The remarkable optical properties and strong biocompatibility of carbon dots make them highly promising for applications in biochemical sensing and environmental testing. These carbon dots possess a surface that is easily modifiable. In this study, carbon dots have been successfully synthesized and modified by the addition of N and B dopants using the microwave method, along with the functionalization of their surface functional groups with bovine serum albumin (BSA). The maximum fluorescence intensity of N, B-CDs is observed at 462 nm when excited at a wavelength of 352 nm. N, B-CDs have a spherical size with a diameter ranging from 2 to 6 nm, confirmed by UV-Vis absorption spectra and the presence of functional groups in the FT-IR absorption patterns. BSA-functionalized N, B-CDs as the fluorescent probe demonstrate great potential as a sensor for Pb(II) ions in water, with a very low detection limit of 1.05 µg/L. This research could contribute to the development of fluorescence nanosensors.

Facile synthesis of reduced-graphene oxide (rGO) has been conducted in this study using the extract of Caesalpinia sappan L. as a green reducing agent. Graphite sheets were first exfoliated using an improved Hummer process to produce graphene oxide (GO). Then, the reduced-graphene oxide (rGO) was obtained by reducing GO with Caesalpinia sappan L. extract at various concentrations in an autoclave hydrothermal process. Analytical methods such as XRD, Raman spectroscopy, FTIR, SEM-EDX, TEM, UV–visible absorption, TG-DTA, and zeta potential value were used to characterize the graphite, GO, and rGO materials. A cyclic voltammetric study was also conducted to measure the performance of the synthesized materials. All rGO show good electrochemical properties, and the highest oxidation and reduction currents are observed for rGO-10. The characterization results show that Caesalpinia sappan L. extract can effectively reduce GO to rGO, and the best rGO can be obtained by adjusting the level of the extract.

The toxicity test of zinc metal in soil samples around the textile industry in Bantul on the growth of spinach (Amaranthus gangeticus) and bean sprouts (Phaseolus aureus) has been investigated in relation with the environmental assesment for the impact of industrial activities. This research was conducted to study physicochemical properties, adsorption-desorption, and zinc metal toxicity in the soil around the textile industry on the growth of spinach and bean sprouts. The study of physicochemical properties were water content, pH, electrical conductivity, ash content, total organic carbon, cation exchange capacity, metal content, and characterization using FTIR (Fourier transform infrared) spectrophotometry. Various zinc concentrations were studied for the adsorption capacity, whereas citric acid concentrations were used for the desorption. Atomic absorption spectrophotometry (AAS) was applied to measure metal concentrations for all samples. A toxicity tests were conducted on the growth of spinach and bean sprouts. The maximum zinc concentration was measured in point I, at 532.03 mg kg-1. Adsorption of zinc followed the Langmuir and Freundlich isotherms, and desorption process occurred at optimum concentration 0.7 mol L-1 citric acid and a pH of 3. In the zinc metal toxicity test, large concentration of zinc metal revealed inhibition effect on spinach and bean sprouts growth. Keywords: Adsorption, desorption, toxicity test, zinc.

This present research deals with a systematic study on doping TiO2 with Fe from iron rusty waste to improve the activity under visible light irradiation through gap narrowing in the TiO2 semiconductor structure. The doping was conducted by the sol-gel method by interacting titania tetra isopropoxide (TTIP) with Fe3+ ions dissolved from the iron rusty waste in aqua regia. The concentration of the Fe3+ was varied giving mole ratio to TiO2 as (1:0.04), (1:0.08), (1:0.12), (1:0.16), and (1:0.20). The activity of TiO2-Fe was examined for Rhodamine-B dye photodegradation through batch technique. The influences of the Fe fraction, irradiation time, photocatalyst weight, and solution pH were also evaluated to find the best condition for the dye degradation. The research results attribute that doping TiO2 with Fe3+ from the rusty waste has successfully shifted the band gap energy into the visible regime, which remarkably increases the TiO2 activity under visible light irradiation. The increase is controlled by the Fe fraction in the photocatalyst, and the best performance is shown by TiO2-Fe with a 1:0.12 mole ratio. From the dye photodegradation, it is found that the highest degradation effectiveness (99.20%) of 5 mg/L Rhodamine B in 50 mL of the solution, can be obtained by using 50 mg of TiO2-Fe (1:0.12), pH 5, in 90 mins. The photocatalyst can be reused twice in the photodegradation process without a significant decrease in photoactivity. It is implied that the rusty waste has potential as a Fe dopant source creating a better visible responsive photocatalyst.

