Profil Penguasaan Konsep Sistem Periodik Unsur pada Siswa Kelas X MIPA SMA Negeri 1 Palangka Raya Tahun Ajaran 2018/2019

Kimia memiliki beberapa jenis konsep dari segi dimensinya, salah satunya adalah keabstrakan. Sistem periodik unsur merupakan salah satu materi dalam kimia yang bersifat abstrak. Tujuan penelitian ini adalah untuk mendeskripsikan penguasaan konsep siswa kelas X MIPA 7 SMA Negeri 1 Palangka Raya.             Subjek penelitian ini adalah 28 siswa kelas X MIPA 7 SMA Negeri 1 Palangka Raya tahun ajaran 2018/2019 yang sudah menerima pembelajaran sistem periodik unsur. Data penelitian ini berupa dokumen RPP yang didapat dari guru yang bersangkutan, data penguasaan konsep yang didapat melalui tes uraian sistem periodik unsur berjumlah 11 butir soal dari 3 indikator dan data hasil wawancara siswa. Data-data yang diperoleh kemudian dianalisis secara deskriptif. Hasil penelitian menunjukkan bahwa profil penguasaan konsep siswa pada topik sistem periodik unsur yaitu sebesar 61,7% dan berada pada kategori sedang. Penguasaan konsep siswa terbagi kedalam 2 kategori yaitu tinggi dan sedang. Sebanyak 5 siswa berada pada kategori tinggi, dan sebanyak 23 siswa berada pada kategori sedang. Siswa mampu menjelaskan perkembangan sistem periodik unsur menurut Triade Dӧbereiner, Oktaf  Newlands, Mendeleev, dan Moseley dengan penguasaan konsep sebesar 37,5% dan berada pada kategori rendah. Siswa mampu menentukan letak suatu unsur di dalam tabel periodik berdasarkan konfigurasi elektron dengan penguasaan konsep sebesar 100% dan berada pada kategori tinggi. Siswa mampu menentukan sifat periodik suatu unsur berdasarkan sifat keperiodikan unsur seperiode dengan penguasaan konsep sebesar 56,8%  dan berada pada kategori sedang

Praziquantel meets Niclosamide: a dual-drug antiparasitic cocrystal

In this paper we report a successful example of combining drugs through cocrystallization. Specifically, the novel solid is formed by two anthelminthic drugs, namely praziquantel (PZQ) and niclosamide (NCM) in a 1:3 molar ratio, and it can be obtained through a sustainable one-step mechanochemical process in the presence of micromolar amounts of methanol. The novel solid phase crystallizes in the monoclinic space group of P2(1)/c, showing one PZQ and three NCM molecules linked through homo- and heteromolecular hydrogen bonds in the asymmetric unit, as also attested by SSNMR and FT-IR results. A plate-like habitus is evident from scanning electron microscopy analysis with a melting point of 202.89 °C, which is intermediate to those of the parent compounds. The supramolecular interactions confer favorable properties to the cocrystal, preventing NCM transformation into the insoluble monohydrate both in the solid state and in aqueous solution. Remarkably, the PZQ - NCM cocrystal exhibits higher anthelmintic activity against in vitro S. mansoni models than corresponding physical mixture of the APIs. Finally, due to in vitro promising results, in vivo preliminary tests on mice were also performed through the administration of minicapsules size M

Assessment on the Use of High Capacity “Sn4_{4}P3_{3}”/NHC Composite Electrodes for Sodium-Ion Batteries with Ether and Carbonate Electrolytes

