Progress in the design of portable colorimetric chemical sensing devices.

The need for precise determination of heavy metals, anions, biomolecules, pesticides, drugs, and other substances is vital across clinical, environmental, and food safety domains. Recent years have seen significant progress in portable colorimetric chemical sensing devices, revolutionizing on-the-spot analysis. This review offers a comprehensive overview of these advancements, covering handheld colorimetry, RGB-based colorimetry, paper-based colorimetry, and wearable colorimetry devices. It explores the underlying principles, functional materials (chromophoric reagents/dyes and nanoparticles), detection mechanisms, and their applications in environmental monitoring, clinical care, and food safety. Noble metal nanoparticles (NPs) have arisen as promising substitutes in the realm of sensing materials. They display notable advantages, including heightened sensitivity, the ability to fine-tune their plasmonic characteristics for improved selectivity, and the capacity to induce visible color changes, and simplifying detection. Integration of NPs fabricated paper device with smartphones and wearables facilitates reagent-free, cost-effective, and portable colorimetric sensing, enabling real-time analysis and remote monitoring.

Inkjet-printed flexible graphene paper electrode for the electrochemical determination of mercury.

Here, we report an inkjet-printed graphene paper electrode (IP-GPE) for the electrochemical analysis of mercuric ions (Hg(ii)) in industrial wastewater samples. Graphene (Gr) fabricated on a paper substrate was prepared by a facile solution-phase exfoliation method in which ethyl cellulose (EC) behaves as a stabilizing agent. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to determine the shape and multiple layers of Gr. The crystalline structure and ordered lattice carbon of Gr were confirmed by X-ray diffraction (XRD) and Raman spectroscopy. The nano-ink of Gr-EC was fabricated on the paper substance via an inkjet printer (HP-1112) and IP-GPE was exploited as a working electrode in linear sweep voltammetry (LSV) and cyclic voltammetry (CV) for the electrochemical detection of Hg(ii). The electrochemical detection is found to be diffusion-controlled illustrated by obtaining a correlation coefficient of 0.95 in CV. The present method exhibits a better linear range of 2-100 µM with a limit of detection (LOD) of 0.862 µM for the determination of Hg(ii). The application of IP-GPE in electrochemical analysis shows a user-friendly, facile, and economical method for the quantitative determination of Hg(ii) in municipal wastewater samples.

A portable smartphone-assisted digital image fluorimetry for analysis of methiocarb pesticide in vegetables: Nitrogen-doped carbon quantum dots as a sensing probe.

The increasing use of pesticides in the agriculture fields strengthen the crop production to meet the needs of increasing population. The residues in water and food materials cause several health hazards. Herein, nitrogen-doped carbon quantum dot (N-CQDs) is designed for determination of methiocarb pesticide in vegetables by fluorescent paper sensor and compared the results with fluorimetry. The fluorescent paper-based detection is performed by recording the change in fluorescence of N-CQDs with introduction of methiocarb using smartphone and ImageJ software. Good linear range was acquired for analysis of methiocarb from 10 to 1000 µgL-1 with a low detection limit (LOD) of 3.5 µgL-1 in fluorimetry; and 700-10,000 µgL-1 with a LOD of 500 µgL-1 in fluorescent paper sensor. A better recovery from 92.0 to 95.4% illustrating the selectivity of both methods for analysis of methiocarb in vegetables. Thus, the advantage of using N-CQDs as a fluorescent sensor for analysis of methiocarb in vegetables is instrument free, portable and user-friendly.

Chemical fractionation of particulate-bound metal(loid)s to evaluate their bioavailability, sources and associated cancer risk in India.

Eleven potentially toxic metal(loid)s (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), proven source markers of mineral based coal-fired industrial emissions and vehicular exhausts, were analysed using the four steps sequential extraction method to evaluate metal(loid)s concentration, in total and fractions of bioavailable and non-bioavailable for fine (PM2.5) and coarse (PM10-2.5) particulate modes. A total of 26-day-wise samples with three replications (total number of samples = 78) were collected in January-December 2019 for each PM10 and PM2.5 at an urban-residential site in India. In both the coarse and fine particulate modes, Pb and Cr have respectively shown the highest and lowest total concentrations of the measured metal(loid)s, indicating the presence of coal-fired power plants and heavy vehicular activities near to study area. In addition, Mn has shown highest bioavailable fraction for both coarse and fine particulate modes. More than 50 % of metal(loid)s concentration, in total to a bioavailable fraction (BAF) were observed in case of As, Cd, Cr, Co, Mn, Ni, and Pb of PM2.5. Mn and Zn have shown similar behaviour in the case of coarse particulate mode. Source apportionment of metal(loid)s bioavailable fractions using positive matrix factorization (PMF 5.0) has found three significant sources: crustal and natural dust (30.04 and 39 %), road traffic (49.57 and 20 %), and industrial emission (20.39 and 41 %) for coarse and fine particulate mode, respectively. Cancer risk through the inhalation pathway was high in total concentration but lower in BAF concentration in both age groups (children and adults).

