonds at room temperature and without catalysts. The chemical lability of the brominated ND surface led to efficient amination with NH3•THF at 298 K, and a catalyst-free Sonogashira-type reaction with an alkyne-amine produced an 11-fold increase in amination rate. Overlapping spectroscopies under inert, temperature-dependent and open-air conditions provided unambiguous chemical assignments. Amine-terminated NDs and folic acid were conjugated using sulfo-NHS/EDC coupling reagents to form amide bonds, confirming that standard amine chemistry remains viable. This work supports that a robust pathway exists to activate a chemically inert diamond surface at room temperature, which broadens the pathways of bond formation when a reactive alkyl-bromide surface is prepared. The unique surface properties of brominated and aminated nanodiamond reported here are impactful to researchers who wish to chemically tune diamond for quantum sensing applications or as an electron source for chemical transformations.

Comment on “In Defence of Oxidation States” by N. C. Norman and P. G. Pringle, Dalton Transactions, 2022, 51, DOI: 10.1039/D0DT03914D

A comment on “In defence of oxidation states” by N. C. Norman and P. G. Pringle: a historical perspective on the Covalent Bond Classification and the use of Valency Number in this context.

Reaction-based fluorescence probes for “turn on” sensing fluoride ions

Introducing a weak covalent bond into an originally highly fluorescent molecule to create a non-fluorescent probe is able to afford a new way to detect some neucleophilic targets with enhanced...

Promoting Charge Separation by Rational Integrate of Covalent Organic Framework on BiVO4 Photoanode

For the first time, the covalent organic frameworks (COF-TpPa and COF-TpPaC) are selected to combine with BiVO4 photoanode through a covalent bond. The heterojunction and covalent connection of COFs and...

Efektivitas LKPD Berbasis Blended Learning Berbantuan Multimedia Interaktif untuk Melatih Visual Spasial Peserta Didik

<p><strong>Abstrak </strong></p><p class="abstrak">Penelitian bertujuan untuk mengetahui keefektifan Lembar Kerja Peserta Didik (LKPD) berbasis <em>blended learning</em> berbantuan multimedia interaktif dalam melatih kemampuan visual spasial peserta didik pada materi Ikatan Kovalen. Metode penelitian menggunakan <em>one group pretest-posttest design</em> dengan melakukan uji coba terbatas pada peserta didik Jurusan Kimia Analisis SMK Negeri 1 Cerme Gresik yang dipilih berdasarkan kemampuan peserta didik dari kemampuan rendah, sedang, dan tinggi sebanyak 15 orang. <em>Pretest</em> dan <em>posttest</em> digunakan sebagai instrumen untuk mengetahui kemampuan visual spasial peserta didik. Data dianalisis secara deskriptif kuantitatif. Hasil penelitian menunjukkan bahwa data <em>pretest</em> dan <em>posttest</em> berdistribusi normal dan hasil rata-rata <em>N-Gain</em> pada kategori tinggi sehingga disimpulkan bahwa LKPD berbasis <em>blended learning</em> berbantuan multimedia interaktif dalam melatih kemampuan visual spasial peserta didik pada materi Ikatan Kovalen efektif sebagai bahan ajar.</p><p class="abstrak"> </p><p><strong><em>Abstract</em></strong></p><p class="abstrak"><em>The research aimed to determine the effectiveness of the Student Worksheet (LKPD) based on blended learning assisted by interactive multimedia in training students' visual-spatial skills in the Covalent Bond material. The research method used a one group pretest-posttest design by conducting a limited trial on students of the Analytical Chemistry Department at SMK Negeri 1 Cerme Gresik who were selected based on the ability of students from low, medium, and high abilities as many as 15 people. Pretest and posttest are used as instruments to determine the visual-spatial ability of students. Data were analyzed descriptively quantitatively. The results showed that the pretest and posttest data were normally distributed with the average N-Gain in the high category, so it can be concluded that the LKPD based on blended learning assisted by interactive multimedia in training students' visual-spatial abilities on the Covalent Bond material is effective as teaching material.</em></p>