Reduced graphene oxide (rGO) has attracted much attention because of its high thermal conductivity, electrical properties, Young's modulus, mechanical strength, optical transmittance as well as theoretical areas. This material is widely used for various applications and normally produced by the reduction of graphene oxide (GO). Currently, the reducing agents used in the rGO synthesis such as hydrazine are harmful to the environment. Therefore, multiple searches for eco-friendly reducing agents have been conducted to replace the toxic ones. This brief review discusses the challenge of using natural extracts as reducing agents and several techniques commonly utilized in the synthesis of rGO from GO. Furthermore, the chemical components and mechanism involved in the reduction process are reviewed and compared. Some mechanisms involved in the GO reduction are discussed from the view point of the chemical contents in the plant extracts. Several fundamental characterization techniques, such as UV-Vis, FTIR, XRD, and Raman spectroscopies are also described. These main characterizations are utilized to justify the success of the reduction process with the hope that it can be used as an initial screening before a complete characterization of the synthesized rGO is conducted. Moreover, the developing use of natural reducing agents faces some challenges, including the complexity of the compounds in the natural extracts and the reproducibility of the synthesis method. This review summarizes the strategy for applying natural agents to reduce GO to rGO so that it can help researchers finding the novel green extracts and use it effectively in the rGO synthesis process.

Exfoliated graphene has been successfully synthesized using electrochemical exfoliation method followed by sonication of the graphite rod. Ammonium sulfate, sodium sulfate, ammonium oxalate, hydrogen peroxide, and ammonium persulfate were used as electrolytes. The effect of sonication time was studied for several products. The exfoliated graphene (EG) was characterized using XRD, Raman, FTIR, SEM-EDS, TEM and electrical con-ductivity measurement. The exfoliation using ammonium sulfate-ammonium persulfate as the electrolyte gives the highest mass-product, with a yield of almost 70%. Adding peroxide to the electrolyte reduces the mass of the exfoliated product. In addition, different sonication times results in different phenomena of particle size changes. The XRD data show that the EG has 2 theta = 26.4 degrees which is lower than its origin graphite. Raman data confirm that the EG has been obtained with the FWHM (G) value of 45-70 cm-1, and the resulting EG is a multilayer (2D peak). The O-H and C-C aromatic group has been assigned from FTIR spectrum. From SEM and TEM images, it was understood that the morphology of material is wrinkled, crumpled, and has a transparent zone, while from EDS data, it is found that the O/C value is in the range of 0.15-0.35. The electrical conductivity of EG reaches 52 S/cm.

Enzymatic hydrolysis is the main target to deal with ACh depletion. However, a recent study indicates that the non-enzymatic one may contribute to the depletion. This study highlights the necessity of considering possible conformers, discrete-continuum models, and dispersive effects for investigating the neutral (non-enzymatic) hydrolysis of flexible molecules in aqueous solution. We systematically built the possible conformers within the first-principles framework. The results confirm the reactivity of high-energy ACh conformer towards neutral hydrolysis. We proposed that conformational changes occur before the hydrolysis. The calculated activation and reaction energy shows that the discrete-continuum solvation model gives the closest result to experimental observations. This study also shows that neglecting dispersive effects brings unreliable structures in the initial state, which leads to unreliable activation energy.

