Eli Rohaeti

Mechanical Properties and Antibacterial Activity of Cellulose Composite based Coconut Water with Addition of Glycerol, Chitosan, and Silver Nanoparticle

This study describes the mechanical properties and antibacterial activity of celluloses and their composites. The cellulose was prepared from coconut water fermented by Acetobacter xylinum. Cellulose was composited with chitosan and glycerol by immersion method and the addition of silver nanoparticles. Preparation of silver nanoparticles performed by chemical reduction of silver nitrate solution and polyvinyl alcohol as a stabilizer. UV-Vis spectroscopy was used to determine the formation of silver nanoparticles. Characterization of composites included observation of physical properties, mechanical properties, as well as antibacterial tests against S. aureus, E. coli, and C. albicans. The addition of glycerol can increase elongation at break of composites. The addition of glycerol and chitosan can decrease elongation at break and strength of the composites. The composite of cellulose glycerol chitosan silver nanoparticles shows the highest antimicrobial activity against S. aureus on 24 h of incubation, whereas composite of cellulose glycerol silver nanoparticles shows the highest antimicrobial activity against E. coli and C. albicans.

Antibacterial activity and the hydrophobicity of cotton coated with hexadecyltrimethoxysilane

In this work, cotton fiber was fabricated using silver nanoparticles to produce hydrophobic and antibacterial material. The silver nanoparticle was prepared with chemical reduction method using trisodium citrate as reducing agent and PVA as stabilizer. Silver nanoparticle was deposited on cotton fibers as antibacterial agent and HDTMS 4% v/v was coated on those as hydrophobic agent. The cotton fibers before and after modification were characterized its functional groups, contact angles, and antibacterials activities. The functional groups of cottons were determined by using ATR-FTIR, hydrophobic properties of cottons were determined by measuring contact angle, and antibacterial activities of cottons were determined by measuring clear zone. The addition of HDTMS decreased the intensity of absorption bands of functional groups but increased contact angle of cotton cloth. The cotton cloth-silver nanoparticle shows the highest antibacterial properties. The antibacterial activity of cotton cloth without and wi...

The development of an integrated assessment instrument for measuring analytical thinking and science process skills

This research aims to develop instrument and determine the characteristics of an integrated assessment instrument. This research uses 4-D model, which includes define, design, develop, and disseminate. The primary product is validated by expert judgment, tested it’s readability by students, and assessed it’s feasibility by chemistry teachers. This research involved 246 students of grade XI of four senior high schools in Yogyakarta, Indonesia. Data collection techniques include interview, questionnaire, and test. Data collection instruments include interview guideline, item validation sheet, users’ response questionnaire, instrument readability questionnaire, and essay test. The results show that the integrated assessment instrument has Aiken validity value of 0.95. Item reliability was 0.99 and person reliability was 0.69. Teachers’ response to the integrated assessment instrument is very good. Therefore, the integrated assessment instrument is feasible to be applied to measure the students’ analytical thinking and science process skills.This research aims to develop instrument and determine the characteristics of an integrated assessment instrument. This research uses 4-D model, which includes define, design, develop, and disseminate. The primary product is validated by expert judgment, tested it’s readability by students, and assessed it’s feasibility by chemistry teachers. This research involved 246 students of grade XI of four senior high schools in Yogyakarta, Indonesia. Data collection techniques include interview, questionnaire, and test. Data collection instruments include interview guideline, item validation sheet, users’ response questionnaire, instrument readability questionnaire, and essay test. The results show that the integrated assessment instrument has Aiken validity value of 0.95. Item reliability was 0.99 and person reliability was 0.69. Teachers’ response to the integrated assessment instrument is very good. Therefore, the integrated assessment instrument is feasible to be applied to measure the students’ analytical th...

An integrated assessment instrument: Developing and validating instrument for facilitating critical thinking abilities and science process skills on electrolyte and nonelectrolyte solution matter

The demanding of assessment in learning process was impact by policy changes. Nowadays, assessment is not only emphasizing knowledge, but also skills and attitudes. However, in reality there are many obstacles in measuring them. This paper aimed to describe how to develop integrated assessment instrument and to verify instruments’ validity such as content validity and construct validity. This instrument development used test development model by McIntire. Development process data was acquired based on development test step. Initial product was observed by three peer reviewer and six expert judgments (two subject matter experts, two evaluation experts and two chemistry teachers) to acquire content validity. This research involved 376 first grade students of two Senior High Schools in Bantul Regency to acquire construct validity. Content validity was analyzed used Aiken’s formula. The verifying of construct validity was analyzed by exploratory factor analysis using SPSS ver 16.0. The result show that all co...

