Optical Sensor for Hexavalent Chromium

Technology: Optical Sensor for heavy metal ions.

Industry: Healthcare, Food, Chemical, Manufacturing Leather, Mining.

Applications: Drinking & wastewater quality monitoring, Blood testing, Environmental compliance and law enforcement agencies

Market: The global optical sensors market is projected at a CAGR of 6.33% during period of 2023-2028.

In present era, Chromium is a widely used heavy metal, because of which hexavalent chromium ions are hazardous pollutants frequently found in natural resources water.
Conventional techniques for Cr6+ detection & quantification by means of the standard methods using atomic absorption spectrometry or mass spectrometry are limited by requirement of expensive infrastructure & skilled personnel including other issues.
Hence, there is a need to introduce present method which mitigate above challenges.

Present invention discloses a method of fabricating a silica optical probe for Cr6+ detection
Further, said invention discussed an optical probe which comprises a U-bent silica optic fiber probe having a first end, a second end & a U-bent region, which is applicable for detecting Cr6+.
Further, said optical probe includes a metal organic framework (MOF) called zeolite imidazole (ZIF-67) coated on an outer surface of the U-bent region shown in below figures.
The method comprises a few steps explained in smart chart & Fig herein

1st Step explains about Fabricating a U-bent silica optic fiber probe
2nd Step explains about Activating an outer surface of the U-bent region to generate hydroxyl groups on the surface
3rd Step explains about Growing a metal organic framework (MOF) and Providing post-thermal treatment to the coated probe
The invention describes about the chemical synthesis of ZIF-67, using 2-methyl imidazole & cobaltous nitrate hexahydrate shown in figures herein below.
The aqueous solution of both chemicals is mixed in certain molarity & this freshly prepared growth mixture solution is used for the in-situ growth of thin films on U-bent silica optical fiber illustrates in figure.

Technical Perspective:

ZIF-67 selectively entrap Cr6+ ions and the high EWA sensitivity of the U-FOS allows specific detection of Cr6+ ions by means of their intrinsic optical absorption around 395 nm.
The MOF coated fiber probes are stable over a month even in humid and at room temperature.
The claimed sensor demonstrates high selectivity for chromium ion detection with respect to other potential interfering heavy metal ions present in water such as Mn7+, Fe3+, Co2+, Cl– , Cu2+,Pb2+, Hg2+, Mg2+, Ca2+ , Ni2+, Cd2+, Zn2+, Li+.
The proposed synthesis method is advantageous for many applications where fresh water may be used as medium for sensing.

Industrial Perspective:

The ZIF-67 coated U-FOS Cr6+ sensor realized with a portable LED-photodetector set-up demonstrates a wide dynamic range & useful detection limits.
Potentiality applicable to develop the U-FOS as a portable on-field sensor, or applicable to any other handheld device.

Biosensors Lab – Prof. Raghavendra Sai V.V,

Department of Applied Mechanics and Biomedical engineering

TRL- 4/5

Proof of Concept, tested & validated

Technology Transfer