Sharif Digital Repository

There is a growing interest in developing high-performance sensors monitoring organophosphate pesticides, primarily due to their broad usage and harmful effects on mammals. In the present study, a colorimetric sensor array consisting of citrate-capped 13 nm gold nanoparticles (AuNPs) has been proposed for the detection and discrimination of several organophosphate pesticides (OPs). The aggregation-induced spectral changes of AuNPs upon OP addition has been analyzed with pattern recognition techniques, including hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA). In addition, the proposed sensor array has the capability to identify individual OPs or mixtures of them in... 

Most array-based sensing platforms, to date, utilize static response patterns for discrimination of a wide variety of analytes, but only a few studies have focused on the important task of quantitatively resolving structural isomers, which are nowadays important because of their broad usage in medicines and industries. A possible way of accomplishing this feat is to combine kinetic (rather than static) sensor response profiles with the chemical tongue strategy to allow the development of array-based sensors for isomeric discrimination. Here, by adding the time dimension, a simple and novel gold nanorod (AuNR)-based chrono-colorimetric sensor array is proposed for chemical discrimination... 

The widespread use of pesticides in pest management has boosted the demands for developing highly sensitive probes for on-site monitoring. Herein we presented a sensitive enzyme-free ratiometric probe for determination of methyl parathion (MP), as an organophosphate pesticide using TGA-capped CdTe QDs and carbon dots (CDs). Unlike previous methods in which hydrolysis product of MP is instrumental in the response of the sensors, here, self-assembly of cetyltrimethylammonium bromide (CTAB) on the surface of non-modified yellow-emissive CdTe QDs facilitates the quenching of CTAB-QDs upon addition of MP while the fluorescence intensity of CDs remains constant. Using a smartphone, the ratiometric... 

As in many other methods that have integrated nanoparticles (NPs), the chemical nose/tongue strategy has also progressed greatly since the entrance of NPs into this field. The fascinating tunable physicochemical properties of NPs have made them powerful candidates for array-based sensing platforms and have enabled the development of real-time, sensitive and portable systems that are able to target complex mixtures of analytes. In particular, the unique optical properties of NPs have a key role in providing promising array-based sensing approaches. This review will describe the main aspects and processes of most common NP-based optical sensor arrays. The fundamental steps in the design of a... 

We report herein the development of a highly sensitive colorimetric method for detection of d-Penicillamine using citrate-capped gold nanoparticles (AuNPs). This assay relies upon the distance-dependent of gold nanoparticles surface plasmon resonance band of gold nanoparticles. By replacing the thiol-containing chelator drug, d-Penicillamine, with citrate on the gold nanoparticles surface, a new peak appearing at a longer wavelength intensifies and shifts further to the red from the original peak position due to aggregation of gold nanoparticles which depends on ionic strength, gold nanoparticles and d-Penicillamine concentration. During this process, the plasmon band at 521 nm decreases... 

In this paper, we present a simple platform for colorimetric detection of glutathione using gold nanorods (AR ∼ 6.5 ± 0.2) as a plasmonic sensor. The functional mechanism of the sensor is based on shifts of longitudinal plasmon resonance during selective transverse overgrowth induced by preferential binding of glutathione at the nanorod tips. Under the optimum conditions, a calibration curve showed two linear regimes at the range of 50 nM to 20 μM of glutathione with a detection limit as low as 40 nM. The nanosensor maintains relatively high selectivity for determination of glutathione in the presence of several other amino acids. However, cysteine at similar concentration levels strongly... 

A reliable, simple, and sensitive fluorescence method was developed for the determination of methyl parathion (MP) in rice using MoS2 quantum dots (QDs). Rapid hydrolysis of MP under alkaline conditions, and thus the formation of p-nitrophenol (p-NP) can be used for MP detection. The functional mechanism of the nanoprobe relies on p-nitrophenol-induced photoluminescence quenching of MoS2 QDs. The high probability of resonance energy transfer (RET) stems from the spectral overlap of MoS2 QD emission spectra and the absorption spectra of p-NP. The high value of the Stern-Volmer constant (KSV = 3.73 × 104 M-1) suggests the efficient quenching of MoS2 QDs by MP in the course of the ET process.... 

