Carbon quantum dots with honeycomb structure: a novel synthesis approach utilizing cigarette smoke precursors.

This study presents a novel approach to synthesizing honeycomb carbon quantum dots (CQDs) from cigarette smoke by a hydrothermal process. A comprehensive characterization of these CQDs, conducted through high-resolution transmission electron microscopy (HRTEM), showcases their unique honeycomb structure, with an average particle size of 6.3 nm. Photoluminescence (PL) in CQDs is a captivating phenomenon where these nanoscale carbon structures emit strong blue luminescence at 461 nm upon exposure to ultraviolet light, with their excitation peak occurring at 380 nm. Fourier Transform Infrared (FTIR) analysis also identifies specific functional groups within the CQDs, offering valuable insights into the mechanisms governing their photoluminescence. Analysis of excitation spectra indicates the presence of both aromatic C=C bonds at 254 nm and C-O bonds from 280 to 420 nm.

Superhydrophobic Ni-Reduced Graphene Oxide Hybrid Coatings with Quasi-Periodic Spike Structures.

Recently, sophisticated technologies are applied to design a certain surface nature that can have superhydrophobic properties. Thus, a simple spray technique was introduced to prepare a superhydrophobic surface using rGO with Ni-S system (rGO-Ni) by using NiSO4 catalyst under microwave irradiation at various reaction times of 5, 10, 20, and 30 min. The GO reduction was conducted at a fixed Ar/H2 ratio, a flow rate of 0.4 L/min, microwave power of 720 W, and a mass of 0.5 g. GO powder with nickel sulfate catalyst was treated under Ar/H2 (4:1) mixture for GO reduction, where Ar and H2 were expected to prevent the rebinding of oxygen released from GO. The result of XRD and Raman measurement confirms that rGO-Ni prepared at reaction time 20 min exhibit the highest reduction of GO and the presence of various Ni-S crystal structures such as NiS, NiS2, Ni3S2, and Ni3S4 due to decomposition of NiSO4. The rGO-Ni coating performance shows superhydrophobic nature with a contact angle of 150.1°. The AFM images show that the addition of nickel to rGO produces a quasi-periodic spike structure, which increases the superhydrophobicity of the r-GO-Ni coated glass with a contact angle of 152.6°. It is emphasized that the proposed simple spray coating using rGO-Ni provides a more favorable option for industry application in obtaining superhydrophobic surfaces.

Turning the Cocopith Waste into Myceliated Biocomposite to Make an Insulator.

Cocopith is the main waste of the coconut coir milling industry, which has not been handled properly until now. Burning cocopith as a response to land availability concerns for storing waste has an impact on pollution for the surrounding environment. Efforts to reduce, reuse, recycle, and remanufacture cocopith waste provide better economic value for waste. The method used in this research is one with quantitative and qualitative approaches. The AAS method is used to test the concentration of cocopith chemical elements, while lignin and cellulose levels were tested using data methods. The test results obtained that the highest chemical elements are sulfur and chlorine; the sulfur content in 1 kg of cocopith is 24,000 mg and chlorine content is 10,371 mg. Meanwhile, the other results showed that lignin levels in cocopith (22.7%) are higher than cellulose content (10.27%). The test results of cocopith characteristics from the methods mentioned above showed that the chemical content of sulfur and chlorine and lignin, more so than cellulose, causes cocopith to have the potential to insulate thermally. Based on this potential, cocopith is processed into mycelium-based biocomposite that serves as an insulator. Maximum stress and tensile stress of this biocomposite have been tested through flexural strength tests with the ASTM-D7264 method. The biocomposite feasibility of the material as an insulator was shown through a thermal conductivity test at temperatures of 13°C-40°C. This showed a thermal conductivity value of 0.0887241 ± 0.002964 W/mK. This value is in the range of 0.01-1.00 W/mK, which is a recommended value for the thermal conductivity insulator.

Molecular weight effects in the third-harmonic generation spectroscopy of thin films of the conjugated polymer MEH-PPV.

Thin spin-cast films of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) were prepared from samples whose weight-average molecular weight (Mw) was varied in the range of 10-1600 kg/mol. We have characterized the films by means of transmission and reflection ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy to derive the linear optical constants, and third-harmonic generation spectroscopy with variable laser wavelengths to get the modulus and phase angles of the complex third-order nonlinear optical susceptibility chi(3). Increasing molecular weight yields films with significantly larger chi(3) values, absorption coefficients, and refractive indices. The chi(3) values of films from the largest and lowest Mw differ by a factor of 4, which is caused by chain orientation effects, local field effects, and changes of the effective conjugation length.

Effect of donor-acceptor substitution on the nonlinear optical properties of oligo(1,4-phenyleneethynylene)s studied by third harmonic generation spectroscopy.

Third-harmonic generation (THG) spectroscopy was performed for oligo(1,4-phenyleneethynylene)s (OPEs) with terminal donor-acceptor (DA) substitution and compared to the results of merely donor substituted OPEs and regular OPE chains with 2,5-dipropoxy benzene rings. Both, extension of the conjugation and push-pull effect enhance the molecular hyperpolarizability gamma, even for the DAOPEs, which exhibit a hypsochromic shift of the long-wavelength absorption for increasing length L of the conjugated chain.