Silica from rice husks (RH) has been used as a starting ingredient in the sonication synthesis of MCM-41 (RH-MCM-41). The impregnation of Fe3+ into RH-MCM-41 pores to produce RH-MCM-41 containing Fe2O3 and Fe (denoted as Fe2O3-Fe-RH-MCM-41) was carried out by examining the effect of various Fe3+ concentrations on the weight percent of Fe-frameworks (Fe3+ that replaces Si4+ in silicate frameworks) and Fe-non-frameworks, i.e., the iron oxide formed outside the silicate frameworks. Fe2O3-Fe-RH-MCM-41 was washed with a 0.01 M HCl solution to remove Fe-non-frameworks from the materials and give Fe-RH-MCM-41 containing Fe-frameworks. The Fe content in Fe2O3-Fe-RH-MCM-41 (Fe-total) and Fe-RH-MCM-41 (Fe-frameworks) for each sample was determined by an AAS (atomic absorption spectrometer), whereas the content of Fe-non-frameworks was calculated from the difference between Fe-total and Fe-frameworks. The XRD (X-ray diffraction) pattern, N2 adsorption-desorption isotherm profile, as well as the TEM (transmission electron microscope) image clearly demonstrate that the RH-MCM-41 exhibits an ordered p6mm hexagonal mesostructure with a large specific surface area and uniform pore size. Based on the weight percents of Fe-frameworks found in each sample, it is clear that the content of Fe-non-frameworks is significantly enhanced compared to that of Fe-frameworks when the more concentrated Fe3+ is used.

An afford to enhance TiO 2 activity under visible light as well as to utilize the iron rusty waste, has been conducted by doping Fe from the waste into TiO 2 . The doping was performed by sol-gel method of titania tetra isopropoxide with Fe 3+ ions dissolved from the iron rust waste. In the doping, the concentration of Fe 3+ was varied giving various mole ratios of TiO 2 :Fe. The doped TiO 2 photocatalysts were characterized using FTIR, XRD, SRUV, and SEM-EDX instruments. The photocatalytic activity of the doped TiO 2 was evaluated by photodegradation of Congo red under visible light. The effect of some parameters that govern the photodegradation process such as the amount of Fe dopant, reaction time, photocatalyst mass, solution pH, and initial concentration of dye was also studied. The characterization results reveal that Fe 3+ ions from the rusty waste have been doped into TiO 2 which can remarkably narrow the band gap energy (Eg), shifting into the visible zone. In accordance, the activity of TiO 2 under visible light in the dye photodegradation is considerably enhanced. The Eg decreasing and actively improving the doped TiO 2 are controlled by the amount of Fe dopant, and the most effective Eg decreasing is shown by TiO 2 –Fe (1:0.8), but the highest activity is observed for TiO 2 –Fe (1:0.4). It is also found that the highest photodegradation of Congo red 5 mg/L in 50 mL of the solution over TiO 2 –Fe (1:0.4) under visible light, that is about 99%, can be reached by applying 60 mg of the photocatalyst mass, in 60 min, and solution pH 5. It is implied that the rusty waste can be utilized to prepare the visible responsive photocatalyst that can be used for preventing dye pollution.

Simultaneous adsorption of Pb(II), Cd(II) and Mg(II) ions using activated coal bottom ash (Act-CBA) and dithizone-immobilized Act-CBA (Dtz-CBA) prepared in an eco-friendly medium of the alkaline solution has been done. The parameters affecting the adsorption, such as pH, contact time, initial concentration, and coexisting cations, were systematically investigated. The optimal adsorption was obtained at pH 5, 90 min of contact time and the adsorption of metal ions on both materials followed the pseudo-second-order kinetic model. Langmuir isotherm model fitted well the adsorption of Pb(II) and Cd(II) ions on both adsorbents. Significant increase in the maximum adsorption capacity (qmax) and Langmuir constant (KL) of both Pb(II) and Cd(II) ions on Dtz-CBA compared to that of Act-CBA indicated the stronger affinity of Dtz-CBA towards these two metal ions, while no significant change in capacity was observed for Mg(II) ions. In the binary solution of Pb(II) and other coexisting metal ions, the adsorption of Pb(II) on Dtz-CBA was not affected by Co(II), Ni(II), Zn(II), Ag(I), or Cd (II). However, mixing of all coexisting metal ions with Pb(II) ion in the solution resulted in the decrease in the adsorption of Pb(II) of about 65% compared to that of the single adsorption of Pb(II) ion, possibly due to the limited number of active sites in the solution. Results of sequential desorption suggested that metal ions interacted with Act-CBA mostly via electrostatic interaction and hydrogen bond, while for Dtz-CBA, the hydrogen bond and metal complexation increased significantly, especially for the interaction of Pb(II) and Cd(II) ions. Post-adsorption characterization of the adsorbents using SEM-EDX, FTIR, and XRD confirmed the adsorption of metal ions on the surface of materials, as indicated by several changes in the adsorbent properties after adsorption.

