Highly Sensitive SERS Detection of Hg²⁺ Ions in Aqueous Media Using Gold Nanoparticles/Graphene Heterojunctions

Gold nanoparticles (AuNPs)/reduced graphene oxide (rGO) heterojunctions were synthesized directly on SiO₂/Si substrates via a seed-assisted growth process. The in situ chemical fabrication strategy has been proven to be quite simple and efficient for generating highly active surface-enhanced Raman scattering (SERS) substrates due to synergistic enhanced protocol from rGO and AuNPs. The SERS substrates with AuNPs/rGO heterojunctions have been utilized for trace analysis of mercury­(II) ions via thymine–Hg²⁺–thymine coordination. Thereby, very low limits of detection, i.e., 0.1 nM or 20 ppt for Hg²⁺, can be achieved in contrast with some other SERS subsrtates, which suggests that the heterojunctions are appropriate as versatile surface-enhanced substrates applied in chemical sensing or biosensing

Results of correlation analysis between clinical variables and GMV in MDD group.

<p>GMV: gray matter volume.</p><p>HDRS: Hamilton Depression Rating Scale.</p><p>nMDD: medication-naïve major depressive disorder.</p><p>tMDD: treated major depressive disorder.</p

Demographic and clinical data of subjects.

<p>S.D.: standard deviation.</p><p>MDD: major depressive disorder.</p><p>HDRS: Hamilton Depression Rating Scale.</p

Regions of differences in gray matter volume in treated participants with major depressive disorder.

<p>A: the axial image (z = 26 mm Montreal Neurological Institute coordinate plane) shows the regions of significantly increased gray matter volume in left thalamus in treated participants with major depressive disorder, compared to healthy controls (p<0.05, corrected). B: the axial image (z = −6 mm Montreal Neurological Institute coordinate plane) shows the regions of significantly increased gray matter volume in right orbitofrontal cortex in treated participants with major depressive disorder, compared to healthy controls (p<0.05, corrected). The color bar represents the range of <i>T</i> values. R =  right.</p

Areas with significant differences on gray matter volume in single episode participants with major depressive disorder compared to health control participants.

<p>nMDD: medication-naïve major depressive disorder.</p><p>tMDD: treated major depressive disorder.</p><p>HC: healthy controls.</p

Regions of differences in gray matter volume in medication-naïve participants with major depressive disorder.

<p>A: the axial image (z = 8 mm Montreal Neurological Institute coordinate plane) shows the regions of significantly decreased gray matter volume in right dorsolateral prefrontal cortex in medication-naïve participants with major depressive disorder, compared to healthy controls (p<0.05, corrected). B: the axial image (z = 42 mm Montreal Neurological Institute coordinate plane) shows the regions of significantly decreased gray matter volume in left middle frontal gyrus in medication-naïve participants with major depressive disorder, compared to healthy controls (p<0.05, corrected). C: the axial image (z = 11 mm Montreal Neurological Institute coordinate plane) shows the regions of significantly increased gray matter volume in left thalamus in medication-naïve participants with major depressive disorder, compared to healthy controls (p<0.05, corrected). D: the axial image (z = 3 mm Montreal Neurological Institute coordinate plane) shows the regions of significantly increased gray matter volume in right insula in medication-naïve participants with major depressive disorder, compared to healthy controls (p<0.05, corrected). The color bar represents the range of <i>T</i> values. R =  right.</p

Demographic and clinical data of participants.

<p>Demographic and clinical data of participants.</p

The correlation between the strength of these functional connectivities and the FA Value of the fornix within each group.

<p>The correlation between the strength of these functional connectivities and the FA Value of the fornix within each group.</p

Compared with the HC group, the MDD group had lower FA values in the right Parahippocampal gyrus in voxel-based diffusion tensor analysis (A:red; B: red in superimposed on WM tracts template).

<p>Abbreviation: HC, healthy control; MDD, major depressive disorder; FA, fractional anisotropy; WM, white matter.</p

Compared with the HC group, the MDD group had lower FA values in the left anterior cingulate (A: red; B: red in superimposed on WM tracts template).

<p>Abbreviation: HC, healthy control; MDD, major depressive disorder; FA, fractional anisotropy; WM, white matter.</p