Opportunity integrated assessment facilitating critical thinking and science process skills measurement on acid base matter

Recognizing the importance of the development of critical thinking and science process skills, the instrument should give attention to the characteristics of chemistry. Therefore, constructing an accurate instrument for measuring those skills is important. However, the integrated instrument assessment is limited in number. The purpose of this study is to validate an integrated assessment instrument for measuring students’ critical thinking and science process skills on acid base matter. The development model of the test instrument adapted McIntire model. The sample consisted of 392 second grade high school students in the academic year of 2015/2016 in Yogyakarta. Exploratory Factor Analysis (EFA) was conducted to explore construct validity, whereas content validity was substantiated by Aiken’s formula. The result shows that the KMO test is 0.714 which indicates sufficient items for each factor and the Bartlett test is significant (a significance value of less than 0.05). Furthermore, content validity coef...

Aktivitas Antibakteri Kain Poliester dengan Penambahan Heksadesiltrimetoksisilan (HDTMS) terhadap Staphylococcus aureus ATCC 25924

This research aims to determine the antibacterial activity of polyester which was deposited by hexadecyltrimethoxysilane (HDTMS) against bacteria Staphylococcus aureus ATCC 25924. The HDTMS solution was made by dissolving the HDTMS compound in 4% ethanol. The HDTMS solution was then deposited on a polyester fabric sample. The antibacterial activity test of P-HDTMS was conducted with diffusion method by measuring the diameter of clear zone around the sample. The results of this research showed that HDTMS compound has been deposited on polyester fabrics. The clear zone test results showed that P-HDTMS has diameter of clear zone of 9.25 mm at incubation time of 60 hours. Thus, P-HDTMS has an antibacterial activity against Staphylococcus aureus ATCC 25924.

Bacterial Cellulose From Rice Waste Water With Addition Chitosan, Glycerol, And Silver Nanoparticle

This study aimed to prepare silver nanoparticles chemically, deposite silver nanoparticles on bacterial cellulose-chitosan-glycerol composite based rice waste water, as well as test the antibacterial activity of bacterial cellulose and its composite. Preparation of silver nanoparticles was conducted by chemical reduction of silver nitrate solution, as well as trisodium citrate as the reductor. Bacterial cellulose from rice waste water is fermented by the bacteria Acetobacter xylinum for 7 days. The dried bacterial cellulose was composited with chitosan and glycerol by immersion method on 2% of chitosan solution and 0.5% of glycerol solution. UV-Vis spectroscopy is used to determine the formation of silver nanoparticles and Particle Size Analyzer to test the size and particle size distribution. Characterization was conducted to bacterial cellulose and its composite included functional groups by FTIR, the mechanical properties by Tensile Tester, crystallinity by XRD, surface photograph by SEM, and antibacterial test against S. aureus and E. coli by the shake flask turbidimetry method. Silver nanoparticle characterization indicated that silver nanoparticles are formed at a wavelength of 421.80 nm, yellow, diameter particle size of 61.8 nm. SEM images showed that the surface of bacterial cellulose had deposited silver nanoparticles and antibacterial test showed an inhibitory effect of bacterial cellulose, bacterial cellulose-chitosan composite, and bacterial cellulose-chitosan-glycerol composite which are deposited silver nanoparticles against the growth of S. aureus and E. coli bacteria.

Pengaruh Penambahan 1,4-Butanadiol dan Polietilen Glikol (PEG) 1000 terhadap Kemudahan Biodegradasi Bioplastik dari Biji Nangka (Artocarpus heterophyllus)

The influences of plasticizer on the biodegradability of bioplastic film synthesized from starch obtained from jackfruit seeds with a help of Acetobacter xylinum were investigated. In this study, 1,4-butanediol and polyethylene glycol (PEG) 1000 were used as plasticizer. The biodegradation behavior of the resulted bioplastic films was characterized by calculating changes in their mass loss and rate of mass loss. The Fourier Transform Infrared (FTIR) spectroscopy was also conducted to analyze theirfunctional group. The results shows that all the bioplastic films were well biodegradated, where PEG 1000 with concentration of 0,5% and 1,0% can successfully improve the biodegradability of bioplasticfilm. Meanwhile, the used of 1,4-butanediol with concentration of 0,5% and 1,0% can increase and decrease the biodegradability of sample, respectively.