Modification of silica purified from the Merapi volcanic ash with magnetic material of Fe3O4 and attachment of cetyl triamine bromide (CTA-Br) on the magnetic cored has been performed to provide recoverable and positive surfaced of natural adsorbent. The magnetic cored was prepared via co-precipitation and CTA-Br attachment was conducted by a facile strategy. Then, the modified adsorbents were characterized by SEM, TEM, XRD, and FTIR instruments and examined for removing anionic Cr(VI) from the water media. The characterization data confirmed that crystals of Fe3O4 coated by SiO2 that has been bound with CTA-Br have been successfully formed. Additionally, increasing CTA-Br loaded gives thicker lamination on Fe3O4@SiO2/CTA-Br, but the CTA-Br loaded with higher than 0.25 mmol, leads to the coating peeled out. It is also demonstrated that Fe3O4@SiO2/CTA-Br prepared with CTA-Br 0.25 mmol is ideal for Cr(VI) anionic removal, regarding to the highest adsorption and very good separation or recovery process. Moreover, the optimal dose of Fe3O4@SiO2/CTA-Br in the Cr(VI) removal was observed at 0.25 g/20 mL under condition of pH 3 for 60 min. The adsorption of Cr(VI) well fits the Langmuir isotherm model with an adsorption capacity of 3.38 mg g-1 and is in a good agreement with pseudo-second order giving kinetic constant at 0.005 g mg-1 min-1. Thus, it is clear that the natural adsorbent material with recoverable properties for more efficient and wider application of removal Cr(VI) contaminant was expected from this study.

In this study, isotherm and kinetic adsorption of malachite green (MG) using coal fly ash (CFA) as the adsorbent was investigated. This study aimed to examine the character of CFA analyzed by Atomic Absorption Spectrophotometry (AAS), Fourier-Transformed Infra-Red (FTIR), and X-Ray Diffraction (XRD) analysis. In addition, the adsorption of MG on CFA was also studied, including the effect of solution pH, adsorbent mass, contact time, and concentration of malachite green on the adsorption process. From the experimental data, the kinetic parameters isotherms and energy of the adsorption were determined. Kinetic study showed that the kinetic adsorption of MG on CFA fit well the Ho and McKay's pseudo-second-order, with an adsorption rate constant ( k 2 ) of 0.0377 g mg -1 min -1 . Furthermore, the Langmuir isotherm model was the most suitable model to describe adsorption. Changes in the standard Gibbs free energy calculated from equilibrium constant ( K L ) at room temperature (303 K) showed that the adsorption process occurred spontaneously through chemical interaction (chemisorption) and most probably formed a monolayer on the surface of the adsorbent.

