Fisika

Matematika dibangun dari operasi dasar penjumlahan dan perkalian, sehingga penguasaan dua operasi tersebut mutlak diperlukan untuk menguasai matematika. Dalam sudut pandang bilangan, seluruh himpunan bilangan dalam matematika dibangun oleh bilangan prima, sehingga pemahaman bilangan prima pun mutlak diperlukan untuk memahami seluruh sifat bilangan dalam matematika.

Hidrogel Superabsorban (HSA) CMC-g-PKA/NaAlg telah disintesis menggunakan iradiasi sinar gamma sebagai crosslinker dengan dosis 10 kGy. HSA disintesis dengan variasi massa CMC, yaitu 1,0 g, 1,5 g, 2,0 g, dan 2,5 g. Kemampuan HSA dalam menyerap ion logam Cu (II) telah dipelajari menggunakan spektrofotometer UV-Vis. Pengujian dilakukan dengan variasi konsentrasi ion logam Cu (II) yaitu, 1%, 2%, 3%, 4%, dan 5% selama 30 menit. Nilai absorbansi pada ion logam Cu (II) meningkat seiring dengan peningkatan massa CMC. Nilai absorbansi terbesar, yaitu 74% pada massa CMC 2,5 g. Pengujian FTIR mencirikan adanya interaksi antara gugus (OH) hidroksil, (NH 2) amina, dan karboksilat (COOH), terhadap ion logam Cu (II) pada bilangan gelombang 3653,18 1/cm, 1442,75 1/cm, dan 1587,42 1/cm.

Carbon dots (C-dots) are a new type of fluorescent nanoparticles that can be readily synthesized from natural sources, such as cassava's peels. In this work, C-dots were synthesized from cassava's peels using low temperature green synthesis based. The Green synthesis techniques were done by using water as a solvent non-chemical and natural sources. The Synthesis was done using various concentrations of precursor from 0.25%, 0.50%, 1.0% and 2.0%. Optical properties of C-dots were characterized using spectrophotometer UV-Vis, photoluminescence (PL) and time resolved photoluminescence (TRPL). The concentration of precursor lead to differences in molecular density and content of preparation thus affecting optical properties. The performance of C-dots optical properties were dominated by the transition of electrons n-π* on structure aromtic C=O which originate from the surface of C-dots. The result of C-dots sample with a concentration of 2.0% precursors has the best emission effiency. This provides the potential for C-dots cassava's peels in the aqueous solution to be applied as cellular bioimaging and biosensing metal ions and salts.

Carbon dots (C-dots) are a new type of phosphorescent nanoparticles that can be easily synthesized from natural sources or raw materials. The outer shell of cassava is the second waste obtained from cassava skin waste which is less attention to be utilized. Synthesis of C-dots from the outer shell of dried cassava has been successfully carried out with Microwave techniques. Synthesis of C-dots was carried out using water as a solvent with a variation of the concentration of precursor solutions to the microwave duration. Microwave duration causes changes in the structure and optical properties of C-dots. C-dots are characterized to study the optical properties of the UV-Vis absorbance spectrum and emission intensity in the form of emissions. The observed optical properti es aim to determine the C-dots energy transition, such as surface and core energy. The core energy level becomes dominant in the transition π→π* compared to the transition of n→π* in surface energy when the C-dots concentration increases so that energy shifts. This phenomenon is known from the top of the broad C-dots emission spectrum and shifts to longer wavelengths. In addition, we suspect that the difference in C-dots emissions is caused by the molecular density and content of the preparation based on the concentration of precursor solutions and the length of microwave time.

Superabsorbent hydrogel (SAH) is a hydrophilic polymer network that can absorb and retain a large amount of water in swelling conditions. SAH has been synthesized from Carboxymethylcellulose (CMC) with variations in weight (1.0 g, 1.5 g, 2.0 g, 2.5 g) grafted by poly (acrylic acid) (PAA) and composited with natrium alginate (NaAlg). Samples were crosslinked using gamma-ray irradiation technique in a dose 10 kGy (at a dose rate of 5 kGy/hour). CMC can increase porosity and influence swelling properties. Characteristics of swelling properties in aqueous solutions which are influenced by weight variations of the CMC were evaluated, such as aquadest, urea solution with various concentrations (0.25%, 0.50%, 0.75%, and 1.00%) and salt solution of NaCl and CaCl2 with variation of concentrations (0.09%, 0.9%, and 1.9%). The Swelling ratio in salt solutions decreased significantly compared to in aquadest. Swelling capacity increased with decreasing cation content (Ca2+<Na+). A different phenomenon occurs in urea solution, because urea is a neutral molecule, so the presence of urea molecules are not influenced by the electrostatic repulsion of COO- groups in the polymer chain. FTIR measurement showed PAA grafting reaction on CMC and NaAlg cross-linked with gamma-ray irradiation. From SEM measurement the SAH had heterogeneous porosity.

Carbon dots (C-dots) have been successfully synthesized from cassava peels using the hydrothermal method. The C-dots are further passivated using poly (ethylene glycol) (PEG) with a variation of the volume of 0.5 ml, 1.0 ml, and 1.5 ml. The properties of photoluminescence C-dots before and after PEG were characterized using photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectrophotometers. PEG succeeded in influencing PL C-dots properties, such as peak wavelength, PL intensity, and electron time decay. The addition of 0.5 ml of PEG to C-dots is the optimum condition and best with the peak wavelength, the PL intensity and, time decay electron is 507.52 nm, 5302 a.u, and 3.794031133 ns, respectively.

Carbon dots (C-dots) are a new type of fluorescent nanoparticles that can be easily synthesized from natural resources. The synthesis of C-dots from bamboo leaves was successfully carried out using microwave assisted green synthesis techniques. Green synthesis techniques are carried out using water as a non-chemical solvent and natural sources. Synthesis is carried out using variations in the concentration of precursors to be studied for their effects on the physical and optical properties. The physical properties of C-dots show transparent colors under visible light, and green color under the UV 405 nm laser. The optical properties of C-dots were characterized using a UV-Vis spectrophotometer, and a Fluorescence spectrophotometer with an excitation source of 405 nm. Precursor concentrations affect excitation and emission intensity, but Stokes's shift to C-dots has excellent stability in aqueous solutions. Stokes' shift originated from the transition state n-π* from structure of aromatic bond C=O on surface of C-dots. We obtained C-dots which have the potential to be applied as cellular bioimaging in vivo and in vitro and biosensing metal ions and salts.

Carbon dots (C-dots) is a new type of luminescense nanoparticles that can be synthesized easily from natural sources, such as cassava peels. C-dots has been synthesized from cassava peels based green synthesis using low temperature. The surface of C-dots was passivated by poly(ethylene glycol) (PEG) with variations in volume from 0.5 ml, 1 ml, and 1.5 ml. Luminescense properties before and after passivasive with PEG characterized using photoluminescense (PL) and time resolved photoluminescence (TRPL) spectrophotometer. Peak wavelength spectrum of PL shows a red shift when 0.5 ml PEG was added. However, when the addition of PEG increases, peak wavelength spectrum of PL shows a blue shift. PL intensity decreased along with increasing of PEG volume. PL intensity influenced C-dots electron time decay linearly. C-dots electron time decay increased along with decreased of PL intensity. This results assigned potency that C-dots in water solution can be applied as bioimaging and metal ion and salt biosensing. however, it needs extra optical measurements to support our discovery.