Smartphone-integrated printed-paper sensor designed for on-site determination of dimethoate pesticide in food samples.

Herein, a user-friendly and portable smartphone-integrated printed-paper sensor was designed with Cu@Ag nanoparticles (NPs) for on-site monitoring of dimethoate pesticide in food samples, and the results obtained are compared with those obtained by UV-vis spectrophotometry. The working principle for identification of dimethoate pesticide is the change of yellow color NPs to reddish-yellow with associated bathochromic shift of absorption peak when pesticide introduced onto the fabricated paper or glass vial containing the NPs. A smartphone-color detector App and colorimetry were used for quantitative analysis of dimethoate in food samples. Linearity range for analysis of dimethoate using paper sensor and colorimetry were 100-2000 µgL-1 and 50-2500 µgL-1 with detection limit of 30 and 16 µgL-1, respectively. The advantages of using smartphone-integrated paper devices are rapid, instrument-free detection and economic in terms of consumption of lower amounts of NPs solution compared to other NPs-based colorimetric methods.

Citrate functionalized gold nanoparticles assisted micro extraction of L-cysteine in milk and water samples using Fourier transform infrared spectroscopy.

This paper describes the sensing application of citrate functionalized gold nanoparticles (AuNPs) employing for the determination of L-cysteine in food and water samples. It is established with diffuse reflectance Fourier transform infrared (DRS-FTIR) spectroscopic analysis. The disappearance of the thiol (-SH) band in the FTIR spectra and the shift in the peaks of the amino group (NH3+) and carboxylate group (-COO-) indicated the Au-S interaction and the aggregation of the NPs. The signal intensity of L-cysteine was enhanced due to hot-spots formed by the aggregation of AuNPs producing the effective absorption of electromagnetic radiation in the IR region for molecular vibration. The relationship between AuNPs and L-cysteine was theoretically investigated by the Density Function Theory (DFT) based on LANL2DZ with the aid of the Gaussian 09 (C.01) software. Interaction between AuNPs and L-cysteine molecules resulted to a shift to higher wavelengths in the plasmon bands, further verified by transmission electron microscopes (TEM), which have indicated random aggregated particles. Further dynamic light scattering (DLS) measurements showed a relatively high degree of polydispersity confirming the aggregation of the particles. Under optimized conditions, the calibration curve showed a good linearity range from 20 to 150 µg mL-1 with a correlation coefficient (R2) 0.990. The limit of detection and quantification were 1.04 and 3.44 µg mL-1, respectively by DRS-FTIR. This modified AuNPs sample was used successfully in milk and water samples with adequate results to determine L-cysteine.

Inkjet-printed paper-based colorimetric sensor coupled with smartphone for determination of mercury (Hg2+).

We report an inkjet-printed paper based colorimetric sensor with silver nanoparticles (AgNPs) using smartphone and color detector App for on-site determination of mercuric ion (Hg2+) from environmental water samples. The AgNPs printed on Whatman filter paper (No. 1) is employed for detection of Hg2+ which is reliant on the color change of NPs from yellow to discoloration depending on the concentration of target analyte in sample solution. The quantitative determination was performed by calculating the signal intensity of AgNPs on printed paper substrate after the introduction of Hg2+ using smartphone and RGB color detector. The mechanism for detection of Hg2+ on paper substrate is verified using UV-Vis spectrophotometry (UV-Vis), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS) and basic chemical assays. The linear range acquired for paper based colorimetric detection in the range of 40-1200 µgL-1 with limit of detection of 10 µgL-1. The results obtained using an inkjet-printed paper-based chemical sensor combined with a smartphone is validated with data of inductively coupled plasma-atomic emission spectroscopy (ICP-AES) measurement. The advantages of paper based detection are simple, rapid, economic and can be applied at the sample sources for determination of Hg2+.