Silica from rice husks (RH) has been used as a starting ingredient in the sonication synthesis of MCM-41 (RH-MCM-41). The impregnation of Fe3+ into RH-MCM-41 pores to produce RH-MCM-41 containing Fe2O3 and Fe (denoted as Fe2O3-Fe-RH-MCM-41) was carried out by examining the effect of various Fe3+ concentrations on the weight percent of Fe-frameworks (Fe3+ that replaces Si4+ in silicate frameworks) and Fe-non-frameworks, i.e., the iron oxide formed outside the silicate frameworks. Fe2O3-Fe-RH-MCM-41 was washed with a 0.01 M HCl solution to remove Fe-non-frameworks from the materials and give Fe-RH-MCM-41 containing Fe-frameworks. The Fe content in Fe2O3-Fe-RH-MCM-41 (Fe-total) and Fe-RH-MCM-41 (Fe-frameworks) for each sample was determined by an AAS (atomic absorption spectrometer), whereas the content of Fe-non-frameworks was calculated from the difference between Fe-total and Fe-frameworks. The XRD (X-ray diffraction) pattern, N2 adsorption-desorption isotherm profile, as well as the TEM (transmission electron microscope) image clearly demonstrate that the RH-MCM-41 exhibits an ordered p6mm hexagonal mesostructure with a large specific surface area and uniform pore size. Based on the weight percents of Fe-frameworks found in each sample, it is clear that the content of Fe-non-frameworks is significantly enhanced compared to that of Fe-frameworks when the more concentrated Fe3+ is used.

The hydrothermal synthesis of amikacin modified carbon dots-doped nitrogen and zinc- (N,Zn-CDs) and its capacity to detect Escherichia coli (E. coli) have been investigated. Amikacin is one of the aminoglycoside antibiotics utilized in this study as a ligand of N,Zn-CDs to attach to E. coli. This study also examined the effect of nitrogen (N) and zinc (Zn) dopant content on enhancing N,Zn-CDs fluorescence emission intensity. N,Zn-CDs were characterized using a spectrofluorometer, UV-Vis spectrophotometer, FTIR, EDX, XRD, and TEM, which revealed their amorphous nature and average particle size of 3 nm. The emergence of bond vibrations of C=O, CN, and ZnO indicates the success of N and Zn dopants. Amikacin was then included in the structure of N,Zn-CDs to enhance their ability to detect E. coli. The maximum fluorescence intensity was seen in N,Zn-CDs with a mole ratio of 1:4:4 mmol for the carbon precursor, N, and Zn dopants, and a volume of 0.1 mL amikacin. Based on the fluorescence response of amikacin-modified N,Zn-CDs against E. coli, a limit of detection 1,490 cfu mL-1 was obtained.

Biosorption of Cu (II) using bacteria Pseudomonas aeruginosa FNCC-0063 was immobilized on calcium alginate (PAI). This research examined the effect of various parameters such as pH, contact time, and initial Cu (II) concentration. The biosorption mechanism of Cu (II) was studied by sequential desorption with H2O, KNO3 1 M, HNO3 0.5 M and Na2EDTA 0.1 M. Cu (II) concentration was analyzed using atomic absorption spectrophotometer (AAS). The results showed that optimum Cu (II) ion biosorption occurred at a pH biosorption rate constant of 0.03724 g mg-1.min-1. The kinetics studies showed that Cu (II) biosorption follows pseudo-second-order. The biosorption capacities of 36.60 mg/g. Cu (II) Biosorption followed the Freundlich equation, as shown by a high correlation coefficient (R2) of about 0.99. Ionic bonds dominated the biosorption mechanism of Cu (II) ion on immobilized PAI.

The chiral separation of econazole, an antifungal drug with one chiral center has been successfully carried out using the high-performance liquid chromatography (HPLC) method. Enantioresolution of econazole (Rs = 2.29) was achieved using cyclodextrin-based chiral column (Astec Cyclobond, 25 cm × 4.6 mm × 5 μm), mobile phase composition of acetonitrile : water (0.2% HCOOH) (20:80, v/v), and UV detection of 220 nm.The optimized HPLC method has been applied for the quantitative determination of econazole in the pharmaceutical (liquid) sample withpercentage recovery of 100.75 % (RSD = 0,95%; n = 3). The effect of several HPLC parameters on the chiral separation of econazole was also evaluated and the method was successfully validated in terms of linearity, accuracy, precision, and selectivity. The present HPLC method was simple, short analysis time, and high resolution.