This work reports the facile synthesis of a Sn–P composite combined with nitrogen doped hard carbon (NHC) obtained by ball-milling and its use as electrode material for sodium ion batteries (SIBs). The “Sn$_{4}$P$_{3}$”/NHC electrode (with nominal composition “Sn$_{4}$P$_{3}$”:NHC = 75:25 wt%) when coupled with a diglyme-based electrolyte rather than the most commonly employed carbonate-based systems, exhibits a reversible capacity of 550 mAh g$_{electrode}$$^{−1}$ at 50 mA g$^{−1}$ and 440 mAh g$_{electrode}$$^{−1}$ over 500 cycles (83% capacity retention). Morphology and solid electrolyte interphase formation of cycled “Sn$_{4}$P$_{3}$”/NHC electrodes is studied via electron microscopy and X-ray photoelectron spectroscopy. The expansion of the electrode upon sodiation (300 mAh g$_{electrode}$$^{−1}$) is only about 12–14% as determined by in situ electrochemical dilatometry, giving a reasonable explanation for the excellent cycle life despite the conversion-type storage mechanism. In situ X-ray diffraction shows that the discharge product is Na$_{15}$Sn$_{4}$. The formation of mostly amorphous Na$_{3}$P is derived from the overall (electro)chemical reactions. Upon charge the formation of Sn is observed while amorphous P is derived, which are reversibly alloying with Na in the subsequent cycles. However, the formation of Sn$_{4}$P$_{3}$ can be certainly excluded

Study on Polymer-Surfactant Interactions for the Improvement of Drug Delivery Systems Wettability

One of the possible causes of failure of the mechanochemical activation of poorly soluble drugs relies on the scarce drug wettability. Indeed, the mechanochemical process comports the disposition of drug nano-crystals and amorphous drug, generated by the destruction of original drug macro-crystals, on the surface of the carrier (acting as stabiliser), usually represented by crosslinked polymeric particles. Accordingly, the scarce drug wettability can reduce the beneficial action of mechanochemical activation (nano-crystals and amorphous drug are characterised by a higher solubility with respect to the original macro-crystals). In this light, this paper is focussed on the use of surfactants for the increase of delivery system (drug plus carrier) wettability. In particular, the surfactant-polymer systems are characterised for what concerns their bulk and surface properties. This allows to select the best surfactant and to experimentally verify its effect on the release kinetics of a poorly soluble and wettable drug

Formation and physicochemical properties of crystalline and amorphous salts with different stoichiometries formed between ciprofloxacin and succinic acid

YesMulti-ionizable compounds, such as dicarboxylic acids, offer the possibility of forming salts of drugs with multiple stoichiometries. Attempts to crystallize ciprofloxacin, a poorly water-soluble, amphoteric molecule with succinic acid (S) resulted in isolation of ciprofloxacin hemisuccinate (1:1) trihydrate (CHS-I) and ciprofloxacin succinate (2:1) tetrahydrate (CS-I). Anhydrous ciprofloxacin hemisuccinate (CHS-II) and anhydrous ciprofloxacin succinate (CS-II) were also obtained. It was also possible to obtain stoichiometrically equivalent amorphous salt forms, CHS-III and CS-III, by spray drying and milling, respectively, of the drug and acid. Anhydrous CHS and CS had melting points at ∼215 and ∼228 °C, while the glass transition temperatures of CHS-III and CS-III were ∼101 and ∼79 °C, respectively. Dynamic solubility studies revealed the metastable nature of CS-I in aqueous media, resulting in a transformation of CS-I to a mix of CHS-I and ciprofloxacin 1:3.7 hydrate, consistent with the phase diagram. CS-III was observed to dissolve noncongruently leading to high and sustainable drug solution concentrations in water at 25 and 37 °C, with the ciprofloxacin concentration of 58.8 ± 1.18 mg/mL after 1 h of the experiment at 37 °C. This work shows that crystalline salts with multiple stoichiometries and amorphous salts have diverse pharmaceutically relevant properties, including molecular, solid state, and solubility characteristics.Solid State Pharmaceutical Cluster (SSPC), supported by Science Foundation Ireland under grant number 07/SRC/ B1158

A sodium-ion battery based on olivine iron phosphate cathode and nanostructured tin carbon anode