Colorimetric determination of L-cysteine in milk samples with surface functionalized silver nanoparticles.

A simple, selective and sensitive method is proposed for determination of cysteine (Cys) in milk samples using ionic liquid functionalized silver nanoparticles (ILs-AgNPs) as a colorimetric probe. ILs-AgNPs was synthesized by simple reduction method using silver nitrate as a precursor and sodium borohydride as a reducing agent and functionalized with ILs to prevent particles from self-aggregation. The sensing mechanism has been dependent on the color change of ILs-AgNPs and red shift of absorption band from 395 nm to 560 nm in the visible region, which is found proportional to the concentration of target analyte in sample. ILs-AgNPs was characterized in absence and presence of Cys by UV-vis, Fourier transform-infrared (FTIR) spectroscopy, transmission electron microscope (TEM) and dynamic light scattering (DLS). The linear range was acquired in the range of 0-100 ng mL-1, with correlation coefficient (R2) of 0.996 and limit of detection (LOD) of 4.0 nM. The binding mechanism and interactions between Cys and ILs-AgNPs was confirmed by calculating the binding constant and thermodynamic parameters such as enthalpy (∆H), entropy (∆S) and Gibb's free energy (∆G). The use of ILs-AgNPs exhibited high colorimetric selectivity for Cys in milk samples in presence of other amino acids. This proposed strategy possessed the advantages of simplicity and selectivity, hence is applied for analysis of Cys in milk samples.

A simple and cost-effective paper-based and colorimetric dual-mode detection of arsenic(iii) and lead(ii) based on glucose-functionalized gold nanoparticles.

We report a simple and cost-effective paper-based and colorimetric dual-mode detection of As(iii) and Pb(ii) based on glucose-functionalized gold nanoparticles under optimized conditions. The paper-based detection of As(iii) and Pb(ii) is based on the change in the signal intensity of AuNPs/Glu fabricated on a paper substrate after the deposition of the analyte using a smartphone, followed by processing with the ImageJ software. The colorimetric method is based on the change in the color and the red shift of the localized surface plasmon resonance (LSPR) absorption band of AuNPs/Glu in the region of 200-800 nm. The red shift (Δλ) of the LSPR band observed was from 525 nm to 660 nm for As(iii) and from 525 nm to 670 nm for Pb(ii). The mechanism of dual-mode detection is due to the non-covalent interactions of As(iii) and Pb(ii) ions with glucose molecule present on the surface AuNPs, resulting in the aggregation of novel metal nanoparticles. The calibration curve gave a good linearity range of 20-500 µg L-1 and 20-1000 µg L-1 for the determination of As(iii) and Pb(ii) with the limit of detection of 5.6 µg L-1 and 7.7 µg L-1 for both metal ions, respectively. The possible effects of different metal ions and anions were also investigated but did not cause any significant interference. The employment of AuNPs/Glu is successfully demonstrated for the determination of As(iii) and Pb(ii) using paper-based and colorimetric sensors in environmental water samples.

Food safety monitoring of the pesticide phenthoate using a smartphone-assisted paper-based sensor with bimetallic Cu@Ag core-shell nanoparticles.

Presently, the use of several pesticides has been continuously rising owing to the increase in the production of food materials to meet the requirements of the growing population of the world. The safety of food materials with regards to pesticides is an important health concern for people. With this aim, we have developed a smartphone-assisted paper-based sensor impregnated with citrate capped Cu@Ag core-shell nanoparticles (NPs) for selective determination of phenthoate pesticides in water and food samples. The mechanism for selective detection is based on the high affinity of phenthoate to interact with silver NPs present on the surface of CuNPs, which results in aggregation and a change in the color of the paper device. Furthermore, the proposed mechanism and interaction of phenthoate with Cu@Ag NPs was theoretically investigated by density functional theory (DFT) using Gaussian 16.0 software. The linear range for the determination of phenthoate was found in the range of 50-1500 µg L-1, with a limit of detection of 15 µg L-1, and a 92.6 to 97.4% recovery, and the interference studies demonstrated the selectivity for the determination of the target analyte from complex sample matrices. Finally, paper impregnated with Cu@Ag was exploited for the monitoring of the phenthoate pesticide in different water and food samples. The advantages of this paper-based sensor, coupled with a smartphone readout system, are that is it is user-friendly, easy-to-use, cost-effective, and can be applied at the sample source compared to sophisticated analytical instruments.

