Norhayati Abu Bakar

The detection of pesticides in water using ZnCdSe quantum dot films

This paper reports an attempt to develop a sensor system for detecting pesticides based on the effect of an analyte on the photoluminescence (PL) intensity of ZnCdSe quantum dot (QD) films. The ZnCdSe QDs were synthesized using a wet-chemical process. The sensor system comprises an excitation light source made of a laser diode, a dual arm fibre optic probe, a spectrometer and a sensor chamber. The QD films were deposited by dropping QD solution onto the probe surface and drying them at ambient temperature. The pesticides used in this study were Dipel, Siven 85% WP and Water-Dispersible Granules WG insecticides. The detection of pesticides was done by comparing the photoluminescence (PL) spectra of the films dipped in the deionized water and in pesticide solutions by varying the concentration of the pesticide solutions from 2.5 to 2500 μg l−1. It was observed that the PL intensity of the films was quenched by the presence of the pesticide molecules. The quenching degree increased with the concentration of the pesticide solutions. There is a linear relationship between the pesticide solution concentrations and the QD film sensor sensitivities. The sensitivity of the sensor system depended on the type of pesticides successively from the highest to lowest sensitivity in the order Siven 85% WP, Dipel and Water-Dispersible Granules WG. The QD films could be used as fluorescence sensors to detect water that is contaminated by pesticides.

Synthesis of CdSe quantum dots: Effect of surfactant on the photoluminescence property

This paper reports the synthesis of highly lumimescence CdSe quantum dots via wet-chemical process and the study of the surfactant concentration effect on the improvement of the photoluminescence characteristic. Here, we also discussed in detail the quantum dots synthesis procedure and the mechanism for the improvement of the luminescence characteristic of CdSe quantum dots under a different surfactant concentration.

Localized Surface Plasmon Resonance Sensor Using Gold Nanoparticles for Detection of Bisphenol A

This paper reports an attempt to develop an optical sensor system to detect Bisphenol A (BPA) in water based on plasmonic property of Gold Nanoparticles (GNPs). Spherical GNPs of the average size of ca. 31±7 nm were grown on quartz substrate using seed mediated growth. An optical sensor system was setup, comprises a tungsten lamp light source, a duplex fiber optic probe, a spectrometer and a sensor chamber. Detection of BPA was done by comparing the Localized Surface Plasmon Resonance (LSPR) spectra of the GNPs film immersed in the deionised water and in BPA solutions by varying the concentration of BPA solutions from 58 mg/L to 0.003 ng/L. The LSPR spectra of GNPs sample were very sensitive to the presence of BPA where the shifted of their peaks position and the changed of their intensities are increases with the concentration of the BPA solutions.

Highly red luminescence properties from ternary ZnCdTe quantum dots

This paper reports the synthesis of ternary ZnCdTe quantum dots (QD) system with highly luminescent in the red region. The ternary QD system was prepared by quick injection of trioctylphosphine telluride (TOPTe) into a reactor that contains a hot mixed cadmium and zinc precursors, trioctylphosphine oxide and oleic acid at temperature of as low as 300°C. After the injection of TOPTe, the reaction was left undisturbed for a period of time to facilitate the growth of QDs and then quenched the reaction at a certain period of time. Photoluminescence analysis found that the ZnCdTe QDs exhibited highly luminescent properties with the quantum yield was calculated as high as ca. 60%. The emission wavelength was found to be in the range of 640 to 675 nm. It was also found that the QDs showed a relatively narrow spectral width, namely ca. 28 nm, reflecting a narrow quantum dots size distribution. Owing to their interesting photoluminescence properties, the ternary ZnCdTe QDs should find an extensive used in light-emitting diode, solar cell, laser and biolabelling.

Detection of creatinine on triangular silver nanoplates surface using surface-enhanced Raman scattering sensor

In this study, we attempt to detect various concentrations of creatinine molecules on the triangular silver nanoplate films surface using a self-build surface-enhanced Raman scattering (SERS) sensor. The SERS sensor system consists of a butterfly laser diode, Inphotonic Raman fibre, Ocean Optics spectrophotometer and sensor chamber to contain the creatinine sample. Triangular-shaped silver nanoplate films were prepared on quartz surface by self-assembly technique. Detection of creatinine was done by irradiating creatinine on the triangular nanoplates surface using 785 nm of the laser light. It was found that the enhancement of the creatinine Raman peaks is linear with the creatinine concentrations. The lowest creatinine concentration that was detected by this SERS sensor is 0.005 M.

Direct deposition of silver nanoplates on quartz surface by sequence pre-treatment hydroxylation and silanisation

Graphical abstract

Detection of fungicide in water by ZnCdSe quantum dots thin film

Quantum dots (QDs) thin film sensor was developed to detect fungicide in water by optical sensing system. The ZnCdSe QDs was synthesized using a wet-chemical process to apply in this fluorescent sensor. A sensor system was setup, comprises an excitation light source made of laser diode, a dual arm fiber optic probe, a spectrometer and sensor chamber. The QDs thin film was deposited by dropping QDs solution onto the probe surface and let them dried in the ambient temperature. The detection of fungicide was done by comparing the photoluminescence (PL) spectra of the thin film dipped in the deionised water and in fungicide solutions. The PL spectrum of the thin film was quenched by the presence fungicide solutions where the drop of PL peak intensity is depended on the concentration of fungicide solutions.

Fluorescence Properties of Hybrid CdTe Quantum Dots‐Porphyrins Thin Films in Organic Vapors

This paper reports a study on the fluorescence properties of thin films utilizing quantum dots (QDs) of cadmium telluride (CdTe) hybridized with porphyrins (tetraphenyl porphine cobalt (II)) (CoTTP) thin films under exposure of various gases. The high yellow luminescence QDs were synthesized using a wet‐chemical process at moderate temperature (350° C). CdTe QDs, CoTTP porphyrin and CdTe‐CoTTP hybrid thin films were deposited onto the surface of fiber optic probe and dried in the ambient temperature. The quantum dots showed their ability to activate photo luminescence property of porphyrin molecules in the hybrid thin film of quantum dots‐porphyrin. The fluorescence properties of thin films were studied by observing the change of photoluminescence (PL) spectra of thin films in nitrogen (N2) and after exposing in various organic gases. The PL quenching effect was occurred for both PL peaks for QDs and CoTTP in the hybrid thin film.

Fluorescence gas sensor using CdTe quantum dots film to detect volatile organic compounds

This paper reports a study on fluorescence sensing properties of cadmium telluride (CdTe) quantum dots (QDs) film under exposure of volatile organic compounds; ethanol, 2-propanol and acetone. The high luminescence QDs were synthesized using a wet-chemical process. CdTe QDs film was deposited onto the surface of fiber optic probe by drop-casting method. The fluorescence properties of the film were studied by observing the change of photoluminescence (PL) spectra of the films in nitrogen (N2) and after exposing in organic vapors. It was observed that the PL of the film was quenched by the presence of the organic vapors. The amount and the rate of quenching are depended on the kind of the organic vapors