  We report our new spectropolarimetric observations for 67P dust over
4,000--9,000 Angstrom using the ESO/Very Large Telescope in January--March 2016
(phase angle ranging $\sim$26--5 deg) to constrain the properties of the dust
particles of 67P and therefrom diagnose the dust environment of its coma and
near-surface layer at around the end of the Southern summer of the comet. We
examined the optical behaviours of the dust, which, together with Rosetta
colour data, were used to search for dust evolution with cometocentric
distance. Modelling was also conducted to identify the dust attributes
compatible with the results. The spectral dependence of the polarisation degree
of 67P dust is flatter than found in other dynamical groups of comets in
similar observing geometry. The depth of its negative polarisation branch
appears to be a bit shallower than in long-period comets and might be getting
shallower as 67P repeats its apparitions. Its dust colour shows a change in
slope around 5,500 Angstrom, (17.3 $\pm$ 1.4) and (10.9 $\pm$ 0.6) % (1,000
Angstrom)$^{\rm -1}$ for shortward and longward of the wavelength,
respectively, which are slightly redder but broadly consistent with the average
of Jupiter-Family comets. Observations of 67P dust in this study can be
attributed to dust agglomerates of $\sim$100 $\mu$m in size detected by Rosetta
in early 2016. A porosity of 60 % shows the best match with our polarimetric
results, yielding a dust density of $\sim$770 kg m$^{\rm -3}$. Compilation of
Rosetta and our data indicates the dust's reddening with increasing nucleus
distance, which may be driven by water-ice sublimation as the dust moves out of
the nucleus. We estimate the possible volume fraction of water ice in the
initially ejected dust as $\sim$6 % (i.e. the refractory-to-ice volume ratio of
$\sim$14).
