Journal of Fluorescence

, Volume 29, Issue 5, pp 1213–1219 | Cite as

Nitrogen Doped Carbon Quantum Dots Modified by Lens culinaris β-Galactosidase as a Fluorescent Probe for Detection of Lactose

  • Ranjana SinghEmail author
  • Anjali Yadav
  • Shashank Shekhar
  • Ranjan K. Ajad
  • Ranjan K. SinghEmail author
  • Arvind M. KayasthaEmail author


Nitrogen doped carbon quantum dots (NCQDs) were synthesized via hydrothermal route. The NCQDs are thermally and optically stable with high flouresence yield. For the synthesis of NCQDs, citric acid and urea was taken as carbon and nitrogen sources, respectively. The Transmission Electron Microscopy (TEM) of these quantum dots revealed nearly spherical shape and average size of 1.5 nm, which was calculated using Image J software. The quantum dots were also well-characterized using spectroscopic techniques such as FTIR, UV-Visible absorption and fluorescence. These synthesized and characterized dots were utilized for selective detection of lactose in Milli Q water. The bioprobe provide a wide linear range varying from (10.00–77.41) μM with limit of detection 11.36 μM and sensitivity equal to (0.0065 ± 0.0002) μM−1.

Graphical Abstract


Lactose Fluorescence β-Galactosidase Lens culinaris Biosensor 



Anjali Yadav is grateful to UGC, New Delhi, for fellowship in the form of junior research fellowship and senior research fellowship (F./2015-16/NFO-2015-17-OBC-UTT-32658/ (SA-III-website). Ranjana Singh is grateful to CSIR New Delhi, Govt. of India for providing financial support in terms of CSIR Research Associate ship with file no 09/13 (0846)/2018-EMR-I dated 29/03/2019. Shashank Shekhar want to acknowledge CSIR (09/013(0739)/2017-EMR-I), New Delhi for financial support. Ranjan K. Singh is grateful to AvH Foundation, Germany, DST, India for FIST programme. Authors are extremely thankful to Biophysics Laboratory, Department of Physics, B.H.U. Varanasi, India to access the Edinburg FL 900 fluorescence spectrophotometer for fluorescence measurement.

Compliance with Ethical Standards

Conflict of Interests

The authors declare no competing financial interest.

Supplementary material

10895_2019_2430_MOESM1_ESM.docx (8.2 mb)
ESM 1 (DOCX 8428 kb)


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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Physics, Institute of ScienceBanaras Hindu UniversityVaranasiIndia
  2. 2.Department of PhysicsCentral University of South BiharGayaIndia
  3. 3.School of Biotechnology, Institute of ScienceBanaras Hindu UniversityVaranasiIndia

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