Muhammad Bilal Khan Niazi

Preparation of antibacterial cotton fabric using chitosan-silver nanoparticles

The aim of this study was to prepare antibacterial cotton fabric using chitosan-silver nanoparticles (CS-AgNPs). CS-AgNPs were used as finishing agent for 100 % pure cotton fabric. AgNPs were prepared by Turkevich method. CSAgNPs were synthesized by mixing chitosan solution with silver nanoparticles. Fourier transform infrared (FTIR) spectrometer technique supported the formulation of CS-AgNPs. Cs-AgNPs crystalline peaks were in perfect agreement with JCPDS card no. 89-3722. Two gram negative bacteria Escherichia coli, Pseudomonas aeruginosa and two gram positive bacteria Bacillus cereus, Staphylococcus aureus were used to test the bacterial efficacy of synthesized AgNPs and CSAgNPs. Scanning electron micrograph of cotton fabric revealed the presence of CS-AgNPs on the surface of cotton fabric. The presence of small amount of silver nanoparticles in the composite was enough to enhance antibacterial activity significantly compared to pure chitosan.

Understanding the role of plasticisers in spray-dried starch

Amorphous thermoplastic starch (TPS) films were produced by compression moulding of solution spray-dried TPS powder and by direct solution casting. Oxidised potato starch was used as a feedstock for production of plasticised formulations containing glycerol or urea, or their combinations with maltodextrin (DE=19.1) as processing aid. The crystallinity index of freshly moulded films made from solution spray-dried powder was significantly lower than that for casted films. FTIR analysis showed that starch interacted in hydrogen bond formation with glycerol and urea plasticisers, reducing the glass transition temperature to 136 °C and 106 °C, respectively. Formulations containing maltodextrin did not show a Tg. Glycerol-plasticised and co-plasticised films immediately started to retrogradate in the presence of moisture, while urea based systems only showed slow recrystallization at the highest moisture exposure. In line with retrogradation behaviour, urea plasticised and co-plasticised films exhibited a more ductile behaviour, whereas glycerol based ones showed more brittle behaviour.

Preparation and characterization of PVA/nanocellulose/Ag nanocomposite films for antimicrobial food packaging

Antimicrobial packaging is an area of emerging interest and is rapidly expanding with application of nanotechnology. The present work investigates the effect of nanocellulose (NC) and Ag NPs on the physical, mechanical and thermal properties of PVA nanocomposite films. The tensile strength of PVA was improved from 5.52 ± 0.27 MPa to 12.32 ± 0.61 MPa when filled with 8 wt% of NC. Nanocomposite films exhibited strong antibacterial activity against both Staphylococcus aureus (MRSA) and Escherichia coli (DH5-alpha). The maximum inhibition zone at 0.5 g Ag NPs with 12 wt% NC against DH5-alpha was 14 ± 0.70 mm. While, the maximum inhibition zone at 0.3 g Ag NPs for 16 wt% NC was 13.6 ± 0.68 mm against MRSA. Moreover, nanocomposites films have no cytotoxicity effect on HepG2 and cell viability was more than 90%. Based on mechanical properties and antibacterial potential of the developed nanocomposite films, it can be envisaged to use these films for packaging applications.

Effect of concentration of Surfactant on the Exfoliation of Graphite to Graphene in Aqueous Media

Graphite was exfoliated to graphene by tip sonic using sodium cholate as a surfactant in the presence of Millipore water as a medium. The use of water as a solvent for exfoliation purposes is very important due to its environmentally friendly nature and almost no cost, contrary to organic media. Two different concentration ratios of surfactants are used in the present work. As a result, graphene dispersions with two different concentrations of 5 mg/ml and about 7 mg/ml respectively were obtained in aqueous media. It was observed that the optimum concentration of surfactant has an effective role in the exfoliation of graphite to graphene. Concentrations of graphene dispersions were studied through UV spectroscopy, while Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to study the quality of the exfoliated graphene flakes.

Effects of selected size of graphene nanosheets on the mechanical properties of polyacrylonitrile polymer

Mechanical properties of polyacrylonitrile (PAN) polymer can be significantly improved by the incorporation of graphene nano-sheets of different sizes. The graphite was exfoliated to graphene using sonic tip in the presence of N-methyl pyrrolidinone (NMP) as a solvent. Exfoliated graphene was separated from unexfoliated graphitic crystallites using selected speed (rpm) of centrifuge for specific time. The exfoliated graphene nano-sheets were classified into two different groups on the basis of flake size, (i.e. 1 μm and 3.5 μm). Then these graphene sheets were incorporated into PAN to study the effects of their flake size on mechanical properties. Different mechanical properties such as Young’s modulus, ultimate tensile strength (UTS) and elongation at break (dL at break) were studied. Young’s modulus and UTS improved more than 45 % and 25 %, for 3.5 μm graphene flake size respectively. While more than 40 % and 21 %, improvement in modulus and UTS for 1 μm graphene sheet were observed respectively.