Phytochemical screening and determination of phenolics and flavonoids in Dillenia pentagyna using UV-vis and FTIR spectroscopy.

Here, we report an ultrasonic-assisted extraction (UAE) of phytochemicals from bark, leaves, sepals, fruits, and seeds of Dillenia pentagyna (Roxb) using different organic solvents such as chloroform, ethanol, and n-hexane. The preliminary phytochemical screening results showed that the ethanolic extract is enriched with phenolics, flavonoids, tannin, saponin, alkaloid, and terpenoids. The profiling of phytochemicals is carried out employing UV-Vis and Fourier-transform infrared (FTIR) spectroscopy analyses. The higher amount of phenolic compounds obtained in the ethanolic extract of bark and leaves as compared to other parts of the plant. Consequently, a higher amount of total flavonoid compounds unveiled in the bark of targeted species. The ethanolic extract of bark and leaves showed good free radical scavenging activity using DPPH with inhibition percentage of 90.58 ± 1.89% and 76.46 ± 1.58%, respectively, in comparison to standard ascorbic acid at 10 µg/mL. Moreover, the half-maximal inhibitory concentration (IC50) value of bark and leaves are 5.64 and 6.54 µg/mL, respectively, in comparison to standard ascorbic acid. With the best of our knowledge, it is the first report pertaining to characterization and quantification of phenols and flavonoids as well as the investigation of the medicinal property in D. pentagyna.

Colorimetric and smartphone-integrated paper device for on-site determination of arsenic (III) using sucrose modified gold nanoparticles as a nanoprobe.

An optical colorimetric and smartphone-integrated paper device (SIPD) is demonstrated for determination of As (III) in water and soil samples using sucrose modified gold nanoparticles (AuNPs/Suc) as a nanoprobe. The mechanism for determination of As(III) is experimentally validated by performing UV-Vis, transmission electron microscope (TEM), Fourier transforms infra-red spectroscopy (FTIR) and dynamic light scattering (DLS) measurements. The density function theory (DFT) calculations using B3LYP with 6-311G (2d,2p) and LANL2DZ basis sets is used to theoretically prove the mechanism for determination of As(III). In addition, the paper fabricated with AuNPs/SuC was used as a nanoprobe for quantitative determination of As(III) using smartphone and ImageJ software. Calibration plot was linear over 10-800 µgL-1 for colorimetric determination of As(III) with limit of detection (LOD) of 4 µgL-1 acquired when the absorbance ratio obtained at 594 nm/515 nm. The linearity range of 50-3000 µgL-1 with LOD of 20 µgL-1 was determined using smartphone-integrated paper device. AuNPs/Suc is successfully employed for determination of As (III) from contaminated water and soil samples in colorimetry and SIPD. Graphical abstractColorimetric and Smartphone-integrated paper device used for selective detection of arsenic from contaminated water samples using sucrose modified gold nanoparticles (AuNPs/Suc) as a sensing probe.

L-cysteine modified silver nanoparticles for selective and sensitive colorimetric detection of vitamin B1 in food and water samples.

The use of L-cysteine modified silver nanoparticles (Cys-capped AgNPs) as a colorimetric probe for determination of vitamin B1 (thiamine) is described in the present work. This method is based on the measurement of red shift of localized surface plasmon resonance (LSPR) band of Cys-capped AgNPs in the region of 200-800 nm. The color of Cys-capped AgNPs was changed from yellow to colorless by the addition of vitamin B1. The mechanism for detection of vitamin B1 is based on the electrostatic interaction between positively charged vitamin B1, which causes the red shift of LSPR band from 390 nm to 580 nm. The interaction between Cys-capped AgNPs and vitamin B1 was theoretically explored by density function theory (DFT) using LANL2DZ basis sets with help of Gaussian 09 (C.01) program. The morphology, size distribution and optical properties of Cys-capped AgNPs were characterized by transmission electron microscope (TEM), UV-Visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS) techniques. The method is linear in the range of 25-500 µg mL-1 with correlation coefficient (R2) 0.992 and limit of detection of 7.0 µg mL-1. The advantages of using Cys-capped AgNPs as a chemical sensor in colorimetry assay are being simple, low cost and selective for detection of vitamin B1 from food (peas, grapes and tomato) and environmental (river, sewage and pond) water samples.