The pharmaceutical industry is facing enormous challenges due to high drug attribution rates. For the past decades, novel methods have been developed for safety and efficacy testing, as well as for improving early development stages. In vitro screening methods for drug-receptor binding are considered to be good alternatives for decreasing costs in the identification of drug candidates. However, these methods require lengthy and troublesome labeling steps. Biosensors hold great promise due to the fact that label-free detection schemes can be designed in an easy and low-cost manner. In this paper, for the first time in the literature, we aimed to compare the potential of label-free optical and... 

Discrimination of chiral targets is generally achieved with chiral nanomaterials. However, the limited number of intrinsic chiral nanostructures as well as their complex synthesis procedure has led to the production of chirality-induced nanomaterials as alternatives. Chirality can be induced in nanomaterials by either chirality transfer or the formation of chiral assemblies. Using the latter approach, in this work, we have provided chiral supramolecular assemblies of CdTe quantum dots (QDs) from achiral starting materials. CTAB-QD assemblies showed chiroptical activities, and their orange emission in combination with the blue emission of carbon dots was utilized as a ratiometric chiral... 

Discrimination of chiral targets is generally achieved with chiral nanomaterials. However, the limited number of intrinsic chiral nanostructures as well as their complex synthesis procedure has led to the production of chirality-induced nanomaterials as alternatives. Chirality can be induced in nanomaterials by either chirality transfer or the formation of chiral assemblies. Using the latter approach, in this work, we have provided chiral supramolecular assemblies of CdTe quantum dots (QDs) from achiral starting materials. CTAB-QD assemblies showed chiroptical activities, and their orange emission in combination with the blue emission of carbon dots was utilized as a ratiometric chiral... 

The unique optical properties of plasmonic gold (Au) and silver Ag) nanoparticles (NPs) due to localized surface plasmon resonance (LSPR), surface modifications of Au and Ag NPs through non-covalent/covalent conjugations, and their applications in colorimetric detection of various ionic and neutral analytes are discussed in this chapter. The chapter begin with the basics of LSPR phenomenon, and then the effects like surrounding medium, composition, size, shape, structural configuration and interparticle coupling that influenced the LSPR of Au and Ag NPs are discussed. The different design principles for colorimetric assays using plasmonic Au and Ag NPs, such as analyte-induced aggregation... 

In the ratiometric fluorescent (RF) strategy, the selection of fluorophores and their respective ratios helps to create visual quantitative detection of target analytes. This study presents a framework for optimizing ratiometric probes, employing both two-component and three-component RF designs. For this purpose, in a two-component ratiometric nanoprobe designed for detecting methyl parathion (MP), an organophosphate pesticide, yellow-emissive thioglycolic acid-capped CdTe quantum dots (Y-QDs) (analyte-responsive), and blue-emissive carbon dots (CDs) (internal reference) were utilized. Mathematical polynomial equations modeled the emission profiles of CDs and Y-QDs in the absence of MP, as... 

Signal generation techniques for visual detection of analytes have received a great deal of attention in various sensing fields. These approaches are considered to be advantageous when instrumentation cannot be employed, such as for on-site assays, point-of-care tests, and he althcare diagnostics in resource-constrained areas. Amongst various visual detection approaches explored for non-invasive quantitative measurements, ratiometric fluorescence sensing has received particular attention as a potential method to overcome the limitations of intensity-based probes. This technique relies on changes in the intensity of two or more emission bands (induced by an analyte), resulting in an effective... 

In the present work, high-energy mechanical alloying (MA) was employed to synthesize a nanostructured magnesium-based composite for hydrogen storage. The preparation of the composite material with composition of MgH2–5at% (TiCr1.2Fe0.6) was performed by co-milling of commercial available MgH2 powder with the body-centered cubic (bcc) alloy either in the form of Ti–Cr–Fe powder mixture with the proper mass fraction (sample A) or prealloyed TiCr1.2Fe0.6 powder (sample B). The prealloyed powder with an average crystallite size of 14nm and particle size of 384nm was prepared by the mechanical alloying process. It is shown that the addition of the Ti-based bcc alloy to magnesium hydride yields a... 

Chiral discrimination has always been a hot topic in chemical, food and pharmaceutical industries, especially when dealing with chiral drugs. Enantiomeric recognition not only leads to better understanding of the mechanism of molecular recognition in biological systems, but may further assist in developing useful molecular devices in biochemical and pharmaceutical studies. By emerging nanotechnology and exploiting nanomaterials in sensing applications, a great deal of attention has been given to the design of optical nanoprobes that are able to discriminate enantiomers of chiral analytes. This review explains how engineering nanoparticles (NPs) with desired physicochemical properties allows...