Influence of Amphiphilic Plasticizer on Properties of Thermoplastic Starch Films

ABSTRACT Thermoplastic starch powders and films were produced by using different combinations of hydrophilic (malic acid and water) and amphiphilic (isoleucine and butyric acid) plasticizers. Spray drying was used to produce thermoplastic starch powder followed by compression molding for the development of films. In all plasticized formulations, the rate of retrogradation was inhibited until the seventh day. The crystallinity and moisture sensitivity of the freshly prepared films were dependent on amphiphilic plasticizer quantity in formulation. Fourier transform infrared spectroscopy and thermogravimetric analysis showed an effective interaction of starch with isoleucine. Isoleucine formulated films showed the highest tensile strength, whereas malic acid-rich films showed better strain values. GRAPHICAL ABSTRACT

The effect of large area graphene oxide (LAGO) nanosheets on the mechanical properties of polyvinyl alcohol

Abstract Large area graphene oxide sheets were synthesized, dispersed in water and used as nanofiller for mechanical improvement in terms of Young’s modulus and ultimate tensile strength (UTS) of polyvinyl alcohol (PVA) at low loading. The molecular level dispersion and interfacial interactions between the graphene oxides and polymeric matrix PVA were the real challenges. An excellent improvement in mechanical properties at 0.35 wt% loading was observed. Modulus improved from 1.58 GPa to 2.72 GPa (~71% improvement), UTS improved from 120 MPa to 197 MPa (~65% improvement), and in spite of these improvements, interestingly, there was no fall in elongation at break at this loading.

Effect of drying parameters on the physical, morphological and thermal properties of spray-dried inulin

Abstract This study focuses on the thermal, morphological and physical properties of spray-dried chicory root inulin using a thermogravimetric analyzer, environmental scanning electron microscopy, X-ray diffractogram and modulated differential scanning calorimetry. Different spray-drying conditions were investigated by varying inlet temperature, outlet temperature and aspirator speed. The starting material was semicrystalline. A feed temperature of 95°C was employed, which produced a completely transparent solution for spray drying. At that particular temperature, the powder samples obtained were entirely amorphous and morphology resembled each other except for higher solid content. The low glass transition temperature (Tg) (106.83°C) was evident by treating low-molecular-weight samples, whereas high-molecular-weight samples exhibited high Tg (125.81°C). The semicrystalline samples due to the high concentration and milky dispersion exhibited high decomposition temperature. The feed temperature, molecular weight and concentration of the samples tend to have a significant effect on the properties of spray-dried inulin.

Synthesis and characterization of zinc-coated urea fertilizer

ABSTRACT The research was focused on the synthesis and characterization of zinc (Zn)-coated urea fertilizer. Zinc oxide (ZnO) particles were coated on urea granules through two different coating techniques, i.e., slurry coating and wet coating, and the release rate of the coated Zn was measured up to 24 hours. Slurry coating technique showed better Zn release rate and morphology of coated urea granules as compared with wet coating technique using different binders, i.e., water, molasses, paraffin oil, and the combined mixture of honey bee wax and gum arabica. Urea granules synthesized through wet coating technique have a low amount of Zn as compared with slurry-coated urea granules. Urea granules coated through slurry coating technique and molasses, paraffin oil, and water (MPW) as a binder were the best in term of coating efficiency, uniform size distribution of ZnO-coated particles, granules morphology, and release rate of Zn from coated formulations.

Influence of carboxylic acids on mechanical properties of thermoplastic starch by spray drying

Biodegradable packaging is gaining much attention in food industry as the awareness on sustainability has increased. Thermoplastic starch is a possible alternative. This study evaluated the influence of malic acid (MA) and citric acid (CA), used as a plasticizer, on the mechanical properties of thermoplastic starch (TPS) obtained by spray drying. TPS powder was produced from solution spray drying. This powder was further compression molded to prepare TPS dog-bone test samples. X-ray Diffraction (XRD) results showed that both the spray dried TPS powder and dog-bone test samples were amorphous in nature irrespective of the amount of plasticizer added. Scanning electron microscope (SEM) was used to examine the morphology of solution spray dried TPS powder. No noticeable difference was observed in the morphology. Particles were spherical in shape with homogenous surface. The FT-IR analysis indicated the interaction of plasticizers with starch chains by hydrogen bonding. During TGA analysis, apart from moisture loss at 100 °C, samples were thermally stable up to 170 °C. Mechanical testing of TPS dog-bone revealed that sample containing malic acid as plasticizer exhibited a more elastic behavior as compared to citric acid plasticized formulations. It was revealed that the tensile strength of TPS dog-bone samples was inversely proportional to the quantity of plasticizer used.