Smartphone coupled with paper-based chemical sensor for on-site determination of iron(III) in environmental and biological samples.

We report a smartphone-paper-based sensor impregnated with cetyltrimethylammonium bromide modified silver nanoparticles (AgNPs/CTAB) for determination of Fe3+ in water and blood plasma samples. The methodology for determination of Fe3+ is based on the change in signal intensity of AgNPs/CTAB fabricated on a paper substrate after the deposition of analyte, using a smartphone followed by processing with ImageJ software. The mechanism of sensing for detection and determination of Fe3+ is based on the discoloration of AgNPs which impregnated the paper substrate. The discoloration is attributed to the electron transfer reaction taking place on the surface of NPs in the presence of CTAB. Fe3+ was determined when the paper was impregnated with 1 mM AgNPs for 5 min of reaction time and the substrate was kept under acidic conditions. The linear range for determination of total iron in terms of Fe3+ was 50-900 µg L-1 with a limit of determination (LOD) of 20 µg L-1 and coefficient of variation (CV) of 3.2%. The good relative recovery of 91.3-95.0% and interference studies showed the selectivity of the method for determination of total iron in water and blood plasma samples. Smartphone-paper-based sensors have advantages of simplicity, rapidity, user-friendliness, low cost, and miniaturization of the method for on-site determination of total iron compared to methods that require sophisticated analytical instruments. Graphical abstract Smartphone-paper-based sensor with cetyltrimethylammonium bromide modified silver nanoparticles for determination of Fe3+ in water and blood plasma samples.

A KBr-impregnated paper substrate as a sample probe for the enhanced ATR-FTIR signal strength of anionic and non-ionic surfactants in an aqueous medium.

Herein, we report a KBr-impregnated paper substrate as a sample probe to enhance the attenuated total reflection-Fourier transform infrared (ATR-FTIR) signal strength of anionic surfactants (AS) and non-ionic surfactants (NS) in an aqueous solution. The mechanism for the sensing of AS and NS is based on the strong interaction of surfactants with the silicate groups (SiO4 4-) of the KBr-impregnated paper substrate. The role of SiO4 4- on the surface of the paper is to enhance the adsorption of AS and NS, resulting in improved IR signal intensities for the target analytes. The improved signal intensity at 1253 cm-1 (SO4 2-, symmetric stretching) for AS and 1114 cm-1 (C-O-C, stretching vibration) for NS were selected for quantification. SEM-EDX was employed to determine the elemental compositions of pre- and post-adsorbed AS and NS on glass fibre filter paper (GFF). The linear range for the determination of AS and NS was 10-100 µg L-1 with a method detection limit (MDL) of 4 µg L-1 and method quantification limit (MQL) of 12 µg L-1. The good relative recovery of 71.4-109.7% and the interference studies showed the selectivity of the method for the determination of AS and NS in environmental water and commodity samples. The advantages of this method include its cost-effectiveness, enhanced sensitivity, disposability and accessibility of the paper substrate.

Citrate-capped gold nanoparticles as a sensing probe for determination of cetyltrimethylammonium surfactant using FTIR spectroscopy and colorimetry.

A novel, facile, and low-cost method was developed for determination of cetyltrimethylammonium (CTA+) cationic surfactant in water samples using diffuse reflectance Fourier transform IR (FTIR) spectroscopy and colorimetry. Cetyltrimethylammonium bromide was chosen as a model compound to demonstrate the optimization of the method for determination of CTA+ in water samples. The absorption peak at 3015.96 cm-1 (for CTA+) was enhanced when gold nanoparticles were used as a chemical sensor in diffuse reflectance FTIR spectroscopy, and this absorption peak was used for determination of CTA+. Alternatively, the color change from wine red (525 nm) to blue (740 nm) and the redshift of the localized surface plasmon resonance band in the visible region were used as a sensing probe for determination of CTA+. A linear calibration curve for determination in water samples was obtained in the range from 10 to 100 ng mL-1 with a limit of detection of 3 ng mL-1 by diffuse reflectance FTIR spectroscopy and in the range from 20 to 400 ng mL-1 with a limit of detection of 7 ng mL-1 by colorimetry. The advantageous features of the methods are their simplicity, rapidity, and sensitivity for the determination of CTA+ in water samples. Graphical abstract.