Carbon/Alginate/Chitosan Composite (CAC) as a sorbent for solid-phase extraction of Cu(II) (pre-concentration) with atomic absorption spectrometry for analysis was successfully prepared. The sorbent was made with a mass ratio of chitosan:alginate:carbon = 1:1:1. CAC sorbents were characterized using FTIR for functional group analysis while SEM-EDX characterization was performed to determine surface morphology and percentage of elements. SPE parameters were optimized for adsorption-desorption efficiency under various conditions, i.e. of pH 5, Cu(II) concentration of 4 mg/L, the flow rate of Cu(II), and Na2EDTA eluent at 5 mL/min, the volume of Cu(II) sample and Na2EDTA eluent 25 mL and 1.0 M of Na2EDTA eluent concentration. Applying CAC-based SPE for Cu(II) analysis in water samples at optimum conditions gave 80.9–83.6% recovery. In bottled drinking water samples, a pre-concentration factor of 2.5–5 times was obtained, and the Cu(II) concentration of 0.017–0.020 mg/L was detected.

A fluorescent probe has been developed by synthesizing N,S co-doped carbon dots (N,S-CDs) through a microwave-assisted process for early detection of Cr(VI) in the environment. In this work, the optimization of irradiation time and ammonium persulfate mass as a source of N and S dopants were studied. The optimal conditions were then employed to synthesize N,S-CDs. Further research on pH, sensitivity, selectivity, and anti-interference to other metal ions were evaluated. Based on FT-IR spectra, it was confirmed that N and S atoms had been successfully passivated on the CDs surface as pointed by the presence of characteristic vibrations of N–H, C = N and C-N bonds for N atom as well as S–H and -SO3 for S atom. Characterization by TEM exhibited that N,S-CDs had an average size of 5 nm with some agglomerated parts. The highest fluorescence intensity was obtained at an irradiation time of 50 min with an ammonium persulfate mass of 50

By optimizing rice husk silica mass and sonication time, SBA-15 was successfully synthesized in a more efficient and environmentally friendly way. The solution of Pluronic P-123 was mixed with the solution containing NaOH and various masses of rice husk silica (4–12 g), followed by sonication for a certain time (30–150 min). The mixture was filtered and washed with distilled water and ethanol until neutral, then dried at 110 °C for 2 h and calcined at 500 °C for 6 h. The results showed that the optimal mass of rice husk silica was 8 g, while the optimal sonication time was 30 min. The product has a cylindrical pore shape with good crystallinity and pore structure regularity. The specific surface area (SBET), the pore diameter (DBJH), the specific pore volume (VBJH), and the wall thickness (WT) of the product were 601 m2 g–1, 4.76 nm, 0.88 mL g–1, and 5.02 nm, respectively. These results are not considerably different from the porosity of SBA-15, synthesized previously using conventional hydrothermal techniques from various silica sources. In addition, it is also comparable to the porosity of SBA-15 produced from TEOS by sonochemical methods as well as with commercial SBA-15.

In the present study, new greener approach of dithizone immobilization on coal bottom ash as a source of silica-alumina materials in alkaline (NaOH) solution has been developed to replace previously used method utilizing more toxic solvents such as toluene, carbon tetrachloride or chloroform. Some parameters influencing the effectiveness of dithizone immobilization including reaction time, concentration of NaOH solution as well as washing procedures were optimized. FTIR (Fourier Transform Infra-Red), XRD (X-Ray Diffraction) and DSC/TGA (Differential Scanning Calorimetry/Thermogravimetric Analysis) analysis were employed to characterize the obtained materials. The adsorbents also tested for the adsorption of Pb(II) ion. Results suggest the use of greener alkaline medium has doubled the effectiveness of dithizone immobilization on the surface of coal bottom ash and hence enhances the capacity and selectivity of adsorbent towards heavy metals.