Lithium-ion battery is presently the most diffused energy storage system in the electronic portable devices market, this in view of its high energy density and intrinsic safety due the replacement of the reactive lithium-metal by the lithium-insertion, graphite anode. [1,2] The increased demand of lithium and its concentration in few countries contributed to a rapid rise of the price. As consequence, rechargeable electrochemical cells based on sodium, designed for the energy storage, are now attracting large interest due to its abundance and low cost. [3,4] We report here the behavior of a sodium-ion battery based on a NaFePO4 cathode, obtained by electrochemical Li-Na conversion of LiFePO4 olivine, and a nanocomposite tin-carbon (Sn-C) alloying anode. [5,6] We show that, by adopting a refined, unique electrochemical process, the LiFePO4 can be successfully and efficiently converted in NaFePO4 and demonstrate that this material can be used as cathode in a sodium-ion battery characterized by the reversible electrochemical process NaFePO4 + SnC = Na(1-x)FePO4 + SnxC with good reversibility and rate capability

Advanced materials for Sodium-ion batteries

Energy conversion and storage have become key issues concerning our welfare in daily life. Electrochemical systems, such as batteries and super capacitors, that can efficiently store and deliver energy on demand are playing a crucial role in this field. Presently, lithium-ion batteries (LIBs) are the most widespread rechargeable batteries in the consumer electronic and portable device markets because of their unique properties. Due to their high energy density, LIBs are already considered in the transportation field and used to power hybrid and full electric vehicles.[1] However, the increased demand of lithium and the comparably limited geographic location of resources is reflecting in a rapid rise of its price. As a consequence, the identification of energy storage systems alternative to lithium is now seen as a valid step to lead to the development of economically sustainable secondary batteries. Among these, sodium-based batteries appear as very promising candidates due to the low cost and high abundance of sodium.[2] Here we will present an overview about Na-ion battery materials, with the aim of providing a wide view of the systems studied in our group. We will focus on poly-anionic networks and layered compounds as cathode materials and alloying nanostructured compounds at the anode side for conventional sodium-ion batteries based on the intercalation chemistry process. [3] Furthermore recent studies on ‘‘low temperature’’ Na–S batteries, analogous to Li–S batteries which offer great promise as low-cost, high-capacity energy storage systems will be presented

A sodium-ion battery based on a P2-Na0.5Ni0.22Fe0.11Mn0.66O2 cathode and a nanostructured Sb-C anode in a ionic liquid based electrolyte

Na-based storage systems working at room-temperature have recently gained the interest of the research community thanks to the large availability and low cost of sodium.[1,2] The real challenge in the sodium-based battery field is represented by the substitution of the extremely reactive metallic sodium anode that represents a serious issue to face in order to increase the intrinsic safety of the sodium cells. To further improve the safety level of sodium cells, we propose here the substitution of the more common organic-carbonate based electrolytes with an ionic liquid-based electrolyte characterized by higher thermal stability, lower volatility and non flammability.[3] Here we propose the study of a sodium-ion battery based on a P2-type, Na0.5Ni0.22Fe0.11Mn0.66O2 transition metal layered oxide cathode material and a nanostructured Sb-C alloying anode in a 0.2m NaTFSI-Py14TFSI electrolyte. The improved morphology of the electrode materials here investigated ensure an enhanced electrochemical behavior in terms of cycle stability and delivered capacity

Supercaps Beyond Lithium Ion Batteries

The next best thing: In this Editorial, we present the body of work of this Special Collection, which aims at highlighting the dynamic research environment surrounding the next-generation electrochemical energy storage technologies, bringing together the latest research conducted on “beyond lithium-ion batteries”. It was about thirty years ago, with the first successful commercialization of lithium-ion batteries (LIBs), that a new era begun. These new electrochemical energy storage systems were about to transform the way society communicates, moves, and lives. The journey that led to this success started back in the early 70s until the mid 1980 paving the way for LIBs commercialization in 1991.1 LIBs undoubtably represent the most successful example of secondary battery. Their importance is reflected in the 2019 Nobel Prize for Chemistry awarded to Dr. Yoshino, Prof. Whittingham, and Prof. Goodenough for their pioneering work toward the development of the LIB technology.