Application of functionalized silver nanoparticles as a biochemical sensor for selective detection of lysozyme protein in milk sample.

Silver nanoparticles (AgNPs) functionalized with glutamic acid (GA) was used as a biochemical sensing probe in colorimetry for detection of lysozyme protein in milk samples. The method is based on the color change of AgNPs/GA from yellow to reddish-yellow differentiated with naked eyes for qualitative determination and red shift of localized surface plasmon resonance (LSPR) absorption signal intensity of AgNPs/GA in visible region used for quantitative determination of lysozyme. The control experiments were performed to demonstrate the electrostatic force of interactions between AgNPs/GA and protein molecule. A wide linear range of 3-150 nM with limit of detection of 1.5 nM was acquired for quantitative determination of lysozyme using AgNPs/GA as a biochemical sensing probe. The advantages of using AgNPs/GA as a biochemical sensing probe are simple, label-free and economic for determination of lysozyme from milk samples.

The direct-writing of low cost paper based flexible electrodes and touch pad devices using silver nano-ink and ZnO nanoparticles.

We report a novel and simple approach for the synthesis of silver nanoparticles capped with inositol (Ag NPs/Ino) by the reduction of silver salt with ascorbic acid under basic conditions. UV-vis, TEM, FTIR and TGA techniques were used to characterize the Ag NPs/Ino to determine the size, shape and surface modification of the NPs. Stable silver nano-ink was prepared in aqueous solution containing 1% PVP (stabilizer) and glycerol (cosolvent) and was used for the direct-writing of a paper electrode with a roller ball-point pen for electrochemical applications. The solvent, stabilizing agents, concentration of NPs (10%), paper substrate, sintering temperature (40 °C) and sintering time (15 min) were optimized to obtain a uniform coating of Ag NPs on the paper substrate. Further, the synthesis and fabrication of ZnO NPs on a paper substrate was put forward to design a touch pad device based on the piezoelectric effect. The preparation of paper based devices suggests a direction for the development of a simple, low cost and compatible approach for the direct-writing of paper based flexible electrodes and electronics for future applications.

A direct DRS-FTIR probe for rapid detection and quantification of fluoroquinolone antibiotics in poultry egg-yolk.

We report a novel diffuse reflectance-Fourier transforms infrared (DRS-FTIR) spectral monitoring of fluoroquinolone antibiotics such as ciprofloxacin (CIP) and norfloxacin (NOR) for their quantification in poultry egg-yolks. To the best of our knowledge, this is the first report to describe the rapid quantitative determination of fluoroquinolone antibiotics in poultry egg samples using DRS-FTIR. The characteristic absorption peaks obtained at 1627 and 1026 cm-1 were used for optimization and determination of CIP and NOR, respectively. The linearity range obtained for the determination of CIP and NOR in egg samples was 0.05-0.50 ng mL-1 with limit of detection and limit of quantification of 0.032 and 1.551 ng mL-1 and 0.028 and 0.194 ng mL-1, respectively. Good recoveries were obtained in the range of 83.1-102.3% from poultry eggs samples using DRS-FTIR method. The advantages of the DRS-FTIR method are its simplicity, sensitivity and suitability for high-throughput analysis towards the food samples.

Sucrose capped gold nanoparticles as a plasmonic chemical sensor based on non-covalent interactions: Application for selective detection of vitamins B1 and B6 in brown and white rice food samples.

We report simple and selective method for detection of vitamins B1 and B6 in brown and white rice samples using localized surface plasmon resonance (LSPR) of sucrose capped gold nanoparticles (AuNPs) as a chemical sensor colorimetrically. Here, detection is based on the color change of AuNPs from pink to blue followed by a red shift of LSPR absorption band in UV-vis region with the addition of vitamins B1 and B6 into the NPs solution. A good linear range was observed in the range of 25-1000 ngmL-1 with detection limit of 8 ngmL-1 for B1 and 50-1000 ngmL-1 with detection limit of 15 ngmL-1 for vitamins B6. The employment of AuNPs for detection of B1 and B6 vitamins in rice food samples showed remarkable abilities in terms of the simplicity, low cost, stability, reproducibility and sensitivity.